Abstract:
Methods and systems to remove gas bubbles from liquids and to improve uniform fluid flow through a region of a membrane in a microfluidic device, including to reduce, remove, and/or prevent gas bubbles on a surface of a porous membrane. An example membrane bubble trap system may include a fluid channel connected to a bubble pathway that surrounds an opening sealed with a membrane. The bubble pathway may be configured to collect bubbles in fluid that passes through the membrane through buoyancy forces and through a directional feature of a curved surface placed above the membrane.

Description:
CROSS REFERENCE 
       [0001]    This application is a continuation-in-part of U.S. Utility patent application Ser. No. 12/228,081, filed Jul. 16, 2008, and claims the benefit of: 
         [0002]    U.S. Provisional Application No. 61/253,356, filed Oct. 20, 2009; 
         [0003]    U.S. Provisional Application No. 61/253,365, filed Oct. 20, 2009; 
         [0004]    U.S. Provisional Application No. 61/253,373, filed Oct. 20, 2009; 
         [0005]    U.S. Provisional Application No. 61/253,377, filed Oct. 20, 2009; 
         [0006]    U.S. Provisional Application No. 61/253,383, filed Oct. 20, 2009; and 
         [0007]    U.S. Provisional Application No. 61/266,019, filed Dec. 2, 2009; 
         [0008]    all of which are incorporated herein by reference in their entireties. 
     
    
     TECHNICAL FIELD 
       [0009]    Disclosed herein are methods and systems to capture or trap gas bubbles in liquids, such as to improve uniformity of fluid flow through a region of a membrane in a microfluidic device. 
       BACKGROUND 
       [0010]    When a liquid fluid flows through, or is forced through a membrane, gas bubbles within the liquid may collect on a surface of the membrane and may interfere with liquid flow through the membrane. 
         [0011]    In an assay system, a membrane, such as a nitrous cellulose based membrane, may be used in combination with a fluid sample to detect the possible presence of a chemical or biological target in a sample. These membranes provide support and large binding capacity for immobilizing markers that will indicate the presence of chemical or biological targets, such as taught in U.S. Pat. No. 4,066,512 (Biologically active membrane material, Chung Jung Lai et al). An example of a process that uses these membranes is an enzyme-linked immunosorbent assay (ELISA). 
         [0012]    In a lab, the ELISA process is usually carried in a microtiter plate. The membrane is placed in the bottom of the plate and various fluids are washed over the membrane. Test that are run outside the lab require the chemistry and sample to be applied to a self contained device. In a self contained device, such as a pregnancy test, the reagents needed to carry out the ELISA process are immobilized in different regions of the membrane. Devices such as these began with U.S. Pat. No. 4,999,163 (Disposable, pre-packaged device for conducing immunoassay procedures). These self contained devices use capillary action to move fluid through the membrane. Sample is placed on a collection port and the fluid moves passively through the device as the reaction is carried out. The scale of these devices is too large to have an issue of gas bubbles, unlike microfluidic devices. 
         [0013]    Microfluidic devices deal with small volumes. These devices have been developed for the ELISA process because of the benefit of using much smaller amounts of fluid to run the same test traditionally performed in a micro-titer plate. Most of these microfluidic devices are made cheaply out of polystyrene and manufactured by standard lithography techniques. The surfaces of these devices must provide the proper chemistry for immobilization of molecules needed for the ELISA process. 
         [0014]    Nitrous cellulose membranes can be combined with microfluidic devices to bring the benefit of a larger reaction area in the membrane with the smaller volume use of the microfluidic device. Most microfluidic devices still use capillary forces to move fluid, while some can be assembled so fluid flow is pushed through a region of the membrane, either by gravity or centrifugal forces. 
         [0015]    When fluid contacts the membrane, it is generally retained in pores of the material by surface tension and capillary forces. Certain pressure is required to overcome these forces and push more fluid or gas through the membrane. It has been observed that there is less resistance to push fluid rather than gas through a wet membrane. This imbalance causes a gas bubble trapped on the surface of the membrane to interfere with the fluid flow through that section of the membrane. If uniform fluid flow through that section is required—for example to evenly deposit material contained in the fluid on that membrane or to ensure that material embedded in that membrane has full contact with the fluid—it will not be achieved if a gas bubble is trapped on the surface, as fluid will flow around the gas bubble and not come in contact with the membrane directly underneath it. If the membrane is performing the ELISA process, this can lead to a significant reduction of signal as the fluid sample or reagents cannot fully contact the membrane. 
         [0016]    These gas bubbles can form when fluid with gas travels to a termination region blocked by a membrane. The gas bubbles must either be forced through the membrane or stay in the termination region. As fluid channels are reduced to ever smaller dimensions, a need for effective gas bubble blocking increases. 
         [0017]    To be most effective, microfluidic devices with fluid and gas flow need to deal with the problems created by the presence of interfering gas bubbles. A number of techniques have been tried to mitigate bubble formation and bubble entrapment with varying degrees of success. US application 20090123338 to Guan; Xiaosheng (2009) teaches a method to prevent bubble when filling a microfluidic device. European patent EP1792655 teaches a method for trapping bubbles upstream of a predetermined region. Methods like these try to compensate for unknown amounts of gas in a constantly flowing system. Most methods to mitigate bubble formation have been focused on constantly removing the bubbles so they do not interfere with cell cultures or other biological substances that can be affected by gas bubbles. 
       SUMMARY 
       [0018]    Disclosed herein are methods and systems to capture or trap gas bubbles in fluids, including to trap a predetermined volume of gas bubbles. If the maximum amount of gas needed to trap is known, the system can be designed to work at or below that amount, without the need for complicated vents or active methods to remove gas above a certain amount. 
         [0019]    A gas bubble trap may be positioned proximate to an active region of a porous membrane to capture or trap gas bubbles from a liquid fluid that flows through the membrane, and to maintain the trapped gas away from the membrane. The regions of membrane can be considered termination points that gas bubbles can interfere with. Trapping the gas bubbles around the termination points instead of in contact with them prevents fluid contact problems with the membrane region. Relying on buoyancy or centrifugal force, structures can be made to create pathways that collect the gas bubbles, thus directing them into trapping regions instead of active regions that they may interfere with. 
         [0020]    Systems and methods to trap gas bubbles, as disclosed herein, may be implemented with self-contained, point-of-care, portable, point-of-care, user-initiated fluidic assay systems. Example assays include diagnostic assays and chemical detection assays. Diagnostic assays include, without limitation, enzyme-linked immuno-sorbent assays (ELISA), and may include one or more sexually transmitted disease (STD) diagnostic assays. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
         [0021]    In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the leftmost digit(s) of a reference number identifies the drawing in which the reference number first appears. 
           [0022]      FIG. 1  is a process flowchart of a method of performing an assay with a substantially self-contained, point-of-care, user-initiated fluidic assay system. 
           [0023]      FIG. 2  is a block diagram of a portable, point-of-care, user-initiated fluidic assay system. 
           [0024]      FIG. 3  is a perspective view of a portable, point-of-care, user-initiated fluidic assay system  300 . 
           [0025]      FIG. 4  is a process flowchart of a method of preparing a portable, point-of-care, user-initiated fluidic assay system. 
           [0026]      FIG. 5  is a process flowchart of a method of using an assay system prepared in accordance with  FIG. 4 . 
           [0027]      FIG. 6  is a perspective view of another assay system  600 , including a cover illustrated in a first position. 
           [0028]      FIG. 7  is a cross-sectional view of assay system  600 , including plungers  702 ,  704 , and  706 , wherein the cover is illustrated in the second position. 
           [0029]      FIG. 8  is another cross-sectional view of assay system  600 , wherein plungers  702 ,  704 , and  706  are in corresponding initial or first positions. 
           [0030]      FIG. 9  is another cross-sectional view of assay system  600 , wherein plungers  702 ,  704 , and  706  are in respective first intermediate positions. 
           [0031]      FIG. 10  is another cross-sectional view of assay system  600 , wherein plunger  704  is in a second position, and plungers  702  and  704  are in respective second intermediate positions. 
           [0032]      FIG. 11  is another cross-sectional view of assay system  600 , wherein plungers  702 ,  704  and  706  are in respective second positions. 
           [0033]      FIG. 12  is an expanded cross-sectional view of a portion of assay system  600 , including a portion of plunger  706  in the first position corresponding to  FIG. 8 . 
           [0034]      FIG. 13  is another expanded cross-sectional view of a portion assay system  600 , including a portion of plunger  706  in the intermediate position corresponding to  FIG. 9 . 
           [0035]      FIG. 14  is another expanded cross-sectional view of a portion of assay system  600 , including a portion of plunger  706  in the second position corresponding to  FIGS. 10 and 11 . 
           [0036]      FIG. 15  is a cross-sectional perspective view of another assay system  1500 . 
           [0037]      FIG. 16  is a cross-sectional perspective view of another assay system  1600 . 
           [0038]      FIG. 17  is cross-sectional view of a mechanical actuator system. 
           [0039]      FIG. 18  is a profile view of a membrane bubble trap system. 
           [0040]      FIG. 19  is a cross-sectional view of the membrane bubble trap system. 
           [0041]      FIG. 20  is an upwardly directed view of an upper portion of the membrane bubble trap system. 
           [0042]      FIG. 21A through 21C  depicts example movement of fluid and gas bubbles through fluid channels and collection of gas bubbles. 
           [0043]      FIGS. 22A through 22E  are additional cross-sectional views of the membrane bubble trap system, to illustrate fluid flow and bubble trapping. 
           [0044]      FIG. 23  is an upwardly directed view of an upper portion of another membrane bubble trap system, including multiple interconnected membrane active areas, each including a corresponding bubble termination trap. 
       
    
    
       [0045]    In the drawings, the leftmost digit(s) of a reference number may correspond to the drawing in which the reference number first appears. 
       DETAILED DESCRIPTION 
       [0046]    Disclosed herein are methods and systems to capture or trap gas bubbles in fluids, including to trap a predetermined volume of gas bubbles. 
         [0047]    The methods and systems to trap gas bubbles are described herein with respect to example point-of-care, user-initiated fluidic assay methods and systems, for illustrative purposes. The methods and systems to trap gas bubbles are not, however, limited to the assay methods and systems disclosed herein. Based on the teachings herein, one skilled in the art will understand that the methods and system to trap gas bubbles may be implemented with respect to other assay systems, including diagnostic assays and chemical assays. 
         [0048]    An immunoassay is a biochemical test to detect a substance, or measure a concentration of a substance, in a biological sample such as blood, saliva, or urine, using a reaction between an antibody and an antigen specific to the antibody. 
         [0049]    An immunoassay may be used to detect the presence of an antigen or an antibody. For example, when detecting an infection, the presence of an antibody against the pathogen may be measured. When detecting hormones such as insulin, the insulin may be used as the antigen. 
         [0050]    Accordingly, where a method or system is described herein to detect a primary binding pair molecule using a corresponding second binding pair molecule, it should be understood that the primary binding pair molecule may be an antibody or an antigen, and the second binding pair molecule may be a corresponding antigen or antibody, respectively. Similarly, where a method or system is described herein to detect an antibody or antigen, the method or system may be implemented to detect a corresponding antigen or antibody, respectively. 
         [0051]    Immunoassays may also be used to detect potential food allergens and chemicals, or drugs. 
         [0052]    Immunoassays include labeled immunoassays to provide a visual indication of a binding pair of molecules. Labeling may include an enzyme, radioisotopes, magnetic labels, fluorescence, agglutination, nephelometry, turbidimetry and western blot. 
         [0053]    Labeled immunoassays include competitive and non-competitive immunoassays. In a competitive immunoassay, an antigen in a sample competes with labeled antigen to bind with antibodies. The amount of labeled antigen bound to the antibody site is inversely proportional to the concentration of antigen in the sample. In noncompetitive immunoassays, also referred to as sandwich assays, antigen in a sample is bound to an antibody site. The labeled antibody is then bound to the antigen. The amount of labeled antibody on the site is directly proportional to the concentration of the antigen in the sample. 
         [0054]    Labeled immunoassays include enzyme-linked immuno-sorbent assays (ELISA). 
         [0055]    In an example immunoassay, a biological sample is tested for a presence of a primary binding pair molecule. A corresponding binding pair molecule that is specific to the primary binding pair molecule is immobilized on an assay substrate. The biological sample is contacted to the assay substrate. Any primary binding pair molecules in the biological sample attach to, or are captured by the corresponding binding pair molecules. The primary binding pair molecules are also contacted with labeled secondary binding pair molecules that attach to the primary binding pair molecules. This may be performed subsequent to, prior to, or simultaneously with the contacting of the primary binding pair molecule with the corresponding immobilized binding pair molecule. Un-reacted components of the biological sample and fluids may be removed, or washed from the assay substrate. Presence of the label on the assay substrate indicates the presence of the primary binding pair molecule in the biological sample. 
         [0056]    The label may include a directly detectable label, which may be visible to a human observer, such as gold particles in a colloid or solution, commonly referred to as colloidal gold. 
         [0057]    The label may include an indirect label, such an enzyme whereby the enzyme works on a substrate to produce a detectable reaction product. For example, an enzyme may attach to the primary binding pair molecule, and a substance that the enzyme converts to a detectable signal, such as a fluorescence signal, is contacted to the assay substrate. When light is directed at the assay substrate, any binding pair molecule complexes will fluoresce so that the presence of the primary binding pair molecule is observable. 
         [0058]    An immunoassay may utilize one or more fluid solutions, which may include a dilutent solution to fluidize the biological sample, a conjugate solution having the labeled secondary binding pair molecules, and one or more wash solutions. The biological sample and fluids may be brought into contact, concurrently or sequentially with the assay substrate. The assay substrate may include an assay surface or an assay membrane, prepared with a coating of the corresponding binding pair molecules. 
         [0059]    As described above, the second binding pair molecules may include an antigen that is specific to an antibody to be detected in a biological sample, or may include antibody that is specific to an antigen to be detected in the biological sample. By way of illustration, if the primary binding pair molecule to be detected is an antigen, the immobilized binding pair molecule and the secondary labeled binding pair molecule will be antibodies, both of which react with the antigen. When the antigen is present in the biological sample, the antigen will be immobilized by the immobilized antibody and labeled by the labeled secondary antibody, to form a sandwich-like construction, or complex. 
         [0060]    It is known that non-specific or un-reacted components may be beneficially removed using wash solutions, often between processes and/or prior to a label detection process, in order to improve sensitivity and signal-to-noise ratios of the assay. Other permutations are possible as well. For example, a conjugate solution, such as a labeled secondary binding pair molecule solution may be mixed with or act as a sample dilutent to advantageously transport the biological sample to the assay substrate, to permit simultaneous binding of the primary binding pair molecule and the labeled secondary binding pair molecule to the immobilized binding pair molecule. Alternatively, or additionally, the sample dilutent may include one or more detergents and/or lysing agents to advantageously reduce deleterious effects of other components of the biological sample such as cellular membranes, non-useful cells like erythrocytes and the like. 
         [0061]    Those skilled in the art will readily recognize that such fluid components and the order of the reactionary steps may be readily adjusted along with concentrations of the respective components in order to optimize detection or distinguishment of analytes, increase sensitivity, reduce non-specific reactions, and improve signal to noise ratios. 
         [0062]    As will be readily understood, if the secondary antibody is labeled with an enzyme instead of a fluorescent or other immediately detectable label, an additional substrate may be utilized to allow the enzyme to produce a reaction product which will be advantageously detectable. An advantage of using an enzyme based label is that the detectable signal may increase over time as the enzyme works on an excess of substrate to produce a detectable product. 
         [0063]      FIG. 1  is a process flowchart of a method  100  of detecting a primary binding pair molecule in a biological sample, using a substantially self-contained, point-of-care, user-initiated fluidic assay system. The primary binding pair molecule may correspond to an antibody or an antigen. 
         [0064]    At  102 , a biological sample is provided to the assay system. The biological sample may include one or more of a blood sample, a saliva sample, and a urine sample. The biological sample may be applied to a sample substrate within the assay system. 
         [0065]    At  104 , a fluidic actuator within the assay system is initiated by a user. The fluidic actuator may include a mechanical actuator, such as a compressed spring actuator, and may be initiated with a button, switch, or lever. The fluidic actuator may be configured to impart one or more of a physical force, pressure, centripetal force, gas pressure, gravitational force, and combinations thereof, on a fluid controller system within the assay system. 
         [0066]    At  106 , the biological sample is fluidized with a dilutent fluid. The dilutent fluid may flow over or through the sample substrate, under control of the fluid controller system. 
         [0067]    At  108 , the fluidized biological sample is contacted to a corresponding binding pair molecule that is specific to primary binding pair molecule. The corresponding binding pair molecule may be immobilized on an assay substrate within the assay system. The fluidized biological sample may flow over or through the assay substrate, under control of the fluid controller system. 
         [0068]    Where the fluidized biological sample includes the primary binding pair molecule, the primary binding pair molecule attaches to the corresponding binding pair molecule and becomes immobilized on the assay substrate. For example, where the second binding pair molecule includes a portion of a pathogen, and where the biological sample includes an antibody to the pathogen, the antibody attaches to the antigen immobilized at the assay substrate. 
         [0069]    At  110 , a labeled conjugate solution is contacted to the assay substrate, under control of the fluid controller system. The labeled conjugate solution includes a secondary binding pair molecule to bind with the primary binding pair molecule. Where the primary binding pair molecule is immobilized on the assay substrate with the corresponding binding pair molecule, the secondary binding pair molecule attaches to the immobilized primary binding pair molecule, effectively creating a sandwich-like construct of the primary binding pair molecule, the corresponding binding pair molecule, and the labeled secondary binding pair molecule. 
         [0070]    The secondary binding pair molecule may be selected as one that targets one or more proteins commonly found in the biological sample. For example, where the biological sample includes a human blood sample, the secondary binding pair molecule may include an antibody generated by a non-human animal in response to the one or more proteins commonly found in human blood. 
         [0071]    The secondary binding pair molecule may be labeled with human-visible particles, such as a gold colloid, or suspension of gold particles in a fluid such as water. Alternatively, or additionally, the secondary binding pair molecule may be labeled with a fluorescent probe. 
         [0072]    Where the labeled secondary binding pair molecule attaches to a primary binding pair molecule that is attached to a corresponding binding pair molecule, at  110 , the label is viewable by the user at  112 . 
         [0073]    Method  100  may be implemented to perform multiple diagnostic assays in an assay system. For example, a plurality of antigens, each specific to a different antibody, may be immobilized on one or more assay substrates within an assay system. Similarly, a plurality of antibodies, each specific to a different antigen, may be immobilized on one or more assay substrates within an assay system 
         [0074]      FIG. 2  is a block diagram of a portable, point-of-care, user-initiated fluidic assay system  200 , including a housing  202 , a user-initiated actuator  204 , a fluidic pump  206 , and an assay result viewer  218 . 
         [0075]    Pump  206  includes one or more fluid chambers  210 , to contain fluids to be used in an assay. One or more of fluid chambers  210  may have, without limitation, a volume in a range of 0.5 to 2 milliliters. 
         [0076]    Pump  206  includes a sample substrate  214  to hold a sample. Sample substrate  214  may include a surface or a membrane positioned within a cavity or a chamber of housing  202 , to receive one or more samples, as described above. 
         [0077]    Sample substrate  214  may include a porous and/or absorptive material, which may be configured to absorb a volume of liquid in a range of 10 to 500 μL, including within a range of up to 200 μL, and including a range of approximately 25 to 50 μL. 
         [0078]    Pump  206  includes an assay substrate  216  to hold an assay material. Assay substrate  216  may include a surface or a membrane positioned within a cavity or chamber of housing  202 , to receive one or more assay compounds or biological components, such as an antigen or an antibody, as described above. 
         [0079]    Fluid chambers  210  may include a waste fluid chamber. 
         [0080]    Pump  206  further includes a fluid controller system  208 , which may include a plurality of fluid controllers, to control fluid flow from one or more fluid chambers  212  to one or more of sample substrate  214  and assay substrate  216 , responsive to actuator  204 . 
         [0081]    Actuator  204  may include a mechanical actuator, which may include a compressed or compressible spring actuator, and may include a button, switch, lever, twist-activator, or other user-initiated feature. 
         [0082]    Assay result viewer  218  may include a display window disposed over an opening through housing  202 , over assay substrate  216 . 
         [0083]      FIG. 3  is a perspective view of an portable, point-of-care, user-initiated fluidic assay system  300 , including a housing  302 , a user-initiated actuator button  304 , a sample substrate  306 , and a sample substrate cover  308 . Sample substrate cover  308  may be hingedly coupled to housing  302 . 
         [0084]    Assay system  300  further includes an assay result viewer  310 , which may be disposed over an assay substrate. Assay result view  310  may be disposed at an end of assay system  300 , as illustrated in  FIG. 3 , or along a side of assay system  300 . 
         [0085]    Assay system  300  may have, without limitation, a length in a range of 5 to 8 centimeters and a width of approximately 1 centimeter. Assay system  300  may have a substantially cylindrical shape, as illustrated in  FIG. 3 , or other shape. 
         [0086]    Assay system  300 , or portions thereof, may be implemented with one or more substantially rigid materials, and/or with one or more flexible or pliable materials, including, without limitation, polypropylene. 
         [0087]    Example portable, point-of-care, user-initiated fluidic assay systems are disclosed further below. 
         [0088]      FIG. 4  is a process flowchart of a method  400  of preparing a portable, point-of-care, user-initiated fluidic assay system. Method  400  is described below with reference to assay system  200  in  FIG. 2 , for illustrative purposes. Method  400  is not, however, limited to the example of  FIG. 2 . 
         [0089]    At  402 , a binding pair molecule is immobilized on an assay substrate, such as assay substrate  216  in  FIG. 2 . The binding pair molecule may include an antigen specific to an antibody, or an antibody specific to an antigen. 
         [0090]    At  404 , a first one of fluid chambers  210  is provided with a dilutent solution to fluidize a sample. 
         [0091]    At  406 , a second one of fluid chambers  210  is provided with a labeled secondary binding pair molecule solution. 
         [0092]    At  408 , a third one of fluid chambers  210  is provided with a wash solution, which may include one or more of a saline solution and a detergent. The wash solution may be substantially similar to the dilutent solution. 
         [0093]      FIG. 5  is a process flowchart of a method  500  of using an assay system prepared in accordance with method  400 . Method  500  is described below with reference to assay system  200  in  FIG. 2 , and assay system  300  in  FIG. 3 , for illustrative purposes. Method  500  is not, however, limited to the examples of  FIG. 2  and  FIG. 3 . 
         [0094]    At  502 , a sample is provided to a sample substrate, such as sample substrate  214  in  FIG. 2 , and sample substrate  306  in  FIG. 3 . 
         [0095]    At  504 , a user-initiated actuator is initiated by the user, such as user-initiated activator  204  in  FIG. 2 , and button  304  in  FIG. 3 . The user initiated actuator acts upon a fluid controller system, such as fluid controller system  208  in  FIG. 2 . 
         [0096]    At  506 , the dilutent solution flows from first fluid chamber and contacts the sample substrate and the assay substrate, under control of the fluid controller system. 
         [0097]    As the dilutent fluid flows over or through the sample substrate, the sample is dislodged from the sample substrate and flows with the dilutent solution to the assay substrate. 
         [0098]    At  508 , the labeled secondary binding pair solution flows from the second fluid chamber and contacts the assay substrate, under control of the fluid controller system. The labeled secondary binding pair solution may flow directly to the assay substrate or may flow over or through the sample substrate. 
         [0099]    At  510 , the wash solution flows from the third fluid chamber and washes the assay substrate, under control of fluid controller system  208 . The wash solution may flow from the assay substrate to a waste fluid chamber, 
         [0100]    At  512 , assay results are viewable, such as at assay result viewer  218  in  FIG. 2 , and assay result viewer  310  in  FIG. 3 . 
         [0101]    An assay substrate may include a nitrocellulose-based membrane, available from Invitrogen Corporatation, of Carlsbad, Calif. 
         [0102]    Preparation of a nitrocellulose-based membrane may include incubation for approximately thirty (30) minutes in a solution of 0.2 mg/mL protein A, available from Sigma-Aldrich Corporation, of St. Louis, Mo., in a phosphate buffered saline solution (PBS), and then dried at approximately 37° for approximately fifteen (15) minutes. 1 μL of PBS may be added to the dry membrane and allowed to dry at room temperature. Alternatively, 1 μL of an N-Hydroxysuccinimide (NHS) solution, available from Sigma-Aldrich Corporation, of St. Louis, Mo., may be added to the dry membrane and allowed to dry at room temperature. 
         [0103]    An assay method and/or system may utilize or include approximately 100 μL of PBS/0.05% Tween wash buffer, available from Sigma-Aldrich Corporation, of St. Louis, Mo., and may utilize or include approximately 100 μL of protein G colloidal gold, available from Pierce Corporation, of Rockland, Ill. 
         [0104]    An assay method and/or system may be configured to test for Chlamydia, and may utilize or include a sample membrane treated with wheat germ agglutinin, to which an approximately 50 μL blood sample is applied. Approximately 150 μL of a lysing solution may then be passed through the sample membrane and then contacted to an assay substrate. Thereafter, approximately 100 μL of a colloidal gold solution may be contacted to the assay substrate. Thereafter, approximately 500 μL of a wash solution, which may include the lysing solution, may be contacted to the assay membrane without passing through the sample membrane. 
         [0105]    Additional example assay features and embodiments are disclosed below. Based on the description herein, one skilled in the relevant art(s) will understand that features and embodiments described herein may be practiced in various combinations with one another. 
         [0106]      FIG. 6  is a perspective view of an assay system  600 , including a body  602  having a sample collection region  604  to receive a sample collection pad or membrane  606 , which may include a porous material such as, for example, a glass fiber pad, to absorb a fluid sample. 
         [0107]    In the example of  FIG. 6 , sample collection region  604  is positioned between first and second O-rings  608  and  610 , and system  600  includes a cover  612  slideably moveable relative to body  602 , between a first position illustrated in  FIG. 6 , and a second position described below with reference to  FIG. 7 . 
         [0108]      FIG. 7  is a cross-sectional view of assay system  600 , wherein cover  612  is illustrated in the second position, and sample collection region  604  is bounded by an outer surface of body  602 , an inner-surface of cover  612 , and O-rings  608  and  610 . O-rings  608  and  610  may provide a hermetic seal between sample collection region  604  and an external environment. When cover  612  is in the second position, sample collection region  604  may be referred to as a sample collection chamber. 
         [0109]    In  FIG. 6 , sample collection region  604  includes openings  614  and  616  through the surface of body  602  associated with fluid passages within body  602 . Opening  614  may be positioned adjacent to sample collection pad  606 , and opening  616  may be positioned beneath sample collection pad  606 . System  600  may be configured to provide a fluid through opening  614  into sample collection region  604  and to receive the fluid from sample collection region  604  through opening  616 , to cause the fluid to pass through sample collection pad  606 . 
         [0110]    Body  602  may include an assay region  618  formed or etched within the surface of body  602 , having an opening  620  through the surface of body  602  to receive fluid from an associated fluid passage. Assay region  618  may include one or more additional openings to corresponding fluid passages within body  602 , illustrated here as openings  622 ,  624 , and  626 , to permit the fluid to exit assay region  618 . 
         [0111]    Assay region  618  may be configured to receive a test membrane having one or more reactive areas, each reactive area positioned on the test membrane in alignment with a corresponding one of openings  622 ,  624 , and  626 . 
         [0112]    System  600  may include a substantially transparent cover to enclose assay region  618 , such as to permit viewing of the test membrane, or portions thereof. The cover may include one or more fluid channels to direct fluid from opening  620  to the membrane areas aligned with openings  622 ,  624 , and  626 . Where system  600  includes a cover over assay region  618 , assay region  618  may be referred to as an assay chamber. 
         [0113]    In  FIG. 7 , system  600  includes plungers  702 ,  704 , and  706 . Plunger  706  is illustrated here as a multi-diameter or stepped plunger. Plunger  702  includes O-rings  708  and  710 . Plunger  704  includes an O-ring  712 . Plunger  706  includes O-rings  714  and  716 . O-rings  708 ,  710 ,  712 ,  714 , and  716  may be sized to engage corresponding inner surface portions of body  602 . Plungers  702 ,  704 , and  706  are each moveable within body  602  between respective first and second positions and, together with the inner surfaces of body  602 , define fluid chambers  718 ,  720 ,  722 , and  724 . 
         [0114]    In the example of  FIG. 7 , body  602  includes fluid passages  726  and  728  between corresponding openings  614  and  616  and fluid chamber  724 , a fluid passage  730  between fluid chamber  724  and opening  620  of assay region  618 , and fluid passages between each of openings  622 ,  624 , and  626  of assay region  618  and a waste chamber  740 . Waste chamber  740  may include an absorptive material to receive fluid from one or more fluid chambers of system  600 . Body  602  may include a fluid passage  742  between waste chamber  740  and the outer surface of body  602 , such as to release air displaced by fluid received within waste chamber  740 . 
         [0115]    Body  602  may include one or more of fluid passages  744 ,  746 , and  748  in fluid communication with corresponding fluid chambers  718 ,  720 , and  722 . One or more of fluid passages  744 ,  746 , and  748  may have an opening through the outer surface of body  602 , which may be used to provide one or more assay fluids to a corresponding fluid chamber during preparation procedure. Such an opening through the outer surface of body  602  may be plugged or sealed subsequent to the preparation procedure, such as illustrated in  FIGS. 8-11 . Alternatively, or additionally, one or more of fluid passages  744 ,  746 , and  748  may include an opening to another fluid chamber of system  600 , such as to provide a fluid bypass around one or more other fluid chambers and/or plungers. 
         [0116]    Example operation of system  600  is described below with reference to  FIGS. 8-14 . 
         [0117]      FIG. 8  is a cross-sectional view of system  600 , wherein plungers  702 ,  704 , and  706  are in corresponding initial or first positions. 
         [0118]      FIG. 9  is a cross-sectional view of system  600 , wherein plungers  702 ,  704 , and  706  are in respective first intermediate positions. 
         [0119]      FIG. 10  is a cross-sectional view of system  600 , wherein plunger  704  is in a second position, and plungers  702  and  704  are in respective second intermediate positions. 
         [0120]      FIG. 11  is a cross-sectional view of system  600 , wherein plungers  702 ,  704  and  706  are in respective second positions. 
         [0121]      FIGS. 8-11  may represent sequential positioning of plungers  702 ,  704  and  706  in response to a force in a direction  750  of  FIG. 7 . 
         [0122]      FIG. 12  is an expanded view of a portion of system  600 , including a portion of plunger  706  in the first position corresponding to  FIG. 8 . 
         [0123]      FIG. 13  is an expanded view of a of portion system  600 , including a portion of plunger  706  in the intermediate position corresponding to  FIG. 9 , and including fluid directional arrows. 
         [0124]      FIG. 14  is an expanded view of a portion of system  600 , including a portion of plunger  706  in the second position corresponding to  FIGS. 10 and 11 . 
         [0125]    During a preparation process, fluid chambers  718 ,  720 , and  722 , may be provided with corresponding first, second, and third fluids, and fluid chamber  724  may provided with a gas, such as air. The fluids in one or more of fluid chambers  718 ,  720 , and  722  may be relatively incompressible compared with the gas in fluid chamber  724 . 
         [0126]    In  FIGS. 8 , when the force is applied to plunger  702  in direction  750 , the relatively incompressibility of the fluids in fluid chambers  718  and  720  transfer the force to plunger  706 . Plungers  702 ,  704 , and  706  may move together in direction  750 . 
         [0127]    As plungers  702 ,  704 , and  706  move in direction  750 , fluid within fluid chamber  724 , which may include air, travels from fluid chamber  724 , through fluid passage  730  to assay chamber  732 , and through fluid passages  734 ,  736 , and  738  to waste chamber  740 . 
         [0128]    Prior to O-ring  716  of plunger  706  passing an opening  1202  ( FIG. 12 ) of fluid passage  726 , fluid chamber  722  is substantially isolated and no fluid flows from fluid chamber  722  to fluid channel  728  or from fluid chamber  722  to fluid chamber  724 . 
         [0129]    As O-ring  716  of plunger  706  moves towards opening  1202 , and as fluid chamber  722  is correspondingly moved in direction  750  into a narrower-diameter inner surface portion of body  602 , a volume of fluid chamber  722  decreases. The reduced volume of fluid chamber  722  may increase a pressure of the fluid within fluid chamber  722 . The fluid within fluid chamber  722  may include a combination of a relatively incompressible fluid and relatively compressible fluid, such as air, which may compress in response to the increased pressure. 
         [0130]    In  FIG. 9 , when O-ring  716  is positioned between opening  1202  of fluid passage  726  and an opening  1204  of fluid passage  730 , fluid chamber  722  is in fluid communication with fluid channel  726 , while O-ring  716  precludes fluid flow directly between fluid chambers  722  and  724 . The fluid in fluid chamber  722  may thus travel from fluid chamber  722 , through fluid passage  726  to sample collection region  604 , through fluid passage  728  to fluid chamber  724 , through fluid passage fluid passage  730  to assay region  618 , and through openings  722 ,  724 , and  726  to waste chamber  740 . 
         [0131]    The fluid from fluid chamber  722  may contact and dislodge at least a portion of a sample contained within a sample pad  606 , and may carry the sample to assay region  618 , where the sample may react with a test membrane. 
         [0132]    In  FIGS. 10 , as plunger  706  reaches the second position and O-ring  716  passes opening  1204 , a recess  1002  within an inner surface of body  602  provides a fluid passage around O-ring  714 . Fluid within fluid chamber  720  travels through recess  1002 , alongside plunger  706 , through fluid passage  730  to assay chamber  732 , and through fluid passages  734 ,  736 , and  738  to waste chamber  740 . 
         [0133]    In  FIGS. 11 , as plunger  704  reaches the second position, a recess  1102  within an inner surface of body  602  provides a fluid passage around O-ring  712  of plunger  704 . Recess  1102  may correspond to fluid channel  746  in  FIG. 7 . Fluid within fluid chamber  718  travels through recess  1102 , alongside plunger  704 , through recess  102 , alongside plunger  706 , through fluid passage  730  to assay chamber  732 , and through fluid passages  734 ,  736 , and  738  to waste chamber  740 . 
         [0134]    As illustrated in  FIG. 14 , when plunger  706  is in the second position, O-ring  716  may be positioned between an opening  1402  of fluid channel  728  and an opening  1404  of fluid channel  730  to preclude fluid flow from sample collection region  604  to assay chamber  732  through fluid channels  728  and  730 . This may be useful, for example, where the fluids within fluid chamber  720  and  718  are to contact an assay membrane within assay chamber  732  rather than sample pad  606  within sample collection region  604 . This may be useful, for example, where the fluids within fluid chamber  720  and  718  include a wash fluid and/or a reactive material to wash and/or react with the assay membrane. 
         [0135]      FIG. 15  is a cross-sectional perspective view of a portion of an assay system  1500  including a housing portion  1502  and a fluid controller system, including a plurality of fluid controllers, or plungers  1504 ,  1506 , and  1508 . Fluid controllers  1504 ,  1506 , and  1508  define a plurality of fluid chambers, illustrated here as first, second, and third fluid chambers  1510 ,  1512 , and  1514 , respectively. Fluid controllers  1504 ,  1506 , and  1508  are slideably nested within one another. 
         [0136]    Housing portion  1502  includes a sample chamber  1516  to receive a sample, and may include a sample substrate, membrane or pad  1518 . Housing portion  1502  may include a cover mechanism such as a cover portion  1520 , which may be removable or hingedly coupled to housing portion  1502 , as described above with respect to  FIG. 3 . Housing portion  1502  includes a sample chamber inlet  1522  and a sample chamber outlet  1524 . 
         [0137]    Housing portion  1502  includes an assay chamber  1526  and an assay chamber inlet  1528 , and may include an assay substrate, membrane or pad  1528  to capture, react, and/or display assay results. 
         [0138]    Housing portion  1502  includes an assay result viewer, illustrated here as a display window  1532  disposed over assay chamber  1528 . 
         [0139]    Housing portion  1502  includes a waste fluid chamber  1534  to receive fluids from assay chamber  1526 . 
         [0140]    Housing portion  1502  includes a transient fluid chamber  1536  having one or more fluid channels  1538 , also referred to herein as a fluid controller bypass channel. 
         [0141]    Housing portion  1502  further includes one or more other fluid channels  1558 . 
         [0142]    First fluid chamber  1510  includes a fluid chamber outlet  1560 , illustrated here as a space between fluid controller  1506  and an inner surface of hosing portion  1502 . 
         [0143]    Second fluid chamber  1512  includes a fluid chamber outlet  1548 , illustrated here as a gate or passage through fluid controller  1504 . 
         [0144]    Third fluid chamber  1514  includes a fluid chamber outlet  1554 , illustrated here as a gate through fluid controller  1506 . 
         [0145]    Fluid controllers  1504 ,  1506 , and  1508  include one or more sealing mechanisms, illustrated here as O-rings  1540  and  1542 , O-rings  1544  and  1546 , O-rings  1550  and  1552 , and O-ring  1556 . 
         [0146]      FIG. 16  is a cross-sectional perspective view of a portion of an assay system  1600  including a housing portion  1602  and a fluid controller system, including a plurality of fluid controllers, or plungers  1604 ,  1606 , and  1608 . Fluid controllers  1604 ,  1606 , and  1608  define a plurality of fluid chambers, illustrated here as first, second, and third fluid chambers  1610 ,  1612 , and  1614 , respectively. Fluid controller  1608  is slideably nested within fluid controller  1606 . 
         [0147]    Housing portion  1602  includes a sample chamber  1616  to receive a sample, and may include a sample substrate  1618 , which may include a surface of sample chamber  1616  or membrane therein. Housing portion  1602  may include a cover mechanism such as a cover portion  1620 , which may be removable or hingedly coupled to housing portion  1602 , as described above with respect to  FIG. 3 . Housing portion  1602  includes a sample chamber inlet  1622  and a sample chamber outlet  1624 . 
         [0148]    Housing portion  1602  includes an assay chamber  1626  and an assay chamber inlet  1628 , and may include an assay substrate  1628  to capture, react, and/or display assay results. Assay substrate may include a surface of assay chamber  1626  or a membrane therein. 
         [0149]    Housing portion  1602  includes an assay result viewer, illustrated here as a display window  1632  disposed over assay chamber  1628 . 
         [0150]    Housing portion  1602  includes a waste fluid chamber  1634  to receive fluids from assay chamber  1626 . 
         [0151]    Housing portion  1602  includes a transient fluid chamber  1636  having one or more fluid channels  1638 , also referred to herein as a fluid controller bypass channel. 
         [0152]    Housing portion  1602  further includes fluid channels  1658  and  1662 . 
         [0153]    First fluid chamber  1610  includes a fluid chamber outlet  1660 , illustrated here as a space between fluid controller  1606  and an inner surface of hosing portion  1602 . 
         [0154]    Second fluid chamber  1612  includes a fluid chamber outlet  1648 , illustrated here as a space between fluid controller  1604  and an inner surface of hosing portion  1602 . 
         [0155]    Third fluid chamber  1614  includes a fluid chamber outlet  1654 , illustrated here as a gate or passage through fluid controller  1606 . 
         [0156]    Fluid controllers  1604 ,  1606 , and  1608  include one or more sealing mechanisms, illustrated here as O-rings  1640  and  1642 , O-rings  1644  and  1646 , and O-ring  1656 . 
         [0157]    One or more inlets, outlets, openings, channels, and fluid pathways as described herein may be implemented as one or more of gates and passageways as described in one or more preceding examples, an may include one or more of: 
         [0158]    a fluid channel within an inner surface of a housing; 
         [0159]    a fluid passage within a housing, having a plurality of openings through an inner surface of the housing; 
         [0160]    the fluid passage through a fluid controller; and 
         [0161]    a fluid channel formed within an outer surface of one of the fluid controllers. 
         [0162]    One or more inlets, outlets, openings, channels, fluid paths, gates, and passageways, as described herein, may include one or more flow restrictors, such as check valves, which may include a frangible check valve, to inhibit fluid flow when a pressure difference across the flow restrictor valve is below a threshold. 
         [0163]    In  FIG. 2 , user-initiated actuator  204  may include one or more of a mechanical actuator, an electrical actuator, an electro-mechanical actuator, and a chemical reaction initiated actuator. User-initiated actuator systems are disclosed below, one or more of which may be implemented with one or more pumps disclosed above. 
         [0164]      FIG. 17  is cross-sectional view of a mechanical actuator system  1700 . Actuator system  1700  includes a button  1702  slideably disposed through an opening  1704  of an outer housing portion  1706 , and through an opening  1708  of a frangible inner wall  1710  of outer housing portion  1706 . Button  1702  includes a detent  1712  that extends beyond openings  1704  and  1708  to secure button  1702  between housing portion  1706  and frangible inner wall  1710 . 
         [0165]    Actuator system  1700  includes a compressible spring  1714  having a first end positioned within a cavity  1716  of button  1702 , and a second end disposed within a cavity  1718  of a member  1720 . Member  1720  may be coupled to, or may be a part of a fluid controller system, such a part of a plunger or fluid controller as described and illustrated in one or more examples herein. 
         [0166]    Actuator system  1700  includes an inner housing portion  1722 , slideably engaged within outer housing portion  1706 . Inner housing portion  1722  includes one or more detents, illustrated here as detents  1724  and  1726 , to lockingly engage one or more corresponding openings  1728  and  1730  in an inner surface of outer housing portion  1702 . 
         [0167]    Actuator system  1700  includes one or more frangible snaps  1732  coupled, directly or indirectly, to inner housing portion  1722 . Frangible snap  1732  includes a locking detent  1734 , and member  1720  includes a corresponding locking detent  1736  to releasably couple member  1720  to frangible snap  1732 . 
         [0168]    An assay system as disclosed herein may include a user-rupturable membrane to separate a plurality of chemicals within a flexible tear-resistant membrane. The chemicals may be selected such that, when combined, a pressurized fluid is generated. The pressurized fluid may be gas or liquid. The pressurized fluid may cause fluid controllers to move as described in one or more examples above. Multiple user-rupturable membranes may be implemented for multiple fluid passages. 
         [0169]    Methods and systems to trap or capture bubbles are disclosed below. 
         [0170]      FIG. 18  is a profile view of a bubble trap system  1800 . 
         [0171]      FIG. 19  is a cross-sectional view of bubble trap system  1800 . 
         [0172]      FIG. 20  is an upwardly directed view of an upper portion  1801  of bubble trap system  1800 . 
         [0173]    In  FIG. 19 , system  1800  includes a fluid channel  1810  to provide fluid to an opening or orifice  1904  through a surface of system  1800 . 
         [0174]    System  1800  may include a porous membrane  1804  positioned over orifice  1904  to receive fluid from fluid channel  1810 . Porous membrane  1804  may include an active region, which may coincide with orifice  1904 , and which may include a substance immobilized thereon. The substance may include, for example, an element to participate in a binding reaction, such as to detect the presence of a binding partner in a fluid sample. 
         [0175]    System  1800  further includes a bubble termination pathway  1806  to receive, capture, or trap gas bubbles from fluid that flows through fluid channel  1810  to orifice  1904 . Bubble termination pathway  1806 , or a portion thereof, may be located vertically higher that at least a portion of fluid channel  1810  to permit gas bubbles to rise upwardly from fluid channel  1810 . Gas bubbles may remain within bubble termination pathway  1806  due to buoyancy. 
         [0176]    Bubble termination pathway  1806  may include a cavity  1900  ( FIG. 19 ), having dimensions to hold a predetermined amount or volume of gas bubbles. 
         [0177]    System  1800  may include a core portion  1808  having a lower surface  1902  disposed above orifice  1904  and defining a cavity  1906  therebetween. Lower surface  1902  may be substantially convex, which may assist in directing gas bubbles from cavity  1906 , orifice  1904 , and/or porous membrane  1804 , toward cavity  1900 , such as in response to gravity and/or centrifugal force. 
         [0178]    Bubble termination pathway  1806 , cavity  1900 , core  1808 , orifice  1904 , and/or cavity  1906  may be in substantially vertical alignment with one another. Bubble termination pathway  1806 , cavity  1900 , core  1808 , orifice  1904 , and/or cavity  1906  may have substantially annular shapes, and may be in annular alignment with one another. Cavity  1900  may substantially encircle core  1808 . 
         [0179]    Bubble termination pathway  1806  may include a slanted upper surface, which may encourage distribution of gas bubbles throughout bubble termination pathway  1806 . 
         [0180]    Bubble termination pathway  1806 , or a portion thereof, may be positioned outside of a circumference of orifice  1904 , which may provide improved separation of gas bubbles from fluid, and which may provide an increased volume of space to hold or trap gas bubbles. permit increased. 
         [0181]    Fluid channel  1810  may be in substantially horizontal alignment with a surface of core portion  1808 , which may assist in separating gas bubbles from fluid, and which may assist in trapping gas bubbles in bubble termination pathway  1806 . 
         [0182]    System  1800  may include an upper portion  1801  and a lower portion  1802 , which may be sealed together such as by adhesion, chemical solvents, or mechanical force (such as ultrasonics). 
         [0183]    Upper portion  1801 , or portions thereof, may be implemented with, for example, a substantially rigid clear material, such as a plastic, which may include one or more of styrene, polystyrene, nylon, polycarbonate or other suitable material. 
         [0184]    Lower portion  1802 , or portions thereof, may be implemented with, for example, a relative thin polystyrene material. 
         [0185]    Porous membrane  1804  may be implemented with, for example, a nitrous cellulose membrane, and lower portion  1802  may be implemented with a material that can seal to a nitrous cellulose membrane  1804 . 
         [0186]    Bubble termination pathway  1806  and/or cavity  1900  may be sized to accommodate a predetermined, expected, or anticipated amount of gas to be trapped. 
         [0187]    Orifice  1904  and/or an active area of porous membrane  1804  may be sized to expose a desired amount of membrane  1804  to accommodate the surface area of the active region to be in contact with a fluid. Orifice  1904  and/or an active area of porous membrane  1804  have a diameter of, for example, approximately 0.125 inches, which may provide for suitable involvement with the active region of the membrane although it will be readily recognized by those skilled in the art that many dimensions may be suitable depending on the assay to be performed, the strength of the detectable signal desired and the sensitivity to be achieved. 
         [0188]    Example operation of system  1800  is described below with respect to  FIG. 21A through 21C  and  FIGS. 22A through 22E . 
         [0189]      FIG. 21  depicts movement of fluid that may be a fluid sample, regent fluid or a combination thereof and may contain gaseous bubbles. The active area of the membrane  1804  may contain markers,  2100 , that may bind to substances,  2104 , in the liquid,  2102 , shown in  FIG. 21B . The fluid with these substances flow through the membrane and some of them may be captured by the markers. If a gas bubble,  2105 , shown in  FIG. 21C  stays in contact with the membrane, it prevents access of these substances to the markers. Fluid will still flow through the membrane by going around the gas bubble, but the active region may not have full contact. 
         [0190]      FIGS. 22A through 22E  illustrate example operation of membrane bubble trap system  1800 . 
         [0191]    In  FIGS. 22A through 22C , an active region of membrane  1804 , where fluid is to pass through, is positioned over orifice  1904 . 
         [0192]    Membrane bubble trap system  1800  may be oriented such that upper portion  1801  is opposite to a gravitational pull or centrifugal force, and is substantially level, relative to  FIGS. 22A through 22D , such that bubbles travel to bubble termination pathway  1806  by buoyancy forces, and fluid flows downwardly through membrane  1804 , such as by gravitational force, centrifugal force, and/or fluid pressure. 
         [0193]    In  FIG. 22B , fluid  2100  is enters fluid channel  1810 . Fluid  2100  may include a fluid sample, reagent fluid, or combination thereof, and may contain gaseous bubbles. For purposes of the instant explanation, four bubbles are depicted and labeled B 1 , B 2 , B 3 , and B 4 . 
         [0194]    In  FIG. 22C , when fluid  2100  reaches bubble termination pathway  1806 , bubble B 1  travels upwardly into the slanted portion of cavity  1900 , and bubble B 2  is shown as having been forced into cavity  1906 , such as by a force of fluid  2100 . 
         [0195]    In  FIG. 22D , bubble B 2  may contact membrane  1804 , and lower surface  1902  of core portion  1808  may redirect bubble B 2  upwardly into bubble termination pathway  1806 , as shown in  FIG. 22E . 
         [0196]    Also in  FIG. 22E , bubble B 3  has been pushed, relative to  FIG. 22D , around bubble termination pathway  1806  to a position opposite bubbles B 1  and B 4 . 
         [0197]    Bubble trap system  1800  may include multiple interconnected membrane active areas, each including a corresponding bubble termination trap.  FIG. 23  illustrates an upper portion  2301  including multiple cavities  2302  and  2304  and corresponding curved sections  2306  and  2308 . 
         [0198]    Upper portion  2301  further includes a fluid channel  2310 , including branches  2312  and  2314  to cavities  2302  and  2304 . 
         [0199]    Branches  2312  and  2314  may have similar fluid resistances and may be of similar length to permit fluid to reach corresponding active areas substantially simultaneously. More than one branch can end at the same bubble termination area. 
         [0200]    Bubble trap system  1800  may be implemented within an assay system, such as one or more of assay systems  600 ,  1500 , and  1600 . For example, and without limitation, bubble trap system  1800  may be implemented to trap bubbles in an area proximate to a test membrane within assay region  618  in  FIG. 6 , wherein membrane  1804  of bubble trap system  1800  may be positioned over openings  622 ,  624 , and  626  of assay region  618  in  FIG. 6 , and upper portion  1801  and lower portion  1802  of bubble trap system  1800 , or portions thereof, may be implemented as part of body  602  and/or as part of a cover over assay region  618  of assay system  600 . Fluid channel  110  of bubble trap system  100  may correspond to, or extend from fluid passage  730  of assay system  600  in  FIG. 7 . 
         [0201]    While various embodiments are disclosed herein, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail may be made therein without departing from the spirit and scope of the methods and systems disclosed herein. Thus, the breadth and scope of the claims should not be limited by any of the example embodiments disclosed herein.