Abstract:
A medium having microfluidic circuitry for sampling and analyses. The medium may be a cartridge having a window countersunk into it and containing a flow channel. The flow channel may have items of interest flowing through it. Analyses of these items may be optical involving one or more light sources emanating light to and one or more light detectors receiving light from the channel. There are various configurations so that source and detector light cones may reach the flow channel without obscuration or interference of the light to and from the flow channel in the window.

Description:
DESCRIPTION 
   This present invention is a continuation-in-part of U.S. patent application Ser. No. 10/612,664, filed on Jul. 2, 2003 now U.S. Pat. No. 7,000,330, which claims the benefit of U.S. Provisional Application No. 60/404,876, filed Aug. 21, 2002. This present invention is also a continuation-in-part of U.S. patent application Ser. No. 10/304,773, filed Nov. 26, 2002, which is a continuation-in-part of U.S. patent application Ser. No. 09/630,924, filed Aug. 2, 2000, now U.S. Pat. No. 6,597,438, and claims the benefit thereof. The above-mentioned patent documents are incorporated herein by reference. 

   BACKGROUND 
   The present invention generally relates to cytometery, and particularly to removable media of a cytometer. More particularly, the invention related to an improvement of the media. 
   Over the past several decades there has been an ever increasing use of devices and systems that use, in one form or another, a removable media member. Some illustrative removable media members include, for example, removable or replaceable filters, removable ink and toner cartridges, removable data storage devices such as magnetic or optical disks, removable magnetic tape cartridges, removable memory sticks, and so forth. 
   A limitation of many of the existing systems is that the alignment tolerance between the inserted removable media member and the receiving device is often not very precise. In some cases, the receiving device simply includes a slot for receiving the removable media member. In other cases, a more complex mechanical mechanism is provided, such as the mechanical mechanism used in a conventional video cassette recorder (VCR) for receiving VCR tapes. For some applications, the alignment tolerance that can be achieved using these existing systems is not adequate. 
   Another limitation with many existing systems is that provisions are typically not made for including one or more electrical or optical devices on or in the removable media member. For some applications, however, it may be desirable to provide one or more electrical and/or optical devices on or in the removable media member. In addition, it may be desirable to provide one or more electrical and/or optical links or connections between the electrical and/or optical devices on or in the removable media and the receiving device so that, for example, various functions may be performed by the removable media member. 
   SUMMARY 
   Many advantages may be had by providing methods and apparatus for receiving a removable media member, and more specifically, for providing tighter alignment tolerances between an inserted removable media member and a receiving device. There may also be methods and apparatus for providing one or more electrical or optical device on or in the removable media member itself, and for providing an electrical and/or optical link between the one or more electrical and/or optical devices on or in the removable media and the receiving device. 
   In a first illustrative example, an apparatus is provided for accepting a removable media member. The apparatus includes a first member and a second member, wherein the first member and the second member are adapted to move away from each other to provide a space for receiving a removable media member. Once the removable media member is inserted into the space, the first member and second member can be moved toward each other to engage and/or secure the removable media member. 
   In one illustrative example, the first member has one or more L-shaped cleats that provide a slot to receive the removable media member. The L-shaped cleats may include, for example, a first leg that extends away from the first member and toward the second member, and a second leg that extends from a distal end of the first leg and in a perpendicular direction relative to the first leg so that a channel or receiving slot is formed. The channel or receiving slot may then receive at least one side of the removable media member. 
   In some examples, two L-shaped cleats are provided for providing two spaced channels for receiving opposing sides of the removable media member. That is, the channel or slot of the first L-shaped cleat and the channel or slot of the second L-shaped cleat may be arranged so that the removable media member slides into both channels when it is inserted between the first member and the second member. In one example, the two L-shaped cleats are secured to the first member. 
   During use, the first member and the second member may be moved away from one another, and the removable media member may be slid into the channel or receiving slots provided by the one or more L-shaped cleats. The L-shaped cleats may be positioned so that that when the removable media member is received by the one or more L-shaped cleats, the removable media member is at least roughly aligned with a desired position relative to the first member and/or second member. The first member and the second member may then be moved toward one another to engage and/or secure the removable media member therebetween. 
   To remove the removable media member, the first member and the second member may be moved away from each other. Because at least part of the removable media member is positioned in the channel or slot of the one or more L-shaped cleats, and when the one or more L-shaped cleats are secured to the first member, the removable media member may be pulled away from the second member by the L-shaped cleats as the first member and second member are moved away from each other. 
   To provide better alignment between the removable media member and the first and/or second members, the second member may include one or more alignment pins that extend toward the first member. The removable media member may then include one or more receiving holes for receiving the one or more alignment pins. The alignment pins and receiving holes may provide improved alignment between the removable media member and the first and/or second members when the removable media member is secured between the first member and the second member. 
   The one or more L-shaped cleats may be used to pull the removable media member away from the second member, thereby separating the one or more receiving holes of the removable media member from the one or more alignment pins that are extending from the second member. With the one or more receiving holes separated from the alignment pins, the removable media member then may be more easily removed from between the first member and the second member. 
   In some examples, the removable media member may include one or more electrical and/or optical devices. For example, the removable media member may include one or more transistors, diodes, sensors, vertical cavity surface emitting lasers (VCSELs), LEDs, electro-statically actuated actuators or pumps, or any other suitable electrical and/or optical device. To provide power and/or to communicate or control the one or more electrical and/or optical devices, an electrical and/or optical interface may be provided between the first and/or second member and the removable media member. 
   In one illustrative example, one or more electrical contact pads are provided on a surface of the removable media member. The one or more electrical contact pads may be electrically connected to the one or more electrical and/or optoelectronic devices of the removable media member, such as by a metal trace or the like. In one illustrative example, the first member may include one or more spring biased probes that extend outward away from the first member and toward the second member. The one or more spring biased probes may be positioned to align with the one or more electrical contact pads of the removable media member when the removable media member is at a desired positioned between the first member and the second member. In some cases, the one or more alignment pins discussed above may help provide alignment between the one or more spring biased probes of the first member and the one or more electrical contact pads of the removable media member. When the first member and the second member are moved toward one another to secure and/or engage the removable media member, the one or more spring biased probes of the first member may make electrical contact with the one or more electrical contact pads of the removable media member. 
   To help separate the one or more spring biased probes of the first member from the one or more electrical contact pads when the first member is moved away from the second member, an outward or separating bias may be provided between the first member and the removable media member. This outward bias may be overcome when the first member and the second member are moved toward each other to secure and/or engage the removable media member. However, when the first member and the second member are moved away from each other to release the removable media member, the outward bias may separate the one or more spring biased probes of the first member from the one or more electrical contact pads, which may make the removal of the removable media member from between the first member and the second member easier and may help protect the spring bias probes from damage. 
   In another illustrative example, one or more optical transmitters and/or receivers may be provided on a surface of the removable media member. The one or optical transmitters and/or receivers may be electrically connected to the one or more electrical and/or optoelectronic devices of the removable media member, such as by an optical waveguide, metal trace, or the like. In this example, the first member and/or second member may include one or more optical transmitters and or optical receivers, which may be positioned to align with the one or more optical transmitters and/or receivers of the removable media member when the removable media member is at a desired positioned between the first member and the second member. In some cases, the one or more alignment pins discussed above may help provide alignment between the optical transmitters and/or optical receivers of the first and/or second members and the one or more optical transmitters and/or optical receivers of the removable media member. When the first member and the second member are moved toward one another to secure and/or engage the removable media member, the one or more optical transmitters and/or optical receivers of the first and/or second members become aligned with the one or more optical transmitters and/or optical receivers of the removable media member to provide a communications link therebetween. 
   In some cases, the removable media member may include one or more fluid ports for accepting or delivering fluid to and/or from the removable media member. In one illustrative example, the removable media member may be a fluidic cartridge adapted for use in flow cytometry. The fluidic cartridge may include one or more flow channels. The one or more fluid ports may be in fluid communication with at least some of the flow channels. When so provided, one or more corresponding fluid ports may be provided on the first member and/or second member, as desired. The one or more fluid ports of the first member and/or second member are positioned to align with at least selected ones of the fluid ports of the removable media member when the removable media member is secured and/or engaged by the first member and the second member. 
   In some cases, one or more alignment pins as discussed above may be provided to help provide alignment between the one or more fluid ports of the first member and/or second member and the one or more fluid ports of the removable media member. In addition, an outward bias may be provided between the removable media member and the first member and/or second member to help separate the one or more fluid ports of the first member and/or second member and the one or more fluid ports of the removable media member when the first member is moved away from the second member. 
   In some cases, the manufacture of the removable media member may create a ridge, a burr, or other imperfections, particularly around the outer perimeter of the removable media member. In one example, a fluidic cartridge may be manufactured by laminating several layers or sheets together, and then cutting individual fluidic cartridges from the laminated structure. At the cut lines, ridges, burrs, and other imperfections may arise. To help the removable media member seat correctly along the first and/or second member, a groove or other relief structure may provided in receiving surface of the first and/or second member to accommodate the one or more imperfections in the removable media member. In one illustrative example, a groove may extend along a groove path that corresponds to, for example, the perimeter of the removable media member in anticipation of imperfections that might occur along the perimeter of the removable media member. It is contemplated, however, that a groove or other relief structure may be provided at any location where an anticipated imperfection might occur in the removable media member. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  is a perspective view of an illustrative portable cytometer; 
       FIG. 2  is a schematic view of the illustrative portable cytometer of  FIG. 1 ; 
       FIG. 3  is a more detailed schematic diagram showing the portable cytometer of  FIG. 2  with the cover not yet depressed; 
       FIG. 4  is a more detailed schematic diagram showing the portable cytometer of  FIG. 2  with the cover depressed; 
       FIG. 5  is a perspective view of another illustrative portable cytometer; 
       FIG. 6  is a perspective side view of the illustrative portable cytometer of  FIG. 5 ; 
       FIG. 7  is another perspective view of the illustrative portable cytometer of  FIG. 5 ; 
       FIG. 8  is a perspective view of the first plate or member of the illustrative portable cytometer of  FIG. 5 ; 
       FIG. 9  is a perspective view of the lower cleat of the first plate or member of  FIG. 8 ; 
       FIG. 10  is a perspective view of the upper cleat of the first plate or member of  FIG. 8 ; 
       FIG. 11  is a perspective view of the outward bias wedge of the first plate or member of  FIG. 8 ; 
       FIG. 12  is a perspective view of the second plate or member of the illustrative portable cytometer of  FIG. 5 ; 
       FIG. 13  is a perspective of a modified second plate of member of the illustrative cytometer; 
       FIG. 14   a  is a plan view of an insertable cartridge; 
       FIG. 14   b  is an edge view of the cartridge; 
       FIG. 14   c  is a graph of a cartridge flow test; 
       FIG. 14   d  is a graph of a cartridge test of flow rise and decay signals; 
       FIG. 15   a  is a plan view of the cartridge having several dimensions; 
       FIG. 15   b  is a perspective view of the cartridge; 
       FIG. 16  shows a cross-section view of the top side of the cartridge showing a detector cone and a source cone relative to the flow channel window; 
       FIG. 17  is the same view as  FIG. 16  except with a cone obstruction removed; 
       FIG. 18  is the same view as  FIG. 16  except the positions of the detector and the source are reversed along with their corresponding cones; 
       FIG. 19  is the same view as  FIG. 16  except it has a multiple detector cone arrangement; and 
       FIGS. 20 and 21  show the cartridge rotated about 90 degrees relative to the positions of the detector and source in comparison to  FIG. 16 . 
   

   DESCRIPTION 
   For illustrative purposes, a portable flow cytometer system is described. Present approaches may have wide applicability to numerous other removable media systems including, for example, removable or replaceable filters, removable ink and toner cartridges, removable data storage devices such as magnetic or optical disks, removable magnetic tape cartridges, removable memory sticks, as well as many other systems and/or devices that use removable media. 
     FIG. 1  is a perspective view of an illustrative portable cytometer. The portable cytometer is generally shown at  10 , and includes a housing  12  and a removable or replaceable cartridge  14 . The removable cartridge  14  may have a front side, a back side, and one or more lateral sides extending between the front side and the back side. The illustrative housing  12  includes a base  16 , a cover  18 , and a hinge  20  that attaches the base  16  to the cover  18 . The base  16  includes an array of light sources  22 , associated optics and the necessary electronics for operation of the cytometer. The cover  12  includes a manual pressurizing element, pressure-chambers with control microvalves, and an array of light detectors  24  with associated optics, as further described in U.S. Pat. No. 6,597,438, issued Jul. 22, 2003, to Cabuz et al., and entitled “Portable Flow Cytometer”, and U.S. patent application Ser. No. 6,549,275, issued Apr. 15, 2003, to Cabuz et al., and entitled “Optical Detection System for Flow Cytometry”, both of which are incorporated herein by reference. 
   The removable member (e.g., cartridge)  14  may receive a sample fluid via a sample collector port  32 . A cap  38  may be used to protect the sample collector port  32  when the removable cartridge  14  is not in use. The removable cartridge  14  may perform blood dilution, red cell lysing, and hydrodynamic focusing for core formation. The removable cartridge  14  may be constructed similar to the fluidic circuits available from Micronics Technologies, some of which are fabricated using a laminated structure with etched fluid channels. 
   The removable cartridge  14  is inserted into the housing when the cover  18  is in the open position. The removable cartridge  14  may include holes  26   a  and  26   b  for receiving registration pins  28   a  and  28   b  in the base  16 , which help provide alignment and coupling between the different parts of the instrument. The removable cartridge  14  may also include a transparent flow stream window  30 , which is in alignment with the array of the light sources  22  and light detectors  24 . When the cover is moved to the closed position, and the system is pressurized, the cover  18  provides controlled pressures to pressure receiving ports  34   a ,  34   b , and  34   c  in the removable cartridge  14  via pressure providing ports  36   a ,  36   b  and  36   c , respectively. 
   To initiate a test, the cover  18  is lifted and a new cartridge  14  is placed and registered onto the base  16 . A blood sample is introduced into the sample collector  32 . The cover  18  is closed and the system is manually pressurized. Once pressurized, the instrument performs a white blood cell cytometry measurement. The removable cartridge  14  provides blood dilution, red cell lysing, and hydrodynamic focusing for core formation. The light sources  22 , light detectors  24  and associated control and processing electronics perform differentiation and counting of white blood cells based on light scattering signals received by the light detectors  24 . Rather than using a hinged construction for the housing  12 , it is contemplated that a sliding cartridge slot or any other suitable construction may be used, including that described further below with respect to  FIGS. 5-12 . 
     FIG. 2  is a schematic view of the illustrative portable cytometer of  FIG. 1 . As above, the base  16  may include an array of light sources  22 , associated optics and the necessary control and processing electronics  40  for operation of the cytometer. The base  16  may also include a battery  42  for powering the cytometer. The cover  12  is shown having a manual pressurizing element  44 , pressure-chambers  46   a ,  46   b  and  46   c  with control microvalves, and an array of light detectors  24  with associated optics. The removable cartridge  14  may receive a sample fluid via the sample collector port  32 . When pressurized by the cover  18 , the removable cartridge  14  performs blood dilution, red cell lysing, and hydrodynamic focusing for core formation in an example. Once formed, the core is provided down a flow stream path  50 , which passes the flow stream window  30  of  FIG. 1 . The array of light sources  22  and associated optics in the base provide light through the core stream via the flow stream window  30 . The array of light detectors and associated optics receive scattered and non-scattered light from the core, also via the flow stream window  30 . The controller or processor  40  receives output signals from the array of detectors, and differentiates and counts selected white blood cells that are present in the core stream. 
   It is contemplated that the removable cartridge  14  may include a fluid control block  48  for helping to control the velocity of each of the fluids. In the illustrative example, the fluid control block  48  includes flow sensors for sensing the velocity of the various fluids and report the velocities to the controller or processor  40 . The controller or processor  40  may then adjust the microvalves associated with pressure-chambers  46   a ,  46   b  and  46   c  to achieve the desired pressures and thus desired fluid velocities for proper operation of the cytometer. In some examples, and as further described below, one or more electrical connections may be provided between the processor  40  in the base  16  and the flow sensors on the removable cartridge  14 . 
   Because blood and other biological waste can spread disease, the removable cartridge  14  may have a waste reservoir  52  downstream of the flow stream window  30 . The waste reservoir  52  receives and stores the fluid of the flow stream in the removable cartridge  14 . When a test is completed, the removable cartridge may be removed and disposed of, in a container compatible with biological waste. 
     FIG. 3  is a more detailed schematic diagram showing the portable cytometer of  FIG. 2  with the cover  18  not yet depressed.  FIG. 4  is a more detailed schematic diagram showing the portable cytometer of  FIG. 2  with the cover depressed. The cover  18  is shown having a manual pressurizing element  44 , pressure-chambers  46   a ,  46   b  and  46   c , and control microvalves generally shown at  60 . The array of light sources and detectors are not shown in these Figures. 
   There are three pressure chambers  46   a ,  46   b  and  46   c , one for each fluid to be pressurized. In the illustrative example, pressure chamber  46   a  provides pressure to a blood sample reservoir  62 , pressure chamber  46   b  provides pressure to a lyse reservoir  64 , and pressure chamber  46   c  provides pressure to a sheath reservoir  66 . The size and shape of each pressure chamber  46   a ,  46   b  and  46   c  may be tailored to provide the desired pressure characteristics to the corresponding fluid. 
   Pressure chamber  46   a  includes a first pressure chamber  70  and a second pressure chamber  72 . A first valve  74  is provided between the first pressure chamber  70  and the second pressure chamber  72  for controllably releasing the pressure in the first pressure chamber  70  to a second pressure chamber  72 . A second valve  76 , in fluid communication with the second pressure chamber  72 , controllably vents the pressure in the second pressure chamber  72 . Each valve may be an array of electrostatically actuated microvalves that are individually addressable and controllable, as described in, for example, co-pending U.S. patent application Ser. No. 09/404,560, entitled “ADDRESSABLE VALVE ARRAYS FOR PROPORTIONAL PRESSURE OR FLOW CONTROL”, and incorporated herein by reference. Pressure chambers  46   b  and  46   c  include similar valves to control the pressures applied to the lyse reservoir  64  and sheath reservoir  66 , respectively. Alternatively, each valve may be an array of electrostatically actuated microvalves that are pulse modulated with a controllable duty cycle to achieve a controlled “effective” flow or leak rate. Alternatively, each valve may be a similar to that described in co-pending U.S. patent application Ser. No. 1100.1174101, entitled “ELECTROSTATICALLY ACTUATED VALVE”, which is incorporated herein by reference. 
   The removable cartridge  14  has pressure receiving ports  34   a ,  34   b , and  34   c  for receiving the controlled pressures from the cover  18 . The controlled pressures are provided to the blood reservoir  62 , lyse reservoir  64  and sheath reservoir  66 , as shown. The lyse reservoir  64  and sheath reservoir  66  may be filled before the removable cartridge  14  is shipped for use, while the blood reservoir  62  is filled from sample collector port  32 . A blood sample may be provided to the sample collector port  32 , and through capillary action, the blood sample may be drawn into the blood reservoir  62 . Once the blood sample is in the blood reservoir  62 , the cover  18  may be closed and the system may be pressurized. 
   A flow sensor is provided in-line with each fluid prior to hydrodynamic focusing. Each flow sensor  80 ,  100  and  102  measures the velocity of the corresponding fluid. The flow sensors may be thermal anemometer type flow sensors, and/or of the microbridge or microbrick type flow sensor. Microbridge flow sensors are described in, for example, U.S. Pat. Nos. 4,478,076, 4,478,077, 4,501,144, 4,651,564, 4,683,159, and 5,050,429, all of which are incorporated herein by reference. An output signal from each flow sensor  80 ,  100  and  102  is provided to controller or processor  40  via one or more electrical connection between the removable cartridge and the base. 
   The controller or processor  40  opens the first valve  74  when the velocity of the blood sample drops below a first predetermined value and opens the second valve  76  when the velocity of the blood sample increases above a second predetermined value. Valves  84 ,  86 ,  94  and  96  operate in a similar manner to control the velocities of the lyse and sheath fluids. 
   During operation, and to pressurize the system, the manual pressurizing element  44  is depressed. In the example shown, the manual pressurizing element  44  includes three plungers, with each plunger received within a corresponding one of the first pressure chambers. The plungers create a relatively high non-precision pressure in the first pressure chambers. Lower, controlled pressures are built in the secondary chambers by opening the first valves  70 ,  84  and  94 , which produce a controllable leak into the secondary chambers. If two much pressure builds up in the secondary pressure chambers, the corresponding vent valve  76 ,  86  and  96  are opened to relieve the pressure. 
   When closing the cover  18 , the normally open first valves  74 ,  84  and  94  are closed while the vent valves  76 ,  86  and  96  are open. When a predetermined pressure P is achieved in the first pressure chambers, the vent valves  76 ,  86  and  96  are closed, and the first valves  74 ,  84  and  94  are opened to build a lower pressure P′ in the secondary pressure chambers. The controlled pressure in the secondary pressure chambers provide the necessary pressures to the fluidic circuit of the removable cartridge  14  to produce fluid flow for the blood, lyse and sheath. The velocity of the fluid flow is then measured by the downstream flow sensors  80 ,  100  and  102 . Each flow sensor provides an output signal that is used by the controller or processor  40  to control the operation of the corresponding first valve and vent valve to provide a desired and constant flow rate for each fluid. 
   Downstream valves generally shown at  110  may also be provided. Controller or processor  40  may close downstream valves  110  until the system is pressurized. This may help prevent the blood, lyse and sheath from flowing into the fluid circuit before the circuit is pressurized. In another example, downstream valves  110  are opened by mechanical action when the cover is closed. 
     FIG. 5  is a perspective view of another illustrative portable cytometer. The basic operation of the portable cytometer of  FIG. 5  is similar to that described above with respect to  FIGS. 1-4  above. The portable cytometer of  FIG. 5  is generally shown at  120 , and includes a base  122 , a first member  124 , a second member  126 , a clamp frame  128  with clamp lever  130 , an air buffer module  132 , a valve module assembly  134  with polymer microvalves, an air accumulator module  136 , and an optics assembly  140 . 
   In the illustrative example, the second member  126  is fixed to the base  122 . A number of shoulder screws  142   a ,  142   b ,  142   c  and  142   d  ( 142   d  not shown in  FIG. 5 ) pass through holes in the first member  124  and are secured to the second member  126 . Springs  144   a ,  144   b ,  144   c  and  144   d  ( 144   d  not shown in  FIG. 5 ) are placed between the first member  124  and the head of the corresponding shoulder screw  142   a ,  142   b ,  142   c  and  142   d . The springs  144   a ,  144   b ,  144   c  and  144   d  provide a bias force to the first member  124  toward the second member  126 . 
   The clamp frame  128  is secured to the second member  126  as shown. The clamp lever  130  interacts with the clamp frame to provide an outward bias force to the first member away from the second member  126 . By moving the clamp lever  130  in a first direction, the first member  124  is moved away from the second member  126  by overcoming the inward bias force provided of spring  144   a ,  144   b ,  144   c  and  144   d . By moving the clamp lever  130  in a second opposite direction, the first member  124  is moved toward the second member  126 , assisted by the inward bias force provided of spring  144   a ,  144   b ,  144   c  and  144   d.    
   During operation, the clamp lever  130  may be moved in the first direction to move the first member  124  away from the second member  126 , leaving a space therebetween. A removable media member, such as a removable fluidic cartridge  150 , may then be slid into the space. The removable cartridge  150  may have a front side, a back side, and one or more lateral sides extending between the front side and the back side, as shown. The clamp lever  130  may then be moved in the second direction to move the first member  124  toward the second member  136  to secure and/or engage the removable media member  150 , as shown in  FIG. 5 .  FIG. 6  is a perspective side view of the illustrative portable cytometer of  FIG. 5 . 
   In one illustrative example, the removable media member  150  has one or more fluid ports in the front and/or back sides, similar to that described above with respect to  FIGS. 1-4 . It is contemplated that the one or more fluid ports may be adapted to accept either a gas or a liquid, depending on the application. The second member  126  of the illustrative example includes corresponding fluid ports that align with the one or more fluid ports of the removable media member  150 . One such fluid port is shown at  160  in  FIG. 6 . A fluid port gasket (see  FIG. 12  below) may be secured to the second member  126  to help provide a better seal, if desired. 
   A fluid control module may then be fluidly coupled to the fluid ports of the second member  126 . In the illustrative example, the fluid control module includes the air accumulator module  136 , the valve module assembly  134  with polymer microvalves, and the air buffer module  132 . The air accumulator module  136  includes an internal chamber for accumulating air pressure. A port (not shown) may be provided from the internal chamber of the air accumulator  136  to an air pressure source. The accumulated air pressure may be supplied to the valve module assembly  134 . The valve module assembly may include one or more microvalves, such as polymer microvalves as disclosed in U.S. patent application Ser. No. 1100.1174101, entitled “ELECTROSTATICALLY ACTUATED VALVE”, which is incorporated herein by reference. In the illustrative example, the valve module assembly  134  may provide three separate pressure channels including a blood channel, a lyse channel and a sheath channel, as shown and described above with respect to  FIGS. 1-4 . The valve module assembly  134  may be controlled by a controller in base  122  to provide three separate controlled pressures to air buffer module  132 . Air buffer module  132  buffers the controlled pressures, and delivers the pressurized air to the fluid ports of the removable media member  150  via the fluid ports that pass in or through the second member  126 . 
   In some cases, the removable media member  150  may include one or more electrical and/or optical devices. For example, and in the illustrative example, the removable media member  150  may include three flow sensors, with each flow sensor measuring the flow rate of the pressurized fluid through one of the three separate pressure channels of the removable media member  150 . Like above, the flow sensors may be thermal anemometer type flow sensors, and/or of the microbridge or microbrick type flow sensor, commercially available from Honeywell International. Microbridge flow sensors are described in, for example, U.S. Pat. Nos. 4,478,076, 4,478,077, 4,501,144, 4,651,564, 4,683,159, and 5,050,429, all of which are incorporated herein by reference. An output signal from each flow sensor is provided to controller or processor in base  122 , via an electrical and/or optical coupling between the removable media member and the second member  126 . 
   The optical assembly module  140  may include one or more light sources (e.g. VCSELs) on one side of the removable cartridge  150 , one or more light detectors on the opposite side of the removable cartridge  150 , and associated optics. When so provided, the removable cartridge  150  may include a transparent flow stream window, which is in alignment with the one or more light sources and one or more light detectors. The air buffer module  132 , valve module assembly  134 , and air accumulator module  136  may be controlled to form a core stream down a flow stream path that passes the flow stream window in the removable cartridge  150 . The light sources, when activated, provide light through the core stream via one side of the flow stream window. The optical detectors receive scattered and non-scattered light from the core stream via the opposite side of the flow stream window. A controller or processor in the base  122  then receives output signals from the detectors, and differentiates and counts selected white blood cells that are present in the core stream. 
     FIG. 7  is another perspective view of the illustrative portable cytometer of  FIG. 5 , further illustrating additional detail.  FIG. 7  shows a hole  170  through the first member  124  and second member  126 . The hole  170  may allow the one or more light sources and one or more light detectors of the optical assembly module  140  to directly access the flow stream window of the removable cartridge (not shown in  FIG. 7 ). 
     FIG. 7  also shows one or more spring biased probes secured to the first member  124 . The one or more spring biased probes may be positioned to align with the one or more electrical contact pads on the removable cartridge when the removable cartridge is at a desired positioned between the first member  124  and the second member  126 . In the illustrative example, three arrays of spring biased probes  174   a ,  174   b  and  174   c  are provided, with each array mounted via a small PC board and secured within a corresponding hole in the first member  124 . The holes in the first member  124  may provide access to the reverse side of the spring bias probes, which in some examples, may provide a convenient location to make an electrical connection between a controller in the base  122  and each spring bias probe. 
   In addition, or alternatively, it is contemplated that one or more optical transmitters and/or optical detectors may be secured to the first and/or second member. The one or more optical transmitters and/or optical detectors may be positioned to align with the one or more optical detectors and/or optical transmitters on the removable cartridge when the removable cartridge is at a desired positioned between the first member  124  and the second member  126 . This may provide an optical link between the removable cartridge and the first member and/or second member  126 , as desired. 
     FIG. 8  is a perspective view of the first member  124  of the illustrative portable cytometer of  FIG. 5 .  FIG. 8  shows the opposite side of the three arrays of spring biased probes  174   a ,  174   b  and  174   c  of  FIG. 7 . As can be seen, each spring bias probes is biased by a spring in an outward direction away from the first member  124  and toward the removable cartridge (not shown in  FIG. 8 ). The spring biased probes may be positioned to align with the one or more electrical contact pads on the removable cartridge when the removable cartridge is at a desired positioned between the first member  124  and the second member  126 . When the first member  124  and the second member  126  are moved toward one another to secure and/or engage the removable cartridge, the spring biased probes may make electrical contact with the one or more electrical contact pads on the removable cartridge. 
   To help separate the spring biased probes from the one or more electrical contact pads on the removable cartridge when the first member  124  is moved away from the second member  126 , an outward or separating bias  178  may be provided between the first member  124  and the removable cartridge. Referring momentarily to  FIG. 11 , the outward bias  178  may include a wedge  180  and a spring  182 . The spring  182  may be positioned in a recess  184  in the first member  124 , with the wedge  180  biased in an outward direction by the spring  182 . 
   Referring back to  FIG. 8 , the outward bias  178  may be overcome when the first member  124  and the second member  126  are moved toward each other to secure and/or engage the removable cartridge. However, when the first member  124  and the second member  126  are moved away from each other to release the removable cartridge, the outward bias  178  may separate the one or more spring biased probes  174   a ,  174   b  and  174   c  from the one or more electrical contact pads of the removable cartridge, which may make the removal of the removable cartridge from between the first member  124  and the second member  126  easier and may help protect the spring bias probes from damage during the removal process. 
   The first member  124  may also have one or more L-shaped cleats that provide a slot to receive the removable cartridge. In the illustrative example of  FIG. 8 , an upper L-shaped cleat  190  and a lower L-shaped cleat  192  are provided. The L-shaped cleats  190  and  192  may each include, for example, a first leg  194  that extends away from the first member  124  and toward the second member, and a second leg  196  that extends from a distal end of the first leg  194  and in a perpendicular direction relative to the first leg  194  so that a channel or receiving slot  198  is formed. The channel or receiving slot  198  may then receive one side of the removable media member. In the illustrative example, the upper L-shaped cleat  190  includes a second leg  196  that extends in a downward direction, and the lower L-shaped cleat  192  includes a second leg that extends in an upward direction. In addition, the upper L-shaped cleat  190  and the lower L-shaped cleat  192  are spaced so that two spaced channels  196  are provided for receiving opposing sides (e.g. upper side and lower side) of the removable cartridge. That is, the channel or slot of the upper L-shaped cleat  190  and the channel or slot of the lower L-shaped cleat  192  are arranged so that the removable cartridge slides into both channels when it is inserted between the first member  124  and the second member  126 . In the illustrative example, the two L-shaped cleats are secured to the first member  124 . 
   An alignment pin  200  may be provided toward the back of the first member  124  to engage the back of the removable cartridge. The alignment pin  200  may be positioned to stop the removable cartridge at or near the desired insertion position between the first member  124  and the second member  126 . 
   During use, the first member  124  and the second member  126  may be moved away from one another, and the removable cartridge may be slid into the channel or receiving slots  198  provided by the L-shaped cleats  190  and  192  until the removable cartridge engages the alignment pin  200 . The L-shaped cleats  190  and  192  may be positioned so that that when the removable cartridge is received by the L-shaped cleats  190  and  192 , the removable cartridge is at least roughly aligned with a desired position relative to the first member  124  and/or second member  126 . The first member  124  and the second member  126  may then be moved toward one another to engage and/or secure the removable cartridge therebetween. 
   To remove the removable cartridge, the first member  124  and the second member  126  may be moved away from each other. Because the upper and lower edges of the removable cartridge are positioned in the channel or slot  198  of the L-shaped cleats  190  and  192 , the removable cartridge is pulled away from the second member  126  by the second legs  196  of the L-shaped cleats  190  and  192  as the first member  124  and second member  126  are moved away from each other. 
   To provide better alignment between the removable media member and the first member  124  and/or the second members  126 , the second member  126  may include one or more alignment pins  200   a - 200   c  that extend toward the first member (see  FIG. 12 ). The removable media member  150  may then include one or more receiving holes for receiving the one or more alignment pins  200   a - 200   c . The alignment pins  200   a - 200   c  and receiving holes may provide improved alignment between the removable media member  150  and the first member  124  and/or second member  126  when the removable media member  150  is secured between the first member  124  and the second member  126 . 
   The L-shaped cleats  190  and  192  may be used to pull the removable media member  150  away from the second member  126 , thereby separating the one or more receiving holes of the removable media member  150  from the one or more alignment pins  200   a - 200   c  that are extending from the second member  126 . With the one or more receiving holes separated from the alignment pins  200   a - 200   c , the removable media member  150  then may be more easily removed from between the first member  124  and the second member  126 . 
     FIG. 9  is a perspective view of the lower cleat  192  of  FIG. 8 . The illustrative lower cleat  192  includes a first leg  194   a  and a second leg  196   a , wherein the second leg  196   a  extends from a distal end of the first leg  194   a  and in a perpendicular direction to form a channel or receiving slot  198   a . A mounting leg  202   a  may extend from the first leg  194  as shown, for mounting the lower cleat  192  to the first member  124 . 
     FIG. 10  is a perspective view of the upper cleat  190  of  FIG. 8 . The illustrative upper cleat  190  includes a first leg  194   b  and a second leg  196   b , wherein the second leg  196   b  extends from a distal end of the first leg  194   b  and in a perpendicular direction to form a channel or receiving slot  198   b . A mounting leg  202   b  may extend from the first leg  194   b  as shown, for mounting the upper cleat  190  to the first member  124 . 
     FIG. 12  is a perspective view of the second plate or member  126  of the illustrative portable cytometer of  FIG. 5 . The second member  126  may be fixed to the base  122  by screws that are threaded into screw holes  210   a  and  210   b . As detailed above, the second member  126  may further include a hole  170  that may allow the one or more light sources and one or more light detectors of the optical assembly module  140  to directly access the flow stream window of the removable cartridge. 
   In the illustrative example, the second member  126  includes a flat major surface with a recessed portion for receiving the removable cartridge. To provide better alignment between the removable cartridge and the first member  124  and/or the second members  126 , the second member  126  may include one or more alignment pins  200   a - 200   c  that extend toward the first member. The removable cartridge  150  may then include one or more receiving holes for receiving the one or more alignment pins  200   a - 200   c . The alignment pins  200   a - 200   c  and receiving holes may provide improved alignment between the removable cartridge and the first member  124  and/or second member  126  when the removable cartridge is secured between the first member  124  and the second member  126 . 
   Additional recesses  212  and  214  may be included to receive the second legs  196   a  and  196   b  of the upper L-shaped cleat  190  and lower L-shaped cleat  192 , respectively (see  FIGS. 8-10 ). By providing relief for the second legs  196   a  and  196   b  of the upper L-shaped cleat  190  and lower L-shaped cleat  192 , the removable cartridge may directly engage the surface of the second member  126 . 
   In some cases, the manufacture of the removable cartridge may create a ridge, a burr, or other imperfections, particularly around the outer perimeter of the removable cartridge. In one example, a fluidic cartridge may be manufactured by laminating several layers or sheets together, and then cutting individual fluidic cartridges from the laminated structure. At the cut lines, ridges, burrs, and/or other imperfections may arise. To help the removable cartridge seat flush with the surface of second member  126 , a groove  216  or other relief structure may be provided in the receiving surface of the second member  126  to accommodate the one or more imperfections in the removable cartridge. In the illustrative example of  FIG. 12 , a groove  216  may extend along a groove path that extends around the perimeter of the removable cartridge. It is contemplated, however, that a groove or other relief structure may be provided at any location where an anticipated imperfection might occur in the removable cartridge. It is also contemplated that a groove or other relief structure may be provided in the receiving surface of the first member  124 , if desired. 
   In one illustrative example, the removable cartridge has one or more fluid ports, similar to that described above with respect to  FIGS. 1-4 . It is contemplated that the one or more fluid ports may be adapted to accept either a gas or a liquid, depending on the application. The second member  126  of the illustrative example includes corresponding fluid ports  220   a - 220   c  that align with the one or more fluid ports of the removable cartridge. A fluid port gasket  222  may be secured to the second member  126  to help provide a better seal, if desired. 
     FIG. 13  is a perspective view of the second member  126  with the single gasket  222  of  FIG. 12 . This single gasket may have been fraught with difficulties such as leaks. A cure against leaks at the interface having the single piece gasket  222  may have included a thicker tape under the gasket and more clamp pressure from the first element  124  on the cartridge  150  to push the cartridge with greater force against the second element  126 . Gasket  222  may be removed and replaced with three separate gaskets  223 ,  224  and  225 , for the ports  220   a ,  220   b  and  220   c  for the movement of the sheath fluid, the lyse and the sample, respectively, from second member  126  to the cartridge  150  at its input ports  231 ,  232  and  233 . The gaskets may be O-ring shaped and made from a silicone or like material. The replacement of gasket  222  with the individual gaskets  223 ,  224  and  225  may provide much greater assurance for prevention of leaks at those fluidic connections between the cartridge  150  and the second member  126 . In view of  FIG. 6 , insufficient clamp pressure of first member  124  against the cartridge  150  towards the second member  126  may affect the integrity of the seals at the interface of the two sets of ports, particularly without the individual gaskets. Leaks at this interface not only may result in fluid coming out of the system but allow air to enter the fluidic network or circuit. 
   For easier insertion of cartridge  150  and accurate alignment of the cartridge with the second member  126 , alignment pins  234 ,  235  and  236  may be shorter ( FIG. 13 ) than the original pins and replace the one or more original alignment pins  200   a ,  200   b  and  200   c  ( FIG. 12 ). The key alignment may be provided by pin  234  of the second member  126  relative to hole  237  of card  150 . The other pins  235  and  236  may be present to prevent swinging of the cartridge about the pivot guide pine  234 . More or less alignment pins may instead be present in the second member  126 . Alignment pins  234 ,  235  and  236  may fit into alignment holes  237 ,  238  and  239 , respectively. 
   Flow sensors  226 ,  227  and  228  may be situated in cartridge  150  and may be connected via three arrays of spring biased probes  174   a ,  174   b  and  174   c , respectively, on the first member  124  to electronics situated off the cartridge. The flow sensors  226 ,  227  and  228  may be utilized for the monitoring the flow of the sheath fluid, the lyse and the sample, respectively. The flow sensors may be placed in the cartridge in an area  240  of  FIG. 14   a . The flow sensors  226 ,  227  and  228  may be countersunk into the cartridge with their electrical contacts facing away from the cartridge so that when cartridge  150  is inserted in the direction  199  in the slot between members  124  and  126 , from left to right in  FIG. 7 , such that the contacts of the flow sensors line up with the arrays of the spring based probes  174   a - 174   c , in the upper right portion  240  ( FIG. 14   a ), so as to make an appropriate electrical contact with them. Between the flow sensors and a surface of the cartridge to make connection with fluid ports communication with the sheath fluid, lyse and the sample, there may be a tape and/or adhesive on the surface with holes to the ports to seal the flow sensor and prevent leakage of the sheath, lyse and/or sample from the fluidic connections between the flow sensors and the cartridge. To better insure against leakage, the tape and/or adhesive may be replaced or overlaid with a gasket of similar shape having three holes lining up with the ports. The gasket may be a custom molded gasket for the interface between the flow sensors and the cartridge. Or the interface may incorporate separate O-ring-like gaskets or seals. An adhesive on the flow channel at the top of the respective sensor may be used along with the custom gasket to ease the interchangeability and reusability of the flow sensors from one cartridge to another. The flow sensors may be insertable and removable relative to the cartridge. Once a cartridge is used and becomes disposable, the flow sensors may be removed, cleaned and inserted into a new cartridge to be used for testing and analysis of a sample. Inexpensive flow sensors may be placed in the cartridge in a more permanent manner and be disposed along with the cartridge after completion of the usage. The flow sensor gasket placed in the cartridge may facilitate the moving of the flow sensors from cartridge to cartridge without the risk of leakage. 
   The cartridge  150  may be fabricated from a plastic or a plastic-like material. Some portions of the walls are thicker for structural rigidity and other portions are thinner so as to provide space in the cartridge for storage of fluids, microfluidic channels and mechanisms. Also, the portion with the fluid flow channel has thin walls to provide a narrow channel for single file flow of the particles in a core stream and to adequately support the light source and detector optics for correct focusing and observation of the core stream in the flow channel. Thin walls may be situated where the various fluid reservoirs and mixing channels are located in the cartridge. 
   An illustrative layer arrangement of cartridge  150 , from the bottom up as cartridge  150  is positioned in  FIG. 14   a  with the flow channel  247  to the left at the bottom side, and with an edge view of the cartridge  150  in  FIG. 14   b , may include: layer  261 —PET—5 mils normal; layer  262 —ACA—6 mils normal; layer  263 —PET—2 mils normal; layer  264 —ACA—4 mils normal; layer  265 —PET—2 mils inverted; layer  266 —ACA—6 mils normal; layer  267 —PET—5 mils inverted; layer  268 —ACA—4 mils normal; layer  269 —PET—5 mils inverted; layer  270 —ACA—6 mils normal; layer  271 —acrylic—125 mils normal; layer  272 —ACA—6 mils normal; and layer  273 —PET—5 mils normal. There may be more or less layers sometimes depending on the desired specifications and application of card  150 . The Figures are not necessarily to scale. 
   The thin layers may be of a very precisely controlled thickness. Again, the cytometer flow channel, mixing channels, sample storage, serpentine channels (such as those for mixing lyse and blood), and other items of critical dimensions may be located in these layers. The walls of the storage should be adequate to ensure compliance of the storage. The thick layer is of less precise thickness. The reagent storage and waste reservoirs are located in this layer. The thick layer provides the mechanical stiffness to the cartridge. The thin precise layers may “interface” with the cartridge clamp frame in such a manner to provide precise alignment of the cartridge relative to the optical subsystem incorporating the light source and detection arrangement. The precision thickness film may be made so as to control the spacing between the sample flow and the light source to ensure appropriate focusing. The thin precise layers may have a very carefully controlled thickness with possibly a less than four percent variation of the thickness. Thickness variation may be more critical in the optical area of the flow channel than other areas of the cartridge. 
   The thin walls may at times present observable phenomena relative to the cartridge, where there is a slow flow rise and decay with starting and stopping of a flow. Effects of those phenomena may be noted in graphed checks of a cartridge.  FIG. 14   c  shows a sample flow signal of the cartridge having a removable embedded flow sensor. The graph reveals plot in terms of signal in volts versus measurement units. Curves  301 ,  302 ,  303 ,  304 ,  305 ,  306 ,  307 ,  308  and  309  indicated 7 micro liters per minute (um/min), 5 um/min, 3 um/min, 1.4 um/min, 1 um/min, 0.7 um/min, 0.5 um/min and 0 um/min, respectively. The high signal volts versus a small number of measurement units reveal a good star-up and the converse reveals a slow start-up which may be due to wall flexing and/or air in the system.  FIG. 14   d  reveals sheath flow rise and zero flow decay signals for the cartridge. The measurements are signal in volts versus time in seconds. Plots  311 ,  312  and  313  represent zero A, zero F and zero D data, respectively. Plots  314 ,  315  and  316  represent 300 E, 500 C and 700 B data, respectively. 
   Flexing may affect the focus of the optics relative to the flow channel and problematic data taking. Also, thin walls may affect the pumping and the flow of the fluids in the microfluidic circuits thereby affecting the data taking. One reason is the reservoir walls may flex or have a concave or convex shape relative to the other portions of the cartridge. For instance, the surface of the reagent reservoir may be concave on some of the cartridges. That may prevent the surface touching the manifold surface of the cartridge holder when clamped, and thereby permits the thin wall to flex during operation of the fluidic elements in the cartridge. On the other hand, the thin wall surface is convex, particularly if the reservoir is filled, though it may remain convex when the reservoir is empty. Or the wall of a reservoir may be concave when the reservoir is sort of empty and convex when it is rather full. That means when a flow such as a sheath fluid flow is shut off there may be a slow change of pressure or a remnant of fluid that continues to flow. When the flow is turned on, there may be a delay of the starting of the fluid flow or a build up to operating pressure. These delays of fluidic action may be due to the contraction and expansion of the reservoir volume, respectively due the flexing of the thin walls. Sheath fluid control may be very critical and significantly affected by flexing thin walls. The change of sheath fluid flow may affect the width and speed of the core stream in the flow channel and lead to inaccurate or unreliable data accession by the cytometer detection system. Flexing of the thin walls may lead to air bubbles entering the system thereby affecting proper operation of the microfluidics of the cartridge, since air in the fluidic network may resulting in notable expansion and contraction with changes in pressure and/or temperature. There should be no flow when the sheath fluid is shut off. The start of the flow and/or pressure should be almost immediate when the flow is turned on. Without good starts and stops of the fluid, data taking may not be as reliable. When the cartridge is clamped, there may be backflow at a vent hole at the filter near the edge of the cartridge above the sample inlet. That may be because a check valve, if there is any, did not work to stop the backflow. 
   The thin walls may be reinforced with ridges. Ridges or beam-like structures may be also added along one of the dimensions (e.g., the lengthwise dimension) on the thin walls. Or these walls may be made thicker. These walls may consist of thin film material or materials. Additional films may stiffen the thin wall with a minimal thickness increase without compromising the small variation in thickness of the thin wall. Ridges or beam-like structures may also be added to further reinforce the thickened thin walls. Care should be taken because thickened and/or ridge-reinforced walls may prevent adequate clearance for the fluid and/or result in an air bubble trap. Also, the areas of thin walls on the cartridge may be made smaller or minimized where practical along with achieving the ensured performance expected of the components affected by conditions of the thin walls. 
   The reagent reservoirs of the cartridge originally had small holes at the top of them, one hole for each, for the independent filling them. However, there occasionally appeared to be an issue with bubbles entering the reagent reservoirs and a subsequent introduction of “compliance” in the fluidic network. For instance, when the reservoir was filled, it may be difficult to be sure that it was filled up to the top of the hole when closing, sealing or plugging the hole without any air being trapped in at the fill hole. For example, sealing a reagent reservoir fill hole may often inject an air bubble into the reservoir. The reservoirs may instead be filled thought the input ports to eliminate the issue. The small holes may be permanently plugged. The input ports would be used anyway for flow purposes. It may be noted that positive pressure in the cartridge after flow testing is stopped may force air bubbles back to the large reservoir. The pressure in the reservoir forced a backflow which returned the air to the reservoir. The disposable cartridges may have prepackaged fluids put on the cartridges during assembly. 
   As to the waste reservoir, the porous vent membrane may be moved further from the inlet since the entry of water would tend to seal the vent. The vent may be better moved to the opposite side of the reservoir without the membrane. However, for the finished cartridge the membrane or something like it may be used in the new vent location. The old vent may be intentionally plugged. 
   The cartridge may have three bellows valves that may be activated with a single lever on the edge of the cartridge. However, the valves may be individually activated to aid in filling. The reservoirs may be bench filled with a Harvard syringe pump. There may be fluid creep between the reservoirs when moving between reservoirs which could be due to a flexible surface of the reservoir wall. Individually activated valves that could be closed after a reservoir is filled may alleviate this problem. The volume of the large reservoir is not the same among the cartridges which may be due to reservoir compliance. Increased wall thickness may solve this issue, although it might have an effect on the optics referencing. There may be a concern relative to making electrical contact to the sensor since it would be recessed deep into the cartridge. 
   Cartridge  151  may be modified to accommodate advanced optics for the cytometer system. There are several approaches that may be achieved.  FIG. 16  shows a cross-section view of the top side of the cartridge  150  showing a detector cone  244  and a source cone  243  relative to the flow channel windows  241  and  242 , respectively. A counter-sunk opening  251  on the detector side may be sunk below the broad surface  246  of the cartridge  150  where a flow channel  247  is situated within thin layers  253  close to the general surface  245  opposite of surface  246  and close to a top surface  252  of opening  251 . The source cone  243  may have an angle  281  of about a 20 degree wide spread. In other embodiments, the source cone  243  may have an angle that ranges up to 50 degrees. The direction of the light source cone  243  to the flow channel  247  may be at an angle  282  of about 45 degrees relative to the surface  245 . There appears to be no interference of the cartridge window  242  relative to cone  243  since the window may be rather close to the surface  245 . The flow channel  247  may contain a core stream that flows upwards out of the sheet containing the  FIG. 16 . Alternatively, the core stream may instead flow downward into the sheet of the figure; however, there might be a greater probability of air being taken into the core stream. The source cone and the detector cone are set at an angle relative to the window surface or flow channel of the cartridge so that there is not a line-of-sight or direct impingement of the source light through the flow channel to the detector. Nominally, the directions of the source and detector cones may be at about 90 degrees relative to each other. 
   Detector cone  244  may have an angle width  283  of about 60 degrees. In other embodiments, the detector cone  244  may have an angle width  283  that ranges up to 65 degrees. The direction  284  of the detector cone relative to the surface  252  may be about 45 degrees. That means the lower portion of detector cone  244  towards the surface  246  may be at about an angle of 15 degrees or so relative to surfaces  246  and  252 . The length  275 , thicknesses  276 ,  277  and  295 , and lengths  278  and  279  may affect the clearances for the respective cones. The window thickness  277  may be about one-sixty-fourth of an inch, i.e., 0.015625 in. The step or depth  295  of the opening  251  in the cartridge  150  maybe about one-eighth of an inch, i.e., 0.125 in. Many of the dimensions may be available or inferable from  FIGS. 14   b  and  15   a . The opening  251  has an edge on one side at the surface  246  and a point at a center of the edge has a distance y or depth  295  to the surface  252  along a line approximately perpendicular to the surface  246 . The point has a distance z from the edge along a straight line in the opening  251  to the target area or flow channel  247 . The ratio of y/z may be less than 0.3. In other embodiments, the ratio of y/z is less than 0.26. Detector cone  244  has a vertex situated at the target area. The vertex angle may have a cosine greater than 0.1. In other embodiments, the vertex angle may have a cosine equal to or greater than 0.5. Since the flow channel  247  is close to surface  252  and the angle of cone  244  is wide and the direction of the cone is significantly to one side, the cone  244  may encounter an obstruction at the edge of opening  251  on or near the surface  246 . This obstruction may prevent some light having significant data from being detected from cone  244 . Some of the light being provided to the flow channel  247  may be occluded. This obstruction may prevent proper illumination of the flow channel. The consequence may include detected signals with low signal to noise ratios or no signals which may have been present were it not for the obstruction. If y/z is not less than 0.26, and in some embodiments, not less than 0.2, the obstruction may be eliminated by removing some of the material from the surface  246  of the cartridge  150  at the edge of the opening  251  to make a clearance for cone  244  at a new surface  254 , thus increasing z as shown in  FIG. 17 . 
   Another approach to the detector cone  244  obstruction issue may be to swap the positions of the light source and detector with the corresponding cones  243  and  244 , respectively, as shown in  FIG. 18 . Then source cone  243  may be facing window  241  proximate to surface  252  of opening  251 . With the direction of the source cone  243  relative to the surface  252  being at an angle  282  of about 45 degrees and the cone  243  having an angle of  281  about 20 degrees wide, the portion the cone  243  closest to surface  252  may be at an angle of about 35 degrees relative to a plane parallel to the surfaces  246  and  252 . It is apparent that the source cone  243  easily clears the edge of the opening  251  proximate to surface  246  of the cartridge  150 . On the other side of the cartridge having surface  245 , the wide detector cone  244  appears to encounter no obstruction relative to window  242  and surface  245  of the cartridge  150 . The reason apparently is that the flow channel  247  and its encompassing structure of thin films  253  are so close the surface  245  that there is virtually no obstruction from a small edge of window  242 . 
   If the 20 degree source cone  243  is replaced with a 45 degree angle  285  or greater source cone  248  at window  241 , as shown in  FIG. 19 ; there might be a slight obstruction of the cone  248  at the edge of the opening  251  at surface  246 , if cone  248  were rotated further to the right than illustrated by an angle  286  in the Figure. If this obstruction or occluding occurred, it may be cleared by removing some of the material from the cartridge  150  at the edge of the opening  251  and surface  240 , as shown in  FIG. 17 . Also added may be a 30 degree angle  287  detector cone  249  for detecting scattered light and/or direct light. Cone  249  direction angle  288  may be about 45 degrees. In the configuration of  FIG. 19 , detector cone  244  appears situated adequately in that no obstruction is apparent. 
   However, several other approaches that do not involve removal of cartridge  150  material for any of wide cone arrangements may solve the above-noted obstruction issues. One is to turn the orientation of the cut-out opening  251  in the plane of surface  246  about 90 degrees clockwise or counterclockwise relative to the source and detector cones. The dimensions  255  and  256  of the opening  251  may be approximately about 15 by 20 millimeters, respectively. The dimensions  257  and  258  of window  241 ,  242  may be approximately 2 by 5 millimeters, respectively. The dimensions may have different values. Dimensions  289  and  291  may be calculated.  FIG. 21  shows the shorter dimension  255  parallel to the direction of the slant of the cones  243 ,  244 ,  248  and  249 , along the length of flow channel  247 . Thus, in  FIG. 21 , the orientation angles  293  and  294  of cones  243  and  244 , respectively, may be about 90 degrees. This orientation of the flow channel  247  is also evident in  FIGS. 16-19 . The turning the opening  251  about 90 degrees may put the longer dimension  256  (about 33 percent longer) of the opening  251  and the direction of the flow channel  247  approximately parallel to the cone slants so as to provide more clearance relative to the edge of the opening  251  at surface  246  to avoid being be an obstruction or occlusion to, for instance, cones  244  or  248  at an edge of the surface  246  on the side of cartridge  150 . 
     FIGS. 20 and 21  show the source cone  243  and detector  244  configuration of  FIG. 16  accommodated by the longer dimension  256  of opening  251 , which may be accomplished as noted above. The approach here would involve shifting the orientation of the slants of the axes of the source and detector cones  243 ,  244 ,  248  and  249  to be towards the direction of the flow channel  247 .  FIG. 21  is an end view of a cross-section of opening  251 . Contrary to  FIGS. 20 and 21 ,  FIGS. 16-19  show the angles of the detector and source cones as transverse to the direction of the flow channel  247 .  FIGS. 16-21  are not necessarily drawn to scale. 
   In the present specification, some of the matter may be of a hypothetical or prophetic nature although stated in another manner or tense. 
   Although the invention has been described with respect to at least one illustrative example, many variations and modifications will become apparent to those skilled in the art upon reading the present specification. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.