Modern chemical engineering has a tendency to use very small reactors. These reactors are often of submillimeter size and are sometimes constructed on silicon chips using the same technology used to fabricate microelectronic or VLSI circuits. It can be appreciated that the output rate of reaction products from a single microreactor is very small. Therefore, to achieve a required productivity level, a large number of such microreactors may be operated simultaneously.

One of the advantages of the small size of the microreactors is the capability to control precisely the process conditions under which the reaction takes place.

This capability follows as a consequence of the effective and fast response of the microreactors to control actions. It is often possible to have a controller resident on the same chip as the microreactor. The typical parameters that can be controlled in such a microreactor include the temperature or pressure in the reactor and the product composition.

A product composition analyser can be used to monitor the operation of a reactor. When operating or testing, for example, a catalytic process, a product composition analyser is typically connected to the output of the microreactor. It can be appreciated that the

analyser must be appropriate to or configured for the reaction product produced by the catalytic process under test. It is clearly not a cost effective option, in circumstances where more than one chemical reactor is being monitored, to have one analyser per reactor.

Whenever the variations in the processes are sufficiently slow, that is, the processes do not vary significantly during a sampling cycle, a single analyser may be used to monitor a number of reactors.

Ehrfeld W. (Ed) :"Microreaction Technology : Industrial Prospects", Springer, Berlin 2000, ISBN 3-540- 66964-7 discloses multiplexers that are suitable for taking fluid samples from mini-reactors and supplying them to a product composition analyser. These known multiplexers operate using moving components. Therefore, they are large, that is, cannot be fabricated on a chip, require external mechanical drives, are prone to malfunctions, that is, breakage and/or seizure of the moved or flexed parts, and are not suitable for high temperature applications.

It is an object of the present invention to at least mitigate some of the problems of the prior art.

Accordingly, a first aspect of the present invention provides a fluidic multiplexer for supplying to a common outlet channel one fluid selected from at least a first fluid channel and a second fluid channel each for carrying respective first and second fluid flows; the multiplexer comprising a first fluidic valve to prevent to flow of the first fluid from the first fluid channel to the common outlet channel in response to flow of first

control fluid from a first control inlet; and a second fluidic valve to prevent the flow of the second fluid from the second fluid channel to the common outlet channel in response to flow of a second control fluid from a second control inlet.

Advantageously, the first and second fluids represent, in a preferred embodiment, the reaction products of respective chemical reactors. These reaction products can be selectably directed to a common outlet channel under the control of the fluidic valves. The output of the common outlet channel will be either the first fluid or the second fluid according to whether the first or second fluidic valve has been actuated to prevent the flow of the first and second fluids respectively.

It can be appreciated that a single analyser can be used to sample reaction products of the two chemical processes occurring in the microreactors that are used to feed the first fluid channel and the second fluid channel respectively. Further, the use of a single analyser finds particular application in chemical processes that vary slowly as compared to the time required for the analyser to cycle through all chemical processes.

Fluidic valves that operate by preventing or restricting the flow of a reaction product out of a corresponding supply nozzle may adversely affect the process conditions in a reactor by, for example, reducing the flow rate of reactants or reaction product through the reactor or by varying the temperature or pressure in the reactor. It can be appreciated that such changes in

a catalytic process can be disadvantageous.

Accordingly, an embodiment of the present invention provides a fluidic multiplexer in which the first fluidic valve comprises a first vent arranged to allow flow of the first fluid through the first vent in response to the first control fluid preventing the flow of the first fluid to the common outlet channel.

A further embodiment of the present invention provides a fluidic multiplexer in which the second fluidic valve comprises a second vent arranged to allow flow of the second fluid through the second vent in response to the second control fluid preventing the flow of the second fluid into the common outlet channel.

Advantageously, the fluid flow in the first and second fluid channels can be arranged to be continuous even though the first and/or second fluidic valves has/have been actuated to prevent corresponding fluid flow to the common outlet channel. This ensures that the reactor conditions or chemical process conditions remain substantially constant, that is, the flow rate, amongst other things, through a reactor may be maintained at a given value rather than there being a temporary cessation during sampling of another reaction product carried in another fluid channel.

A further embodiment of the present invention provides a fluidic multiplexer arranged to control selectably the flow of first and second fluids into a common outlet channel using first and second fluidic valves, the first fluidic valve having a first inlet to

supply the first fluid to a first outlet channel and a first control inlet to prevent flow of the first fluid to the first outlet channel; the second fluidic valve having a second inlet to supply the second fluid to a second outlet channel and a second control inlet to prevent flow of the second fluid to the second outlet channel; the first and second outlet channels being arranged to feed the common outlet channel.

Often the process conditions within a reactor and in relation to a reaction product are unsuitable for an analyser, which can be a relatively expensive and delicate item of equipment. For example, the pressure of a reaction product may be incompatible with the operating conditions of an analyser.

Accordingly, an embodiment of the present invention provides a fluidic multiplexer comprising a pressure regulator to establish, in use, a predeterminable pressure in the common outlet channel.

Advantageously, the predeterminable pressure can be set to a pressure value that is acceptable to the analyser notwithstanding the pressures required by the chemical process under test.

A still further embodiment of the present invention provides a fluidic multiplexer further comprising a pressure regulator for changing the pressure of at least one of either the first and second fluids from respective first and second pressures to a selectable pressure prior to feeding the common outlet channel.

A further advantage of the embodiments of the present invention is that fluid sampling can be undertaken without using any moving components.

Therefore, the fluid multiplexer is capable of operating under adverse conditions such as high temperature and/or in an aggressive fluid chemical environment under which corresponding electromechanical fluid valves would fail.

Still further the operation of the valve is not adversely effected by mechanical acceleration, and/or vibration.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which : figure 1 shows schematically a fluidic multiplexer; figure 2 illustrates an embodiment of a fluidic valve for use in the multiplexer shown in figure 1; figure 3 illustrates a further embodiment of a fluidic valve that can be used in the multiplexer shown in figure 1; figure 4 illustrates a still further embodiment of a fluidic valve that can be used in the multiplexer shown in figure 1 ; figure 5 illustrates an embodiment of a fluidic multiplexer that uses a fluidic valve as shown in figure 3; figure 6 illustrates an embodiment of a multiplexer that uses fluidic valves as shown in figure 4; and figure 7 illustrates a further embodiment of a multiplexer that uses fluidic valves as shown in figure 4.

Referring to figure 1 there is shown schematically a fluidic multiplexer 100 for directing a plurality of

fluids 102 to 110 to a common outlet channel 112 using a plurality of fluidic valves 114 to 122 which can be selectively actuated to prevent or allow flow of a corresponding one of the plurality of fluids 102 to 110.

Optionally, each channel for carrying the plurality of fluids 102 to 110 is interrupted by a gap which forms a corresponding vent 124 to 132 that is arranged to maintain the fluid flow 102 to 110 of the plurality of fluids 102 to 110 even upon actuation of at least one of the fluidic valves 114 to 122. In the absence of such vents, the fluid flows 102 to 110 would have to be terminated.

In the schematic embodiment shown in figure 1, there are only five inlets 134 to 142 for receiving, for example, corresponding reaction products, that is, the plurality of fluid flows 102 to 110. However it will be appreciated that the present invention is not limited thereto and, in practice, a significantly greater number of reaction product flows can be provided.

Each of the fluidic valves 114 to 122 is actuated by a corresponding flow of fluid, that is, a corresponding flow of control fluid 144 to 152. Each fluidic valve 114 to 122 comprises a respective control nozzle 154 to 162.

The dimensions of each of the channels and control nozzles 154 to 162 are arranged, taking into account the velocities of the control fluids 144 to 152 and the reaction products 102 to 110 and the viscosities of the control fluids 144 to 152 and the reaction products 102 to 110, to result in extremely low respective Reynolds numbers such that the presence of a control fluid 144 to 152 in the path of a reaction product flow 102 to 110 can be, in some embodiments, sufficient to stop or at least

reduce that reaction product flow 102 to 110.

Preferably, the Reynolds numbers are less than 100 and more preferably less than 40.

An embodiment is provided in which such a blocking effect is achieved by ensuring the viscosities of the control fluids 144 to 152 are greater than the viscosities of the reaction products 102 to 110.

Alternatively, the control fluids 144 to 152 and the reaction products 102 to 110 can be arranged to be mutually immiscible. Still further, an embodiment is provided in which the control fluid is a liquid and the reaction product is a gas. In such a situation the control fluid is strongly held in position by the action of surface tension and viscous forces.

It can be appreciated from figure 1 that the fourth fluid flow 108 is the fluid that is coupled to the common outlet channel 112 while the remaining reaction product flows 102,104,106 and 110 are vented via the corresponding vents 124,126,128 and 132 to a common vent 164 in response to actuation of fluidic valves 114, 116,118 and 122. Accordingly, only the reaction product of the fourth channel is coupled to the common outlet channel for sampling by an analyser.

Referring to figure 2, there is shown, according to an embodiment, a fluidic valve 200 for controlling the flow of reaction product 102 to the common outlet channel 112. It can be appreciated from figure 2 that the fluidic valve 200 is shown in a closed state. The embodiment shown in figure 2 can be manufactured by etching substantially planar material to an appropriate depth. It can be appreciated from figure 2 that since the fluidic valve 200 is in a closed state the reaction

product 102 will continue to flow via the channels 202 and 204 that form part of the vent rather than flowing into the outlet channel.

The action of the control fluid in preventing the flow of the reaction product 102 shown in figure 2 can be accomplished by ensuring the control fluid 114 is a very viscous liquid and, preferably, immiscible with fluids to be sampled, that is, the reaction product flows. If the above conditions are satisfied, only a small amount of control fluid needs to be introduced into the path of a reaction product flow. However, if the control fluid and the reaction products are miscible and the control fluid cannot be expected to be held in or to maintain a stationary position by the action of viscosity or under surface tension, it will be appreciated that some of the control fluid may be carried into the common outlet channel 112. It will also be appreciated that, under such circumstances, the flow of some of the control fluid into the common outlet channel 112 may also take place during initial closure of the fluidic valve 114. During the initial stages, that is, during partial closure of the fluidic valve 200, a small amount of the control fluid emerging from a corresponding nozzle into the relatively strong full flow of the reaction product 102 will result in a small amount of that control fluid being carried into the common outlet channel 112. It is only after delivery of a sufficient volume of control fluid 148 into the path of the reaction product 102 that the fluidic valve will close and prevent the flow of the reaction product 102 into the common outlet channel.

While, under some circumstances, the flow of the control fluid into the common outlet channel may be acceptable, under other circumstances such flow may not

be acceptable. Therefore, an embodiment is provided in which the control fluid is selected so that an analyser connected to the common outlet channel 112 does not generate a corresponding signal in response to the presence of such a control fluid.

Still further, under certain circumstances, the flow of the control fluid into the analyser may represent a relatively large volume of the sample taken by the analyser and accordingly decrease, by way of dilution of the sample, the effectiveness of the analysis, that is, the analyser will have a product concentration threshold below which a reaction product cannot be reliably analysed. Therefore, an embodiment provides a fluidic valve 114 in which the flow of control fluid is arranged to have a greater component opposing the direction of flow of the reaction product as compared to the component in the direction of flow of the reaction product.

Referring to figure 3 there is shown an embodiment of a fluidic valve for achieving this aim. In the embodiment shown it can be seen that figure 3 provides a first channel 302 for carrying a reaction product 102. The first channel comprises a first nozzle 304 for directing the reaction product 102 towards a first outlet 306 that is arranged to feed a common outlet channel 112 via a pair of symmetrically shaped conduits 308 and 310. There is also provided a control nozzle 154 that is arranged to produce a flow of control fluid 312 which opposes the flow of reaction product through the first outlet channel 306. It can be appreciated that under certain circumstances the control fluid may extend into a vented cavity 124. The control nozzle is contained within the first outlet channel that leads the common outlet channel in the embodiment shown. This arrangement reduces the extent of any backflow 314 of control fluid into the

outlet channel during valve actuation or operation.

It can be appreciated that the embodiment shown in figure 3 may be manufactured by CVD and etching as appropriate.

Referring to figure 4 there is shown a further embodiment of a fluidic valve 400 for achieving a more effective suppression of flow of the control fluid into the first outlet channel 402. It can be appreciated that the direction of flow of the reaction product and the control fluid are mutually opposite, and the control nozzle is inclined relative to the first outlet channel.

The first outlet channel 402, as with the above embodiments, is arranged to feed the common outlet channel 112. The embodiment shown in figure 4 has the advantage that there does not result an island of etched material, such as island 316 shown in figure 3, which would lead to manufacturing complications if the valve structures from which the valves are constructed were deposited on a suitable substrate after etching rather than prior to etching. It can be appreciated from figure 4 that at relatively high Reynolds numbers such as, for example, 200, the jet or relatively fast flowing stream of control fluid would prevent the formation of a flow of the control fluid into the common outlet and, preferably, generate a suction effect which would draw the fluid contained within the first outlet channel 402 in a direction which opposes the flow of supply fluid towards the common outlet channel 112.

Referring to figure 5 it can be seen there is disclosed a parallel arrangement of first and second channels 502 and 504 for carrying respective reaction products. The first and second channel 502 and 504 are

directed towards respective outlet channels 506 and 508 that are arranged to feed a common outlet channel 510.

The control nozzles 512 and 514 are arranged to direct respective control fluids such that they oppose the flow of reaction products flowing via the first and second inlet nozzles 516 and 518. It can be appreciated that the first and second inlet nozzles are substantially wider than the corresponding inlets 520 and 522 of the outlet channels and the control nozzles 512 and 514.

There is also provided, in the embodiment shown in figure 5, a common vent 524.

Referring to figure 6 there is shown an embodiment of the present invention in which each of a number of fluidic valves 602 to 608 controls the flow of a respective reaction product 610 to 616 using respective control fluids 618 to 624 fed via control fluid nozzles 626 to 632. The embodiment is arranged to control the flow of reaction products 610 to 616 into corresponding outlet channels 634 to 640. It can be seen from figure 6 that pairs of outlet channels of the fluidic valves, that is, outlet channels 634 and 636 and outlet channels 638 and 640, merge into first 642 and second 644 common outlet channels. The first 642 and second 644 common outlet channels also merge to form an overall common outlet channel 646. The merging pairs of outlet channels have the advantage that they at least reduce or prevent the loss of a fluid sample currently under investigation via backflow into the channel of a fluid that is not current under investigation. The same applies to corresponding features of figure 7.

It can be seen from figure 6 that each fluidic valve 602 to 608 has a vent 648 to 654. Each vent 648 to 654 has a corresponding opening 656 to 662 which is formed in

an overlaying, vertically disposed, plate or larger having respective holes 656 to 662 etched therein.

It can be appreciated that an alternative embodiment to that shown in figure 6 is one in which, rather than having separate respective vents 648 to 654, at least two of the vents can be combined into a common vent. A still further embodiment is envisaged in which all of the vents 640 to 654 are combined into a single vent as shown in figure 7 at 700.

Models tested in the laboratory used Syngas as a supply fluid at a temperature of 400°C and a viscosity of 50 x 10-6 m2/s. The velocity of the supply fluid at the nozzle exit was 5 m/s. The laboratory models had the following dimensions: supply nozzle width 0.34 mm, control nozzle width 0.24 mm and the nozzle depths were 0.15 mm. The gap between the supply nozzle exit and the output channel entrance was 1.14 mm. However, it will be appreciated in actual microfluidic applications, the dimensions will be smaller. Typically, the dimensions may be three to five times smaller.

It can be appreciated that, due to the very low Reynolds numbers used in some or all of the embodiments of the present invention, the mere presence of a blockage or control fluid can be sufficient to close a valve since, in those embodiments, no use of fluid inertia is made to close the valve as in the prior art. The extremely low Reynolds numbers are such that the inertial effects are quickly damped or countered by fluid viscosity. Typically, the Reynolds numbers of the fluid flows of the embodiments of the present invention will be less than 100 and in some instances can be less than 40.

Embodiments of the present invention utilise a 0.34 mm nozzle width. Each value occupies about a 5 mm x 5mm area. A complete fluidic multiplexer occupies a 80 mm x 15 mm area. The depths of the channels of the above embodiments are 0.1016 mm.

It can be seen that the above embodiments have been described within a catalysis context, that is, within the context of controlling the flow of reaction products.

However, it will be appreciated that the present invention is not limited thereto. Embodiments can be realised in which the fluids flows that are controlled are fluids other than reaction products.

The magnitudes of the fluid flows of conventional fluidic valves are such that the supply fluid flow is significantly greater than the control fluid flow.

However, the embodiments of the present can equally well use fluid flow magnitudes in which the control fluid flow is at least equal to or significantly greater than the supply fluid flow. In some embodiments that control fluid flow may be at least 10 times greater than the supply fluid flow.

In applications such as, for example, high throughput catalysis testing, the range of volumes flows for the above embodiments may be between 10 cubic centimetres per minute and 30 cubic centimetres per minute, which corresponds to 60.10-6 kg/s to 180.10-6 kg/s.

The above volume flow rate limits were imposed, in practical realisations, by the operating parameters of the infrared analyser used to undertake the testing and do not reflect any hydrodynamic limitations of the above embodiments. It will be appreciated that the

hydrodynamic limitations are determined from the Reynolds number, Re, by Re.h.# M [kg/s] = v where v= fluid viscosity v= fluid specific volume; and h= the cavity depths in metres.

At one end of the spectrum, the skilled man could envisage the flow of a gas at # = 10. 10-6 m2/s, v= 0.5 m3/kg at an Re = 1 in a microchannel for which the nozzle depth is 5pm, which give a value of M=100. 10-2 kg/s. However, it will be appreciated that the other end of the spectrum may have the following prevailing conditions #=10.10-6 mils, v= 10.10-3 m3/kg at an Re = 1000 in a microchannel for which the nozzle depth is 2mm, which give a value of M=20. 10-3 kg/s.

Furthermore, in the above embodiments it is envisaged that the control flow could be between 0.1 and 5 times that of the supply flow.