Patent Publication Number: US-2020290036-A1

Title: Cuvette Assembly Having Chambers For Containing Samples To Be Evaluated Through Optical Measurement

Description:
RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Application Ser. No. 61/912,763, filed Dec. 6, 2013, titled “Multi-Cuvette,” which is herein incorporated by reference in entirety. 
    
    
     COPYRIGHT 
     A portion of the disclosure of this patent document may contain material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever. 
     FIELD OF THE INVENTION 
     The present invention relates generally to the field of optical measurements of contained liquid samples. Specifically, the present invention relates to a cuvette assembly having multiple chambers for containing samples, such as liquid samples, that will be evaluated by optical measurements through windows associated with the chambers. 
     BACKGROUND OF THE INVENTION 
     Many applications in the field of analytical research and clinical testing utilize optical methods for analyzing liquid samples. Among those methods are absorbance, turbidity, fluorescence/luminescence, and optical scattering measurements. Optical laser scattering is one of the most sensitive methods, but its implementation can be very challenging, especially when analyzing biological samples in which suspended particles are relatively transparent in the medium. In this case, most of the scattering process occurs in the forward direction near the incident laser beam. To detect this forward scattering signal, high extinction of the incident beam is required. 
     One particle that often requires evaluation within a liquid is bacteria. The presence of bacteria is often checked with biological liquids, such as urine, amniotic, pleural, peritoneal and spinal liquids. In a common analytical method, culturing of the bacteria can be time-consuming and involve the use of bacterial-growth plates placed within incubators. Normally, laboratory results take several days to determine whether the subject liquid is infected with bacteria. 
     In some systems, cuvettes have been used to receive liquid samples that are then subjected to the optical measurement by transmission of an input beam through the cuvette and observation of the forward scatter signals. These devices have been used relative to the detection of bacteria within the liquid. However, the cuvettes are not conducive to mass production for commercial use. Nor do these prior art cuvettes have user friendly features that permit for ease of use by operators. Furthermore, these prior art cuvettes lack mechanisms that permit the easy flow of the liquid sample into the optical chamber through a filter. 
     Accordingly, there is a need for an improved cuvette that is easy to mass produce, permits easy use by the operator, and more readily delivers the liquid sample into the optical chamber through the filter. 
     SUMMARY OF THE INVENTION 
     The present invention is a cuvette assembly for use in optically measuring at least one characteristic of particles within a plurality of liquid samples. The cuvette assembly comprises a main body having internal walls and external walls, and a plurality of cuvettes within the main body are at least partially defined by the internal walls. Each of the plurality of cuvettes has a liquid-input chamber for receiving a respective one of the plurality of liquid samples, a filter, and an optical chamber for receiving a respective filtered liquid sample caused by passing the respective one of the plurality of liquid samples through the filter. Each of the optical chambers includes an entry window for allowing transmission of an input light beam through the filtered liquid sample and an exit window for transmitting a forward scatter signal caused by the particles within the filtered liquid sample. 
     In another aspect, the present invention involves a cuvette assembly for use in optically measuring at least one characteristic of particles within a plurality of liquid samples. The cuvette assembly includes a main body having a plurality of openings. Each opening is for receiving a respective one of the plurality of liquid samples. Each of the plurality of openings leads to an associated liquid-input chamber that is in fluidic communication with an associated optical chamber. Each optical chamber has an entry window for allowing transmission of an input light beam through the respective liquid sample and an exit window for transmitting a forward scatter signal caused by the particles within the respective liquid sample. The cuvette assembly further includes a plurality of individual closure mechanisms. Each of the plurality of closure mechanisms is associated with a respective one of the plurality of openings. Each of the plurality of closure mechanisms is movable from an initial opened position for receiving the respective liquid sample to a closed position that inhibits leakage from the associated liquid-input chamber. 
     In a further aspect, the present invention is a cuvette assembly for use in optically measuring at least one characteristic of particles within a plurality of liquid samples. The cuvette assembly includes a main body having internal walls that at least partially define a plurality of optical chambers for receiving a respective one of the plurality of liquid samples. Each of the optical chambers includes an entry window for allowing transmission of an input light beam through the respective liquid sample and an exit window for transmitting an optical signal caused by the particles within the respective liquid sample. The main body further including a lower surface that is at an angle relative to a central axis of the input light beam. A first pair of registration structures is associated with the angled lower surface of the main body. The first pair of registration structures is intended to mate with a corresponding pair of registration features on a platform in an instrument associated with a light source producing the input light beam. 
     In yet a further aspect, the present invention is a cuvette assembly for use in optically measuring at least one characteristic of particles within a plurality of liquid samples. The cuvette assembly comprises a plurality of cuvettes. Each of the plurality of cuvettes has a liquid-input chamber for receiving a respective one of the plurality of liquid samples, a filter, and an optical chamber for receiving a respective filtered liquid sample from the filter. Each optical chamber includes a vent for allowing displaced gas to escape as the filtered liquid sample enters the optical chamber. 
     In yet another aspect, the present invention is a cuvette assembly for use in optically measuring at least one characteristic of particles within a plurality of liquid samples. The cuvette assembly comprises a plurality of cuvettes. Each of the plurality of cuvettes has a liquid-input chamber for receiving a respective one of the plurality of liquid samples, a filter, and an optical chamber for receiving a respective filtered liquid sample from the filter. The cuvette assembly includes ports to receive applied pressure to the liquid samples within the liquid-input chamber so as to force the samples through the filters and into the optical chambers. Or, the cuvette assembly includes port(s) associated with the optical chamber to apply a suction force (or a vacuum) to draw the filtered liquid sample through the filter and into the optical chamber. 
     In another aspect, the present invention is a cuvette assembly for use in optically measuring at least one characteristic of particles within a plurality of liquid samples. The cuvette assembly comprises a plurality of cuvettes within a main body of the cuvette assembly. Each of the plurality of cuvettes has a liquid-input chamber for receiving a respective one of the plurality of liquid samples and an optical chamber for receiving a respective liquid sample from the associated liquid-input chamber. Each of the optical chambers includes an entry window for allowing transmission of an input light beam through the liquid sample and an exit window for transmitting an optical signal caused by the particles within the liquid sample. At least one window assembly is attached to the main body that includes either (i) all of the entry windows for the plurality of optical chambers or (ii) all of the exit windows for the plurality of optical chambers. 
     In another aspect, the present invention is a cuvette assembly for use in optically measuring at least one characteristic of particles within a plurality of liquid samples. The cuvette assembly comprises a plurality of cuvettes. Each of the plurality of cuvettes has a liquid-input chamber for receiving a respective one of the plurality of liquid samples and an optical chamber for receiving a respective liquid sample from the associated liquid-input chamber. Each of the optical chambers includes an entry window for allowing transmission of an input light beam through the liquid sample and an exit window for transmitting an optical signal caused by the particles within the liquid sample. Each cuvette is preloaded with one or more chemo-effectors for mixing with liquid sample located therein. 
     Additional aspects of the invention will be apparent to those of ordinary skill in the art in view of the detailed description of various embodiments, which is made with reference to the drawings, a brief description of which is provided below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates a sectional view through the liquid-input chamber and optical chamber of one cuvette of a cuvette assembly in accordance with the present invention. 
         FIG. 2  is a top plan view of the cuvette assembly of  FIG. 1 . 
         FIG. 3  is an exploded view of another embodiment of a cuvette assembly having multiple chambers in accordance with the present invention. 
         FIG. 4  is a perspective view of a cuvette assembly of  FIG. 3  with the first optical chamber and associated liquid-input chamber illustrated in a sectional view. 
         FIG. 5  is a cross-sectional view through the exit window assembly taken along line  5 - 5  of  FIG. 7 . 
         FIG. 6  is a schematic view of one optical chamber of the cuvette assembly of  FIG. 3  in response to an input beam being transmitted through the entry window. 
         FIG. 7  is an exploded view of the cuvette assembly of  FIG. 4  showing the various alignment and registration features at the bottom of the cuvette assembly. 
         FIG. 8  illustrates the cuvette assembly of  FIG. 4  registered on a platform that is typically located within an optical measurement instrument. 
         FIG. 9  illustrates a cuvette assembly having a contamination-prevention film located over the upper structure of the cuvette assembly. 
         FIG. 10  illustrates yet another embodiment of the cuvette assembly according to the present invention that includes a frangible film directly below the openings of the cuvette assembly. 
         FIG. 11  illustrates yet a further embodiment of the cuvette assembly according to the present invention that includes a manual pump to help force a liquid within the upper liquid-input chamber through a filter so that it enters the lower optical chamber. 
         FIG. 12  schematically illustrates one application for the cuvette assemblies according to the present invention in which a single cuvette assembly contains a control sample and four different drug samples, or a control sample and four different dosages of a single drug sample. 
     
    
    
     While the invention is susceptible to various modifications and alternative forms, specific embodiments will be shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     The drawings will herein be described in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated. For purposes of the present detailed description, the singular includes the plural and vice versa (unless specifically disclaimed); the words “and” and “or” shall be both conjunctive and disjunctive; the word “all” means “any and all”; the word “any” means “any and all”; and the word “including” means “including without limitation.” 
       FIGS. 1 and 2  schematically illustrate a first embodiment of the cuvette assembly  10  according to the present invention. As shown in  FIG. 2 , the cuvette assembly  10  includes five optical chambers  12   a,    12   b,    12   c,    12   d,    12   e  defined by internal and external walls on a lower portion  13  of the main body of the cuvette assembly  10 . As illustrated in  FIG. 1 , a liquid-input chamber  14  is located above each optical chamber  12  and is also defined by internal and external walls on the upper portion  15  of the main body of the cuvette assembly  10 . Each liquid-input chamber  14  and its associated optical chamber  12  form an individual cuvette. The cuvette assembly  10  is preferably made of plastic material, such as polycarbonate, polystyrene, or ABS, and is preferably disposable. 
     The optical chamber  12  of the cuvette assembly  10  includes an entry window  16  and an exit window  18 . A light source  20 , such as a laser, provides an input beam (solid line) that passes from the entry window  16 , through a liquid sample within the optical chamber  12 , and through the exit window  18 . When the liquid sample includes particles, a forward scattering signal (dashed lines) is produced by the impingement of the input beam on the particles within the liquid sample and is detected by a sensor  22 . The forward scattering signal provides characteristics (e.g., quantity, size, or concentration) of the particles present in the liquid sample, which is useful for diagnostic applications, medical applications, non-medical applications, and research applications. In one particularly useful application, the particles are bacteria, which can be detected and counted by various techniques that are generally described in U.S. Pat. Nos. 7,961,311 and 8,339,601, both of which are commonly owned and are herein incorporated by reference in their entireties. 
     As seen in  FIGS. 1-2 , the optical chamber  12  within the lower portion  13  of the main body has angled walls in the horizontal and vertical planes. The angled walls provide an optical chamber that is roughly conic with a smaller entry window  16  than the exit window  18  so that light can spread from the entry window  16  without impinging on the walls. In one embodiment, the opposing angled walls are within 12° to 16° of parallel to the input beam (i.e., each vertical wall and horizontal wall is within about 6° to 8° of a central axis of the optical chamber  12 ). Also, angled “light traps” might be incorporated into the angled walls of the optical chamber  12  to trap, absorb, and/or contain interior light reflections from the windows  16 ,  18  or wall surfaces. 
     The windows  16 ,  18  at each end of the optical chamber  12  are transparent to the input beam. The windows  16 ,  18  are thin (less than 1 mm) and are tipped at an angle to ensure that the surfaces of the windows  16 ,  18  are not normal to the input beam so as to reduce retro-reflections that might interfere with the measurement of the forward scattering signal at the sensor  22 . The windows  16 ,  18  can be angled in the same or different planes. The windows  16 ,  18  can be glass or plastic, and can also be a plastic film. They must have low surface roughness (preferably a surface microroughness less than 100 angstroms rms) and minimum inclusions that would produce scatter, which could also interfere with the measurement of the forward scattering signal at the sensor  22 . 
     Regarding the transfer of the liquid sample from the upper portion  15  to the lower portion  13  of the cuvette assembly  10 , the liquid sample is initially located within the liquid-input chamber  14  and is then passed through a filter  32  (e.g., a permeable membrane  32 ) into the optical chamber  12 . The filter  32  removes particles of a particular size, for example excluding particles larger than bacteria by filtering to below about 0.01 mm (about 10 microns), leaving only certain sized particles present in the filtered liquid sample located in the optical chamber  12 . An intermediate partition  30  within the cuvette assembly  10  supports the filter  32  and includes a group of openings that permit the filtered liquid sample to pass from the liquid-input chamber  14  into the optical chamber  12 . Alternatively, the intermediate partition  30  may have openings that are sized and shaped to provide enough filtering so as to avoid the need for the additional filter  32 . 
     The cuvette assembly  10  may also include a foil or frangible membrane  34  (or one-use frangible feature) below an opening  40  on the upper structure  38  of the main body to seal the interior of the liquid-input chamber  14  before use of the cuvette assembly  10 . The foil or frangible membrane  34  could be pierced or displaced by a standard pipette, syringe tip, sharp cannula, or other tube that injects the liquid sample into the liquid-input chamber  14 . This foil or frangible membrane  34  serves to protect the integrity or sterility of the interior of the liquid-input chamber  14  and the optical chamber  12  prior to use, and also provides tamper-evidence or use-evidence for a user. The frangible membrane  32  could also be a resilient or rubber material so that it could be pierced by a sharp cannula, but still retain the liquid sample inside the liquid-input chamber  14  and below the frangible membrane  32  after being pierced. Several mechanisms exist for blunt cannula access (such as those mechanisms used in needleless infusion devices) might be incorporated to allow transfer of the liquid sample into the interior of the liquid-input chamber  14 . For example, these mechanisms may include a slideable or deformable rubber element mounted in a tubular body, with a slit or opening in the element that is forced open by being displaced by a syringe luer taper. They may also include a spring-loaded valve poppet or moveable element that can be displaced from a sealing ring by being displaced by a blunt cannula, or a “duck-bill” collapsed rubber tube that can be forced open by a blunt cannula. 
     The intermediate partition  30  may also help to form a vent (not shown in  FIGS. 1-2 ) from the optical chamber  12  to the upper region of the liquid-input chamber  14  to facilitate venting air (or other gas) that is displaced from the optical chamber  12  upon receipt of the filtered liquid sample. There may also be a feature to connect this vent through a wall of the liquid-input chamber  14  to an apparatus outside the cuvette assembly  10  for applying a vacuum to the optical chamber  12  to promote liquid moving through the filter membrane  32  and/or intermediate partition  30 , which is shown in more detail in  FIG. 9 . This vent may be small (e.g., less than 3 mm diameter, or less than 1 mm) or include a restrictive section or aperture so that fluid pulled by vacuum through the vent encounters substantial flow resistance (back pressure), which can be detected by the vacuum apparatus to indicate that the optical chamber  12  is filled and to cease applying the vacuum. Once the filtered liquid sample is within the optical chamber  12 , the optical measurements associated with the light source  20  and the sensor  22  may be initiated. 
     To maintain liquid samples within the cuvette assembly  10  after they have been introduced into the liquid-input chambers  14  via the openings  40 , a closure mechanism  42  is associated with each of the liquid-input chambers  14  of the cuvette assembly  10 . The closure mechanism  42  is preferably a single-use sliding closure that preferably provides a locking feature after it is moved from an initial opened position (solid lines) to a closed position (dashed lines). The sliding closure mechanism  42  could have a ratchet or pall device incorporated therein to lock it in the closed position on the upper structure  38  so that the cuvette assembly  10  is assured of only a single use. The sliding closure mechanism  42  also served as evidence of use. The sliding closure mechanism  42  preferably includes a wiping feature to ensure a liquid-tight closure that inhibits or precludes leakage of liquid from the liquid-input chamber  14 . The sliding closure mechanism  42  and associated wiping feature also ensure that exterior contaminants cannot be introduced into the liquid-input chamber  14  after the sliding closure mechanism  42  is in the closed position. Furthermore, the sliding closure mechanism  42  preferably has a configuration that is tailored to fit a pipette or loading tube to preclude liquid or gas leaking around the tube, or to wipe the end of the tube as it is withdrawn from the opening  40 . Alternatively, the closure mechanism  42  can be a hinged closure with a locking pall or snap feature, which also serves to ensure a single use and also as evidence of use. The hinged closure mechanism is also preferably liquid-tight when closed. 
       FIGS. 3-7  illustrate another embodiment of a cuvette assembly  110  that is similar to the cuvette assembly  10  of  FIGS. 1-2 , where similar structures are now referenced with 100-series reference numerals. Referring initially to  FIGS. 3-4 , the cuvette assembly  110  includes four separate cuvettes, each of which includes an optical chamber  112  and a liquid-input chamber  114 . As with the previous embodiments, the internal and external walls of the lower portion  113  of the main body of the cuvette assembly  110  define the optical chamber  112 . For example, the first optical chamber  112  is partially defined by the side external wall, an internal wall, and a bottom wall of the lower portion  113 , as well as the entry and exit windows  116 ,  118 . The associated liquid-input chamber  114  is partially defined by a side external wall, an internal wall, and a pair of front and back external walls on the upper portion  115  of the main body of the cuvette assembly  110 . 
     Each of the four entry windows  116  is a part of an entry window assembly  117  that is attached to the lower portion  113  of the main body of the cuvette assembly  110 . Similarly, each of the four exit windows  118  is part of an exit window assembly  119  that is attached to the lower portion of the main body opposite the entry window assembly  117 . In other words, the present invention contemplates a single unitary optical structure that provides the transmission of the input beam into all four respective optical chambers  112 , and a single unitary optical structure that provides for the exit of the forward scattering signals from the respective optical chambers  112 . The lower portion  113  of the main body includes structural recesses that mate with the corresponding structures on the window assemblies  117 ,  119  for registering them in a proper orientation during assembly of the cuvette assembly  110 . 
     An intermediate partition  130  within the cuvette assembly  110  separates the lower portion  113  defining the four optical chambers  112  from the upper portion  115  defining the liquid-input chambers  114 . The intermediate partition  130 , which is shown as being part of the lower portion  113  (although it could be part of the upper portion  115 ), includes four separate groups of openings that permit the flow of liquid from the liquid-input chamber  114  into the associated optical chamber  112 . The openings can be a variety of shapes that permit the flow of the liquid. As shown, the openings progressively get longer moving from the entry window  116  to the exit window  118  because the shape of the optical chamber  112  increases in area in the same direction. Additionally, the filter  132  rests upon the intermediate partition  130 , such that the same filter  132  is used for each of the four regions. When the same filter  132  is used for all four regions, the interior walls of the upper portion  115  must provide adequate pressure at the filter  132  to prevent crossing fluid flows through the filter  132  between adjacent liquid-input chambers  112 . In a further alternative, no filter  132  is present because the intermediate partition  130  includes adequate sized openings to provide the necessary filtering of the liquid sample, or because the liquid samples are pre-filtered before entering each liquid-input chamber  114 . 
     To provide the initial introduction of the liquid samples into the cuvette assembly  110 , the upper structure  138 , which is attached to the upper portion  115  of the main body of the cuvette assembly  110 , includes four openings  140  corresponding to the four liquid-input chambers  114 . Four sliding mechanisms  142  are located within four corresponding grooves  144  on the upper structure  138  and are initially placed in an opened position such that the openings  140  are initially accessible to the user for introducing the liquid samples. Each of the sliding mechanisms  142  includes a pair of projections  148  that engage corresponding side channels at the edges of each of the corresponding grooves  144  to permit the sliding action. Within each groove  144 , there is a latching ramp  146  over which the sliding mechanism  142  is moved when transitioning to its closed position. A corresponding latch  147  ( FIG. 4 ) on the underside of the sliding mechanism  142  moves over the latching ramp  146  and creates a locking mechanism when the sliding mechanism  142  has been fully moved to the closed position. The upper structure  138  of the cuvette assembly  110  also includes a gripping handle  150  that permits the user to easily grasp the cuvette assembly  110  during transport to and from an instrument that incorporates the light source  20  and the sensor  22 . 
     To help seal the cuvette assembly  110  after the liquid samples have been placed within the respective liquid-input chambers  114 , the periphery of the sliding mechanism  142  adjacent to the opening  140  can be configured to tightly mate with the walls defining the groove  144  (or undercut channels within the groove  144 ) to inhibit any leakage around the opening  140  in the upper structure  138 . Alternatively, a resilient plug-like structure can be located on the underside of the sliding mechanism  142  that fits within the opening  142  create a seal and inhibit leakage. Or, a gasket can be provided around the opening  140  to provide a sealing effect on the underside of the sliding mechanism  142 . 
     The upper portion  115  and the lower portion  113  of the main body of the cuvette assembly  110  can be attached to each other through various techniques, such as ultrasonic welding, thermal welding, with adhesive, or through interfering snap-fit connections. Similarly, the upper structure  138  can be attached to the upper portion  115  of the main body through similar techniques. And, the window assemblies  117 ,  119  can be attached to the lower portion  113  through the same attachment techniques. The width dimension of the overall cuvette assembly  110  across the four cuvettes is roughly 4 cm. The length dimension of the overall cuvette assembly  110  (i.e., parallel to the input beam) is approximately 2 cm. The height dimension of the overall cuvette assembly  110  is approximately 2 cm, such that each of the liquid input chambers  114  is approximately 1 cm in height and each of the optical chambers  112  is approximately 1 cm in height (although the optical chambers  112  have a varying height along the length direction due to their conical shape). In some embodiments, each optical chamber  112  is designed to contain approximately 1.2 to 1.5 cubic centimeters (i.e., approximately 1.2 to 1.5 ml) of a fluid sample. Each liquid-input chamber  114  is designed to hold slightly more of the liquid sample (e.g., 1.7 to 2.5 ml), which is then fed into the corresponding optical chamber  112 . 
     Because each of the cuvette assemblies  110  may be used for different applications, the cuvette assembly  110  may use barcodes or RFID tags to identify the type of test supported by the particular cuvette assembly  110 , as well as other measurement data to be taken. The instrument that includes the light source  20  and the sensor  110  preferably reads the RFID or barcode, and selects the software to run the appropriate optical measurement tests on the cuvette assembly  110 . Accordingly, the cuvette assembly  110  preferably includes an identification label  170 , which may include barcodes and/or quick response codes (“QR-code”) that provide the necessary coded information for the cuvette assembly  110 . Other codes can be used as well. Specifically, when bacteria is a particle being checked within the liquid sample, one of the codes on the label  170  may provide the protocol for the test (e.g., temperature profile over duration of test, frequency of the optical measurements, duration of test, etc.). Another one of the codes may be associated with information on the patient(s) from whom the liquid samples were taken, which may include some level of encryption to ensure that patient data is kept confidential. Another code may provide a quality-assurance check of the part number or the serial number for the cuvette assembly  110  to ensure that the cuvette assembly  110  is an authentic and genuine part, such that improper cuvettes are not tested. The code for the quality-assurance check may also prevent a cuvette assembly  110  from being tested a second time (perhaps after some type of cleaning) if it is intended for only single use. 
     The cuvette assembly  110  also includes a vent  180  that extends from the optical chamber  112  into the upper portion  115  of the main body the cuvette assembly  110 . The vent  180  includes a chimney-like portion that extends upwardly from the intermediate partition  130 . The chimney-like portion is then received in a channel in the upper portion  115 , which extends to an opening  182  leading into the liquid-input chamber  114  just below the upper structure  138  that defines the upper boundary of the liquid-input chamber  114 . Accordingly, the gas (e.g., air) that is initially present in the optical chamber  112  can be readily displaced as the optical chamber  112  receives the filtered liquid sample from the liquid-input chamber  114  (via the filter  132 ). The vent  180  can also lead to the external environment on the outside of the cuvette assembly  110 . 
       FIG. 5  illustrates a cross-section taken along line  5 - 5  of the exit window assembly  119  in  FIG. 7 . The exit window assembly  119  includes the four exit windows  118  for the four optical chambers  112 . To help minimize reflections from the input beam as it impinges on each surface of each exit window  118 , each of the exit windows  118  is angled relative to the central axis of the input beam by an angle “A.” The angle “A” is preferably about 5°, but can range from about 2° degrees to about 15°. 
       FIG. 6  schematically illustrates the effects of the input beam within the optical chamber  112  of the cuvette assembly  110 , as well as the geometry of the optical chamber  112 . In particular, the light source  20  provides an input beam that is transmitted towards the entry window  116 . The entry window  116  is tilted at an angle relative to the input beam such that the input beam refracts upwardly toward the intermediate partition  130  of the cuvette assembly  110 . As the input beam passes through the liquid sample within the optical chamber  112 , a forward scatter signal (dashed lines) is produced due to the input beam impinging upon particles within the liquid sample. Due to various reflections and optical scatter, the upper portion  112   a  of the optical chamber  112  becomes an irrelevant region for optical measurement. Only the forward scatter signal that is received by the lower portion  22   a  of the sensor  22  is relevant to determining the characteristics (e.g., quantity, size, and/or concentration) of the particles present within liquid sample in the optical chamber  112 . As mentioned previously, the optical chamber  112  is conical with the angle “B” that provides for expansion of the cross-sectional area of the optical chamber  112  in the direction of the exit window  118 . The angle “B” is in the range of about 12° to 16°. 
     Preferably, each of the entry windows  116  and the exit windows  118  meets the intermediate partition  130  at acute interior angles “C” and “D”, respectively. Assuming the input beam from the light source  20  is substantially parallel to the intermediate partition  130 , the acute interior angles help to reduce the reflections that would otherwise interfere with the forward scatter signal that is received at the lower portion  22   a  of the sensor  22 . For example, angle “C” may be roughly 85° such that the input beam impinges upon the entry window  116  at an angle of approximately 85° so as to refract upward slightly, while providing minimal internal reflections toward the lower portion  22   a  of the sensor  22 . Similarly, angle “D” for the exit window  118  is roughly 89° so as to again minimize the internal reflections that could be received at the lower portion  22   a  the sensor  22 , while maximizing the amount of forward scatter signal that can be received at the lower portion  22   a  the sensor  22 . And, as noted above relative to  FIG. 5 , the exit window  118  is also angled in the opposing place as well. In summary, the optical chamber  112  and the windows  116 ,  118  are configured to maximize the amount of forward scatter signal that is received by the lower portion  22   a  of the sensor  22 , while minimizing the amount of internal reflections that could be received in the lower region  22   a  of the sensor  22 . Furthermore, it should be noted that the input beam, which has a much higher intensity than the forward scatter signal, can be blocked or attenuated by a beam dump after leaving the exit window  118  to reduce or eliminate the transmission of the input beam signal at the sensor  22 . 
     Referring now to  FIGS. 7-8 , the cuvette assembly  110  also includes different types of registration features to allow the cuvette assembly  110  to be located properly on a registration platform  210  ( FIG. 8 ) within the instrument that is used for the optical measurements. In particular, the cuvette assembly  110  includes a pair of side registration features  192  located on the lower portion  113  of the cuvette assembly  110 . Further, the cuvette assembly  110  includes lower registration features  194   a  and  194   b  on a lower surface of the lower portion  113  of the cuvette assembly  110 . Finally, lower segments of the front and back walls  196   a  and  196   b  extending downwardly from the lower surface also serve as registration features for the cuvette assembly  110 . 
     With reference to  FIG. 8 , the side registration features  192  undergo sliding engagement within corresponding vertical grooves  212  on pillars associated with the registration platform  210 . Additionally, lower registration features  194   a  and  194   b  can slide within horizontal grooves  214  on an upper surface of the registration platform  210 . The horizontal grooves  214  terminate in openings that receive the lower registration features  194   a  and  194   b  (illustrated as projections) on the cuvette assembly  110 . Finally, the distance between the lower segments of the front and back walls  196   a  and  196   b  corresponds to the width of the registration platform  210  such that cuvette assembly  110  becomes nestled between adjacent pillars with the front and back walls  196   a  and  196   b  overlying the front and back edges of the registration platform  210 . 
     As can be seen best in  FIGS. 4 and 6 , the lower surface of the lower portion  113  of the cuvette assembly  110 , which includes the lower registration features  194   a  and  194   b,  is at angle relative to the upper structure  138  of the cuvette assembly  110  and to the input beam from the light source  20  due to the conical geometry of the optical chamber  112 . Accordingly, the upper surface of the registration platform  210  is angled in an opposing manner that allows the input beam to be generally horizontal (and generally parallel to the upper structure  138  of the cuvette assembly  110 ) when the cuvette assembly  110  is placed on the registration platform  210 . It should be noted, however, that the cuvette assembly  110  can be properly registered on the registration platform  210  with less than these three distinct registration features illustrated in  FIGS. 7-8 . 
     Once the cuvette assembly  110  is nestled properly on the registration platform  210 , the light source  20  can sequentially transmit the input beam through each of the four optical chambers  112  of the cuvette assembly  110  and the forward scatter signal associated with the particles within each of the liquid samples can be sequentially received by the sensor  22 . For example, the light source  20  and sensor  22  can be controllably indexed between positions to receive optical measurements taken in adjacent optical chambers  112 . As can be seen in  FIG. 8 , each platform  210  is capable of receiving four cuvette assemblies  110 , such that optical measurements can be taken from sixteen different liquid samples within the four cuvette assemblies  110  nestled on the registration platform  210 . 
       FIG. 9  illustrates an alternative cuvette assembly  310 , which is slightly different from the embodiments previously illustrated. In particular, the cuvette assembly  310  includes a thin film  340  located over the upper structure  138  and the sliding mechanisms associated with the openings on the upper structure  138 . The thin film  340  provides an extra layer of protection to ensure no contamination enters the openings when the sliding mechanisms located under the film  340  are in their open positions prior to use. Once the user has chosen to use the cuvette assembly  310 , he or she tears the thin film  340  from the upper structure  138  and places the four liquid samples into each of the four liquid-input chambers  114 . Alternatively, the film  340  may have multiple perforations  342  to allow for the removal of four distinct thin films over the four openings. 
     Additionally,  FIG. 9  illustrates four vacuum ports  350  that provide access to the four interior vacuum channels, each of which is associated with a respective one of the optical chambers  112 . The interior vacuum channels are similar in structure to the vents  180  in  FIG. 4 , except they do not have the upper openings  182 , thereby causing a draw of gas (e.g., air) only within the optical chambers  112 . Because some types of liquid samples may not easily pass through the filter  132 , applying a lower pressure to the four vacuum ports  350  serves to draw the liquid sample through the filter  132  and into the optical chamber  112 . The cuvette assembly  310  may be placed on a vacuum or suctioning platform (similar to the registration platform  210  in  FIG. 8 ) and a corresponding set of aligned tubes or a longer manifold can overlie the vacuum ports  350  to automatically apply the negative pressure, thereby resulting in the liquid sample being pulled through the filters  132  into the corresponding optical chambers  112 . Other manual methods for applying the negative pressure to the vacuum ports  350  can be used as well. 
       FIG. 10  illustrates another alternative cuvette assembly  410  having a membrane  440  directly below the openings on the upper structure  138 . The membrane  440  could be pierced or displaced by a standard pipette, syringe tip, sharp cannula, or other tube that injects the liquid sample into the liquid-input chamber  114 . This membrane  440  serves to protect the integrity and/or sterility of the interior of the liquid-input chambers  114  within the upper portion  115  of the main body, and also the optical chamber  112  prior to use. It further provides tamper-evidence or use-evidence for a user. The membrane  440  could also be resilient or rubber material so that it could be pierced by a sharp cannula, and still retain the interior liquid sample within the liquid-input chamber  114  after the sharp cannula is refracted. Furthermore, to the extent that the liquid-input chamber  114  is depressurized so as to help draw the liquid sample into the liquid-input chamber  114 , the membrane  440  can seal the liquid-input chamber  114  to maintain a pressure lower than the ambient environment (or maintain a vacuum) within the liquid-input chamber  114 . 
     The interior of the liquid-input chamber  114  of the cuvette assembly  410  could be manufactured under a vacuum, or could contain a lyophilized material, such as an antibiotic or some other chemo-effector. If manufactured under a vacuum, piercing the frangible membrane  440  with a pipette or cannula would apply this vacuum to the pipette or cannula and, thus, draw the contents into the liquid-input chamber  114 . Similarly, the frangible membrane  440  and permeable filter membrane  132  ( FIG. 3-4 ) can be configured so that a vacuum in the cuvette assembly  410  would draw deposited liquid samples through the permeable filter membrane  132  for filtration of the liquid sample and/or for exposure of the liquid sample to a chemical coating (e.g., chemo-effector) on the permeable filter membrane  132 . 
     In an alternative embodiment of  FIG. 10 , a lower frangible membrane or seal could be incorporated below the permeable filter membrane  132 . A mechanical feature can then pierce this lower frangible membrane by user action, such as by the loading pipette or a separate tool, by flexing of devices in the cuvette body, or by the motion of the sliding or hinged closure mechanisms. As an example, the lower surface of the permeable filter membrane  132  directly adjacent to the lower frangible membrane can have a plurality of projecting features that, when forced downwardly, cause the lower frangible membrane to be pierced. In this alternative, the optical chamber  112  and fluid input chamber  114  are isolated until this lower frangible membrane is pierced or displaced. The lower optical chamber  112  could be in a vacuum (or other low pressure state) compared with the liquid-input chamber  114 , and piercing this membrane could serve to apply the vacuum to the lower face of the permeable filter membrane  132  and, thus, draw flow of the liquid sample through the permeable filter membrane  132 . 
       FIG. 11  illustrates another alternative cuvette assembly  510  having a manual pump  512  on the upper structure  138  of the cuvette assembly  510 . The manual pump  512  can be actuated by the user by pushing downwardly to force a volume of air within the cuvette assembly  510  to be forced onto the sample liquids that have been placed in the four liquid-input chambers  114 . After the sliding mechanisms  142  ( FIGS. 3-4 ) have been moved to the closed position, thereby providing some sealing effect around the openings  140 , the user actuates the manual pump  512 , which causes the sample liquids to be forced downwardly through the filter  132  and into the optical chamber. Again, like the suctioning effect from the vacuum ports  350  in  FIG. 9 , providing a pressure differential across the filter  132  enhances the flow of the sample liquid from the fluid input chamber  114 , through the filter  132 , and into the optical chamber  112 . While one common manual pump  512  is disclosed, the present invention contemplates a single manual pump for each of the liquid-input chambers  114 . Of course, an automatic pump can also apply pressure to the liquid samples through ports in the upper portion of the cuvette assembly  510 . 
       FIG. 12  illustrates the use of the cuvette assembly  10  in one particular application. While  FIG. 12  illustrates the application relative to the cuvette assembly  10  of  FIGS. 1-2 , the application equally applies to the cuvette assemblies  110 ,  310 ,  410  and  510  illustrated in  FIGS. 3-11 . In first optical chamber  12   a,  a liquid sample serves as a control for the test. For example, the first optical chamber  12   a  may be a liquid sample from the patient having an infection (e.g., a urinary tract infection). The second optical chamber  12   b  may have the same patient&#39;s liquid sample, but mixed with a first drug (“Drug  1 ”) applied thereto. Similarly, the third optical chamber  12   c  may have the same patient&#39;s liquid sample, but mixed with a second drug (“Drug  2 ”). Likewise, the fourth optical chamber  12   d  may have the same patient&#39;s liquid sample, but mixed with a third drug (“Drug  3 ”). Finally, the fifth optical chamber  12   e  may have the same patient&#39;s liquid sample, but mixed with a fourth drug (“Drug  4 ”). The cuvette assembly  10  provides for a simplistic method for determining the effect of each of the four drugs on the patient by measuring the bacterial content (bacteria particles) over a period of time. For example, the untreated control sample in the first optical chamber  12   a  may result in a forward scatter signal that increases due to the growth of bacteria in the untreated liquid sample. But, that same liquid sample from the patient may experience less growth in the number of bacteria when exposed to Drugs  3  and  4 . And, that same liquid sample from the patient may experience no growth or a decrease in the growth in the number of bacteria when exposed to Drugs  1  and  2 . 
     Alternatively, Drugs  1 ,  2 ,  3 , and  4  can be the same type of antibiotic, but at different levels such that the cuvette assembly is useful in determining the “minimum inhibitive concentration” that is needed to reduce or retard bacterial growth. In short, each of the cuvette assemblies of the present invention are useful in determining the effects of a chemo-effector (such as an antibiotic, or a nutrient growth medium) by allowing for an easy measurement of changes in microbial growth rates for liquid samples exposed to different chemo-effectors or liquid samples exposed to the same chemo-effector, but at different concentrations. 
     In one particular example, the cuvette assembly  10  has a plurality of chambers that are loaded with different combinations of chemo-effectors (for example, pre-mixed sterile liquid growth media such as Luria Broth, each with a different concentration of some number of antibiotics). The user can load a small amount (e.g. 0.05 mL) of a chemo-effector sample into each liquid-input chamber  14  by piercing the membrane, depositing the sample, removing the pipette or cannula. The chemo-effector sample and liquid sample can mix, and the cuvette assembly  10  can then be measured and incubated in an instrument with the light source  20  and the sensor  22 . The different rates of growth of a pathogen could be measured for each chamber that holds variable concentrations of the antibiotic, and a “minimum inhibitive concentration” can be established from these results in a short period. This may be incorporated into a cuvette assembly  10  having chambers with no chemo-effectors, or chambers that do not receive liquid samples but are simply present to provide control or calibration standards for the optical measurements associated with the light source  20  and the sensor  22 . In other words, the present invention contemplates an optical chamber in the cuvette assembly as containing a control or calibration liquid. 
     With regard to the specific use of a chemo-effectors, a chemo-effector may be a dry (e.g., lyophilized) material, a coating on a surface of one of the chambers or on the filter, a liquid or solution, a gaseous atmosphere (such as Argon, O2, or CO2), or some combination. In the present invention, the chemo-effector is preferably pre-loaded into the cuvette assembly  10 , and closed by one of the internal membranes, films, foils, or other frangible or moveable feature for future use. The chemo-effector may be a growth media combined with an antibiotic and combined with other biochemical reagents. In particular, the chemo-effector could be loaded into the fluid-input chamber  14 , enclosed with a frangible membrane above it and/or below it (for example, membrane  34 , filter membrane  32 ,  132 , film  340 , membrane  440 , and/or a film below the filter  132  and above the intermediate partition  130 ) to isolate it from the optical chamber  12 . The cuvette assembly  10  would permit the piercing of the frangible membranes in a sequence to provide for exposure of the chemo-effector to a loaded liquid sample, to another chemo effector, to a vacuum or gaseous environment, or to a permeable filter membrane, prior to or in the process of transferring the fluid sample to the optical chamber  14 . 
     Each of these embodiments and obvious variations thereof is contemplated as falling within the spirit and scope of the claimed invention, which is set forth in the following claims. Moreover, the present concepts expressly include any and all combinations and subcombinations of the preceding elements and aspects.