TECHNICAL FIELD

The present invention relates to a micro- or millifluidic pump suitable for the propulsion of fluids as well as to the manufacturing and use of such pumps. The micro- or millifluidic pumps of the present invention are particularly useful within lab-on-a-chip, point-of-care diagnostics and drug delivery applications.

BACKGROUND ART

In the last two decades, lab-on-a-chip (LOC) devices have proven their potential and advantages in numerous microfluidic applications, such as biosensing, analytical chemistry, proteomics, biology, and environmental monitoring. Nowadays, a wide part of the research is focused on health care applications, including early diagnostic, point-of-care (POC), and medical laboratory technologies. However, only few LOC devices were converted from a proof-of-concept to commercially available products.

Miniaturization is one of the key aspects of lab-on-a-chip (LOC) devices as it enables limited sample and reagent consumption, reduced time-to-results, portability, and high parallelization and multiplexing. However, the majority of traditional LOC platforms still requires external large and relatively expensive pumping mechanisms to control the liquid flow, such as syringe pumps, electro-pneumatic or pressure-driven systems. This issue has been tackled already by various completely autonomous and self-powered pumping solutions. For instance, systems based on capillary forces of intricate microstructures are capable of drawing liquids into a microfluidic network and can perform complicated multi-step assays. These systems are fabricated using different substrates, such as silicon or polydimethylsiloxane (PDMS) but require hydrophilization of these materials to obtain the capillary effect. Other platforms are based on the so called "degas- driven flow" concept, which takes advantage of the inherent high porosity and air solubility of PDMS. The air is initially extracted from the PDMS in a vacuum chamber and only when brought back to the atmospheric conditions, it reabsorbs the air. When a liquid sample is loaded on the inlet port of a PDMS device, it is drawn into the microfluidic channel due to the lower pressure created inside the channel. However, this approach is limited to permeable materials while the control over flow rate and timing is challenging. Paper microfluidics is another approach in the LOC field, attracting large attention in recent years. Here, paper, or other porous materials such as textile, are exploited as pumping element relying on capillary action to move liquids. The paper strip are often patterned with different reagents at different locations with the final goal to perform multi-step tests. The most successful commercially available self-powered devices to date are the lateral flow strips which have been used to develop a wide variety of point-of-care (POC) tests, including HiV, influenza A/B, malaria, and hCG hormone testing. However, the transport of analytes and reagents in the paper matrix remains an important limitation since it decreases sensitivity and specificity of the tests, leading mainly to qualitative results. Recently, the focus has shifted to the development of quantitative or semi-quantitative tests which, however, require an external reader reducing their portability. In order to solve this issue, hybrid solutions have been presented, where paper as pumping element is combined with traditional continuous microfluidics. ¹ ' ² Here, analytes and reagents flow in microfluidic channels without getting in contact with the porous material of the self-powered low cost devices.

The presented self-powered LOC platforms are designed to pull the liquid inside the channel or matrix. Only a few solutions have been described in literature that show the ability to push the liquid through the channels or matrix. This concept drastically expands the number of microfluidic applications and the ability to manipulate liquids on-chip. For instance, such infusion pumping could allow also for drug delivery systems whereas the combination of infusion and suction systems would enable the LOC devices with complex and multistep protocols. Different mechanisms were proposed so far for infusion pumping: i) a pressurized gas generated by a chemical reaction that pushes the downstream liquid through the microfluidic channel; ³ ii) sequential pressing on polyethylene pouches, injecting the reagents into the microfluidic network; ⁴ iii) a PDMS micro sponge prefilled with liquid, squeezed on the device inlet releasing and injecting the liquid in the circuit; ⁵ iv) a silicon tube, coupled to the inlet of a microfluidic device, where a check-valve prevents backward flow, is repeatedly compressed with the finger to infuse a preloaded sample in the system; ⁶ v) a pumping lid, coupled to the inlet/outlet of a microfluidic chip, able to generate a controlled pressure, positive or negative, to infuse or withdraw fluids in a microfluidic device. ⁷ Although promising, these approaches suffer from several limitations, such as complicated fabrication, limited control and narrow range of flow rates, excessive size and cost of the device, or limited pumping duration.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a flexible propulsion pump system for use in micro- or millifluidic systems. This objective is accomplished by a device according to embodiments of the present invention.

In the microfluidic field, two crucial limitations prevent the affirmation of LOC and POC devices, both in academic and industrial world. Most of the microfluidic devices still need an external power source (i.e. syringe pump, electro mechanical systems, ...) that limits the portability and increase the complexity and price of the final device. On the other hand, the very large majority of the microfluidic platforms are able to handle the fluids only in withdraw mode, narrowing the panel of the possible microfluidic operations. The present invention is based on the finding that by guiding the fluids, typically gas, expulsed from a solid sorbent during the absorption of a liquid by said solid sorbent into a milli- or microfluidic channel, referred to as outlet channel, this fluid flow provides a propulsion force, which allows for pushing a fluid contained in said outlet channel and/or connected a milli- or microfluidic network over a predictable trajectory. Moreover, it was found that the expulsed fluid flow allowed for generating a pressure within said outlet channel and/or connected milli- or microfluidic network, which was higher or at least comparable to that of all the microfluidic pumps presented in literature. However, the propulsion pump system of the present invention has the important advantage over the pump systems of the prior art in that it can be made self-powered by incorporating the liquid needed for driving the absorption based propulsion pump system within the milli- or microfluidic system comprising the pump. It is clear that such propulsion pump systems may be particularly useful in many different milli- and microfluidic applications such as in LOC or POC diagnostic devices or in the, for instance intradermal, delivery of therapeutic compounds to a human or animal in need thereof.

Therefore, in a first aspect, the present invention provides a milli- or microfluidic propulsion pump, which comprises a solid sorbent enclosed in an enclosure, wherein said solid sorbent contains a first fluid prior to the activation of said pump. Typically, said enclosure of the solid sorbent comprises a first opening through which said solid sorbent can be contacted with a liquid and a second opening connecting the enclosure to an outlet channel. The propulsion pump according to the present invention is adapted for being activated by contacting said solid sorbent with a liquid via said first opening, resulting in the absorption of at least part of said liquid by the solid sorbent. This absorption is typically associated with the expulsion of at least part of said first fluid from the cavities in said solid sorbent into said outlet channel. The flow of said first fluid into the outlet channel allows for propulsing and/or compressing a second fluid contained in said outlet channel and/or in a microfluidic network connected to said outlet channel.

The propulsion pump according to embodiments of the present invention works in infusion mode, pushing with a predetermined flow rate. By tuning the shape and properties of parts of the propulsion pump, different flow rates can be achieved, based on the application requirements, and the flow rates can be defined as constant, decreasing or increasing flow rate. Parameters that can be tuned to achieve a predetermined flow rate are the geometrical shape of the enclosed sorbent material and/or its properties, such as pore size, pore distribution in the sorbent material, porosity and/or wetting properties; the inlet and/or outlet channel dimensions (diameter and/or length); the load upstream and/or downstream of the pump, e.g. the volume of working liquid and outlet liquid; the properties of the applied fluids (working liquid and/or active substance). The pump system of embodiments of the invention requires no external power and addresses the POC or LOC requirements. At the same time it is robust, easy to fabricate, inexpensive, easy to use, and suited for mass replication technologies. Moreover, the propulsion pump system of embodiments of the present invention allows to achieve predictable flows as well as high pressures. These properties allow to also use the propulsion pump of embodiments of the present invention for drug delivery applications, where a sufficient pressure is required to inject the drug through the skin into the body.

In particular embodiments of the present invention, the solid sorbent of the milli- or microfluidic propulsion pump may be any of a porous materials, wherein said cavities are interconnected pores; or a capillary material, wherein said cavities are capillaries, preferably open ended capillaries; or a mixed material comprising both capillaries and pores.

In embodiments of the present invention, the first fluid may be a gas. Nevertheless, the skilled person understands that said first fluid may be a liquid in case the liquid being absorbed has a higher wetting affinity towards said solid sorbent than said first fluid.

In a first embodiment said first opening of the enclosure of the solid sorbent of a milli- or microfluidic propulsion pump according to the present invention connects to an inlet channel suitable for bringing a liquid into contact with said solid sorbent through said first opening in order to activate said propulsion pump. In particular embodiments, said inlet channel contains a liquid and/or connects to a reservoir containing a liquid, the liquid being referred to as working liquid. Prior to the activation of the propulsion pump the working liquid is prevented from contacting said solid sorbent. Typically, the contact between said working liquid and the solid sorbent is prevented by the presence of a gas between the working liquid and the solid sorbent. The propulsion pump according to embodiments of the present invention may comprise an activation means for moving the working liquid in the inlet channel such that it contacts said solid sorbent via said first opening resulting in the absorption of at least part of the working liquid by said solid sorbent. In a particular embodiment this activation means comprises a flexible wall integrated in a wall of said inlet channel and/or reservoir, wherein said propulsion pump is adapted for being activated by applying a sufficient pressure on said flexible wall whereby the deformation of said pressed flexible wall acts on the working liquid in the inlet channel and/or reservoir such that the working liquid moves in the inlet channel and contacts said solid sorbent via said first opening resulting in the absorption of at least part of the working liquid by said solid sorbent.

In a particular embodiment of a propulsion pump according the first embodiment of the invention the inlet channel and/or reservoir containing said working liquid may be further connected to a micro- or millifluidic network. Upon activation of such propulsion pump the absorption of said working liquid from the inlet channel and/or reservoir by said solid sorbent exerts a suction force on the fluids contained in said connected micro- or millifluidic network. In certain embodiments said micro- or millifluidic network comprises a channel having an inlet opening wherein said suction force allows for pulling in a liquid positioned on said inlet opening into said channel. The availability of such channel having an inlet opening operably connected to a propulsion pump according to the present invention, which also generates a suction force is particularly useful in LOC or POC diagnostic devices as it allows to draw in an analyte sample into a micro- or millifluidic system.

Embodiments of the present invention provide a milli- or microfluidic propulsion pump wherein an analytical zone is in fluid connection to the outlet channel, the analytical zone being adapted for receiving an analyte. The analytical zone can be a channel, a chamber such as a reaction chamber, a compartment; any region that allows for some kind of fluid flow and then detection. The analytical zone is connected to a channel that allows the delivery of sample and reagents. The analytical zone is furthermore provided with a detector unit for detecting properties of analyte in the analytical zone. The detector unit may be any suitable type of detector unit, irrespective of the detection method e.g. any analytical sensor for detecting analytes in fluids, a colorimetric sensor, etc. The detector unit may be, but does not need to be, an optical detector. In particular embodiments, the detector unit may comprise a surface plasma resonance detector, for instance a gold surface plasma resonance detector or a fiber optic surface plasma resonance detector. The detector unit is a system for converting a biological signal into a quantifiable signal (electric, intensity, numbers). The detector unit may comprise a responsive element, responsive to an event; a processing element for generating a detection signal based on the response to the event; and a means for transmitting information between the responsive element and the processing element. The detector unit does not need to be present in the analytical zone, but in that zone an event, e.g. a reaction, must take place to generate a signal that is detectable. The detector unit can be present outside the analytical zone. The detector unit can be integrally connected to a propulsion pump according to embodiments of the present invention. If the detector unit is miniaturized and power (e.g. a battery) is provided, the detector unit can be attached / integrated to the chip comprising the propulsion pump. The connection between the detector unit and the propulsion pump can be via a channel, a pipe or a tube. Such channel, pipe, tube should be connected to the enclosure enclosing the solid sorbent without any fluid leakage.

Particular embodiments of the present invention provide a milli- or microfluidic propulsion pump wherein a unit, for instance a reaction chamber, is in fluid connection to the outlet channel, an analytical zone, for instance an analytical channel, being adapted for receiving reactive fluids. The unit is furthermore physically or functionally connected with a responsive element. The responsive element may comprise a fiber optic surface plasma resonance detector. The responsive element may be part of the body of the reaction chamber. The responsive element may be attached to the wall of the reaction chamber. Alternatively, the responsive element may be free of attachment to the reaction chamber. The responsive element may be sealed in the reaction chamber. The responsive element may be addressed by one or more electrodes located outside the reaction chamber. The responsive element may be addressed remotely. The transmitting means comprises one or both of electrical and optical elements. The said transmitting means may comprise one or both of mechanical and radiation elements. The radiation element provides radiation selected from the group consisting of acoustic waves, actinic radiation, nuclear radiation, and magnetism. The reaction chamber may further comprise one or more of reaction component(s), intermediate(s), and reaction product(s). The responsive element can be selected from the group consisting of thermocouples, interdigitated transducers (IDTs) and acoustic sensors (SAWs, QCMs). The responsive element can be an analytical sensor. The analytical sensor can monitor a physical property, a chemical property, a biological property. The analytical sensor can be disposable.

In a second aspect, the present invention provides a milli- or microfluidic system comprising a propulsion pump according to embodiments of the first aspect of the present invention. In a particular embodiment said milli- or microfluidic system further comprises a suction pump. The suction pump may serve as an activation means for a propulsion pump according to embodiments of the first aspect of the present invention. In milli- or microfluidic systems according to this particular embodiment the inlet channel of the propulsion pump is typically operably connected to said suction pump such that following the activation of the suction pump a liquid can be moved into the inlet channel of said propulsion pump such that it contacts said solid sorbent via said first opening resulting in the absorption of at least part of the liquid by said solid sorbent and the expulsion of at least part of said first fluid from the solid sorbent into the outlet channel of the propulsion pump. The suction pump may comprise a further solid sorbent enclosed in a further enclosure. The further enclosure of said solid sorbent comprises one or more vent-holes and an opening connecting the further enclosure to a further inlet channel and/or to a further reservoir, which either or both contain a liquid, referred to as further working liquid. Said further inlet channel and/or further reservoir are operably connected to an inlet channel of a propulsion pump according to embodiments of the first aspect of the present invention. The suction pump is adapted for being activated by contacting said the further working liquid to the further solid sorbent of the suction pump, which results in the absorption of the further working liquid from said further reservoir and/or further inlet channel by this further solid sorbent. The pressure fall resulting from the absorption of the further working liquid from said further inlet channel and/or further reservoir generates a suction force on a liquid introduced or contained in the inlet channel of said propulsion pump such that said liquid is moved towards and brought into contact with said solid sorbent of the propulsion pump. Milli- or microfluidic systems according to the second object of the invention may comprise two propulsion pumps according to embodiments of the first aspect of the present invention wherein a first propulsion pump can serve as an activation means for a second propulsion pump. Thereto, the outlet channel connected to the enclosure of the solid sorbent of said first propulsion pump connects with the reservoir and/or inlet channel containing a working liquid and being connected to the enclosure of the solid sorbent of said second propulsion pump. After activation of said first propulsion pump the fluid flow from the outlet channel of said first propulsion pump into said reservoir and/or inlet channel activates the second propulsion pump by pushing the working liquid contained therein towards and into contact with the enclosed solid sorbent of said second propulsion pump, resulting in the absorption of the working liquid by this sorbent and the expulsion of at least part of said first fluid from the solid sorbent into the outlet channel of the second propulsion pump.

In other embodiments, milli- or microfluidic systems according to the second object of the invention may comprise more than two propulsion pumps, acting on a different or the same outlet channel. The plurality of propulsion pumps may be connected in series and activate one another as explained above. Alternatively, two propulsion pumps may be connected in parallel, either with their inlet to the outlet of a third propulsion pump, for being activated by this third propulsion pump; or with their outlets both to the inlet of a third propulsion pump, for both together activating the third propulsion pump.

In a third aspect, the present invention provides a milli- or microfluidic point of care diagnostic device comprising a propulsion pump according to embodiments of the present invention.

In a fourth aspect, the present invention provides a lab-on-chip device comprising a propulsion pump according to the present invention.

The present invention provides the use of a milli- or microfluidic propulsion pump according to any of the embodiments of the first aspect in a milli- or microfluidic system wherein said milli- or microfluidic system is a lab-on-chip or point of care diagnostic device.

In a fifth object, the present invention provides a delivery system for delivering a target molecule or agent, for instance a bioactive compound, into a target location, for instance through an injection needle or one or more microneedles. The target location can be a cell, a tissue or a living organism such as a plant or animal. The present invention for instance provides a patch for the delivery of a medicinal or veterinary compound wherein said patch comprises a propulsion pump according to embodiments of the first aspect of the present invention and at least one hollow microneedle, the microneedle comprising a channel connecting a needle inlet opening with an open free end, adapted for being introduced in a human or animal tissue. Within said patch the outlet channel of said propulsion pump comprises a solution or suspension containing said compound to be delivered or is connected to a reservoir comprising such solution or suspension. Said outlet channel or reservoir is further connected to the inlet of said hollow microneedle such that by activating the propulsion pump said solution or suspension can be pumped via said inlet towards the open free end of the microneedle and preferably into a tissue in which the microneedle is introduced.

Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.

For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

The above and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

BRIEF DESCRIPTION OF DRAWINGS The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows the schematics of pump design and prefilling steps.

Figure 2 shows the schematic representation of the activation and operation of an embodiment of the propulsion pump of the present invention.

Figure 3 shows the fabrication of an embodiment of a microfluidic propulsion pump of the present invention.

Figure 4 shows a stepwise representation of the prefilling of a microfluidic propulsion pump according to the embodiment of Figure 3 of the present invention, in side view and in top view.

Figure 5 shows a schematic representation of the operation of an embodiment of a propulsion pump system according to the present invention.

Figure 6 shows an embodiment of a propulsion pump according to the present invention for investigating the use of said pump for generating a pressure in a microfluidic system. Figure 7 shows the trend of the pressure building in the device of Figure 6.

Figure 8 shows an exemplary microfluidic system comprising a propulsion pump according to embodiments of the present invention.

Figure 9 and 10 shows different exemplary embodiments of a microfluidic system with two propulsion pumps according to embodiments of the present invention, activated with suction pump.

Figure 11 shows an embodiment of a microfluidic system comprising a suction pump being activated by a propulsion pump.

Figure 12 shows a microfluidic system comprising two propulsion pumps according to the present invention.

Figure 13 shows an assay system comprising a suction and propulsion pump combination.

Figure 14 shows a detection system for use in a microfluidic bioassay.

Figure 15 shows an assay system for use in a microfluidic bioassay involving a coupled enzyme reaction.

Figure 16 illustrates a further embodiment of the present invention, in which a surface plasmon resonance optical fiber is integrated with a propulsion pump according to embodiments of the present invention, in a system or chip, for data readout.

The drawings are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not necessarily correspond to actual reductions to practice of the invention.

Any reference signs in the claims shall not be construed as limiting the scope.

In the different drawings, the same reference signs refer to the same or analogous elements.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims.

The terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. Moreover, directional terminology such as top, bottom, front, back, leading, trailing, under, over and the like in the description and the claims is used for descriptive purposes with reference to the orientation of the drawings being described, and not necessarily for describing relative positions. Because components of embodiments of the present invention can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration only, and is in no way intended to be limiting, unless otherwise indicated. It is, hence, to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.

It is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

It should be noted that the use of particular terminology when describing certain features or aspects of the invention should not be taken to imply that the terminology is being re-defined herein to be restricted to include any specific characteristics of the features or aspects of the invention with which that terminology is associated.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

The present invention provides a milli- or micro fluidic propulsion pump 100 comprising a solid sorbent 101 enclosed in an enclosure 102. The solid sorbent 101 contains cavities comprising a first fluid. The first fluid may be a liquid, or a gas such as for instance air. The enclosure 102 of the solid sorbent 101 comprises a first opening 103 through which the solid sorbent 101 can be contacted with a liquid. The enclosure 102 furthermore comprises a second opening 104, through which the first fluid can be evacuated from the enclosure 102. The second opening 104 connects the enclosure 102 to an outlet channel 105. The propulsion pump 100 is adapted for being activated by contacting said solid sorbent 101 with a liquid via said first opening 103, for instance a liquid flowing in an inlet channel 106, resulting in the absorption of at least part of said liquid by the solid sorbent 101. This absorption of liquid by the solid sorbent 101 is associated with the expulsion of at least part of the first fluid from the cavities of the solid sorbent 101 through the second opening 104 into the outlet channel 105. The flow of the first fluid into the outlet channel 105 allows for propulsion and/or compression of a second fluid contained in the outlet channel 105 and/or in a channel or reservoir connected to said outlet channel 105.

Figure 1 illustrates different steps in the process of prefilling of a milli- or microfluidic propulsion pump 100 according to embodiments of the present invention, i.e. before the propulsion pump 100 is actually used as a pump.

Figure 1 : A) Before its prefilling the pump 100 comprises an enclosure 102 101, said enclosure 102 comprising a first opening 103 connected with an inlet channel 106, a second opening 104 connected with an outlet channel 105 and a vent-hole 107. B) Solid sorbent 101, in the example illustrated for instance in the form of porous material comprising cavities filled with air, is hosted in the enclosure 102 and the vent-hole 107 is open. C,D) With the vent-hole 107 still open, the inlet channel 106 is filled with working liquid 108 until it is close to the porous material 101, but does not contact the porous material 101 yet. E) With the vent-hole 107 still open, outlet liquid 109 is then injected in the outlet channel 105. By having the vent-hole 107 open, overpressure in the propulsion pump 100 can be avoided. F) When the device 100 is properly prefilled, the vent-hole 107 is closed and the device 100 is ready to use or to be stored for later use.

Figure 2 illustrates steps in the actual use of a device 100 as a propulsion pump.

Figure 2: A) Following the prefilling of said propulsion pump 100 (see Figure 1), the pump 100 comprises a solid sorbent 101 (porous material) enclosed in an enclosure 102 connected via a first opening 103 to an inlet channel 106 containing a working liquid 108, and via a second opening 104 to an outlet channel 105 containing the outlet liquid 109. The vent-hole 107 is closed. The starting step illustrated in Figure 2 A) corresponds to the finishing step of the pre-filling process as illustrated in Figure 1 F). Neither the working liquid 108 nor the outlet liquid 109 contact the solid sorbent 101. The device 100 may have been pre-filled immediately before the actual use as a pump, or it may have been pre-filled a longer time before, and have been stored. B) The pump 100 is activated by generating a pressure 200 on the working liquid 108 in the inlet channel 106, thus moving the working liquid 108 such that it contacts the solid sorbent 101, for instance at the first opening 103, and gets absorbed. C) The absorbed working liquid 108 expulses the air out of the porous material 101 into the outlet channel 105, and this expulsed air, in turn, pushes the outlet liquid 109 further in the outlet channel 105, away from the enclosure 102. D) The pump operation terminates (i) when all the working liquid 108 is drawn in the porous material 101 or (ii) when the porous material 101 gets saturated with working liquid 108. During this whole process, the vent- hole 107 remains closed.

Figure 3 illustrates how a micro fluidic propulsion pump 100 according to embodiments of the present invention may be manufactured. In embodiments of the present invention, the microfluidic propulsion pump 100 may be assembled from a plurality of layers and/or elements with different characteristics and functions. In the embodiment illustrated, the propulsion pump 100 is assembled from three layers, and a chamber is filled with solid sorbent material.

Figure 3: A) Representation of the four different elements to be assembled in one embodiment of a fabrication method of the pump 100:

(i) A bottom layer 301 in solid material, for supporting the propulsion pump 100. In particular embodiments, the solid material of the bottom layer 301 may be a light weight material, as this is a useful property in for instance LOC and POC applications.

The solid material of the bottom layer 301 may be cheap material, which is desirable in case the propulsion pump 100 is embedded in a disposable device. The solid material of the bottom layer 301 should be resistant against, e.g. not corroded by, and not absorbing, the fluids present in or flowing through the enclosure 102, the inlet channel 106 and the outlet channel 105. In particular embodiments, the solid material of the bottom layer 301 is hydrophobic material, to prevent the liquid to move autonomously by capillarity, In embodiments of the present invention, the solid material of the bottom layer 301 may be transparent, for instance to allow visual inspection. The solid material of the bottom layer 301 may be shatter resistant. The thickness of the bottom layer may be limited; it may for instance not more than a few μιη, such that the bottom layer in fact may be nothing more than a sheet of material. The solid material may for instance be plastic material (e.g. PVC or PMMA).

(ii) A double sided pressure sensitive adhesive (PSA) layer 302 in which a milli- or microfluidic channel 303 is cut, for instance with an electronic craft cutting machine.

The milli- or microfluidic channel 303 comprises at least a section which, upon assembling the elements, will form the enclosure 102 for enclosing the solid sorbent 101. The milli- or microfluidic channel 303 may furthermore comprise at least part of the inlet channel 106 and/or the outlet channel 105.

(iii) A solid sorbent material 101. The solid sorbent material 101 may be a porous material

(e.g. filter paper) suitably shaped, for instance with an electronic cutting machine, to fit in the part of the milli-or microfluidic channel 303 which will form the enclosure 102. (iv) A top layer 304 for covering the pressure sensitive adhesive layer 302 and closing the milli- or microfluidic channel. In the top layer 304, an inlet hole 305, for introducing working liquid 108 into the inlet channel 106; an outlet hole 306, for introducing outlet liquid 109 into and evacuating outlet liquid from the outlet channel 105; and a vent- hole 107 may be provided, for instance with an electronic cutting machine. The top layer 304 may be made from any suitable material, for instance a plastic material like PVC or PMMA. Characteristics of the top layer 304 may be similar to the characteristics of the bottom layer 301. The top layer and the bottom layer may be, but do not need to be, made from the same material.

B) The fabrication sequence is shown: the pressure sensitive adhesive 302 is attached, by applying pressure, on the bottom layer 301 ; the solid sorbent 101, e.g. the filter paper, is inserted in the section in the milli- or microfluidic channel 303 cut in the pressure sensitive adhesive 302, which will form the enclosure 102 ; the chip is closed with the top layer 304 positioned and attached on the pressure sensitive adhesive layer 302. C) Representation of the assembled device.

Figure 4 is a stepwise representation of the pre-filling of a microfluidic propulsion pump according to the embodiment illustrated in Figure 3. The different steps are illustrated in side view in the left hand column, and in top view at the right hand column. Figure 4: Α,Β) before its prefilling the pump 100 comprises i) a bottom layer 301, ii) a layer 302 comprising channels and chambers cut in a pressure sensitive adhesive material, iii) a solid sorbent 101 (porous material), iv) a top layer 304 with an inlet hole 305, an outlet hole 306 and a vent- holes 107. The solid sorbent material 101, e.g. porous material, is hosted in the enclosure 102 forming a porous material chamber, and the vent-hole 107 is open during the prefilling phase, as also explained with reference to Figure 1. Figure 4 A) is a cross-sectional side view of the device which is illustrated in top view both in Figure 3 C) and in Figure 4 B). C,D) The inlet channel 106 is filled, via the inlet hole 305, with working liquid 108. The working liquid 108 is made to approach but not contact the solid sorbent material 101, e.g. porous material. The working liquid 108 may be forced to travel through the inlet channel 106 by applying an external force, for example by injection. E,F) Next, outlet liquid 109 is introduced, e.g. injected, in the outlet channel 105, via the outlet hole 306, also without contacting the solid sorbent material 101, e.g. porous material. G,H) When the device 100 is properly pre-filled the vent-hole 107 is closed and the device 100 is ready to use or to be stored. Closure of the vent-hole 107 can be performed for instance by means of small patches of tape, for instance double sided tape, which can be removed on activation. In particular embodiments, the tape may be gas impermeable.

Figure 5 is a schematic representation of the operation of an embodiment of a propulsion pump system according to the present invention.

Figure 5: A) Prior to its activation the propulsion pump 100 comprises a solid sorbent 101 (porous material) enclosed in an enclosure 102, preferably in the shape of a circle sector. Using the shape of a circle sector for the enclosure 102 is not a strict requirement for the working of the principle itself but it has been shown in literature that a circular sector shape provides a constant flow rate of the liquids manipulated by the pump, which is a preferred condition in microfluidics.

The enclosure 102 is connected to an inlet channel 106 and to an outlet channel 105. The inlet channel 106 is further connected to an inlet reservoir 501 having a flexible wall, wherein the inlet reservoir 501 and the inlet channel 106 contain a working liquid 108. The outlet channel 105 comprises an outlet liquid 109 and is connected to an outlet reservoir 502 positioned downstream of the solid sorbent 101. B) Activation: the propulsion pump 100 is activated by applying a pressure 503 to, e.g. by compressing, the flexible wall of the inlet reservoir 501 connected to the inlet channel 106, thus moving the working liquid 108 in the inlet channel 106 so that it contacts the solid sorbent 101 leading to the absorption of the working liquid 108 by the solid sorbent 101. C) Operation: while the working liquid 108 is absorbed into the solid sorbent 101, it expulses the fluid, for example air, present in the cavities in the solid sorbent 101 into the outlet channell05. This fluid influx in the outlet channel 105 pushes the outlet liquid 109 towards and into the outlet reservoir 502 downstream of the outlet channel 105. D) Termination: the action of the pump 100 is terminated either when all the working liquid 108 is absorbed into the solid sorbent 101 or when the solid sorbent 101 is saturated by the working liquid 108. The outlet liquid 109 may all be pushed into the outlet reservoir 502, or may still partially be present in the outlet channel 105.

Figure 6 shows an alternative embodiment of a propulsion pump 100 according to the present invention. It is used for investigating the use of this pump 100 for generating a pressure in a microfluidic system.

Figure 6: A) The microfluidic pump 100 comprises a solid sorbent 101 (porous material) enclosed in an enclosure 102. The enclosure 102 comprises a first opening 103 for contacting a liquid to said solid sorbent 101 and a second opening 104 connecting the enclosure 102 to an outlet channel 105. Prior to the activation of the microfluidic pump 100, a liquid plug of outlet liquid 109 was preloaded in said outlet channel 105 via an outlet hole 306, which was sealed after provision of the liquid plug 109. B) Activation: a droplet of a working liquid 108 is deposited on the inlet of the propulsion pump 100, e.g. on the first opening 103. C) Operation: while the working liquid 108 is absorbed into the solid sorbent 101, it pushes out the fluid, typically air, present in the cavities in the solid sorbent 101. This fluid, e.g. air, pushes the liquid plug of outlet liquid 109 towards the closed end of the outlet channel 105, i.e. towards the end where the outlet hole 306 has been closed in the pre- filling phase after provision of the liquid plug 109. D) Termination: the pumping operation is terminated either when all working liquid 108 is absorbed into the solid sorbent 101 or when the solid sorbent is saturated by the working liquid 108. Pressurized air 504 is generated, or any other suitable type of fluid is put under pressure, between the liquid plug 109 and the closed end (at the closed outlet hole 306) of the outlet channel 105. The amount of displacement of the liquid plug 109 after termination is indicative of the pressure that would be generated, as a result of the action of the propulsion pump 100 of the present invention, in a microfluidic system connected to the propulsion pump 100. Figure 7 shows the trend of the pressure building in the device of Figure 6 as a function of time after the activation of the propulsion pump 100. It can be seen that pressure gradually builds up, up to a particular moment in time, in the embodiment illustrated about 24 minutes, when the pressure levels out. This moment in time corresponds to the time required for all working liquid 108 to be absorbed into the solid sorbent 101 or for the solid sorbent to be saturated by the working liquid 108. Hence the moment in time when the pressure stops building up determines the termination of the pumping action. The time required before the pumping action terminates is a function of the shape and dimensions of the enclosure 102, and/or of the type and amount of solid sorbent material 101 filling the enclosure 102, and/or of the amount of working liquid 108 provided to be brought into contact with the solid sorbent 101. Figure 8 illustrates a milli - or microfluidic system 800 comprising a propulsion pump 801 according to embodiments of the present invention, operably connected to a suction pump 802, wherein said suction pump 802 serves as an activation means for said propulsion pump 801.

Figure 8 A) Before activation of the propulsion pump 801, the milli- or microfluidic system 800 comprises a suction pump 802 comprising a solid sorbent 803, e.g. porous material, enclosed in a suction pump solid sorbent enclosure 804 in the shape of a circle sector. The solid sorbent 803 of the suction pump 802 contains cavities comprising a fluid. The enclosure 804 of said solid sorbent material 803, e.g. porous material, comprises one or more vent-holes 805 and an opening 806 connecting the enclosure 804 to a reservoir 807, having a flexible wall, via a channel 808. Said channel 808 and reservoir 807 comprise a working liquid 809. The milli- or microfluidic system 800 furthermore comprises a propulsion pump 801 according to embodiments of the present invention, comprising a solid sorbent 101 enclosed in an enclosure 102. In the embodiment illustrated in Figure 8, the enclosure 102 is wing-shaped, but the present invention is not limited thereto. That particular wing-shape maximizes the size of the porous material without increasing to much the size of the overall chip. It is, however, not a strict requirement to use such wing-shape, and also for instance the shape of a circular sector, similar as for the suction pump, can be used, the invention not being limited thereto. The channel 808 and reservoir 807 of the suction pump 802 are operably connected to the propulsion pump 801 according to embodiments of the present invention, via a channel 810 (analytical zone) comprising an analyte inlet 811. A droplet of a first liquid analyte is placed on the inlet 811 of the analytical channel 810. The wing-shaped enclosure 102 of the solid sorbent 101 (e.g. porous material) of the propulsion pump 801 comprises a first opening 103 connecting the enclosure 102 to said analytical channel 810, and a second opening 104 connecting to an outlet channel 105. The outlet channel 105 is connected to an analyte storage channel 812, which connects to the analytical channel 810. The analyte storage channel 812 is preloaded with a second liquid analyte via an inlet opening 813 in said channel 812. Immediately after loading the second liquid analyte in said analyte storage channel 812 said inlet opening 813 is sealed.

B) Activation of the suction pump 802: the suction pump 802 is activated by applying pressure to the flexible wall of the reservoir 807, e.g. by compressing the reservoir 807 comprising the working liquid 809, so as to contact the working liquid 809 to the solid sorbent 803 of the suction pump 802, thus initiating the absorption of the working liquid 809 by the solid sorbent of the suction pump 802. While the solid sorbent 803 absorbs working liquid 809, liquid is expelled out of the cavities of the solid sorbent 803 of the suction pump, and is evacuated from the enclosure 804 through the vent-holes 805. C) Operation of the suction pump 802: as a result of the absorption of the working liquid 809 of the suction pump 802 by the solid sorbent 803 of the suction pump 802, the pressure in the analytical channel 810 is reduced and the first liquid analyte is drawn into in the channel 810.

D) Activation of the propulsion pump 801 : when the first liquid analyte moving through the channel 810 due to the under-pressure created, contacts the solid sorbent 101, e.g. porous material of the propulsion pump 801, it is absorbed in the solid sorbent 101 and expulses the liquid, e.g. air, from the pores in the solid sorbent 101 into the outlet channel 105. This inflow of the liquid contained in the solid sorbent 101, e.g. air, in the outlet channel 105 pushes the second liquid analyte from said analyte storage channel 812 into the analytical channel 810. The action of the suction pump 802 terminates when all working liquid 809 is absorbed into the solid sorbent of the suction pump 802, or when the solid sorbent of the suction pump 802 is saturated by the working liquid 809.

E) Termination of the propulsion pump 801 : the pumping operation is terminated either when all first liquid analyte is absorbed into the solid sorbent 101 of the propulsion pump 801 or when the solid sorbent 101 of the propulsion pump 801 is saturated with the first liquid analyte.

Figure 9 illustrates a further embodiment of a milli- or microfluidic system 900 according to the present invention. The milli- or microfluidic system comprises two propulsion pumps 901, 902 according to embodiments of the present invention, which are operably connected to a suction pump 802, wherein said suction pump 802 serves as an activation means for said propulsion pumps 901, 902. In this embodiment the suction pump 802 simultaneously activates both propulsion pumps 901, 902.

A) Before activation of the propulsion pumps 901, 902, the microfluidic system 900 comprises a suction pump 802 comprising a solid sorbent 803, e.g. porous material, enclosed in an enclosure 804, preferably in the shape of a circle sector. The enclosure 804 of said solid sorbent 803, e.g. porous material, comprises several vent-holes 805 and an opening 806 connecting the enclosure 804 of the suction pump 802 to a reservoir 807 via a channel 808, wherein said reservoir 807 has a flexible wall. Said channel 808 and reservoir 807 comprise a working liquid 809. The milli- or microfluidic system 900 furthermore comprises a first propulsion pump 901 according to embodiments of the present invention, and a second propulsion pump 902 according to embodiments of the present invention. The first and second propulsion pumps 901, 902 comprise a solid sorbent 101a, 101b, enclosed in an enclosure 102a, 102b, respectively. In the embodiment illustrated in Figure 9, the enclosures 102a, 102b are wing-shaped, but the present invention is not limited thereto. The channel 808 and reservoir 807 are operably connected to the first propulsion pump 901 and to the second propulsion pump 902, via a channel 810 (analytical zone) comprising an analyte inlet 811. A droplet of a first liquid analyte is placed on the inlet 811 of the analytical channel 810. The enclosures 102a, 102b of the preferably wing-shaped solid sorbents 101 a, 101b (e.g. porous material) of the propulsion pumps 901, 902 each comprise a first opening 103 a, 103b connecting the enclosures 102a, 102b, respectively, to said analytical channel 810, wherein said openings 103 a, 103b are positioned at a same position along said analytical channel 810 but at opposite sides thereof. Each of said enclosures 102a, 102n of the preferably wing-shaped solid sorbent material 101 a, 101b further comprises a second opening 104a, 104b connecting each of said enclosures 102a, 102b to a separate outlet channel 105a, 105b. Each of said outlet channels 105a, 105b is connected to a separate analyte storage channel 812a, 812b, which each connect to the analytical channel 810 at a same position along the analytical channel 810 but at opposite sides thereof. These analyte storage channels 812a, 812b are preloaded with a second and third liquid analyte A2, A3, respectively, via the inlet openings 813a, 813b in each of these channels 812a, 812b. Immediately after loading second and third liquid analyte into the storage channels 812a, 812b, said inlet openings 813a, 813b are sealed.

B) Activation of the suction pump 802: the suction pump 802 is activated by applying a force on, e.g. by compressing, the flexible wall of the reservoir 807 comprising the working liquid 809, thus bringing the working liquid 809 into contact with the solid sorbent 803 of the suction pump 802 and initiating the absorption of the working liquid 809 by the solid sorbent 803 of the suction pump 802.

C) Operation of the suction pump 802: as a result of the absorption of the working liquid 809 by the solid sorbent 803 of the suction pump 802, the pressure in the analytical channel 810 is reduced and first liquid analyte is drawn into this channel 810.

D) Activation of the propulsion pumps 901, 902: when the first liquid analyte Al contacts the solid sorbent materials 101a, 101b, e.g. porous materials, of the respective propulsion pumps 901, 902, it is simultaneously absorbed by the solid sorbent materials 101a, 101b, and expulses the liquid, e.g. air, from the pores in both the solid sorbent materials 101a, 101b, into the respective outlet channels 105a, 105b. These air inflows in the respective outlet channels 105a, 105b simultaneously push the second liquid analyte A2 and the third liquid analyte A3 from their analyte storage channels 812a, 812b into the analytical channel, where they can mix. The action of the suction pump 802 terminates when all working liquid 809 is absorbed into the solid sorbent 803 of the suction pump 802, or when the solid sorbent 803 o the suction pump 802 is saturated with the working liquid 809. Preferably, the design of the microfluidic system 900 is such that the action of the suction pump 802 terminates upon activation or shortly after activation of the propulsion pumps 901, 902.

E) Termination of the propulsion pumps901, 902: the operation of each of the propulsion pumps 901, 902 terminates as soon as either the first liquid analyte Al is absorbed by the solid sorbents 101a, 101b, or when the solid sorbents 101a, 101b are saturated with the first liquid analyte Al.

Figure 10 illustrates another milli- or micro fluidic system 1000 according to embodiments of the present invention. The milli- or micro fluidic system 1000 comprises two propulsion pumps 1001, 1002 according to embodiments of the present invention operably connected to a suction pump 802, wherein said suction pump 802 serves as an activation means for said propulsion pumps 1001, 1002. In this embodiment the suction pump 802 sequentially activates the propulsion pumps 1001, 1002. This is obtained by, opposite to the embodiment illustrated in FIG. 9, not having the inlet of the propulsion pumps 1001, 1002 at the same location of the analytical channel 810.

A) Before activation of the propulsion pumps 1001, 1002, the micro fluidic system 1000 comprises a suction pump 802 comprising a solid sorbent 803 enclosed in an enclosure 804, preferably in the shape of a circle sector. The enclosure 804 of the solid sorbent 803 of the suction pump 802 comprises one or more vent-holes 805 and an opening 806 connecting the enclosure 804 to a reservoir 807 via a channel 808, wherein said reservoir 807 has a flexible wall. Said channel 808 and reservoir 807 comprise a working liquid 809 and are operably connected to a plurality of, in the example illustrated two, propulsion pumps 1001, 1002 according to embodiments of the present invention, via a channel 810 (analytical zone) comprising an analyte inlet. A droplet of a first liquid analyte Al is placed on the inlet 811 of the analytical channel 810. The enclosures 102a, 102b of the preferably wing-shaped solid sorbents 101 a, 101b of the propulsion pumps 1001, 1002 each comprise a first opening 103a, 103b connecting the respective enclosures 102a, 102b to said analytical channel 810, wherein said openings 103 a, 103b are positioned at different positions along said analytical channel 81 Oand at opposite sides thereof. Each of said enclosures 102a, 102b of the preferably wing-shaped solid sorbents 101 a, 101b, e.g. porous material, further comprises a second opening 104a, 104b connecting each of said enclosures 102a, 102b to a separate outlet channel 105a, 105b. Each of said outlet channels 105a, 105b is connected to a separate analyte storage channel 812a, 812b, which each connect to the analytical channel 81 Oat different positions along the analytical channel 810and at opposite sides thereof. These analyte storage channels 812a, 8112b are preloaded with a second and third liquid analyte A2, A3 via the inlet openings 813a, 813b in each of these channels 812a, 812b. Immediately after loading the second liquid analyte A2 and the third liquid analyte A3 into the storage channels 812a, 8112b said inlet openings 813a, 813b are sealed. B) Activation of the suction pump 802: the suction pump 802 is activated by applying pressure to, e.g. by compressing, the flexible wall of the reservoir 807 comprising the working liquid 809, thus bringing the working liquid 809 into contact with the solid sorbent 803 of the suction pump, thus initiating the absorption of the working liquid 809 by the solid sorbent 803. C) Operation of the suction pump 802: as a result of the absorption of the working liquid 809 by the solid sorbent 803 of the suction pump 802 the pressure in the analytical channel 810 is reduced and first liquid analyte Al is drawn into this channel 810.

D) Activation of the first propulsion pump 1001 : when first liquid analyte Al contacts the solid sorbent 101 a, e.g. porous material, positioned most upstream relative to the flow of the first liquid analyte Al, it is absorbed and expulses the liquid, e.g. air, from the pores in the solid sorbent 101a of the first propulsion pump 1001 into the outlet channel 105a connected to the enclosure 102a of the solid sorbent 101a. This fluid flow, e.g. air inflow, in said outlet channel 105a subsequently pushes second liquid analyte A2 from its analyte storage channel 812a into the analytical channel 810. The action of the suction pump 802 terminates when all working liquid 809 is absorbed into the solid sorbent 803 of the suction pump 802, or when the solid sorbet 803 is saturated with the working liquid 809.

E) Activation of the second propulsion pump 1002: the activation of the first propulsion pump

1001 results in the flow of part of the first liquid analyte Al further downstream into the analytical channel 810 until Al contacts the solid sorbent material 101b, e.g. porous material, by which it is absorbed leading to the expulsion of fluid, e.g. the air, from the pores in the solid sorbent material 101b of the second propulsion pump 1002 into the outlet channel 105b connected to the enclosure 102b of the solid sorbent material 101b. This fluid flow, e.g. air inflow, in said outlet channel 105b subsequently pushes third liquid analyte A3 from its analyte storage channel 812b into the analytical channel 810. The operation of the first propulsion pump 1001 terminates as soon as the solid sorbent material 101a of the first propulsion pump 1001 is saturated with the first liquid analyte Al.

F) Termination of the second propulsion pump 1002: the operation of the second propulsion pump

1002 is similar to the operation of the first propulsion pump 1001, and terminates as soon as either the first liquid analyte Al is absorbed by the solid sorbent of the second propulsion pump 1002, or when the solid sorbent of the second propulsion pump 1002is saturated with the first liquid analyte Al. Figure 11 illustrates a microfluidic system 1100 comprising a suction pump 1102 being activated by a propulsion pump 1101 according to embodiments of the present invention, wherein said propulsion pump 1101 simultaneously acts as a suction pump.

A) Before activation, the microfluidic system 1100 comprises a first, preferably circular sector shaped, solid sorbent 1103 enclosed in a first enclosure 1104. The first enclosure 1104 of solid sorbent 1103 comprises a first opening 1105 and a second opening 1106, wherein said first opening 1105 connects via a first channel 1107 to a first reservoir 1108 having a flexible wall and said second opening 1106 connects via a second channel 1109 to a second reservoir 1110. Said first channel 1107 and first reservoir 1108 comprise a first working liquid 1111, and said first reservoir 1108 connects to a first analytical channel 1112 comprising an inlet opening on which a drop of a first liquid analyte Al may be deposited. Said second reservoir 1110 is further connected to a third channel leading 1114 to a second enclosure 1115 comprising a second solid sorbent 1116, wherein said second enclosure 1115 comprises one or more vent-holes 1117. Said third channel 1114 and second reservoir 1110 comprise a second working liquid 1118. In addition, said second, preferably circular sector shaped, reservoir 1110 is connected to a second analytical channel 11 19, at the inlet opening 1120 of which a drop of a second liquid analyte A2 may be deposited. The first working liquid 1111 and the second working liquid 1118 are fed into said first reservoir 1108 and second reservoir 1110, respectively, via the first filling channel 1121 and second filling channel 1122. The inlet openings 1123, 1124 of the first and second filling channels 1121, 1122 are sealed immediately after filling the channels.

B) Activation of the propulsion/suction pump 1101 : the propulsion/suction pump 1101 is activated by compressing the flexible wall of the first reservoir 1108, thus bringing the first working liquid into contact with the first solid sorbent 1103 and initiating the absorption of the first working liquid 1111 by the first solid sorbet 1103.

C) Operation of the propulsion/suction pump 1101 and activation of the suction pump 1102: as a result of the absorption of the first working liquid 1111 by the first sorbent 1103, the pressure in the first analytical channel 1112 is reduced, and first liquid analyte Al is drawn into this channel 1112. At the same time the first working liquid 1111 expulses the fluid, e.g. the air, contained in the cavities, e.g. pores, of the first solid sorbent 1103 into said second reservoir 1101 via the second channel 1109. The fluid, e.g. air, inflow into said second reservoir 1110 pushes the second working liquid 1118 into the second enclosure 1115 enclosing the second solid sorbent 1116, resulting in the second working liquid 1118 contacting the second solid sorbent 1116 and thus activating the suction pump 1102.

D) Operation of the suction pump 1102 and termination of the propulsion/suction pump 1101 : Upon contact of the second working liquid 1118 with the second solid sorbent 1116, the absorption of the second working liquid 1118 results in a reduction of pressure in the second analystical channel 1119, and second analytical liquid A2 is drawn into the second analytical channel 1119. The action of the propulsion/suction pump 1101 terminates as soon as the first working liquid 1111 is absorbed by the first solid sorbent 1 103 or when the first solid sorbent 1103 is saturated with the first working liquid 1111.

E) Termination of the suction pump 1102: The action of the suction pump 1102 terminates when all second working liquid 1118 is absorbed by the second solid sorbent 1116 or when the second solid sorbent 1116 is saturated with the second working liquid 1118.

Figure 12 illustrates a milli- or micro fluidic system 1200 comprising two propulsion pumps 1201, 1202 according to embodiments of the present invention wherein one propulsion pump 1201 acts as an activating pump for activating the other propulsion pump 1202, and wherein said activating pump 1201 also acts as a suction pump. A) Before activation, the microfluidic system 1200 comprises a first, preferably circular sector shaped, solid sorbent 1203 enclosed in a first enclosure 1204. The first enclosure 1204 of first solid sorbent 1203 comprises a first opening 1205 and a second opening 1206, wherein said first opening 1205 connects via a first channel 1207 to a first reservoir 1208 having a flexible wall, and said second opening 1206 connects via a second channel 1209 to a second reservoir 1210. Said first channel 1207 and first reservoir 1208 comprise a first working liquid 1211 and said first reservoir 1208 connects to an analytical channel 1212 comprising an inlet opening 1213 through which a liquid plug 1214 is introduced, to be present in the vicinity of said inlet opening 1213. Said second reservoir 1210 is further connected to a third channel 1215 leading to a second enclosure 1216 comprising a second, preferably sector shaped, solid sorbent 1217, wherein said second enclosure 1216 comprises one or more vent-holes 1218. Said third channel 1215 and second reservoir 1210 comprise a second working liquid 1219. The second enclosure 1216 enclosing the second solid sorbent 1217 further connects via a fourth channel 1220 with the analytical channel 1212. Said fourth channel 1220 connects with the analytical channel 1212 at a position closer to the inlet 1213 of the analytical channel 1212 than the position of the connection between the analytical channel 1212 and the first reservoir 1208. The first working liquid 1211 and the second working liquid 1219 are fed into said first and second reservoirs 1208, 1210, respectively, via the first and second filling channels 1221 and 1222. The inlet openings 1223, 1224 of the first and second filling channels 1221 and 1222, respectively, and the vent-hole 1218 in the second enclosure 1216 enclosing the second solid sorbent 1217 are sealed, preferably immediately after filling the channels 1207, 1215 and the introduction of the liquid plug 1214.

B) Activation of the first propulsion/suction pump 1201 : the first propulsion/suction pump 1201 is activated by applying pressure to, e.g. by compressing, the flexible wall of the first reservoir 1208, thus bringing the first working liquid 121 1 into contact with the first solid sorbent 1203 and initiating the absorption of the first working liquid 121 lby the first solid sorbent 1203.

C, D) Operation of the propulsion/suction pump 120 land activation of the second propulsion pump 1202: as a result of the absorption of the first working liquid 1211 by the first solid sorbent 1203, the pressure in the analytical channel 1212 is reduced and the liquid plug 1214 is drawn further into this channel 1212. Typically, the micro fluidic system 1200 is designed such that the liquid plug 1214 is not drawn into the analytical channel 1212 beyond the connection 1225 between the analytical channel 1212 and said fourth channel 1220. At the same time, the first working liquid 1211 expulses the fluid, e.g. air, contained in the cavities, e.g. pores, of the first solid sorbent 1203 into said second channel 1209 connected to said second reservoir 1210. The fluid, e.g. air, inflow into said second reservoir 1210 pushes the second working liquid 1219 into the second enclosure 1216 enclosing the second solid sorbent 1217, resulting in the second working liquid 1219 contacting the second solid sorbent 1217 and thus activating the second propulsion pump 1202. E) Operation of the second propulsion pump 1202 and termination of the first propulsion/suction pump 1201 : Upon contact of the second working liquid 1219 with the second solid sorbent 1217, the absorption of the second working liquid 1219 results in an expulsion of fluid, e.g. air, from the cavities, e.g. pores, in the second solid sorbent 1217 via said fourth channel 1220 into the analytical channel 1212. This fluid, e.g. air, flow into the analytical channel 1212 pushes the liquid plug 1214 back towards the inlet opening 1213 of the analytical channel 1212. The action of the propulsion/suction pump 1201 terminates as soon as the first working liquid 1211 is absorbed by the first solid sorbent 1203 or when the first solid sorbent 1203 is saturated with the first working liquid 1211. Preferably, the design of the micro fluidic system 1200 is such that the action of first propulsion/suction pump 1201 terminates upon activation or shortly after activation of the second propulsion pump 1202.

F) Termination of the second propulsion pump 1202: The action of the second propulsion pump 1202 terminates when all second working liquid is absorbed by the second solid sorbent 1217 or when the second solid sorbent 1217 is saturated with the second working liquid 1219.

Figure 13 illustrates an assay system 1300, comprising a suction and propulsion pump combination in accordance with embodiments of the present invention, for example for use in a 3 steps protocol with two reagents mixing and washing steps. The design and parts of the suction and propulsion pumps, and the activation and operation steps of the suction and propulsion pumps, are similar as described above, and are not repeated here in as many details as above. Reference for further details is made to the description hereinabove. A) Initiation: a first working liquid WLl, a second working liquid WL2), a first reagent Rl, a second reagent R2 and washing buffer WB are preloaded in the respective chambers while a droplet of sample S is placed on the inlet of analytical channel AC. In the analytical channel AC, a detection zone DZ (pre-functionalized with receptors) is present to capture the analyte present in the sample S. B) Activation of suction pump 1301 : suction pump 1301 is activated by applying a pressure to a first reservoir 1302 connected via a first channel 1307 to a first enclosure 1303 comprising first solid sorbent PMl . A first working liquid WLl was contained in the first reservoir and the first channel 1307, and applying the pressure to the first reservoir 1302 causes the first working liquid WLl to be absorbed by the first solid sorbent PMl, e.g. porous material, provided in the first enclosure 1303. C) Operation of suction pump 1301 : the absorption of the first working liquid WLl by the first solid sorbent PMl, generates a reduced pressure in the analytical channel AC, which draws the sample S in the analytical channel AC over the detection zone DZ. After that, the operation of the suction pump 1301 is terminated. D) Activation of the propulsion pumps 1304, 1305: Two propulsion pumps 1304, 1305 are connected in parallel, both being connected with their input opening to a same inlet channel 1308, which at its other end is connected to a second reservoir 1306. The second reservoir 1306 and the inlet channel 1308 are filled with a second working liquid WL2, which before activation of the propulsion pumps 1304, 1305 does not reach the second and third solid sorbents PM2, PM3 in the respective propulsion pumps 1304, 1305. The propulsion pumps 1304, 1305 are activated by applying a pressure to a flexible wall of the second reservoir 1306, and the second working liquid WL2 starts getting absorbed by the second and third solid sorbents PM2, PM3, e.g. porous material, of the propulsion pump circuits, respectively. E) The second working liquid WL2 gets absorbed more and more, and pushes out the fluid, e.g. air, present in the cavities of the second and third solid sorbents PM2 and PM3. This fluid, e.g. air, pushes the first and second reagents Rl and R2, present in output channels of the first and second propulsion pumps 1304, 1305, simultaneously into a mixing zone MZ where they mix. At the same time, the washing buffer WB, present in a further channel 1309 between the mixing zone MZ and the detection zone DZ, is pushed over the detection zone DZ, thus replacing the sample S. The propulsion pumps 1304, 1305 continue their action, and while more and more fluid, e.g. air, is pushed out of the cavities in the second and third solid sorbents PM2, PM3, the mixed reagents Rl + R2 are moved from the mixing zone MZ, through the further channel 1309 to the detection zone DZ. F) Termination propulsion pumps 1304, 1305: When the mixed first reagent Rl and second reagent R2 are moved over the detection DZ, the system stops due to complete absorption of the second working liquid WL2 into the second solid sorbent PM2 and into the third solid sorbent PM3 or due to complete saturation of the second solid sorbent PM2 and the third solid sorbent PM3. The exact moment of stopping of the action of the system can be tuned by tuning design parameters of the systems, e.g. dimensions of the solid sorbents and/or the cavities containing these, lengths of channels, etc.

Figure 14 illustrates a detection system for use in a microfluidic bioassay. The illustrated embodiment is based on the capturing of gold nanoparticles 140 functionalized with streptavidin on a surface 141 pre- functionalized with biotinylated antibodies 142, but of course this is an example only, and the invention is not limited thereto but is much broader applicable in other applications as well. In order to generate a signal that can be detected with bare eyes (for qualitative detection, i.e. yes/no) or with a photodiode (for semi-quantitative detection), a silver enhancement 143 was performed. Silver solution (made of mixed reagent 1 and reagent 2) was brought over the detection zone, and catalyzed by the gold nanoparticles 140, it forms an opaque dark layer. For semiquantitative detection, an electrical circuit consisting of a light source such as a LED 144, a photodiode 145 and a microcontroller 146 was used to measure the intensity loss of light due to reflection on the silver layer. Only the light that passes through was picked up by the photodiode 145 and this information was processed by the microcontroller 146, which then displayed the result of the test on an LCD screen 147. So the less light the photodiode 145 received, the darker and thicker the silver layer is, due to higher concentration of gold nanoparticlesl40. The detection system of this figure 14 can for instance be used in the assay system according to example 11 below, wherein the detection zone is coated with biotinylated antibodies 142.

Figure 15 illustrates an assay system 1500 for use in a microfluidic bioassay involving, as an example, a coupled enzyme reaction, which results in a colorimetric product. This assay system 1500 comprises two propulsion pumps 1501, 1502 and means for diluting and mixing a sample within the assay solution. The design and parts of the propulsion pumps, and the activation and operation steps of the propulsion pumps, are similar as described above, and are not repeated here in as many details as above. Reference for further details is made to the description hereinabove. A) Initiation: A reservoir 1504 is connected via an inlet channel 1505 to the input side of two parallel propulsion pumps 1501, 1502. Working liquid WL, first reagent Rl, and second reagent R2 are preloaded in the respective chambers while a sample S is pipetted in a junction zone JZ through an inlet hole 1503 which is subsequently sealed. The reservoir 1504 and the inlet channel 1505 are filled with working liquid WL, such that the working liquid WL does not reach the solid sorbent of the propulsion pumps 1501, 1502. B) Activation: the propulsion pumps 1501, 1502 are activated by applying a pressure to a flexible wall of the reservoir 1504, which brings the working liquid WL into contact with the solid sorbent materials PM1, PM2, e.g. porous materials, in the first and second propulsion pumps 1501, 1502. Once brought into contact, this is followed by the absorption of the working liquid WL by the solid sorbents, e.g. porous materials. C) This absorption of the working liquid WL results into the expulsion of the fluid, e.g. air, present in solid sorbents PM1 and PM2 into the microfluidic chambers comprising the first and second reagents Rl and R2, respectively. The expulsed fluid, e.g. air, drives the first and second reagent Rl and R2 simultaneously into the junction zone JZ where they dilute the sample S previously provided. The diluted sample is further mixed with the first and second reagents Rl and R2 while passing the mixing zone (MZ). E) Termination: When the fluid comprising the combined first reagent Rl, sample S and second reagent R2 fills the detection zone DZ, the pump system stops due to complete absorption of working liquid WL into the solid sorbents PM1 and PM2 of the propulsion pumps 1501, 1502, or due to complete saturation of the solid sorbents PM1 and PM2 with the working liquid WL. Depending of the concentration of the analyte of interest, the enzyme coupled reaction shall generate more or less of a colorimetric product. The presence of the colorimetric product can be measured in the detection zone DZ in any suitable way, for instance using a spectrophotometer. It is preferred that the detection zone DZ has an higher height than the other parts of the network to ensure a sufficient path length for spectrophotometric detection. Figure 16 illustrates a fiber optic surface plasmon resonance sensor integrated with a milli- or microfluidic propulsion pump, according to further embodiments of the present invention.

Figure 16: A) Prior to its activation the propulsion pump 1600 comprises a solid sorbent 101 (porous material) enclosed in an enclosure 102, preferably in the shape of a circle sector. The enclosure 102 is connected to an inlet channel 106 and to an analytical channel AC. The inlet channel 106 is further connected to an inlet reservoir 501 having a flexible wall, wherein the inlet reservoir 501 and the inlet channel 106 contain a working liquid WL. Analyte A is filled through an analyte hole AH in the analytical channel AC before a measurement starts. Once this is done, the analyte hole AH is sealed. A fiber-optic surface plasma resonance (FO-SPR) probe SP is inserted in the analytical channel AC of the propulsion pump, until the sensing part overcomes the outlet channel OC intersection. The FO-SPR sensor setup consists of a white light source, a spectrophotometer, a bifurcated optical fiber and sensor probes. The bifurcated fiber guides white light to the sensor tip where it is reflected back to the spectrometer. The sensor tip is covered with a gold layer. As the light interacts with the surface of the optical fiber, an SPR is generated in this gold layer. A binding event on the outside of the gold layer disturbs prosthesis surface plasmons, changing the resonance conditions and shifts hence the resonance wavelength. This detection principle allows many biochemical interactions to be monitored in real time.

B) Activation: the propulsion pump 1600 is activated by applying a pressure to, e.g. by compressing, the flexible wall of the inlet reservoir 501 connected to the inlet channel 106, thus moving the working liquid WL in the inlet channel 106 so that it contacts the solid sorbent 101 leading to the absorption of the working liquid WL by the solid sorbent 101. C) Operation: while the working liquid WL is absorbed into the solid sorbent 101, it expulses the fluid, for example air, present in the cavities in the solid sorbent 101 into the analytical channel AC. This fluid influx in the analytical channel AC pushes the analyte A further into the channel AC around the probe of the fiber optic surface plasma resonance detector FO-SPR downstream of the analytical channel AC, for being measured. D) Termination: the action of the pump 1600 is terminated either when all the working liquid WL is absorbed into the solid sorbent 101 or when the solid sorbent 101 is saturated by the working liquid WL.

Description EXAMPLES

Example 1: fabrication of a propulsion pump according to the present invention using double- sided pressure sensitive adhesive and filter paper as solid sorbent

Materials and reagents

Double-sided pressure sensitive adhesive (PSA) tape (200MP 7956MP) and adhesive transfer tape (467MP) were acquired from 3M (USA). Two different thickness of PVC transparent foils (180 μιη or 300 μιη) were tested. Filter papers with different pore sizes (0.22 - 13 μιη ) (413, VWR,

Belgium; SSWP, RAWP, HATF, HVLP, GSTF, Merck Millipore, Belgium) were used.

Poly(methyl methacrylate) (PMMA) plate, 2mm thick, was shaped with laser cutter. A digital tabletop craft cutter (Cameo, Silhouette, USA) was used to cut all the PSA, filter paper and PVC foil elements of the microfluidic device. A digital camera (D3200, Nikon, Japan) with a zoom lens

(AF-S DX Zoom-NIKKOR 18-55mm f/3.5-5.6G ED II, Nikon, Japan) was used to video record the experiments.

Device fabrication

The microfluidic device was fabricated according to the low-cost and rapid prototyping method presented in Yuen et al. and Kokalj et al. ¹ ' ⁸ A digital craft cutter was used to obtain the microfluidic channel in the PSA layer. Using this simple, cheap and fast fabrication method, a device with channel width down to 400 μιη was obtained in a reproducible way. Microfluidic channel height was determined by the PSA thickness, in our case 6 mils (around 152 μιη). The PSA layer was sandwiched between a bottom and a top PVC layers, where the top layer was designed with inlet, outlet and vent-holes. Filter paper, shaped with the digital craft cutter, was inserted into the porous material chamber during the fabrication. For specific applications, adhesive transfer tape was used to seal the porous material to the top and bottom PVC layers. For the pressure measuring system of Figure 6 a PMMA plate was attached to the bottom PVC layer to increase the robustness of the device. The four basic elements of a propulsion pump of embodiments of the present invention, were assembled together as shown in Figure 3.

Device prefilling

After the fabrication, the devices were prefilled for an immediate use or long-term storage. The working liquid and the outlet liquid were injected in the respective chambers manually or with a syringe pump (PHD2000, Harvard Apparatus, USA). A Teflon tube was connected to one side of the syringe via HPLC connector (Peak Finger Tight Fitting, Perkin Elmer, Belgium) and to the other side to a custom made PMMA adapter which was pressed onto the injection channel opening for precise filling of the chamber (Figure 4 C,D). Blue and red food color dyes were diluted in distilled water and used respectively as working liquid and outlet liquid in our experiments. During the prefilling step, a vent-hole connected to the porous material chamber was needed to inject the outlet liquid in its channel. In this way, the air present in the outlet channel was replaced by the outlet liquid and expelled through the vent-hole without pushing back the working liquid (Figure 4 E,F). Once the device was prefilled, the vent-hole was closed with a PSA patch (Figure 4 G,H). Example 2: operation of an embodiment of a propulsion pump fabricated according to example 1

The mechanism underlying the operation of the propulsion pump according the previous examples the porous material used as solid sorbents, such as a filter paper have a given wherein the pores are filled with a gas, typically air. If the porous material is placed between the inlet and outlet of a microfluidic system, when a liquid present in the inlet side of the circuit, namely working liquid, gets in contact with the porous material, the working liquid is absorbed. At the same time, it pushes the air out of the porous material into the outlet channel. If the outlet channel is prefilled with an outlet liquid, the latter is pushed by the air towards the outlet of the microfluidic device. Figure 5 provides a step by step illustration of a propulsion pump according the present invention. Example 3: Flow rate of the forward pumped fluid in a propulsion pump system according to Example 2 in relation to the geometry and/or pore size of the filter paper

When it comes to a microfluidic system, one of the most important characteristic to take into account is the flow rate of the liquids that flow through the network. Different methods can be adopted to tune the flow rate, such as changing the channel geometry to increase or decrease the flow resistance or acting on the pumping mechanism. In the latter case for paper microfluidic solutions, it means to change paper type, shape and size. It was shown that flow rate is influenced by paper geometry; for instance, a circular sector with wider angle leads to an higher flow rate than with a more acute angle. Further it was shown that the higher capillary forces associated with smaller pore sizes resulted in an increasing flow rate with decreasing pore size. Within a device setup as shown in Figure 5 (example 2) it was demonstrated using video analyses that the flow rate gradually increased when using filter paper having a pore size of 5-13, 3, 1.2, 0.45, 0.22 μηι, respectively.

Example 4: Testing the pressure generation in a pump according to embodiments of the present invention

Several POC microfluidic applications (i.e. drug delivery, insulin injection) require that a sufficient pressure is generated to overcome the resistance of a barrier, for instance the skin. Currently, microfluidic pumps still require external power supply (up to hundreds of volts) to reach a limited pressure (up to few tens of kPa). Obviously these specifications do not fit the requirements of a POC device.

To show that the propulsion pump according to embodiments of the present invention can reach higher pressure without any external power, the device presented in Figure 6 was developed. The porous material chamber was positioned just after the inlet opening and further connected to the measuring channel where a liquid plug between 0.5 and 1 μΐ, was preloaded. After the activation of the device by adding a drop of working liquid on the inlet opening, the porous material started absorbing the working liquid and the liquid plug was pushed towards the close end of the measuring channel. This caused an increased pressure between the liquid plug and the end of the measuring channel. In this experiment, the filter paper was squeezed between two layers of transfer tape to ensure a proper sealing with the PVC top and bottom layers in the porous material chamber. This extra step in the fabrication process was necessary to prevent that the air would flow back to the inlet opening, due to the increasing pressure in the measuring channel. Moreover, a PMMA plate was connected with an extra layer of PSA to the bottom PVC layer to avoid any deformation of the device due to the pressure increase.

To correlate the displacement from the initial position of the liquid plug to the change of pressure in the measuring channel, the Boyle law was applied:

Using this theoretical model and the video recorded sequences of the operation, the pressure increment was measured with an high accuracy (few percent error). The trend of the pressure as a function of time is presented in Figure 7.

As depicted in Figure 7, an increase of 65.3 kPa above the atmospheric pressure was achieved in 24 minutes, and kept constant for another 3 minutes after pump termination. This value is higher or at least comparable to all the microfluidic pumps presented in literature, with the substantial difference that our approach is completely self-powered. Example 5: A microfluidic system comprising a suction pump and a propulsion pump according to the present invention

The microfluidic system was prepared using PVC foils, filter paper and a PSA layer as explained in Example 1. The Microfluidic system comprises a propulsion pump according to embodiments of the present invention having a wing-shaped solid sorbent (filter paper) operably connected to a suction pump wherein said suction pump serves as an activation means for said propulsion pump. Before its activation (Figure 8A), the microfluidic system comprises a SIMPLE ¹ suction pump comprising an enclosed filter paper PM1 in the shape of a circle sector. The enclosure of said filter paper comprises several vent-holes and an opening, which connects via a channel to a reservoir having a flexible wall. Said channel and reservoir comprise a working liquid and are operably connected to the propulsion pump via a channel comprising an analyte inlet (analytical zone). A droplet of a first liquid analyte Al is placed on the inlet of the analytical channel. The enclosure of the wing-shaped filter paper PM2 of the propulsion pump comprises a first opening connecting said enclosure to the analytical channel and a second opening connecting to an outlet channel. In turn the outlet channel is connected to an analyte storage channel, which connects to the analytical channel. The analyte storage channel is preloaded with a second liquid analyte A2.

The suction pump is activated by compressing the reservoir comprising the working liquid (Figure 8B), such that the working liquid is brought into contact with the filter paper PM1 initiating the absorption of the working liquid by the filter paper PM 1.

After activation of the suction pump (SIMPLE), the absorption of the working liquid by the filter paper PM1 results in a reduced pressure in the analytical channel whereby the droplet of the first liquid analyte Al is drawn into in the analytical channel.

When the first liquid analyte Al contacts the enclosed wing-shaped filter paper PM2 of the propulsion pump, it is absorbed and expulses the air from the filter paper pores into the outlet channel. This inflow of the air in the outlet channel pushes the second liquid analyte A2 from the analyte storage channel into the analytical channel. The action of the suction pump terminates when all working liquid is absorbed into the filter paper PM1 or when the filter paper PM1 is saturated by the working liquid.

The operation of the propulsion pump according to embodiments of the present invention terminates either when all first liquid analyte Al is absorbed into the wing-shaped filter paper PM2 or when the wing-shaped filter paper PM2 is saturated by the first liquid analyte Al.

Example 6: A microfluidic system comprising a suction pump simultaneously activating propulsion pumps according to the present invention

A microfluidic system was prepared according to the general scheme of Figure 9 using the material and methods of Example 1. Example 7: A microfluidic system comprising a suction pump sequentially activating propulsion pump according to the present invention

A microfluidic system was prepared according to the general scheme of figure 10 using the material and methods of Example 1. Example 8: A microfluidic system comprising a suction pump being activated by a propulsion pump according to the present invention wherein said activating pump simultaneously acts as a suction pump

A microfluidic system was prepared according to the general scheme of Figure 11 using the material and methods of Example 1. Example 10: Microfluidic system comprising two propulsion pumps according to the present invention wherein one propulsion pump activates the other and wherein said activating pump also acts as a suction pump.

A microfluidic system was prepared according to the general scheme of Figure 12 using the material and methods of Example 1. Example 11: Microfluidic assay system comprising two propulsion pumps according to the present invention combined with a suction pump.

A microfluidic assay system was prepared according to the general scheme of Figure 13 using the material and methods of Example 1.

In a specific embodiment the microfluidic assay system of this Example 11 involves a detection system comprising silver enhancement of captured gold coated nanoparticles as previously described. The reference DZ, S, WB, Rl, R2, WB, MZ as used below refer to the corresponding items in Figure 13. The goal of this bioassay is to capture gold nanoparticles (AuNPs) functionalized with streptavidin contained in a sample (S) on a surface (detection zone, DZ) pre- functionalized with biotinylated antibodies. In order to generate a signal that can be detected with bare eyes (for qualitative detection, i.e. yes/no) or with a photodiode (for semi-quantitative detection), a silver enhancement was performed. Silver solution (made of mixed reagent 1 (Rl) and reagent 2 (R2)) is brought over the detection zone (DZ), and catalyzed by the AuNPs, it forms an opaque dark layer. For semi-quantitative detection, an electrical circuit consisting of a LED, a photodiode and a microcontroller is used (Figure 14) to measure the intensity loss of LED light due to reflection of the silver layer. Only the light that pass through was picked up by a photodiode and this information was processed by the microcontroller, which then displayed the result of the test on an LCD screen. So the less light the photodiode receive, the darker and thicker the silver layer is, due to higher concentration of AuNPs. The immobilisation of biotinylated hlgE antibodies on the PMMA bottom plate within the detection zone (DZ) was done by physisorption. Concentration of streptavidin- AuNPs was optimized and 1 :20 dilutions from stock concentration was used to maximize signal generation avoiding at the same time clustering of nanoparticles. The silver enhancement protocol was adapted from Hacker et al. (1988). The Reagent 1 (Rl) (100 mg of silver acetate in 25ml water) and Reagent 2 (R2) (125 mg of hydroquinone in 25ml citrate buffer pH 3.8) cannot be premixed before the incubation in the detection zone and for this reason they were separately prefilled in the respective chambers (Rl, R2). A washing step was performed between the Strep-AuNPs incubation (15 minutes) and the Silver mix incubation (30 minutes), by pumping a washing buffer (WB) that was prefilled in the mixing zone (MZ) of the microfluidic assay system, to remove unbounded AuNPs from the detection zone.

Example 11: Microfluidic assay system comprising two propulsion pumps according to the present invention combined with a suction pump.

A microfluidic assay system was prepared according to the general scheme of Figure 15 using the material and methods of Example 1 and as further specified in the legend to Figure 15.

In this specific example, the goal was to detect the presence of creatinine in plasma with an enzymatic reaction and a spectrophotometric readout. More particularly a plasma sample S comprising spiked creatinine was mixed with reagents (Rl and R2) during the microfluidic assay procedure. Both Rl and R2 comprise a creatinine probe, creatinase, creatininase and creatinine enzyme mix as available in the Sigma Aldrich creatinine assay kit (Catalog number: MAK080). The sample S was diluted in the reagents Rl and R2 in a 1 :8 ratio and was subsequently mixed with said reagents by passage through the mixing zone MZ. In a specific embodiment 5 μΐ of S was diluted in and mixed with 17.5 μΐ of both Rl and R2. The height of the detection zone DZ of a microfluidic device according to this example is preferably higher than that of the other parts of the microfluidic system, for instance through the use of multiple stacked layers of double side tape, in order to obtain an increased path length facilitating spectrophotometric detection. In a particular embodiment the microfluidic network other than the DZ had a height of 254 μηι, while the height of detection zone was 508 μιη. Preferably both the top and bottom layer enclosing the detection zone are transparent or translucent.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The foregoing description details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the invention may be practiced in many ways. The invention is not limited to the disclosed embodiments.

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