Abstract:
A microfluidic device can include: a channel; a fluid inlet to pass fluid into the channel from a reservoir; a sensor disposed in the channel; and a pump actuator disposed in the channel apart from the sensor to induce fluid flow into the channel.

Description:
BACKGROUND 
       [0001]    Microfluidics is an increasingly important technology that applies across a variety of disciplines including engineering, physics, chemistry, microtechnology and biotechnology. Microfluidics involves the study of small volumes of fluid and how to manipulate, control and use such small volumes of fluid in various microfluidic systems and devices such as microfluidic chips. For example, microfluidic biochips (referred to as “lab-on-chip”) are used in the field of molecular biology to integrate assay operations for purposes such as analyzing enzymes and DNA, detecting biochemical toxins and pathogens, diagnosing diseases, etc. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0002]    Some embodiments of the invention are described with respect to the following figures: 
           [0003]      FIG. 1  shows a microfluidic diagnostic system according to an example implementation. 
           [0004]      FIG. 2  is a block diagram showing an exemplary configuration of the diagnostic system shown in  FIG. 1  according to an example implementation. 
           [0005]      FIG. 3  is a block diagram showing a sensor module according to an example implementation. 
           [0006]      FIG. 4  is a schematic diagram of a microfluidic structure suitable for implementing a microfluidic sensor according to an example implementation. 
           [0007]      FIG. 5  is a schematic diagram of a microfluidic structure suitable for implementing a microfluidic sensor according to an example implementation. 
           [0008]      FIG. 6  is a schematic diagram of a microfluidic structure suitable for implementing a microfluidic sensor according to an example implementation. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    A living cell is the basic structural and functional unit of an organism. Most animal and plant cells range in size from  1 - 100  micrometers and contain vital health information. Cell-based diagnostics is the gold standard for detecting infection diseases (HIV, Malaria, Tuberculosis), as well as chronic diseases (cancer, cardiac diseases, autoimmune diseases). Traditional cellular-level diagnostic tools are expensive, require specialized training to operate, and cannot always be deployed at the point-of-care setting. The microfluidic diagnostic system described herein can be used to provide a configurable and mobile platform to address the worldwide need for affordable health diagnostics. In examples described herein, 
         [0010]      FIG. 1  shows a microfluidic diagnostic system  100  according to an example implementation. The example microfluidic diagnostic system  100  includes a microfluidic device  102 , an external fluid reservoir  104 , an electronic controller  106 , and a host device  108 . In general, fluid is placed in the fluid reservoir  104 . The fluid can be a host fluid having particles (e.g., a blood sample, an ink containing pigments/particles, or the like). The fluid  102  is processed through microfluidics and applied to a sensor in the microfluidic device  102  under control of the electronic controller  106 . The microfluidic device  102  provides an electrical output signal representing the sensor data to the electronic controller  106 . The electronic controller  106  is under control of the host device  108 . The host device  108  can send and receive data to and from the electronic controller  106 , including command information for controlling the microfluidic device  102  and sensor data obtained from the microfluidic device  102 . 
         [0011]    The host device  108  generally includes a central processing unit (CPU)  110 , various support circuits  112 , memory  114 , various input/output ( 10 ) circuits  116 , and an external interface  118 . The CPU  110  can include any type of microprocessor known in the art. The support circuits  112  can include cache, power supplies, clock circuits, data registers, and the like. The memory  114  can include random access memory, read only memory, cache memory, magnetic read/write memory, or the like or any combination of such memory devices. The  10  circuits  116  can cooperate with the external interface  118  to facilitate communication with the electronic controller  106  over a communication medium  119 . The communication medium  119  can be any type of electrical, optical, radio frequency (RF), or the like transfer path. 
         [0012]    In an example, the external interface  118  can include a universal serial bus (USB) controller capable of sending and receiving data to the electronic controller  106 , as well as providing power to the electronic controller  106 , over a USB cable. It is to be understood that other types of electrical, optical, or RF interfaces to the electronic controller  106  can be used to send and receive data and/or provide power. 
         [0013]    The memory  114  can store an operating system (OS)  109  and a driver  111 . The OS  109  and the driver  111  can include instructions executable by the CPU  110  for controlling the host device  108  and the electronic controller  106  through the external interface  118 . The driver  111  provides an interface between the OS  109  and the electronic controller  106 . Accordingly, the host device  108  comprises a programmable device that includes machine-readable instructions stored in the form of one or more software modules, for example, on non-transitory processor/computer readable-media (e.g., the memory  114 ). 
         [0014]    The host device  108  can include a display  120  through which the OS  109  can provide a user interface (UI)  122 . A user can use the UI  122  to interact with the OS  109  and the driver  111  to control the electronic controller  106 , and display data received from the electronic controller  106 . It is to be understood that the host device  108  can be any type of general or specific purposed computing device. In an example, the host device  108  can be a mobile computing device, such as a “smart phone,” “tablet” or the like. 
         [0015]    The external fluid reservoir  104  is in fluidic communication with the microfluidic device  102 . The external fluid reservoir  104  is configured to hold and supply fluidic components/samples and/or solutions to the microfluidic device  102 . The microfluidic device  102  can be implemented as a chip-based device. Various example implementations of the device  102  are described below and can generally include inlet/outlet chamber(s)  124 , microfluidic channel(s)  126 , actuator(s)  128 , microfluidic filter(s)  130 , sensor(s)  131 , and an electrical interface  132 . The electronic controller  108  is coupled to the electrical interface  132  for energizing the actuator(s)  128  and sensor(s)  131 . In general, the structures and components of the chip-based microfluidic device  102  can be fabricated using conventional integrated circuit microfabrication techniques such as electroforming, laser ablation, anisotropic etching, sputtering, dry and wet etching, photolithography, casting, molding, stamping, machining, spin coating, laminating, and so on. 
         [0016]    In one example, the electronic controller  108  includes a controller  134 ,  10  circuits  136 , and a memory  138 . The controller  134  can include any type of microcontroller or microprocessor known in the art. In an example, the electronic controller  108  receives power from the host device  108 . In another example, the electronic controller  108  can include a power supply  142 . 
         [0017]    The memory  138  can store firmware  140 , which can include instructions executable by the controller  134  for controlling the microfluidic device  102  and communicating with the host device  108 . Accordingly, the electronic controller  106  comprises a programmable device that includes machine-readable instructions stored in the form of one or more software/firmware modules, for example, on non-transitory processor/computer readable-media (e.g., the memory  138 ). It is to be understood that, which described as a controller executing instructions from a firmware, the electronic controller  108  can be implemented using hardware, software/firmware, or a combination thereof. For example, all or a portion of the electronic controller  106  can be implemented using a programmable logic device (PLD, application specific integrated circuit (ASIC), or the like. 
         [0018]      FIG. 2  is a block diagram showing an exemplary configuration  200  of the diagnostic system  100  shown in  FIG. 1  according to an example implementation. In the example, the fluid reservoir  104 , the microfluidic device, and the electrical interface  132  are part of a first module  202 . The electronic controller  106  is part of a second module  204 . The first module  202  can be mechanically coupled to the second module  204  such that the electronic controller  106  is electrically coupled to the electrical interface  132 . The first module  202  is removably coupled to the second module  204  so that it can be coupled and uncoupled as needed. The electronic controller  106  can be coupled to the host device  108  as described above. 
         [0019]      FIG. 3  is a block diagram showing a sensor module  300  according to an example implementation. The sensor module  300  can be used as the module  202  in the diagnostic system  100  as shown in  FIGS. 1 and 2 . The sensor module  300  includes a substrate  302 , a microfluidic structure  304 , a fluid reservoir  306 , and electrical interface  308 . The electrical interface  308  transfers energy to active components in the microfluidic structure  304  via conductors  310  on the substrate  302 . The fluid reservoir  306  is configured to hold and supply fluidic components/samples and/or solutions to the microfluidic structure  304 . Example microfluidic structures are described below. 
         [0020]      FIG. 4  is a schematic diagram of a microfluidic structure  400  suitable for implementing a microfluidic sensor according to an example implementation. The microfluidic structure  400  includes a microfluidic channel  402 , a pump actuator  404 , a sensor  406 , a nozzle  405  (e.g., outlet), and an inlet  408 . A portion  414  of the fluid reservoir is shown. In an example, a mesh filter  412  can be provided in the fluid reservoir  414  for filtering particles in the applied fluid sample. While the shape of the fluid channel  402  is shown generally throughout this disclosure as “u-shaped”, this is not intended as a limitation on the shape of the channel  402 . Thus, the shape of the channel  402  can include other shapes, such as curved shapes, snake-like shapes, shapes with corners, combinations thereof, and so on. Moreover, the channel  402  is not shown to any particular scale or proportion. The width of the channel  402  as fabricated on a device can vary from any scale or proportion shown in the drawings of this disclosure. The arrows in the channel indicate and example direction of fluid flow through the channel. 
         [0021]    The inlet  408  provides an opening for the channel  402  to receive the fluid. The filter  410  is disposed in the inlet  408 . The filter  410  prevents particles in the fluid of a particular size (depending on the size of the filter  410 ) from entering the channel  402 . The inlet  408  can have a larger width and volume than the channel  402 . 
         [0022]    In an example, the sensor  406  is disposed in the channel  402  near the inlet  408  (e.g., closer to the inlet  408  than the pump actuator  404 ). In another example, the sensor  406  can be disposed in the inlet  408 . The sensor  406  can be an impedance sensor formed using known semiconductor techniques. The sensor  406  can detect impedance changes as particles in the fluid pass over the sensor  406 . 
         [0023]    The pump actuator  404  is disposed near a closed end of the channel  402  downstream from the sensor  406 . The pump actuator  404  can be a fluidic inertial pump actuator, which can be implemented using a wide variety of structures. For example, the pump actuator  404  can be a thermal resistor that produces vapor bubbles to create fluid displacement within the channel  402 . The displaced fluid can be ejected from the nozzle  405 . Actuators can also be implemented as piezo elements (e.g., PZT) whose electrically induced deflections generate fluid displacements within the channel  402 . Other deflective membrane elements activated by electrical, magnetic, and other forces are also possible for use in implementing the pump actuator  404 . 
         [0024]      FIG. 5  is a schematic diagram of a microfluidic structure  500  suitable for implementing a microfluidic sensor according to an example implementation. Elements of  FIG. 5  that are the same or similar to those of  FIG. 4  are described in detail above. In the example of  FIG. 4 , flow fluid is induced by ejection using the pump actuator  404 . In the present example of  FIG. 5 , fluid flow is induced by recirculation using the pump actuator  404 . The channel  402  includes an inlet  504  at the end of the channel  402  opposite an outlet  506 . A filter  502  can be formed in the inlet  504 , and a filter  508  can be disposed in the outlet  506 , to filter particles of a desired size (based on filter size). The arrows denote direction of fluid flow in the channel  402 . Instead of ejecting the fluid, the channel  402  recirculates the fluid back to the reservoir. 
         [0025]      FIG. 6  is a schematic diagram of a microfluidic structure  600  suitable for implementing a microfluidic sensor according to an example implementation. The example of  FIG. 6  shows a cross-flow structure that can separate particles of different sizes within the channel. In this example, the structure  600  includes a primary channel  604  and a secondary channel  605 . Arrows show an example direction of fluid flow from an inlet  618  to an outlet  616 . Note this fluid flow direction is an example, and that the fluid can flow in the reverse direction. Fluid can enter the primary channel  604  from the reservoir through an optional mesh filter  606 . Further, although omitted for clarity, filters can be disposed within the inlet  618  and/or outlet  616  as described in the structures above. A pump actuator  602  is disposed in the primary channel  604  near the inlet  618 . The secondary channel  605  includes an inlet  609  and an outlet  611 . Filters  608  and  614  can be disposed in the inlet  609  and outlet  611 , respectively. A sensor  610  is disposed in the secondary channel  605  near the inlet  609 . A pump actuator  612  is disposed in the secondary channel  605 . 
         [0026]    Fluid flows into the primary channel  604  from the inlet  618 . The pump actuator  602  induces fluid flow into the primary channel  604 . At the inlet  609  of the secondary channel  605 , fluid can flow to the secondary channel  605  and continue along the primary channel  604 . The filter  608  and the filter  614  can be designed such that smaller particles flow into the secondary channel  605  than in the primary channel  604 . The smaller particles rejoin the fluid in the primary channel  604  at the outlet  611 . The pump actuator  612  induces fluid flow into the secondary channel  605 . The sensor  610  can measure the particles in the secondary channel  605  (e.g., impedance sensing). 
         [0027]    By way of example, the microfluidic structure  600  has been shown and described as having two channels (primary and secondary). It is to be understood that the microfluidic structure can have any number of channels. For example, a microfluidic structure can include two different secondary loops fluidically coupled to a primary loop. In another example, a microfluidic structure can include one loop, coupled to another loop, coupled to another loop, and so on. Various configurations of a microfluidic device can be devised having any number of channels or loops. 
         [0028]    In the foregoing description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details. While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover such modifications and variations as fall within the true spirit and scope of the invention.