FIELD OF THE INVENTION

This invention relates to needle-free systems for drawing blood, for example for testing or analysis. BACKGROUND OF THE INVENTION

Presently, there are various devices and methods for drawing blood samples from patients that are commercially available. For example, regular measurement of blood glucose levels is necessary for monitoring the body's ability to metabolize glucose, particularly when it comes to diabetes management.

A typical blood sample collection apparatus usually involves a syringe comprising a hypodermic needle, a plunger, and a cylindrical barrel. When the needle punctures the skin, a suction force is generated as the plunger is pulled by the operator. Blood is then drawn by the suction force into the cylindrical barrel through a nozzle connected to the hypodermic needle. A blood lancet is another device that can be used for drawing a small amount of blood for diagnostic tests. A blood lancet includes a needle that is punctured into the ball of the finger, and a small amount of blood is allowed to freely drop onto a sample holder, such as a glass slide.

However, the applicability of these blood drawing devices are limited because they are usually not reusable, which could make the products expensive because one will need to buy multiples of them repeatedly in those cases where constant monitoring is necessary. Importantly, this traditional blood drawing apparatus requires the use of a needle, which most patients would rather avoid if possible.

US 2015/0342509 discloses a system for needle-free drawing of blood. The device comprises a negative-pressure barrel with a membrane sealing an outlet aperture which is adapted to be placed in contact with the dermal tissue. The negative-pressure barrel defines a chamber. The device also includes an accelerator barrel positioned within the negative-pressure barrel chamber, with an open end aligned with the aperture. The chamber is filled with pressurized gas, and a particle positioned within the accelerator barrel is accelerated by an abrupt gas surge initiated by releasing a trigger valve. The particle thus attains enough momentum to pierce the aperture membrane and penetrates the adjacent dermal tissue. As a result, a micro-emergence of blood can be drawn into the negative- pressure barrel.

There is limited control of the blood drawing phase, in that it simply relies on a pressure difference between the outside and the inside of the chamber. It also has limited control of the pressurizing phase. Furthermore, to provide a sterile solution, a single use device is proposed, which may be price prohibitive.

There is therefore a need for a needle-free blood drawing apparatus which enables sterile use but with efficient reuse of components.

SUMMARY OF THE INVENTION

The invention is defined by the claims.

According to examples in accordance with an aspect of the invention, there is provided a pressurizing apparatus for a system for needle-free drawing of blood, comprising:

a pressurizing chamber having a release opening on a distal side; a piston arranged to reciprocate in the pressurizing chamber;

an electrically-controlled actuator coupled to the piston for controlling a reciprocating motion of the piston;

a coupling interface for removably coupling the apparatus to a blood collection cartridge; and

a controller,

wherein the controller is adapted to control the piston to increase the pressure in the pressurizing chamber during a skin piercing mode, and to reduce the pressure in the pressurizing chamber during a blood drawing mode.

This pressurizing chamber is removably connectable to a blood collection cartridge so that it can be reused. By using an electrically driven piston to control the pressurizing and depressurizing stages, the skin piercing mode and the blood collection mode can be controlled accurately to provide optimum performance.

The electrically-controlled actuator may comprise an electromagnetic drive mechanism.

It may be driven with short duration and high intensity for the skin piercing mode. A lower intensity longer duration drive may be used for the blood collection mode.

The electromagnetic drive mechanism for example comprises a drive coil, wherein a first current is driven through the drive coil in a first direction for the skin piercing mode, and a second current is driven through the drive coil in a second, opposite, direction for the blood drawing mode.

The coupling interface for example includes a puncturable membrane over the release opening. This prevents contamination of the air which will be driven from the pressurizing apparatus.

The coupling interface may comprise a pin and/or hole arrangement to ensure the removable coupling is only possible to a suitably designed blood collection cartridge. This provides added security.

The coupling interface may comprise one-way valves allowing flow into the pressurizing chamber. These valves open during the depressurizing stage, used to draw blood based on a negative relative pressure.

The invention also provides a system for needle-free drawing of blood comprising:

a pressurizing apparatus as defined above; and

a blood collection cartridge.

The blood collection cartridge for example comprises:

an outer housing;

an accelerator barrel having a proximal opening and a distal opening;

an inlet opening to the accelerator barrel;

a cartridge coupling interface for removably coupling the cartridge to a pressurizing apparatus having a release opening, such that the proximal opening is coupled to the release opening when the cartridge is coupled to the pressurizing apparatus; and

a particle located in the accelerator barrel, wherein the accelerator barrel is adapted to pass pressurized gas from the pressurizing apparatus thereby to propel the particle towards the distal opening.

This cartridge can be a single-use device, but does not need any expensive components, since these can all be housed in the pressurizing apparatus to which the cartridge connects.

The cartridge is preferably shaped so that blood does not reach the

pressurizing apparatus, which is reusable.

The outer housing may comprise a puncturable membrane aligned with the accelerator barrel beyond the distal opening. This maintains a clean environment in the cartridge until it is used. The cartridge coupling interface may comprise a pin and/or hole arrangement to ensure the removable coupling is only possible to a suitably designed pressurizing apparatus.

The outer housing may have a hydrophilic portion at its distal end, and optionally also a hydrophobic portion at its proximal end. This ensures that collected blood remains within the cartridge remote from the pressurizing apparatus, which may be reused (with a new membrane applied).

A closure cap may be provided for mounting over the cartridge coupling interface. This means the cartridge may be used as a storage vessel after the blood sampling procedure.

The cartridge may further comprise a blood analysis device within the outer housing. This enables immediate analysis to be performed.

The outer housing may include at least a transparent window. This enables optical analysis of the collected sample, without removing the sample from the cartridge.

Examples in accordance with another aspect of the invention provide a needle- free blood sampling method comprising:

using an electrically-controlled actuator to drive a piston of a pressurizing apparatus towards a release opening on a distal side thereby pressurizing a pressurizing chamber during a skin piercing mode;

puncturing a first puncturable membrane using a gas flow resulting from the pressurizing;

using the gas flow to drive a particle along an accelerator barrel within a cartridge which is coupled to the pressurizing chamber towards a distal opening of the accelerator barrel, through a second puncturable membrane and into the skin;

using the electrically-controlled actuator to drive the piston of the pressurizing apparatus away from the release opening thereby depressurizing a pressurizing chamber during a blood drawing mode, thereby drawing blood into the cartridge.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention will now be described in detail with reference to the accompanying drawings, in which:

Figure 1 is an example device for a needle-free blood drawing system; Figure 2 is a schematic block diagram of a needle-free blood drawing device with removable cartridge;

Figure 3 is a more detailed representation of an example of a needle-free blood drawing device with removable cartridge;

Figure 4 illustrates a locking mechanism for a needle-free blood drawing device with removable cartridge;

Figure 5 illustrates a needle-free blood drawing device with removable cartridge in a particle shooting phase;

Figure 6 illustrates a needle-free blood drawing device with removable cartridge in a blood drawing phase;

Figure 7 illustrates a cartridge with a removable cap; and

Figure 8 is a flowchart illustrating an example method of blood drawing using a needle-free blood drawing device with removable cartridge.

DETAILED DESCRIPTION

The invention provides a system for needle-free drawing of blood. The system combines a cartridge and a pressurizing apparatus coupled together at a releasable coupling interface. The pressurizing apparatus has an electrically actuated piston arranged to reciprocate in a pressurizing chamber. The pressure in the pressurizing chamber is increased during a skin piercing mode, and is reduced during a blood drawing mode. The cartridge has an accelerator barrel coupled to the pressurizing apparatus. The accelerator barrel passes pressurized gas from the pressurizing apparatus thereby to propel a particle towards the distal opening and then to pierce the skin, following which a blood sample is collected. The invention provides the cartridge, the pressurizing apparatus and the system, as well as a blood sample collection method.

The following are definitions of terms as used in the various embodiments of the present invention.

The terms "proximal" and "distal" as used herein refer to the upstream and downstream side of the needle-free blood drawing device, respectively. These terminologies also indicate the direction of both the piston, fluid, or particle motion. As used herein, "fluid" refers to a liquid or gas.

The term "reciprocate" as used herein refers to an up-and-down or back-and- forth motion of the piston inside the pressurizing apparatus. The term "micro-emergence" as used herein refers to the appearance of a small volume, preferably in microliters (μί), of blood or blood and interstitial fluid, resulting from the piercing of the skin.

Figure 1 shows an example of a needle-free blood drawing system with a removable cartridge. The device 100, preferably handheld, may be operated by a medical personnel or a patient. The device 100 is shown in simplified form for illustrating the form and dimensions of the needle-free blood drawing system. The cylindrical form of the device 100 is illustrated as a representative shape. Also, in terms of size, the device 100 is presented relative to the patient's arm 110. As shown in Figure 1, the device 100 comprises a pressurizing apparatus 106, cartridge 102, aperture 104 and a power button 108.

Figure 2 is a block diagram of the needle-free blood drawing device 200 with removable cartridge 204. Note that the sizes of the components and their relative sizes are not necessarily shown to scale.

During operation, the distal end of the removable cartridge 204 is positioned against the skin 208 of a subject from whom a blood sample is to be taken. As Figure 2 shows, the device 200 has an elongated form and comprises a proximal and a distal side. In addition, the orientation of the components is presented with respect to the proximal and distal sides of the device 200 and with respect to each other. The device 200 comprises a pressurizing apparatus 202 at the proximal side (the upper component) and a cartridge 204 at the distal side (the lower component). The pressurizing apparatus 202 and cartridge 204 are connected by coupling elements and are separable such that a new cartridge may be used with the same pressurizing apparatus 202. The pressurizing apparatus 202 comprises a pressurizing chamber 224 (labeled "C"), a piston 226 (labeled "P"), and an electrically- controlled actuator 228 (labeled "A").

As shown in Figure 2, the cartridge 204 comprises a chamber 206, an aperture

212 and a cavity forming member 216 which is positioned longitudinally within the cartridge 204. The cavity forming member 216 defines an accelerator barrel 214 running along its length. The accelerator barrel 214 includes an inlet opening 220 at its proximal end. In addition, the pressurizing chamber 224 is connected to the inlet opening 220 through a puncturable membrane 222. A particle 218 is initially placed near the proximal end of the accelerator barrel 214 at a launch position within the accelerator barrel 214 of the cavity forming member 216. The particle 218 is accelerated by the high pressure gas from the particle's proximal side towards the distal end of the removable cartridge 204, which comprises a membrane 210 which covers the aperture 212. The cartridge and pressurizing apparatus are aligned simply by using a cylindrical design with the aligned openings in the center. Fastening of the cartridge onto the pressurizing apparatus can be obtained be friction, a screw mechanism or any type of locking mechanism. A safety mechanism may additionally be used so that there is no triggering unless a valid cartridge is present. This could be a simple mechanical switch which, unless pressed by a mounted cartridge, would disable the electrical circuit for powering the actuator. In more advanced embodiments, the safety mechanism could be a radio frequeny

communication system, a near field communication system or an electrically readable tag having additional information such as at least one of:

desired pressurizing parameters (force /duration curves) for at least one of pressurizing phase or blood drawing phase,

cartridge expiration date (related to sterile requirement or the lifetime of the active ingredients), or

additional information for controlling a testing device (e.g. test parameter for glucose testing).

Figure 3 is a schematic representation of the needle-free blood drawing device with removable cartridge described in further detail. The device 300 comprises a pressurizing apparatus 302 and a cartridge 312 removably mountable on the pressurizing apparatus 302. The pressurizing apparatus 302 comprises a pressurizing chamber 306, a piston 304 arranged to reciprocate in the pressurizing chamber 306, and an electrically-controlled actuator 332 coupled to the piston 304 for controlling the reciprocating motion of the piston 304.

The electrically-controlled actuator 332 comprises an electromagnetic coil 330, a power button 336, and a power source 338. The piston 304 includes a permanent ferromagnetic armature 334 on its proximal end, at the proximal edge of the actuator coil. The actuator coil 330 surrounds the piston rod and is used to attract or repel the armature 334.

The pressurizing chamber 306 preferably contains ambient air.

The cartridge 312 comprises an aperture 320, chamber 314, and a cavity forming member 322 which is positioned longitudinally within the cartridge. The cavity forming member 322 defines an accelerator barrel 324 running along its length. This barrel defines the cavity in which the particle 310 is housed. The accelerator barrel 324 thus has substantially the same length as the cavity forming member 322 and includes a constriction in the form of a nozzle 308 at its proximal end. A puncturable membrane 328 provides a seal for covering the open proximal end of the cavity forming member 322, as well as for allowing the passage of pressurized gas when it is punctured. The cartridge 312 is preferably made of glass or a polymer such as polyethylene terephthalate (PET).

As shown in Figure 3, the proximal end of the cavity forming member 322 extends slightly into the distal end of the pressurizing chamber 306. The puncturable membrane 328 may be a thin metallic foil or made of Mylar. Moreover, the puncturable membrane 328 may be mechanically or electrically ruptured. Preferably, the puncturable membrane 328 is ruptured as a result of an abrupt increase in pressure when the piston 304 moves downward towards the puncturable membrane 328. Alternatively, the puncturable membrane 328 may include a release actuator to cause the abrupt opening of the puncturable membrane through an applied electric voltage or current.

The cavity forming member 322 preferably has a constant interior cross- sectional shape, except for the nozzle 308 region near the proximal end of the cavity forming member 322. The accelerator barrel 324 preferably does not extend over the entire cartridge length to avoid coming in contact with the drawn blood. A particle 310, preferably micron- size, is arranged in the distal position of the nozzle 308. The particle 310 may have a spherical, ellipsoidal or cylindrical shape, and a diameter range preferably between 200-500 μιη. In a preferred embodiment, the accelerator barrel 324 has a slightly larger diameter range relative to the particle 310 so the particle is able to move smoothly while being effectively propelled by the pressurized gas from behind as it travels from the proximal to the open distal end of the accelerator barrel 324.

The particle 310 is preferably a biodegradable or biocompatible solid or a liquid material. Thus, the term "particle" should not be understood as being limited to a solid particle. It may be a solid or a liquid. For liquid particles, a liquid with a negligible evaporation rate (e.g. fat/oil based) and a very low saturation pressure is preferably used, while solid particles may be an agglomeration of small particles. Solid particles may contain or may be covered with appropriate substances such as anti-coagulants to maintain the small pierced skin opening for a period long enough for blood drawing. Various markers and reagents may also be included to allow the solid particles to react with the blood for easier measurement of any desired blood parameter.

As Figure 3 shows, the distal end of the cartridge 312 has a membrane 318 which covers the aperture 320. The membrane 318 preferably comprises a thin metallic foil or Mylar. The chamber 314 may be kept at the saturation pressure of a liquid particle or at atmospheric pressure for a solid particle. In an embodiment, the cartridge 312 includes a hydrophobic surface 326 at its proximal end and a hydrophilic surface 316 at its distal end so that the blood is not drawn toward the cartridge's proximal end. The hydrophilic surface 316 can be in the form of a pad, wad, or any absorbent material.

Figure 4 illustrates a locking or coupling mechanism of the needle-free blood drawing device. The device 400, as shown in exterior view, comprises a pressurizing apparatus 402 and a removable cartridge 410. The pressurizing apparatus 402 includes a power button 418 at its proximal side and a release-opening 404 at its distal side. The removable cartridge 410 can be fixed onto the pressurizing apparatus 402 via a

positioning/fastening means such that the release-opening 404 of the pressuring apparatus

402 is coupled to a proximal opening 406 of a cavity 408 adjacent to one end of the accelerator barrel 414. Fastening of the cartridge 410 onto the pressurizing apparatus 402 can be achieved through friction, screw, or any type of locking mechanism. The cartridge 410 has an output aperture 412.

An additional cartridge compatibility feature to ensure correct matching of fit and alignment with the pressurizing apparatus is preferably also incorporated to improve operational reliability. For example, particle acceleration can only be allowed to occur only if the proper cartridge is coupled with the pressurizing apparatus. This helps to ensure that the device will work as intended.

As shown in Figure 4, a mechanical and electrical compatibility feature is implemented using multiple matching pins/holes 416 when mounting the cartridge 410 onto the pressurizing apparatus 402. Automatic cartridge recognition may also include wireless readable tags, such as RF tags on the cartridge and the corresponding reading mechanism on the pressurizing apparatus.

Figure 5 illustrates the needle-free blood drawing device of Figure 3 in the particle shooting phase. An electrical current is applied to the electromagnetic coil 522, which attracts the ferromagnetic armature 526 resulting in the movement of the piston 502 towards the distal end of the pressurizing apparatus 500. The resulting pressurized gas 506 from the piston's downward motion exerts a downward force on the puncturable membrane

520 causing it to break. This releases the pressurized gas 506 from the pressurizing chamber

504, which then enters the accelerator barrel 516 and exits from the distal end of a nozzle 518 as a high speed (for example even supersonic) flow 508. The flow 508 then strikes the particle 514 at the launch site, transmitting a sudden impulse and accelerating the particle 514 through the accelerator barrel 516. Figure 5 shows the particle after acceleration along the length of the accelerator barrel. The particle 514, having gained sufficient momentum, pierces the aperture membrane 510 and penetrates the skin 512 at a sufficient depth. The particle penetration causes a micro-emergence of blood at the skin 512 surface.

The ratio between piston area and an accelerator barrel area determines the pressure amplification within the device. A higher ratio produces higher pressure

amplification but requires a corresponding increase in applied force by the actuator and correspondingly, less travel distance of the piston.

Figure 6 illustrates an alternative example of needle-free blood drawing device with removable cartridge 612 and pressurizing apparatus 600 in the blood drawing phase. An electrical current is applied to the electromagnetic coil 616, in a reverse direction, causing the repulsion of the ferromagnetic armature 620 and the movement of the piston 602 towards the proximal side of the pressurizing apparatus 600. The piston movement leads to a suction mechanism and depressurizes the chamber 608 of the cartridge 612. The at least partial vacuum within the chamber 608 is configured to draw at least a portion of the blood from the micro-emergence into the chamber 608 through the pierced aperture membrane 610.

As shown in Figure 6, one-way valves 606 are included in the pressurizing apparatus 600 such that they only open during the blood drawing phase. This is creates a large pressure difference between the pressurizing chamber 604 and the cavity forming member 614 in the shooting phase, leading to a higher acceleration power. In addition, oneway valves 606 ensure that the pressure in the pressurizing chamber and in the cartridge are equal during the drawing phase, since suction efficiency is controlled by the vacuum efficiency in the cartridge 612. The one-way valves are aligned with holes in the cartridge.

Figure 7 illustrates a cartridge integrated with a removable cap. The cartridge 700, as shown in exterior view, comprises a chamber 702 holding a blood sample 704, and a cavity- forming member 712. The cavity- forming member 712 defines an accelerator barrel 710 running along its length. The cartridge 700 may also be used as a storage container for the blood sample. A removable cap 708 seals the cartridge 700 using a mechanical locking mechanism. As shown in Figure 7, the removable cap 708 is attached with the cartridge 700 using matching of pins/holes 706.

The cartridge may include a pad/wad which includes the suitable reagents and it may have a transparent window to enable blood analysis may be done through optical measurements (color change or polarization) using a glucose meter 714. Figure 7 shows a glucose meter that shows a blood sugar level of 113 mg/dl. Electrochemical measurements may instead be taken if the cartridge is provided with suitable external electrical contacts to output the relevant electrical measurements.

Figure 8 is a flowchart illustrating an example method of blood drawing using a needle-free blood drawing device. In step 800, an electric current, preferably in the form of a short electrical pulse, is applied to the electromagnetic coil attracting a permanent ferromagnetic armature that is coupled with a piston. At the same time, the piston travels downward, generating a pressurized gas in the chamber.

Afterwards, the pressurized gas breaks a puncturable membrane causing the pressurized gas to enter into a proximal opening of a cavity in step 802.

The pressurized gas passes through an inlet opening of the barrel and propels a particle through the accelerator barrel in step 804. The particle exits at a distal opening of the cavity forming member and punctures an aperture membrane in step 806.

The particle then pierces a skin to allow a micro-emergence of blood in step 808. An electrical current in reverse direction, preferably in the form of a long electrical pulse, is then applied to the electromagnetic coil repulsing the permanent ferromagnetic armature and moving the piston towards the proximal end of the pressurizing apparatus in step 810.

Simultaneously, this movement depressurizes the cartridge. A small amount of blood from the micro-emergence can then be drawn into the chamber due to the vacuum within the cartridge in step 812.

The skin piercing mode may use a short duration high intensity electrical pulse to pressurize the chamber, leading to pressurization of the accelerator barrel such that the projectile is shot towards the skin. The pulse is calibrated such that the projectile pierces the skin such that blood can be drawn. The blood collection phase uses a long duration lower intensity electrical pulse to depressurize the chamber providing a suction mechanism.

The piston movement in the blood collection mode is likely to be larger than the movement in the skin piercing mode. Hence, a realignment of the start position of the device may then be needed once the cartridge is removed. A safety mechanism may be provided such that this realignment only happens when the cartridge is removed.

The use of an electric actuator means that accurate control is possible of the force, duration and pumping volume. The skin piercing phase require a fast motion and high pressure difference and low travel distance while the blood collection phase requires a slow motion and lower pressure difference but higher travel distance. The length of the piston travel may be used to control the amount of blood being drawn. The example above is based on a solenoid coil arrangement with an external ferromagnetic armature. An alternative is a coil gun arrangement, namely one or more coils arranged around a ferromagnetic shaft which is driven through the coil or coils. For this purpose, multiple coils may be provided in series. The voltage that needs to be applied on the coil to generate a certain force will be proportional to the inductance, which depends linearly on coil length. Hence, since most systems will have a limit on the total voltage they can generate, a higher kinetic energy (e.g. velocity) can be reached by using multiple coils in series. The coils in a coil gun arrangement are switched on and off in a precisely timed sequence, causing the projectile to be accelerated quickly along the barrel via magnetic forces. The current direction controls the travel direction and the current intensity controls the force being applied. The current pulse duration controls the motion travel distance.

Advantageously, complex pulse shapes (current intensity vs. time) can be used.

Other arrangements are possible. For example a rail gun has a direction of acceleration at right angles to the central axis of a current loop formed by conducting rails. Rail guns usually require the use of sliding contacts to pass a large current through the projectile whereas coil guns do not necessarily require sliding contacts. Some simple coil gun concepts can use ferromagnetic projectiles or even permanent magnet projectiles, but most designs for high velocities incorporate a coupled coil as part of the projectile.

Another example is a piezoelectric arrangement making use of piezo actuators. These have the advantage of very fast response (hence high pressures are possible) but the travel distance may be limited. A gear system or difference between piston surface and cartridge surface may be needed to enhance travel or increase the amount of blood being drawn.

By way of example, known coil gun designs for pistols are able to accelerate a 2 - 4 mm steel ball to subsonic speeds of the order of 200-300 m/s. Such particle velocity can easily penetrate skin up to cm depths.

For blood drawing, particles with diameter in the order of 200-500 micrometers are desired. This diameter reduction compared to 2 - 4 mm gives a

corresponding mass or kinetic energy reduction. Hence much smaller and portable mechanisms are possible.

An additional electrically controlled valve may be used which is open during a positioning phase, and closed for other phases. This may be used to avoid pressuring or depressurizing the chamber during a positioning phase. The ratio between the piston surface area and the barrel surface area corresponds to a pressure amplification factor. A higher ratio produces higher pressure amplification but requires a corresponding increase of the travel distance applied by the accelerator barrel. A greater force requires a higher current and a lower travel distance (i.e. a shorter current duration pulse). The accelerator barrel and piston shapes can thus be matched to the desired power transfer mechanism.

Different cartridges may be used with a given pressurizing apparatus. The different cartridges for example may result in different penetration depth, with a different barrel size and different blood drawing volume. The different cartridges may require different control parameters, such as the current pulse profile for each phase. For this purpose, there may be automatic cartridge recognition, which then results in automatic setting of the pressurizing apparatus settings.

This recognition may be mechanical or electrical. For example, a mechanical recognition system may use different pin/hole configurations. An electrical recognition system may use wireless readable tags such as an RF tag on the cartridge and a corresponding reading mechanism on the pressurizing apparatus.

The cartridge may include a pad, wad or other absorbent material to absorb the blood. This can be directly placed in a measurement device (e.g. diabetes testing device). This also prevents blood being drawn to the proximal end and thus prevents contamination of the pressurizing apparatus. An antibacterial skin contact surface may also be used.

It is desired that no blood enters the pressurizing apparatus if it is to be reused, to avoid contamination.

The accelerator barrel does not extend fully to the distal end of the cartridge so that is does not make contact with blood. However there may be a risk that blood will contact the barrel. An option is to have a narrowing of the barrel at the distal end such that the projectile will break the barrel when existing to ensure that blood contamination does not reach the proximal end of the accelerator barrel.

The example above is based on a solid particle projectile. It may contain or be covered with substances such as anti-coagulants to maintain the small piercing open for a period long enough for blood drawing. The particle may also include or be covered with various markers and reagents to induce a reaction with the blood for allowing easier measurement of desired blood parameters.

This use of a solid particle is not essential, and a liquid projectile may be used as is mentioned above, which will absorb automatically into the body. It may for example be a small droplet of water. In order to enable a long lifetime of the projectile in the accelerator barrel, since the cartridge with the projectile in the barrel is sold as a separate disposable item, a liquid with a low evaporation rate (e.g. fat/oil based) and a very low saturation pressure may be used.

The cartridge may be placed in a sealed casing, both for maintaining sterility and for ensuring that the atmosphere inside the sealing filled is with liquid vapors at saturation pressure at room temperature. As long as the cartridge is maintained at room temperature and the seal is not broken the liquid particle will not evaporate. This also means that if the sealing is broken during storage, the disposable may no longer be sterile. In this case, the particle may evaporate and hence the operation of the device will be blocked. In this way, the use of a liquid particle enables a design which means that only sterile cartridges can be used, which improves patient safety.

The system may for example be used by diabetes patients. In one example, a patient with Type I diabetes uses the needle-free blood drawing device for taking blood samples. The patient fastens a fresh cartridge to the multiple-use pressurizing apparatus, for example using a screw locking mechanism. For this use case, the needle-free blood drawing device is integrated with a glucose meter for monitoring blood sugar level after every meal. The patient positions the device against the skin and presses a first button to apply an electric current to the electromagnetic coil. The electromagnetic coil builds up a magnetic field attracting the permanent ferromagnetic armature which is coupled with the proximal end of the piston. The movement of the piston towards the distal end pressurizes the chamber which ruptures the puncturable first membrane releasing the pressurized gas from the chamber. The pressurized gas propels the particle, for example even at a supersonic speed, downstream through the accelerator barrel. The particle exits at the distal opening of the accelerator barrel and breaks the puncturable second membrane. A micro-emergence of blood develops as the particle pierces the patient's skin. Afterwards, the patient presses a second button applying an electrical current, in reverse direction, to the electromagnetic coil. The chamber is then depressurized, followed by the opening of the one-way valves. The opening of the valves then leads to depressurization of the cartridge. The at least partial vacuum generated then causes a small amount of blood to flow from the micro-emergence into the chamber of the cartridge. Afterwards, the glucose meter measures a blood sugar level from the blood sample. This may be displayed by a display device which is part of the system, and/or the data may be transmitted to a remote network server. The remote network server stores the transmitted data for further analysis and storage. This enables remote monitoring of the patient data, so that the patient can be instructed to report for a check-up if this is deemed appropriate.

The purpose of the membrane of the cartridge is to provide a sterile environment for the cartridge. A sterile packaging may be provided which requires opening, or else a puncturable membrane may be used as described above, or both.

An issue with a puncturable membrane is that in order to provide a sterile environment, the membrane must be present on both distal and proximal ends. With respect to the distal end, this is hit by the accelerated particle which should pierce the skin, so there is no problem in piercing this interface. However, the proximal membrane must be broken by the pressure in the pressurizing chamber itself. The surface of the opening would be a circle of e.g. 250 microns, so the total surface would be approximately 2 x 10 ^"4 square centimeters. At 200N/cm ² (which is 20 bar) the total force being developed would only reach 0.05 Newton, which may not be sufficient to break many different possible membrane types. A membrane cutting mechanism may be used instead of pressure alone, such as sharp pins or teeth in the pressurizing head which match holes in the cartridge. These may then pierce the proximal membrane during head mounting.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.