Patent Publication Number: US-9429571-B2

Title: Sensing device for sensing a fluid

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 13/140,175 filed Jun. 16, 2011, which is a national filing of international application serial no. PCT/IB2009/055540, filed Dec. 8, 2011, which claims the benefit of EP application serial no. 08172132.6, filed Dec. 18, 2008, all of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a sensing device and method for sensing a fluid and an analyzing apparatus for analyzing a fluid. 
     BACKGROUND OF THE INVENTION 
     Sensing devices like sensing cartridges can be part of bio sensors or chemical sensors. Such sensing cartridges typically comprise an inlet port and a measurement chamber, which are connected via a fluid channel. In the measurement chamber a sensor surface is provided which can interact with particles of the fluid applied into the inlet port and transported through the fluid channel. The fluid channels are typically capillary fluid channels such that a fluid introduced into the inlet port autonomously travels through the fluid channel to the measurement chamber. This can take between 10 and 60 seconds. It is, however, important to have reproducible results. The results may, however, differ depending on the time elapsed between applying the fluid to the inlet port and the measurement of the fluid in the measurement chamber. This problem can be avoided by inserting the cartridge directly into an analyzer after the fluid has been applied to the inlet port which may not always be possible. On the other hand, if the cartridge is inserted into the analyzer before the fluid is applied into the inlet port, a danger of contamination of the analyzer may be present. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a sensing device and a sensing method for sensing a fluid, wherein the reproducibility of the results can be increased, in particular, without contaminating an analyzing apparatus, if the sensing device is used together with the analyzing apparatus for analyzing the fluid. It is a further object of the present invention to provide a corresponding analyzing apparatus, which can be used together with the sensing device for analyzing the fluid. 
     In an aspect of the present invention a sensing device for sensing a fluid is presented, which comprises:
         an inlet port for receiving the fluid;   a measurement chamber for sensing the fluid;   a fluid channel coupling the inlet port and the measurement chamber for transporting fluid from the inlet port to the measurement chamber; and   a fluid stop unit for stopping and controllably releasing the flow of fluid between the inlet port and the measurement chamber.       

     With such a sensing device a droplet of fluid can be applied into the inlet port, wherein the fluid flows partly along the fluid channel but not into the measurement chamber. As long as the fluid is in the fluid channel it is protected from contamination and also the fluid can not contaminate an analyzing apparatus which might be used together with the sensing device for analyzing the fluid. Once the fluid is released again it can continue to flow into the measurement chamber. 
     Since this releasing is performed controllably, the flow of the fluid into the measurement chamber can be controlled such that the fluid flows in the measurement chamber if the sensing device is ready for sensing the fluid or, if the sensing device is used in combination with an analyzing apparatus, if the sensing device has been inserted into the sensing device and if the analyzing apparatus is ready for analyzing the fluid. These effects of the sensing device allow increasing the reproducibility of the results of sensing or analyzing the fluid, in particular, without contaminating an analyzing apparatus, which might be used for analyzing the fluid present in the measurement chamber of the sensing device. 
     The sensing device itself can be adapted to sense the fluid or the sensing device can be adapted to cooperate with a further device like an analyzing apparatus for sensing the fluid. 
     Sensing or analyzing the fluid includes, for example, detecting target elements in the fluid, wherein the amount or concentration of target elements in the fluid can be regarded as a property of the fluid. 
     The sensing device can comprise several inlet ports and/or several measurement chambers and/or several fluid channels and/or several fluidic stop units. 
     Preferably, the fluid stop unit comprises a venting hole arranged behind the measurement chamber with respect to a flow direction from the inlet port to the measurement chamber and coupled to the fluid channel as well as a seal arranged at the venting hole for hermetically sealing the venting hole. The stop of the fluid in the fluid channel can be released by puncturing the seal arranged at the venting hole. Such a puncturing will release air which was previously enclosed in the venting hole and the fluid channel. 
     The seal is preferentially a foil like an aluminum foil or a plastic foil or a membrane which can be injection molded. If the seal is implemented as a foil or a membrane, the seal can be easily punctured in order to release the enclosed air or gas in the fluid channel and in the venting hole. 
     Preferentially, the fluid channel is a capillary fluid channel such that the fluid introduced into the fluid channel can travel along the fluid channel independently only driven by capillary forces. 
     Preferentially, a filter unit can be arranged between the inlet port and the measurement chamber for filtering the fluid in order to remove particles in the fluid. By means of this filter unit unwanted particles in the fluid can be removed. 
     It is preferred that the fluid stop comprises a fluidic stop element arranged along the fluid channel for stopping a flow of fluid between the input port and the measurement chamber. The fluid stop unit furthermore comprises a pressure control unit for controlling a pressure in a first part of the fluid channel between the inlet port and the fluidic stop element by changing the pressure in the first part of the fluid channel to force the fluid past the at least one fluidic stop element. The flow of the fluid in the fluid channel can be stopped by means of a fluidic stop element and can be released again by changing the pressure in a first part of the fluid channel such that the fluid is forced past the fluidic stop element. Accordingly, a controllable stop of the flow of the fluid can be achieved. 
     The sensing device can comprise several pressure control units. 
     It is preferred that the pressure control unit comprises a cap arranged a first section of the sensing device comprising the inlet port, the cap having an opened position and a closed position. In the opened position the inlet port is uncovered by the cap and a first pressure is present in the first part of the fluid channel. In the closed position the inlet port is sealed, in particular, hermetically sealed, by the cap and a second pressure is produced in the first part of the fluid channel. The second pressure is higher than the first pressure to force the fluid in the fluid channel past the fluidic stop element into the measurement chamber. Preferentially, the cap is slidable for moving the cap from the opened to the closed position. The provision of the cap constitutes an easy and convenient way to overcome the fluidic stop element and release the flow of the fluid again. As the cap covers the inlet port in its closed position, a contamination of the fluid in the inlet port or in the first part of the fluid channel is avoided. 
     It is further preferred that the sensing device comprises a sealing unit for sealing the cap and the first section of the device, at least if the cap is in the closed position. The sealing unit facilitates the provision of the second increased pressure in the first part of the fluid channel. 
     It is further preferred that the cap is irreversibly locked in the closed position. Hence, a manipulation of the fluid in the fluid channel can be avoided. Moreover, a multiple use of the same sensing device is prevented. It is further preferred that the pressure control unit comprises a first hole coupled to the first part of the fluid channel for introducing a pressure into the first part of the fluid channel to force the fluid past the fluidic stop unit. By means of the first hole, for example, air can be pressed into the fluid channel to force the fluid past the fluidic stop element. 
     It is further preferred that the pressure control unit comprises an air chamber coupled to the first part of the fluid channel. The air chamber comprises an elastic cover, which might be a membrane or a foil, for covering, in particular, sealing, an opening of the air chamber. Accordingly, merely by pressing the elastic cover, the pressure in the first part of the fluid channel can be increased to force the fluid past fluidic stop element. 
     The sensing device can comprise several air chambers. 
     It is further preferred that the sensing device is adapted to be cooperable with an analyzing apparatus for allowing the analyzing apparatus to sense the fluid in the measurement chamber. This allows using several sensing devices with the same analyzing apparatus. In particular, the sensing device can be a sensing cartridge, which can be disposed after being used. 
     In a further aspect of the present invention an analyzing apparatus for analyzing a fluid is provided. The analyzing apparatus is adapted to be cooperable with a sensing device which comprises an inlet port for receiving a fluid, a measurement chamber for sensing the fluid, a fluid channel coupling the inlet port and the measurement chamber for transporting fluid from the inlet port to the measurement chamber, and a fluid stop unit for stopping and controllably releasing the flow of fluid between the inlet port and the measurement chamber. The analyzing apparatus comprises a sensing device receiving unit for receiving the sensing device. The analyzing apparatus further comprises a fluid releasing unit for controllably releasing a flow of fluid stopped between the inlet port and the measurement chamber of the sensing device, if the sensing device is inserted into the sensing device receiving unit. 
     The analyzing apparatus can comprise several fluid releasing units. 
     It is preferred that the fluid releasing unit comprises a puncture element for puncturing a seal covering a venting hole arranged behind the measurement chamber with respect to a flow direction from the inlet port to the measurement chamber, when the sensing device is inserted into the sensing device receiving unit. By means of the puncture element, the seal can be punctured to release any gas or air trapped in the fluid channel and the venting hole. 
     It is further preferred that the fluid releasing unit comprises a pressure generating unit for generating a fluid pressure and a second hole coupled to the pressure generating unit for pressing pressure fluid like air or like another gas into a first hole of an inlet port of a sensing device inserted into the sensing device receiving unit for increasing the pressure in the fluid channel such that the flow of fluid between the inlet port and the measurement chamber is controllably released. 
     The analyzing apparatus can comprise several pressure generating units coupled to several second holes for pressing a pressure fluid into several first holes and/or several inlet ports of a sensing device. 
     It is further preferred that the fluid releasing unit comprises an actuator unit for pressing against an elastic cover of a sensing device inserted into the sensing device receiving unit for increasing the pressure in the fluid channel such that the flow of fluid between the inlet port and the measurement chamber is controllably released. By means of the actuator, the pressure inside an air chamber in the sensing device can be increased to force the fluid past the fluidic stop. 
     It is further preferred that the sensing device comprises an inlet cover and optionally also a sealing element like a sealing ring arranged around the inlet port, wherein the inlet cover is adapted to be moveable between a closed position and an open position and wherein in the closed position the inlet port is closed and in the open position the inlet port is open. This allows preventing that the fluid leaves the fluid channel via the inlet port, in particular, if the pressure is increased within the fluid channel for releasing the stop of flow between the inlet port and the measurement chamber. 
     In a further aspect of the invention a method for sensing a fluid is presented. A sensing device having an inlet port for receiving the fluid, a measurement chamber for sensing the fluid, a fluid channel coupling the inlet port and the measurement chamber for transporting fluid from the inlet port to the measurement chamber and a fluid stop unit for stopping and controllably releasing the flow of fluid between the inlet port and the measurement chamber is provided. The fluid is received at the inlet port. The fluid from the inlet port is transported to the measurement chamber. The flow of fluid is stopped and controllably released between the inlet port and the measurement chamber. 
     It is preferred that at least one droplet of fluid is inserted into an inlet port of the sensing device. Then, the sensing device is inserted into a sensing device receiving unit of an analyzing apparatus. The flow of fluid is stopped and controllably released between the inlet port and the measurement chamber. 
     Preferentially, a seal covering a venting hole of the sensing device is punctured when the second end of the sensing device is inserted into the sensing device receiving unit for controllably releasing the flow of fluid between the inlet port and the measurement chamber. 
     It is further preferred that air is pressed into a first hole or an inlet port of the sensing device when the sensing device is inserted into the sensing device receiving unit to force the fluid stopped by the fluidic stop element past the fluidic stop element into a measurement chamber of the sensing device. 
     It shall be understood that the sensing device, the analyzing apparatus and/or the method for sensing a fluid described have similar and/or identical preferred embodiments as described herein and/or defined in the dependent claims. 
     It shall be understood that a preferred embodiment of the invention can also be any combination of the dependent claims with the respective independent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described herein after. In the following drawings: 
         FIG. 1  shows schematically and exemplarily a sectional view of a sensing device, 
         FIG. 2  shows schematically and exemplarily a further sectional view of the sensing device, 
         FIG. 3  shows schematically and exemplarily a further sectional view of the sensing device inserted into an analyzing apparatus, 
         FIG. 4  shows a flow chart illustrating exemplarily a method for sensing a fluid in a sensing device, 
         FIG. 5  shows schematically and exemplarily a sectional view of a further sensing device, 
         FIG. 6  shows schematically and exemplarily a further sectional view of the sensing device, 
         FIG. 7  shows schematically and exemplarily a further sectional view of the sensing device, 
         FIG. 8  shows a flow chart illustrating exemplarily a method for sensing a fluid in a sensing device according to a further embodiment, 
         FIG. 9  shows schematically and exemplarily a sectional view of a sensing device and an analyzing apparatus according to a further embodiment, 
         FIG. 10  shows a flow chart illustrating exemplarily a method for sensing a fluid in a sensing device, 
         FIG. 11  shows schematically and exemplarily a sectional view of a sensing device and an analyzing apparatus according to a further embodiment, 
         FIG. 12  shows a flow chart illustrating exemplarily a method for sensing a fluid in a sensing device according to a further embodiment, 
         FIG. 13  shows schematically and exemplarily a sectional view of a sensing device and an analyzing apparatus according to a further embodiment, 
         FIG. 14  shows a flow chart illustrating exemplarily a method for sensing a fluid in a sensing device according to a further embodiment, 
         FIG. 15  shows schematically and exemplarily an embodiment of an analyzing apparatus, and 
         FIG. 16  shows schematically and exemplarily magnetic particles attached to a surface of a sensing device. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows schematically and exemplarily a sectional view of a sensing device being a sensing cartridge according to a first embodiment. The sensing cartridge  10  comprises first and second ends  11 ,  12 . At the first end  11  an inlet port  20  is provided and at the second end  12  at least one venting hole  40  and at least one measurement chamber  25  is provided. The venting hole  40  is sealed by a seal  50 . Furthermore, a fluid channel  30  having first and second parts  31 ,  32  couples the inlet port  20 , the measurement chamber  25  and the venting hole  40 . In the first part  31  the fluid is stopped, before it is controllably released into the second part  32  for flowing into the measurement chamber  25 . 
     The inlet port  20  serves to receive at least one droplet of a fluid  100 , wherein the properties of the fluid  100  are to be measured or determined. The seal  50  preferably hermetically seals the venting hole  40 . Preferably, the seal  50  is applied to the venting hole  40  during the manufacturing of the sensing cartridge. 
       FIG. 2  shows schematically and exemplarily a further sectional view of the sensing cartridge of  FIG. 1 . In  FIG. 2  a droplet of fluid  100  has been introduced into the inlet port  20  and the fluid  100  has travelled along the first part  31  of the fluid channel  30 . Preferably, the fluid channel  30  is a capillary fluid channel, i.e. the fluid  100  travels along the fluid channel  30  by means of capillary forces. As the venting hole  40  is hermetically sealed by the seal  50 , the fluid  100  can only travel a first distance of the first part  31  along the fluid channel  30 . The fluid  100  will stop at a position where the force generated by the pressure in the remaining unfilled fluid channel  30  is at least equal to the capillary forces in the fluid channel  30 . Accordingly, in  FIG. 2  the situation is disclosed where the droplet of the fluid  100  has been introduced into the inlet port and the fluid has partly travelled along the fluid channel  30 , i.e. along the first part  31  of the fluid channel  30 , but the fluid has not yet reached the measurement chamber  25 . In the situation as depicted in  FIG. 2  flow of the fluid in the fluid channel  30  has been stopped. 
       FIG. 3  shows schematically and exemplarily a sectional view of the sensing cartridge inserted into an analyzing apparatus  200  which is also only schematically shown. Here, the second end  12  of the sensing cartridge  10  (as described according to  FIGS. 1 and 2 ) is inserted into a sensing device receiving unit  210  of the analyzing apparatus  200 . In the sensing device receiving unit  210  a puncture element  220  like a needle is provided such that it punctures the seal  50  covering the venting hole  40  when the second end  12  of the sensing cartridge  10  is inserted into the sensing device receiving unit  210 . By puncturing the seal  50  the gas enclosed in the second part of the fluid channel  30  and in the venting hole  40  can be released such that the fluid  100  in the fluid channel  30  can travel along the second part  32  of the fluid channel  30  towards the measurement chamber  25 . When the fluid has reached the measurement chamber  25 , the fluid can be analyzed, i.e. e.g. properties of the fluid can be determined, by the analyzing apparatus. For example, the concentration of target elements in the fluid present in the measurement chamber can be determined as a property of the fluid for analyzing the fluid. 
     The seal  50  can be implemented as a foil which might be an aluminum foil and which is glued over the venting hole  40 . Alternatively, the seal  50  can be implemented as a membrane which is injection molded. 
     It should be noted that when the seal is punched by the puncture element  50  the flow of the fluid inside the fluid channel can still be determined by capillary forces and is thus independent of any operator. 
     In addition, optionally a filter unit can be provided along the fluid channel  30  for filtering the fluid in order to remove particles in the fluid, for example red blood cells, if the fluid is blood. 
       FIG. 4  shows a flow chart illustrating exemplarily a method for sensing a fluid, i.e. in this embodiment for determining a property of a fluid in a sensing cartridge. In step S 11 , a droplet of fluid  100  is inserted into the inlet port  30 . In step S 12 , the sensing cartridge  10  is inserted into the sensing device receiving unit  210  and in step S 13  the seal is punctured such that the fluid  100  will continue to flow into the measurement chamber  25 . In step S 14 , a measurement is performed when the fluid  100  has reached the measurement chamber  25 . 
       FIG. 5  shows schematically and exemplarily a sectional view of a further embodiment of a sensing device being a sensing cartridge. The sensing cartridge  10  comprises first and second ends  11 ,  12 . An inlet port  20  for receiving a droplet of fluid  100  is arranged at the first end  11  and a measurement chamber  25  is arranged at the second end  12 . Furthermore, a fluid channel  30  having first and second parts  31 ,  32  couples the inlet port  20  and the measurement chamber  25 . Along the fluid channel  30  a fluidic stop unit  70  is provided. Optionally a sealing unit  60  can be provided between the inlet port  20  and the second end  12 , further preferred between the inlet port  20  and the fluidic stop unit  70 . The sealing unit  60  is, in this embodiment, a sealing ring. The sensing cartridge  10  further comprises a cap  300  which preferably has substantially a U-shape in cross-section. However, it should be noted that also other shapes are possible as long as the shape of the cap  300  corresponds to the shape of the first end  11  of the sensing cartridge. The cap  300  is shown in a first or opened position  301  leaving the inlet port  20  uncovered to allow an insertion of fluid. The cap  300  has been designed to at least partly hermetically fit over the first end  11  of the sensing cartridge  10  and to at least partly hermetically seal the inlet port  20  when in the closed position  302 . 
       FIG. 6  shows schematically and exemplarily a further sectional view of the sensing cartridge. In  FIG. 6  the situation is disclosed where a droplet of fluid  100  has been introduced into the inlet port  20  and the fluid  100  has traveled along the first part  31  of the fluid channel  30  until it reaches the fluidic stop unit  70 . Moreover, the cap  300  has been partly placed over the second end  11  of the sensing cartridge and has reached the sealing ring  60 . The fluid  100  in the fluid channel  30  will not travel further than the fluidic stop unit  70  as the driving capillary forces will not be high enough to force the fluid  100  past the fluidic stop unit  70 . The fluidic stop unit  70  can be a geometrical feature and/or a local hydrophobisation while the fluid channel  30  is hydrophilic. 
       FIG. 7  shows schematically and exemplarily a further sectional view of the sensing cartridge. In  FIG. 7  the cap  300  has been completely provided over the first end  11  of the sensing cartridge  10 , i.e. it is in a second or closed position. Now, the ends of the cap  300  have been pushed over the sealing unit  60  such that the air pressure in the inlet port  20  increases to an extend that the fluid  100  in the fluid channel  30  is forced past the fluidic stop unit  70  along the second part  32  and can reach the measurement chamber  25 . The air or another gas present in the space surrounded by the cap  300  is forced into the fluid channel  30  while moving the cap  300  from the opened position to the closed position. In order to allow the gas to be transferred from the space surrounded by the cap  300  to the fluidic channel  30 , the part of the surface of the sensing device at which the inlet port is provided may comprises a recessed channel (not shown in  FIGS. 5 to 7 ) for guiding the gas from the space surrounded by the cap  300  via the recessed channel and via the inlet port  20  into the fluid channel  30 . In another embodiment, another gas connection might be present in the sensing cartridge for guiding the gas surrounded by the cap  300  into the fluid channel  30 . 
     Accordingly, in  FIG. 7  the situation is disclosed where the inlet port  20  is completely covered by the cap  300  and the fluid  100  has reached the measurement chamber  25  such that a measurement of properties of the fluid can start. 
     Preferably, the cap  300  will latch or click into its end position  302 . Preferably the latching or the click is irreversible such that the cartridge can be removed in a sealed state from the analyzing apparatus. This is advantageous as a contamination of the analyzing apparatus can be avoided. 
     Preferably, the fluid channel  30  can be designed such that the fluid which has passed the fluidic stop  70  can continue to flow by capillary action along the second part  32 . 
     If the fluidic stop unit  70  is embodied as a hydrophobic area or region, the fluid channel  30  is designed to avoid that the stream of the fluid breaks up after the hydrophobic region when the external pressure has been applied. 
       FIG. 8  shows a flow chart illustrating exemplarily a method for analyzing a fluid in a sensing cartridge according to a further embodiment. In step S 21 , a droplet of fluid  100  is inserted into the inlet port  20 . In step S 22 , the cap  300  slides from the open to the closed position forcing the fluid  100  past the fluidic stop element  70  into the measurement chamber  25 . In step S 23 , the sensing cartridge  10  is inserted into the sensing device receiving unit  210 . In step S 24  a measurement is performed when the fluid  100  has reached the measurement chamber  25 . In another embodiment, step S 23  can be performed before step S 22 . 
       FIG. 9  shows schematically and exemplarily a sectional view of a sensing cartridge inserted into an analyzing apparatus according to a further embodiment. The sensing cartridge  10  comprises first and second ends  11 ,  12 , an inlet port  20 , a fluid channel  30  having first and second parts  31 ,  32 , a fluidic stop element  70  and a measurement chamber  25 . The fluid channel  30  connects the input port  20 , the fluidic stop element  70  and the measurement chamber  25 . The sensing cartridge substantially corresponds to the sensing cartridge described above with reference to  FIGS. 5 to 7 , without the cap  300  and the sealing ring  60 . The sensing cartridge according to the present embodiment comprises a sealing  80  arranged around the inlet port  20 . 
     The analyzing apparatus  200  comprises a sensing device receiving unit  210  with a hole  230  and an air pressure generating unit  240  coupled to the hole  230  via a coupling channel  231  such that air pressure generated by the air pressure generating unit  240  can be transferred to the hole  230 . When the sensing cartridge  10  is inserted into the sensing device receiving unit  210  the hole  230  in the analyzing apparatus is aligned with the inlet port  20 . Then, the air pressure in the inlet port  20  is increased by means of the hole  230  such that fluid in the first part  31  of the fluid channel  30  is forced past the fluidic stop unit  70  along the second part  32  of the fluid channel  30 . The increase of the air pressure in the hole  230  is determined or controlled by the air pressure generating unit  240 . 
       FIG. 10  shows a flow chart illustrating exemplarily a method for analyzing a fluid in a sensing cartridge according to a further embodiment. In step S 31  a droplet of fluid  100  is inserted into the inlet port  20  and in step S 32  the sensing cartridge  10  is inserted into the sensing device receiving unit  210 . In step S 33  air is pressed into the inlet port forcing the fluid past the fluidic stop element  70  into the measurement chamber  25 . In step S 34  a measurement is performed when the fluid  100  has reached the measurement chamber  25 . Step S 31  is always performed before step S 33 . However, step S 32  can also be performed before step S 31 . 
       FIG. 11  schematically and exemplarily shows a further sectional view of a sensing cartridge inserted into an analyzing apparatus according to a further embodiment. This sensing cartridge substantially corresponds to the sensing cartridge described above with reference to  FIGS. 5 to 7 , without the cap  300  and the sealing ring  60 . In addition, the sensing cartridge comprises a hole  13  which couples the fluid channel  30  to the outside. Furthermore, a sealing ring  90  can be provided adjacent to the hole  13 . 
     The analyzing apparatus  200  comprises a sensing device receiving unit  210  for receiving a second end  12  of the sensing cartridge  10 . The analyzing apparatus  200  further comprises a hole  250  and an air pressure generating unit  260  coupled to the hole  250  via a coupling channel  251  such that air pressure can be generated at the hole  250  by the air pressure generating unit  260 . When the second end  12  of the sensing cartridge  10  is inserted into the sensing device receiving unit  210 , the hole  13  will be aligned with the hole  250 . Then, the air pressure in the hole  13  can be increased by means of the air pressure generating unit  260 . Hence, this increased air pressure will in turn increase the pressure in the fluid channel  30  and forces the fluid  100  past the fluidic stop unit  70  into the measurement chamber  25 . 
     The sensing cartridge further comprises an inlet cover  21  for covering the inlet port  20  such that the fluid does not leave the sensing cartridge via the inlet port  20 , if the pressure is increased in the fluid channel  30 . The inlet cover  21  is, for example, a slidable element or a flap. The inlet cover  21  is moveable between a closed position, in which the inlet port  20  is closed, and an open position, in which the inlet port  20  is open for receiving the fluid. The inlet cover  21  further comprises a sealing element  22  like a sealing ring for reducing the probability that the fluid leaves the fluid channel  30  via the inlet port  20 , if the pressure is increased within the fluid channel. 
       FIG. 12  shows a flow chart illustrating exemplarily a method for sensing a fluid in a sensing cartridge according to a further embodiment. In step S 41 , a droplet of fluid  100  is inserted into the inlet port  30  and the inlet cover  21  is closed. In step S 42  the sensing cartridge  10  is inserted into the sensing device receiving unit  210 . In step  43 , air is pressed into the hole  13  by means of the hole  250  in the analyzing apparatus forcing the fluid past the fluidic stop element  70  into the measurement chamber  25 . In step S 44  a measurement is performed when the fluid  100  has reached the measurement chamber  25 . Also here, step S 41  can be performed after step S 42  has been performed. 
     Instead of using the inlet cover  21  the analyzing apparatus can be adapted to close the inlet port  20  of the sensing cartridge, if the sensing cartridge has been received in the sensing device receiving unit. 
       FIG. 13  shows schematically and exemplarily a sectional view of a sensing device being a sensing cartridge and an analyzing apparatus according to a further embodiment. The sensing cartridge comprises first and second ends  11 ,  12 , an inlet port  20 , a fluid channel  30 , a fluidic stop unit  70  and a measurement chamber  25 . The sensing cartridge  10  further comprises an air chamber  96  which is coupled with the fluid channel  30  via a hole  97 . The air chamber  96  is closed by means of an elastic membrane  95 . 
     The analyzing apparatus  200  comprises a sensing device receiving unit  210 , an actuator unit  270  and optionally an actuator control unit  280 . When the second end  12  of the sensing cartridge  10  is inserted into the sensing device receiving unit  210 , the air chamber  96  and the membrane  95  are aligned with the actuator unit  270 . The actuator control unit  280  can control the actuator  270  to mechanically press against the membrane  95  such that the pressure in the air chamber  96  and the hole  97  is increased. This increased air pressure will force the fluid  100  in the fluid channel  30  past the fluidic stop unit  260  and into the measuring chamber  25 . The sensing cartridge and the analyzing apparatus are advantageous as the amount of pressure which is applied to the air chamber can be controlled very accurately and reliable. 
     Also in this embodiment, the sensing cartridge comprises the inlet cover  21  and the sealing element  22 . 
       FIG. 14  shows a schematic flow chart of a method for sensing a fluid in a sensing cartridge according to a further embodiment. In step S 51 , a droplet of fluid  100  is inserted into the inlet port  20  and the inlet port cover  21  is closed. In step S 52  the sensing cartridge  10  is inserted into the sensing device receiving unit  210 . In step S 53 , the elastic membrane  95  of the sensing cartridge is pressed down by means of an actuator unit  270  of the analyzing apparatus such that the air in the air chamber  96  is forced into the first part of the fluid channel  30  forcing the fluid past the fluidic stop element  70  into the measurement chamber  25 . In step S 54 , a measurement is performed when the fluid  100  has reached the measurement chamber  25 . Also in this embodiment step S 51  can be performed after step S 52  has been performed. 
       FIG. 15  shows schematically and exemplarily a sensing part  118  of an analyzing apparatus for sensing a fluid, in which a sensing cartridge has been inserted. The analyzing apparatus serves to receive sensing cartridges such that the fluid can be examined in the measurement chamber. The sensing part  118  of the analyzing apparatus is adapted for determining a property of the fluid  103 , which is located in the measurement chamber  25  of the sensing cartridge  10 . The sensing part  118  of the analyzing apparatus comprises, in this embodiment, a magnetic element  119 , which provides a magnetic field for forcing magnetic particles  125  within the measurement chamber  25  onto a surface  130  of the sensing cartridge  110 . The magnetic particles  125  on the surface  130  are detected by, in this embodiment, illuminating this surface with a light beam  129  generated by a light source  120 , which is, for example, a laser device or a LED, and by detecting the light reflected from the surface by a detector  123 . The detector  123  is, for example, a photo detector or a two-dimensional camera. Optical elements  121  and  122  can be arranged in the light beam  129  for generating parallel light or focusing the light beam  129 , respectively. The optical elements  121 ,  122  are preferentially lenses. 
     The configuration sketched in  FIG. 15  shows a detection of changes at a surface using the FTIR method (frustrated total internal reflection). If a beam of light reflects on the interface between a medium with a higher refractive index, for example the measurement chamber  25 , and a lower refractive index, for example the fluid, there is a certain critical angle of incidence above which there is a situation of total internal reflection (TIR). The present detection configuration (regarding refractive indices and angle of incidence) is such that there is total internal reflection of the incoming beam. Although the light is totally reflected in such a situation, there is still penetration of the light in a very thin layer of the medium with the low refractive index. This is called evanescent light, the intensity of which decays exponentially in the low refractive index medium with a characteristic penetration depth of the order of the wavelength of the light. So, in practice the penetration depth is preferentially less than 0.5 micrometer. If magnetic particles stick to the surface, the optical properties of this very thin first fluid layer of preferentially about 0.5 micrometer are changed leading to a reduction of the reflected light beam. This is caused by absorption and scattering of the evanescent light (FTIR; frustrated total internal reflection). As a result the signal of the photodetector changes. 
     The objective is preferentially to detect specific target molecules or larger objects in the fluid. In the example sketched in  FIG. 16  this is realized by a so-called sandwich assay. Magnetic beads  125  are coated with a specific antibody  227  that attaches to a target molecule  228  present in the fluid. When the magnetic beads  125  that are freely present in the fluid have reacted with the available target molecules the beads are attracted to the cartridge surface  130  that has been coated with another antibody  226  that can couple to the target molecule. After a sufficiently long reaction time the magnetic field is switched such that the magnetic beads are pulled upwards so that only the specifically bound beads with the correct target molecules stay attached to the surface. At that moment the optical detector can be read out and gives a signal that carries the information on the amount of target molecules in the fluid. So the detection location, in particular the surface  130 , in particular a detection spot in the cartridge, is preferentially covered with a biolayer with antibodies. 
     The determination method described above with reference to  FIGS. 15 and 16  is preferentially used by all embodiments of the sensing cartridge and the analyzing apparatus, which are described above. Correspondingly, the above described embodiments of the sensing cartridge and the analyzing apparatus are preferentially adapted such that they can perform the determination method described with reference to  FIGS. 15 and 16 . In particular, they comprise the features described with reference to  FIGS. 15 and 16 . 
     The features described above with respect to a sensing cartridge and/or an analyzing apparatus can also be embodied in other sensing devices for sensing a fluid that comprise a first end having at least one inlet port for receiving the fluid, a second end having at least one measurement chamber, at least one fluid channel coupling the at least one inlet port and the at least one measurement chamber for transporting fluid from the inlet port to the measurement chamber, and at least one fluid stop unit for stopping and controllably releasing the flow of fluid between the inlet port and the measurement chamber. 
     The fluid stop unit can be a single unit being adapted for stopping and/or controllably releasing the flow of fluid between the inlet port and the measurement chamber. In another embodiment, the fluid stop unit can also be a combination of units being adapted for stopping and/or controllably releasing the flow of fluid between the inlet port and the measurement chamber. Furthermore, the fluid stop unit can be a unit that cooperates with another unit, which might be present at the same sensing device or at another device like an analyzing apparatus, for stopping and/or controllably releasing a flow of fluid between the inlet port and the measurement chamber. 
     In the above described embodiment, the fluid can be blood or any other fluid, in particular, any other body fluid, like saliva or urine. The preferred application for the sensing cartridge and for the analyzing apparatus is in the field of point-of-care diagnostics, in particular, based on a finger prick blood sample, like a cardiac marker detection application. But, the sensing cartridge can also be adapted for filtering and/or debubbling of other fluids, like saliva for Drugs Of Abuse. 
     In the above described embodiment, the analyzing apparatus uses evanescent field techniques for determining the amount of magnetic particles on the surface. In other embodiments, other techniques can be used for determining these particles. For example, magnetic methods, sonic detection, electrical detection and combinations therefore can be used. Furthermore, the analyzing apparatus can comprise any sensor based on the detection of the magnetic properties of the particle on or near to a sensor surface. The analyzing apparatus can be adapted for detecting molecular targets, which often determine the concentration and/or presence of larger moieties, for example, cells, viruses, fractions of cells or fractions of viruses, tissue extract etc. The magnetic particles can be detected directly by the sensing method. As well, the particles can be further processed prior to detection, an example of further processing is that materials are added or that the chemical of biochemical of physical properties of the magnetic labels are modified to facilitate detection. The analyzing apparatus can be adapted for working together with several biochemical assay types, for example, binding/unbinding assay, sandwich assay, competition assay, displacement assay, enzymatic assay etc. The sensing cartridge and the analyzing apparatus can be adapted for sensor multiplexing, i.e. the parallel use of different sensors and sensor surfaces, label multiplexing, i.e. the parallel use of different types of labels, and chamber multiplexing, i.e. the parallel use of different reaction chambers. The sensing cartridge and the analyzing apparatus can be used as rapid, robust and easy to use point-of-care biosensors for small sample volumes. The measurement chamber is preferentially a part of a disposable cartridge, which is to be used with the analyzing apparatus, which contains one or more magnetic field generating means, i.e. the magnetic element, and one or more detection means. The sensing cartridge and the analyzing apparatus can preferentially be adapted for a use in automated high-throughput testing. 
     The magnetic particles are preferentially nano-particles having at least one dimension ranging between 3 nm and 5000 nm, preferably between 10 nm and 3000 nm, more preferred between 50 nm and 1000 nm. 
     Other variations to the disclosed embodiment can be understood and effected by those skilled in the art in practising 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. 
     A single unit or device may fulfill the functions of several items recited in the claims. 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.