Abstract:
The present invention disclosed a biosensor apparatus comprising a substrate on which a reaction region is defined, a fluid channel defining a path to the reaction region, and a venting means communicably coupled with the fluid channel and opening exterior of the biosensor apparatus at a perimeter side of the biosensor apparatus. The present invention allows air to exit the fluid channel through perimeter sides of the biosensor apparatus without adding significant manufacturing complexity.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to Application Ser. No. 61/619,790 filed on Apr. 3, 2012 which is incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to a biosensor apparatus. More particularly, the present disclosure relates to a biosensor apparatus such as a blood glucose test strip that is configured to allow air to exit 
       BACKGROUND 
       [0003]    Aspects of the present invention relate generally to the field of biosensor design, and more specifically to the design of a blood glucose test strip. 
         [0004]    In a blood glucose metering system, a conventional test strip typically employs a venting hole on the cover layer of a test strip. For example, as shown in  FIG. 1 , the test strip consists of a cover layer  100 , a spacer  200  and a base layer  300 . Typically, the spacer  200  is sandwiched between the cover layer  100  and the base layer  300 . Once the spacer  200  is combined with the cover layer  100  and the base layer  300 , a channel  210  is formed, and the blood can flow from the opening of the channel  210  to the reaction area. In order to facilitate the blood flow inside the channel  210 , the bottom surface of the cover layer would be hydrophilic in order to facilitate capillary motion inside the channel. In addition, to further facilitate the blood flow, the cover layer  100  comprises of a venting hole  110  such that, when the blood enters the channel, air can exit through the venting hole  110 . 
         [0005]    A problem in regard to the previous configuration is that forming the venting hole  110  on the cover layer  100  limits the strip&#39;s design flexibility. Moreover, because the blood may stop flowing once reached the venting hole  110 , the venting hole  110  will have to be placed after the reaction zone, thereby further limiting the design flexibility. In addition, the blood may sometimes flow through the venting hole  110 , thereby causing possible contamination. 
         [0006]    Accordingly, there is a need for a design allowing air to exit the channel through lateral sides of the blood glucose test strip, without adding significant manufacturing complexity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The present disclosure is to be read in conjunction with the accompanying drawings, in which: 
           [0008]      FIG. 1  illustrates a schematic diagram of a conventional biosensor apparatus; 
           [0009]      FIG. 2  illustrates a schematic diagram of a biosensor apparatus in accordance with an embodiment of the present disclosure; 
           [0010]      FIG. 3  is a drawing showing a venting means in accordance with an embodiment of the present disclosure; 
           [0011]      FIG. 4  is a drawing showing a venting means in accordance with an embodiment of the present disclosure; 
           [0012]      FIG. 5  is a drawing showing a venting means in accordance with an embodiment of the present disclosure; 
           [0013]      FIG. 6  is a drawing showing a venting means in accordance with an embodiment of the present disclosure; 
           [0014]      FIG. 7  is a drawing showing a venting means in accordance with an embodiment of the present disclosure; 
           [0015]      FIG. 8  illustrates a schematic diagram of a biosensor apparatus in accordance with an embodiment of the present disclosure; 
           [0016]      FIG. 9  illustrates a schematic diagram of a biosensor apparatus in accordance with an embodiment of the present disclosure; 
           [0017]      FIG. 10  illustrates a schematic diagram of a biosensor apparatus in accordance with an embodiment of the present disclosure; 
           [0018]      FIG. 11  illustrates a schematic diagram of a biosensor apparatus in accordance with an embodiment of the present disclosure; 
           [0019]      FIG. 12  illustrates a schematic diagram of a biosensor apparatus in accordance with an embodiment of the present disclosure; 
           [0020]      FIGS. 13A , B and C illustrate the process of fluid flow when stopping chambers are employed in accordance with an embodiment of the present disclosure; 
           [0021]      FIGS. 14A  and B illustrate schematic diagrams of biosensor apparatus in accordance with an embodiment of the present disclosure; 
           [0022]      FIG. 15  illustrates a schematic diagram of a biosensor apparatus in accordance with an embodiment of the present disclosure. 
           [0023]      FIG. 16  illustrates a schematic diagram of a biosensor apparatus in accordance with an embodiment of the present disclosure. 
       
    
    
     SUMMARY 
       [0024]    In light of the above, the present disclosure provides a biosensor apparatus to allow air to exit the channel through perimeter sides of a biosensor without adding significant manufacturing complexity. 
         [0025]    According to one aspect, a biosensor apparatus comprises a substrate on which a reaction region is defined, a fluid channel defining a path to the reaction region, and a venting means communicably coupled with the fluid channel and opening exterior of the biosensor apparatus at a perimeter side of the biosensor apparatus. The apparatus may further comprise a spacer layer disposed on the substrate to define the fluid channel, and a cover layer disposed on the spacer layer. The cover layer may comprise an optically transparent material and wherein a bottom surface of the cover layer adjacent the fluid channel is hydrophilic. This allows the user to observe and determine the volume of introduced blood. 
         [0026]    In one embodiment, the venting means may comprise a passageway disposed on a bottom surface of the cover layer for discharging the air through one or more of lateral sides and back side of the cover layer. Still, the venting means may comprise at least one part of a linear passageway that is substantially perpendicular to the path of the fluid channel. The venting means may otherwise comprise a passageway disposed on an upper surface of the substrate for discharging the air through one or more of lateral sides of the substrate and a back side of the spacer layer opposing an opening of the fluid channel. Still, the venting means may comprise a passageway disposed on the spacer layer and communicably coupled to an end portion of the fluid channel, the passageway capable of discharging the air through one or more sides of the spacer layer. 
         [0027]    In one embodiment, the apparatus comprising a dielectric layer disposed on the substrate, the dielectric layer comprising a reaction chamber that defines the reaction region. The venting means in this embodiment may comprise a passageway disposed on a rear portion of the dielectric layer for discharging the air through one or more of lateral sides and a back side of the dielectric layer. The dielectric layer may comprise a stopping chamber communicably coupled between an end portion of the fluid channel and the venting means, wherein the stopping chamber comprises a cross sectional area substantially greater than that of the fluid channel. In another embodiment, the spacer layer may further define a stopping chamber at an end portion of the fluid channel, the stopping chamber having a cross sectional area substantially greater than that of the fluid channel. The stopping chamber may be communicably coupled between the fluid channel and the venting means, wherein the stopping chamber may comprise a cross sectional area substantially greater than that of the fluid channel. This stopping chamber helps slow down the velocity of blood inflow into the fluid channel. 
         [0028]    In one embodiment, a top surface, a bottom surface, and said perimeter side define a geometrical dimension of the biosensor apparatus. 
         [0029]    In one embodiment, a biosensor apparatus may comprise a substrate on which a reaction region is defined, a fluid channel for introducing a fluid sample to the reaction region, a venting channel communicably coupled with the fluid channel, and a sample reservoir communicably coupled between the fluid channel and the venting channel. In this embodiment, the sample reservoir may comprise a cross sectional area substantially greater than that of the fluidic channel. 
         [0030]    In one embodiment, the biosensor apparatus may further comprise a spacer layer disposed on the substrate to define the fluid channel. In another embodiment, the biosensor apparatus may further comprise a cover layer disposed on the spacer layer, wherein the venting channel is disposed on a bottom surface of the cover layer for discharging the air through a perimeter side of the cover layer. In these embodiments, the venting channel may be disposed on a rear portion of the spacer layer for discharging the air through a perimeter side of the space layer. In addition, the venting channel is disposed on an upper surface of the substrate for discharging the air through a perimeter side of the substrate. 
         [0031]    In one embodiment, the biosensor may further comprise a dielectric layer disposed between the spacer layer and the substrate, the dielectric layer comprising a reaction chamber that defines the reaction region, and a stopping chamber that defines the sample reservoir. The stopping chamber may comprise a cross sectional area substantially greater than that of the fluid channel. It is to be noted that the description above is only a summary of the invention and a person having ordinary skill in the art would appreciate that the present invention may be applied in a different way other than the disclosed. 
       DETAILED DESCRIPTION 
       [0032]    Embodiments of the present invention provide a blood glucose test strip that employs a capillary channel for the blood flow and at least one venting means to allow air to exit the capillary channel once the blood flows inside. It should be noted that, although the present invention is preferably employed to test glucose level inside a blood sample, a person of ordinary skill in the art would appreciate that the present invention may be applied to all kinds of biological samples (such as blood, urine, and saliva) and may be employed to test one or more biological characteristics within the biological sample. The biological characteristics include, but not limited to, uric acid, cholesterol, hemoglobin, ketone body, glycohemoglobin (HbA1c), and alpha-fetoprotein (AFP). 
         [0033]    As best shown in  FIG. 2 , the test strip may generally have a layered structure. Working upward from the lowest layer, the test strip may comprise a base layer  300  extending along the entire length of the test strip. 
         [0034]    The base layer  300  may preferably consist of an electrically insulating material and may have a thickness sufficient to provide necessary structural support for the test strip. For example, the insulating material for a base layer  300  may be polyester, polytetrafluoroethylene (Teflon), FR-1, CEM-1, CEM-3, FR-2 (Phenolic cotton paper), FR-3 (Cotton paper and epoxy), FR-4 (Woven glass and epoxy), FR-5 (Woven glass and epoxy), FR-6 (Matte glass and polyester), G-10 (Woven glass and epoxy), CEM-1 (Cotton paper and epoxy), CEM-2 (Cotton paper and epoxy), CEM-3 (Non-woven glass and epoxy), CEM-4 (Woven glass and epoxy), CEM-5 (Woven glass and polyester), or any other insulating material that can provide necessary support for the test strip. In addition, the base layer  300  may comprise conductive electrodes, wires, and contact pads, which may be used for testing or for communicating with the test meter. For example, electrodes  301  and  302  may measure the voltage drop or current flow across electrodes  301  and  302 . The test meter may contact electrodes  301  and  302  to detect one or more biological characteristics associated with the blood sample in the reaction chamber and may use the other electrodes to check whether a sufficient amount of blood sample has been obtained, or to check whether a test strip has been properly inserted. These conductive electrodes, wires, and contact pads may be made of thin copper foil, gold, or any other non-insulating material. 
         [0035]    The next layer in the test strip may be a dielectric layer  400  disposed on the base layer  300 . The dielectric layer  400  may cover only part of the base layer  300 . In addition, it may include a reaction chamber  401  that is used to deposit the reagent or testing enzyme used to react with the blood sample. A dielectric layer  400  may be made of any insulating material, such as polyester. 
         [0036]    The next layer in the test strip may be a channel layer  200 . A hollow in a channel layer  200  may form a channel  210  that allows the blood sample to reach the reaction chamber  401 . The channel layer  200  may preferably be made of an adhesive material that allows a channel layer  200  to adhere to the dielectric layer  400  and the cover layer  100 . 
         [0037]    The next layer in the test strip may be a cover layer  100  that is used to form a protective shield for a channel layer  200 , and possibly to form the upper boundary of the channel  210 . The lower boundary of the channel  210  may be formed by the dielectric layer  400 , or by the combination of the dielectric layer  400  and the base layer  300 . A cover layer  100  may be made of a transparent material such that the user of the test strip may observe the blood sample in the channel  210 , and therefore may determine whether a sufficient amount of blood sample has been provided to the test strip. 
         [0038]    As previously mentioned, in order to facilitate the blood flow inside the channel  210 , the bottom surface of the cover layer may be hydrophilic to pull the blood sample toward the reaction chamber  401 . In addition, the base layer  300  and the dielectric layer  400  may also receive hydrophilic surface treatment to further increase the pulling force applied on the blood sample. 
         [0039]    When the blood sample enters the channel  210 , the air inside the channel  210  becomes compressed, thereby reducing the blood flow velocity and possibly causing the blood to stop flowing completely. Thus, discharging the air inside the channel  210  is necessary to allow the blood sample to reach the reaction chamber  401  efficiently. 
         [0040]    In  FIG. 2 , the venting hole  110  is formed on the cover layer  100 . The venting hole is located above the channel  210 , thereby allowing the air to exit through the venting hole  110  when the blood sample enters the channel  210 . 
         [0041]    Alternatively, the venting channel  120  may be formed on the cover layer  100  to allow the air to enter through the venting channel  120  and exit through its opening(s). For example, in  FIG. 3 , the air inside the channel  210  may be vented through the venting channel  120  and exits through the two openings located on the lateral sides of the cover layer  100 . 
         [0042]    A person of ordinary skill in the art would appreciate that the direction of the venting channel  210  is not material for the present invention. For example, as shown in  FIG. 4 , the exit opening of the venting channel  120  may be located at the back side of the cover layer  100 . 
         [0043]    In addition, a person of ordinary skill in the art would appreciate that the cover layer may comprise multiple venting channels and/or venting holes to discharge the air in the channel  210 . For example, in  FIG. 5 , the cover layer  100  may comprise the venting channel  120  and the venting channel  121 . A person of ordinary skill in the art would appreciate that not all venting channels must be overlapped with the channel  210 —the air inside the channel  210  may first enter a first venting channel and then redirected or divided into a second venting channel. 
         [0044]    A person of ordinary skill in the art would appreciate that the similar venting mechanism may also be employed in the base layer. For example, the venting channel may be formed on the base layer  100 . As depicted in  FIG. 6  (for the sake of clarity, the electrodes, wires, contact pads and dielectric layers are omitted), the venting channel  320  may be formed on the base layer  300  so that the air may exist from venting channel  320  once the blood enters into the channel  210 . The direction of the venting channel  320  may be substantially perpendicular to the channel  210 , as depicted in  FIG. 6 , or parallel to the channel  210 , as depicted in  FIG. 7 . A person of ordinary skill in the art would appreciate that multiple venting channels and/or venting holes may be formed on the base layer  300  and the directions of the venting channels are not material for the present invention. 
         [0045]    Similarly, the venting channel  220  may also be formed on the spacer  200 . As depicted in  FIG. 8  (for the sake of clarity, the electrodes, wires, contact pads and dielectric layers are omitted), the venting channel  220  is connected to the channel  210  such that air may exist from the venting channel  220  once it enters into the channel  210 . 
         [0046]    In addition to forming the venting channel on the cover layer, on the base layer, or on the dielectric spacer, the venting channel may also be formed on a separate layer that is adjacent to the channel layer. For example, as depicted in  FIG. 9 , the venting channels  402  and  403  in the dielectric layer  400  may be used to discharge air inside channel  210 . Thus, when the blood sample enters into the channel  210 , air may exit from the venting channels  402  and  403  located in the dielectric layer  400 . 
         [0047]    The dielectric layer  400  may have multiple venting channels. For example, in  FIG. 10 , the dielectric layer  400  may have 3 venting channels, two at the lateral sides of the dielectric layer  400  and one at the back of the dielectric layer  400 . In  FIG. 11 , the dielectric layer  400  may have 5 venting channels, four at the two lateral sides of the dielectric layer  400  and one at the back side of the dielectric layer  400 . 
         [0048]    As previously described, the venting channels  210  may be formed on the base layer  300 , the dielectric layer  400 , the channel layer  200 , and the cover layer  100 . In addition, the vent openings may be formed on the cover layer  100  and the base layer  300 . A person of ordinary skill in the art would appreciate that the principle of the present invention applies to different combinations of the venting mechanisms. For example, the air inside the channel  210  may be vented through both the venting channels in the dielectric layer  400  and the venting channel on the cover layer  100 . 
         [0049]      FIG. 12  depicts another embodiment of the present invention. As shown, the channel layer  200  comprises of a channel  210  and the blood-stopping chambers  211  and  212 . By adding the blood-stopping chambers  211  and  212 , when the blood sample flows through the interface between the channel  210  and the blood-stopping chambers  211  and  212 , the flow would substantially slow down. Slowing down the blood flow at the interface can prevent the blood sample from flowing into the venting channels or venting holes, thereby prevent possible contamination. 
         [0050]    The flow of the blood sample inside the channel layer  200  may be explained in  FIGS. 13   a, b , and  c . In order to maintain an accurate measurement of glucose concentrations, the channel  210  for the sample fluid, whether the blood sample or a control solution, must have a constant cross sectional area, in which the cross sectional area is calculated by multiplying the height of the channel by the width of the channel, for the sample fluid to sip into the channel  210  by capillary force. In  FIG. 13   a , the blood sample  220  enters into the channel  210 . As previously described, the compressed air may exit through the channel through any of the described venting mechanisms. Based on the theory of physics, i.e. continuity equation, in which represents density, V represents flow velocity for fluid and A represents cross sectional area, in a biosensor, the density of the sample fluid does not change over time, and thus the equation becomes A 1 V 1 =A 2 V 2 . Therefore, if the width of the cross sectional area behind the channel  210  is smaller than that of the channel  210 , the flow velocity for the fluid to travel behind the channel  210  will be faster than that in the channel  210 , for the same volume of fluid to travel. On the contrary, if the width of the cross sectional area behind the channel  210  is larger than that of the channel  210 , the flow velocity for the fluid to travel behind the channel  210  will be slower than that in the channel  210 . In the event that if the width of the cross sectional area behind the channel  210  is much larger than that of the channel  210 , the flow velocity for the fluid to travel behind the channel  210  will be much slower than that in the channel  210 . In  FIG. 13   b , the blood sample  220  reaches the interface between the channel  210  and the blood-stopping chambers  211  and  212 . At this point in time, the blood sample flow would be slowed down once it begins to enter the blood-stopping chambers  211  and  212 . In  FIG. 14   c , the blood sample reaches the blood-stopping chambers  211  and  212  and its flow velocity is substantially lowered. 
         [0051]      FIGS. 14   a  and  b  depict embodiments of the present invention. In  FIGS. 14   a  and  b , the blood sample flow may be slowed down by the abrupt increase in the available flow space caused by the chamber  420  in the dielectric layer  400 . In  FIG. 14   a , the air may exit through the lateral venting channel  410 . In  FIG. 14   b , the air may exit through the back venting channel  410 . 
         [0052]      FIG. 15  depicts an embodiment of the present invention. As shown, the channel layer  200  has incorporated the blood-stopping chambers previously described to slow down the blood flow. The dielectric layer  400  has incorporated the venting channels  402  and  403 . Thus, when the blood sample enters into the channel  210 , the air inside the channel may exit through the venting channels  402  and  403 . In addition, once the blood sample reaches the blood-stopping chambers in the channel layer  200 , the flow of the blood sample would be substantially slowed down. 
         [0053]    A person of ordinary skill in the art would appreciate that the previously described venting mechanisms may be combined with the different types of the blood-stopping mechanisms previously described. For example, in  FIG. 16 , the blood-stopping mechanism on the channel layer  200  may be combined with the  5  venting channels in the dielectric layer  400 .