Patent Description:
Chemical sensors can be fabricated using semiconductor technology. The use of semiconductor manufacturing can result in a reduction of size of the chemical sensor as well as mass fabrication of chemical sensors, thereby reducing per unit cost of each sensor. More generally, the use of semiconductor manufacturing to manufacture sensors produces the same or similar benefits as it does for electrical circuits: low cost per sensor, small size, and highly reproducible behavior.

Semiconductor manufacturing technology also provides precise control of layer thickness and lateral dimensions, so that the sensors can be miniaturized, and so that they will have well-controlled characteristics. By making the sensors small, one can calibrate them with small volumes of calibration solution. Sample volumes can be small (which may not be important in testing water, but may be important in testing other solutions, such as blood samples from newborns). Operation of the sensors also requires rinsing between samples, and storage in a controlled solution. Volumes of all of these solutions can be smaller if the sensors are miniaturized, as they are on the silicon substrates.

<CIT> discloses an elastomer, especially a fluoropolymeric elastomer, meets requirements necessary for use as a gasket in contact with primary membranes of electrochemical sensors of both blood gas and ionic species in blood. The elastomer can electrochemically seal an electrode of a diced chip (sensor) from a sample chamber, and can electrochemically seal electrodes of neighboring diced chips from each other.

Chemical sensors, such as ion selective electrodes (ISEs), can be used in microfluidic sensor chips. The polymeric sensing membranes used to form the ISEs do not adhere well to silicon nitride or silicon dioxide surfaces that are often used to insulate silicon dies and to protect the conducting layers in the die from the solution under test and from the internal filling solution that is between the electrode and the membrane. Poor membrane-to-sensor-die adhesion results in unreliable sensors and short sensor lifetimes. Polymeric membranes can be adhered to the sensor surface by salinizing the silicon dioxide surface and interposing adhesion layers between this surface and the polymeric membrane. The deposition of these additional layers adds complexity to the manufacturing process, and the components of the adhesion layers can poison the sensing membrane. This disclosure describes a mechanical method of adhering a polymeric membrane to the surface of a solid-state liquid chemical sensor, thereby making the sensor more reliable and robust, and giving the sensor a longer lifetime.

Aspects of the embodiments are directed to a microfluidic chip that includes a microfluidics channel in the microfluidic chip. The chip also includes a top surface and an intermediate surface, wherein the intermediate surface is lower in height than the top surface. The microfluidic chip also includes an opening in the intermediate surface exposing a microfluidic channel; a clamping bump projecting from the intermediate surface and surrounding the opening; and a solid-state chemical sensor residing on a sensor die, at least a portion of the solid-state chemical sensor in contact with the clamping bump of the microfluidic chip, the solid-state chemical sensor exposed to the microfluidics channel.

In some embodiments, the solid-state chemical sensor includes a sensor substrate residing on the microfluidic chip, the sensor substrate comprising a sensor device residing on a sensor-side of the substrate. The sensor-side of the sensor device can face the microfluidics channel. The sensor device can include a sensor-side electrode on the sensor-side of the substrate, the sensor-side electrode facing the microfluidics channel; a first polymer ring surrounding the sensor-side electrode; a second polymer ring surrounding the first polymer ring; a polymeric membrane encapsulating the sensor-side electrode and being contained by a second polymer ring.

In some embodiments, the clamping bump is in contact with the polymeric membrane at a location between the first polymer ring and the second polymer ring, the clamping bump clamping the sensor die to the microfluidic chip.

Some embodiments can also include a glue stop projecting from the intermediate surface and surrounding the clamping bump; and the substrate of the sensor device being in contact the glue stop.

In some embodiments, the glue stop defines an open space between the top surface and the intermediate surface, the microfluidic chip further comprising an adhesive substance in the space, the adhesive substance contacting the substrate, and securing the substrate to the intermediate surface.

In some embodiments, the sensor die comprises a plurality of solid-state chemical sensors, each of the plurality of solid-state chemical sensors exposed to the microfluidics channel.

In some embodiments, the clamping bump may be lower in height than the glue stop.

Some embodiments also include a trench between the clamping bump and the glue stop.

In some embodiments, the sensor die is clamped to the microfluidic chip by an adhesive.

In some embodiments, the sensor die can include a sensor side and a backside. The backside can including a backside electrode; and the sensor die can include a through-silicon via electrically connecting the sensor-side and the backside electrode.

Some embodiments also include a rigid structure affixed to the microfluidic chip, the printed circuit board comprising a contact pad, the backside electrode electrically connected to the contact pad by a wire.

In some embodiments, the rigid structure comprises a printed circuit board.

In some embodiments, the rigid structure is affixed to the microfluidic chip by one or more screws.

In some embodiments, the rigid structure is affixed to the microfluidic chip by doubled sided tape.

In some embodiments, the sensor die comprises a plurality of sensor devices.

In some embodiments, the opening is defined by a conical shape exposing the microfluidics channel.

There is also provided a method for forming a microfluidic system comprising a sensor device. The method can include providing a microfluidic chip, the microfluidic chip comprising a sensor device mounting surface, the sensor device mounting surface comprising an opening revealing a microfluidic channel and a clamping bump surrounding the opening and a glue stop surrounding the clamping bump; providing a substrate with a chemical sensor device onto the sensor device mounting surface, the chemical sensor device comprising an ion-selective sensor facing the microfluidic channel, the chemical sensor device further comprising a polymeric membrane facing the microfluidic channel, the substrate contacting the glue stop and the clamping bump surface contacting the membrane between two polymeric rings residing on the sensor die; applying a compressive load to the substrate in a direction towards the sensor device mounting surface; applying an adhesive substance to the substrate and an outer sidewall of the glue stop; and curing the adhesive substance under the compressive load.

In some embodiments, the chemical sensor comprises an electrode on a backside of the chemical sensor device electrically connected to the ion selective sensor and opposite the microfluidic channel. The method can also include adhering a printed circuit board to the microfluidic chip, the printed circuit board comprising an electrical contact pad; and electrically connecting the electrode on the backside of the chemical sensor to the electrical contact pad on the printed circuit board.

Chemical sensors, such as ion selective electrodes (ISEs) can be made using ionophore-doped polymeric membranes. For example, an ISE can use an ion-selective polymeric membrane that contains the ionophore Valinomycin for detecting potassium, or <NUM>-tert-Butylcalix[<NUM>]arene-tetraacetic acid tetraethyl ester for detecting sodium. The ionophore is a selective binding site for the analyte. The polymeric membrane establishes a barrier between the sensor electrode and an analyte solution. The polymeric membrane facilitates the introduction of an analyte to the ionophore, which binds the charged ion, creating a charge separation between the interior of the polymeric membrane and the external aqueous solution. The charge separation creates a voltage that can be measured to determine the presence and concentration of the specific analyte. An example chemical sensor is described in <CIT>.

Polymeric membranes do not adhere well to silicon nitride surfaces that are often used to insulate the silicon and to protect the silicon and other conducting layers from the solutions under test and from the internal filling solution that is between the electrode and the membrane. Additionally, polymeric membranes adhere better to silicon dioxide than to silicon nitride.

In this disclosure, a "gripping trench" is formed in the silicon nitride, with the bottom of the trench being the silicon dioxide passivation layer. The trench surrounds the entirety of the silver/silver chloride electrode. The polymeric sensing membrane can be deposited on the electrode (or on the hydrogel buffer solution) and the gripping trench to form a seamless membrane filling the gripping trench around the entire electrode. Electrical contact to the silver/silver chloride electrode is made with a conductive via (e.g., a through-silicon via) through the silicon substrate, from sensor-side to backside.

The backside electrode electrically coupled to the silver/silver chloride electrode through a via eliminates the need to wire-bond to the front side of the wafer, making practical the use of a physical clamp over the outer portion of the sensing membrane to hold the membrane onto the sensor die. The trench (also referred to herein as a gripping trench) is filled with cured membrane material, giving the clamp the ability to hold the outer portion of the membrane firmly in place, even when the center of the membrane stretches due to osmotic pressure in the internal filling solution. The gripping trenches can completely encircle the active sensor, thereby eliminating areas in which solution shunts could form between the internal fill and the sample solution. Polyimide, SU-<NUM>, or other high-aspect-ratio photopolymers can be used to form structures (e.g., polyimide rings or SU-<NUM> rings) to "contain" the deposited internal fill solution and membrane cocktail (e.g., through surface tension). In this disclosure, the specific embodiment that uses polyimide rings is described, for easy of discussion. It should be noted, however, that other polymers can be used for the polymer rings without deviating from the scope of the disclosure.

<FIG> is a schematic diagram of a sensor device <NUM> in accordance with embodiments of the present disclosure. The schematic diagram shown in <FIG> is not drawn to scale. Sensor device <NUM> includes a substrate <NUM>. Substrate <NUM> can include silicon <NUM>, such as silicon <<NUM>>. The substrate <NUM> includes a "sensor-side" <NUM> and a "backside" <NUM>. The sensor-side <NUM> can include a sensor-side first passivation layer <NUM>, which can be a silicon dioxide (SiO<NUM>) layer <NUM>. The substrate backside <NUM> can also include a backside passivation layer <NUM>, which can be silicon dioxide <NUM>. The term "layer" is used throughout this disclosure and is meant to include one or more layers of a material, and is not limited to meaning a monolayer or single atomic layer of a material.

The silicon substrate <NUM> can be doped to make it conductive, and can include an electrically isolated doped region <NUM>. The electrically isolated doped region <NUM> can include a p-type dopant, such as a boron p-type dopant. The sensor device <NUM> includes sensor-side electrode <NUM> and a backside electrode <NUM>. The electrically isolated doped region <NUM> can electrically connect the sensor-side electrode <NUM> with the backside electrode <NUM> and can be electrically isolated from the rest of the substrate by a passivation layer (e.g., SiO2 layer <NUM>). This electrically isolated doped region <NUM> can be referred to as a via <NUM> (which can be a through-silicon via <NUM>).

The backside electrode <NUM> can include a conductive material, such as a metal. In some embodiments, the backside electrode <NUM> may include gold (Au). The backside electrode <NUM> can be accessed by a bonding pad <NUM>. In some embodiments, another backside passivation layer <NUM> can be deposited over the backside electrode to protect the backside <NUM> from damage. The backside passivation layer <NUM> can include silicon nitride or silicon dioxide.

The sensor-side <NUM> can include a sensor-side electrode <NUM>. The via <NUM> is physically and electrically connected to the sensor-side electrode <NUM>. The sensor-side electrode can include silver (Ag) and silver chloride (AgCI). Silver chloride has a stable interfacial potential to the internal filling solution and desirable Ohmic properties.

In some embodiments, the via <NUM> is electrically and physically connected to a thin platinum disc <NUM>. The platinum disc <NUM> can be completely covered by silver. The silver has a chloridized surface, resulting in a silver/silver-chloride electrode.

On the sensor-side first passivation layer <NUM>, is a sensor-side second passivation layer <NUM>. The sensor-side second passivation layer <NUM> can include silicon nitride (Si<NUM>N<NUM>) and silicon dioxide (SiO<NUM>). As an example, the sensor-side second passivation layer <NUM> can be silicon nitride, or can include a layer of silicon dioxide on top of silicon nitride.

In some embodiments, adjacent to the sensor-side electrode <NUM> is a polyimide ring structure 126a residing on the sensor-side second passivation layer <NUM>. The polyimide ring 126a can be circular or substantially circular, and surround the sensor-side electrode <NUM>.

A gripping trench 122a can be etched into the sensor-side second passivation layer <NUM> adjacent to the polyimide ring structure 126a. The gripping trench 122a can be a first gripping trench 122a; multiple gripping trenches, such as the second gripping trench 122b can be formed adjacent to the first gripping trench 122a. The first and second gripping trenches 122a and 122b can be circular or substantially circular and can surround the sensor-side electrode <NUM> (and in some embodiments, surround the polyimide ring 126a).

The gripping trenches 122a and 122b can be etched to stop on the underlying sensor-side first passivation layer <NUM> (i.e., the silicon dioxide <NUM>). The shape of the gripping trenches 122a and 122b prevent the membrane from pulling toward the center of the sensor when the membrane hydrates, creating osmotic pressure in the internal filling solution.

In some embodiments, a second polyimide ring 126b can reside on the sensor-side second passivation layer <NUM>. The second polyimide ring 126b can be circular or substantially circular and can surround the sensor-side electrode <NUM> and the gripping trench 122a (and 122b or others, if present).

Though described as a silicon substrate, substrate <NUM> could in some embodiments be composed of glass or ceramic or other suitable material.

<FIG> is a schematic diagram <NUM> of a sensor device <NUM> that includes a polymeric membrane <NUM> in accordance with embodiments of the present disclosure. The diagram <NUM> of <FIG> shows the sensor device <NUM> of <FIG> with the addition of the polymeric membrane <NUM> as well as the hydrogel buffer solution <NUM>. In <FIG>, the first polyimide ring 126a can be shown to define the size of the hydrogel buffer solution <NUM>. The outer polyimide ring 126b defines the size of the polymeric membrane <NUM> that acts as the transducer of the sensor device <NUM>.

Also shown in <FIG> is the polymeric membrane <NUM> filling gripping trenches 122a and 122b. The polymeric membrane <NUM> can be "confined" by the second polyimide ring 126b based on the shape of the polyimide ring and based on surface tension of the deposited polymeric membrane cocktail solution, composed of the membrane components and organic solvent.

The polymeric membrane <NUM> is shown to contact the hydrogel buffer solution <NUM>. The hydrogel buffer solution <NUM> can reside within the first polyimide ring 126a and contact the electrode <NUM>. To provide a well-poised electrical contact to the polymeric membrane <NUM>, a hydrogel buffer solution <NUM> can be used between the silver/silver chloride electrode <NUM> and the polymeric membrane <NUM>. This hydrogel-based filling solution <NUM> is buffered with high concentrations of salts. The polymeric membrane <NUM> hydrates when exposed to aqueous solutions, and the high salt content of the hydrogel buffer solution <NUM> can generate considerable osmotic pressure on the polymeric membrane <NUM> as water moves through the membrane into the hydrogel.

By avoiding the need to put bonding wires on the sensor side of the die, the via <NUM> allows a mechanical clamp to be used to hold the polymeric membrane tightly onto the sensor device. The mechanical clamp and the gripping trench(es) 122a (and 122b) prevent the osmotic pressure created by the hydrogel buffer solution <NUM> from causing the hydrogel buffer solution to leak out from under the polymeric membrane <NUM>, forming an electrical short circuit path around the membrane.

<FIG> is a schematic diagram of a sensor die <NUM> that includes multiple sensor devices in accordance with embodiments of the present disclosure. Sensor die <NUM> can include a substrate <NUM>, as described above. The substrate <NUM> can include multiple sensors <NUM>. Each sensor <NUM> can include a membrane <NUM> confined by rings 126a and 126b. The membrane can cover gripping trenches 122a and 122b. A through-silicon via <NUM> can electrical connect the sensor <NUM> with a metal electrode on the substrate <NUM>. The substrate <NUM> can also include a ring <NUM>. Ring <NUM> can be formed to be the same or similar height as the rings 126a and 126b. Ring <NUM> can be a polyimide ring formed in the same or similar way as rings 126a and 126b. Ring <NUM> can be used as a glue stop, as described below. The sensor die <NUM> can include a plurality of sensors <NUM>, and two are shown in <FIG> as an example.

<FIG> is a schematic diagram <NUM> of a top-down sectional illustration of a sensor device <NUM> in accordance with embodiments of the present disclosure. At the center is the via <NUM>. Above the via <NUM> is the platinum disk <NUM>. Above the platinum disk <NUM> is the silver/silver chloride electrode <NUM>. Around the electrode <NUM> is the first polyimide ring 126a. Gripping trenches 122a and 122b surround the first polyimide ring 126a. The second polyimide ring 126b surrounds the gripping trenches 122a and 122b.

<FIG> is a schematic diagram of a top-down view of a portion of a microfluidic chip that includes multiple fluid channel access areas in accordance with embodiments of the present disclosure. The microfluidic chip <NUM> includes a top surface <NUM>, a first intermediate surface <NUM>, and a second intermediate surface <NUM>. The first intermediate surface <NUM> is lower in height than the top surface <NUM>, defining a step-wise transition from the first intermediate surface <NUM> to the top surface <NUM>. The second intermediate surface <NUM> is lower in height than the first intermediate surface <NUM>. The second intermediate surface <NUM> can include a glue stop <NUM>. Glue stop <NUM> can be a raised portion extending from the second intermediate surface <NUM>. Glue stop <NUM> can be substantially rectangular in shape. The glue stop <NUM> can have a height, such as <NUM> microns or similar.

The second intermediate surface <NUM> can include one or more sensor locations <NUM>. Each sensor location <NUM> can include an opening to receive a chemical sensor device, such as sensor device <NUM>. The second intermediate surface <NUM> can include a clamping bump <NUM> proximate to and surrounding the opening. The clamping bump <NUM> can have a width of about <NUM> microns and a height of about <NUM>-<NUM> microns. In some embodiments, the glue stop <NUM> can be taller than the clamping bump. In some embodiments, the glue stop <NUM> and the clamping bump <NUM> can have substantially the same or similar height dimensions.

The microfluidic chip <NUM> can have an x-dimension of (or substantially of) <NUM> and a y-dimension of (or substantially of) <NUM>. Ten chemical sensor locations are shown, which can be located at various locations on microfluidic chip <NUM>. Any combination of chemical sensor locations can be used (e.g., a single sensor can be used or a plurality in any combination of locations can be used).

The microfluidic chip <NUM> can be made of a poly methyl methacrylate (PMMA), polycarbonate, polystyrene, or other thermoplastic polymer.

<FIG> is a schematic diagram of a sectional view A-A <NUM> of a portion of a microfluidic chip in accordance with embodiments of the present disclosure. The microfluidic chip <NUM> includes a top surface <NUM>. The first intermediate surface <NUM> is shown as a step down from the top surface <NUM>. In embodiments, the first intermediate surface <NUM> creates a glue stop and glue application point for a sensor die <NUM> to be clamped onto the microfluidic chip. The second intermediate surface <NUM> is shown as a step down from the first intermediate surface <NUM>. The second intermediate surface <NUM> includes a glue stop <NUM> that surrounds a set of openings (e.g., opening 410a and 410b) to a microfluidic channel <NUM>. The second intermediate surface <NUM> also includes a clamping bump <NUM> that surrounds each opening <NUM>. In embodiments, the second intermediate surface <NUM> can include a trench <NUM> that can act as an additional glue stop. The trench <NUM> can be between the glue stop <NUM> and the set of openings.

<FIG> is a schematic diagram of a side sectional view B-B <NUM> of a microfluidic chip <NUM> in accordance with embodiments of the present disclosure. The side sectional view <NUM> illustrates the opening <NUM> that exposes the microfluidic channel <NUM>. The side sectional view <NUM> illustrates the top surface <NUM>, the first intermediate surface <NUM> stepped down from the top surface <NUM>; and second intermediate surface <NUM> stepped down from the first intermediate surface <NUM>. The glue stop <NUM> is shown extending from the second intermediate surface <NUM> and surrounding the openings 410a and 410b. The second intermediate surface <NUM> also includes a clamping bump <NUM> surrounding each opening (e.g., opening 410a). A trench <NUM> can be between the clamping bump <NUM> and the glue stop <NUM>. The trench <NUM> can act as an additional glue stop for clamping the sensor die <NUM> onto microfluidic chip <NUM>.

<FIG> is a schematic diagram of a close-up view of the microfluidic chip of <FIG> in accordance with embodiments of the present disclosure. As shown in <FIG>, the clamping bump <NUM> can be the same or similar height as the glue stop <NUM>.

<FIG> is a schematic diagram of a side sectional view <NUM> of a sensor die <NUM> clamped to a microfluidic chip <NUM> in accordance with embodiments of the present disclosure. The sensor die <NUM> is placed onto the microfluidic chip <NUM> under an applied pressure. While under pressure, an adhesive <NUM> is applied to a gap between the first intermediate surface <NUM> and the second intermediate surface <NUM>. The adhesive <NUM> is cured under pressure. An example adhesive is a UV-cured acrylated urethane, though other adhesives can be used. The sensors are aligned over the openings 410a and 410b. The clamping bump <NUM> contacts the membrane <NUM> in a location between rings 126a and 126b. The applied pressure can cause the membrane <NUM> to be compressed into the gripping trenches 122a and 122b.

<FIG> is a schematic diagram of a close-up view <NUM> of a sensor die <NUM> clamped to the microfluidic chip <NUM> of <FIG> in accordance with embodiments of the present disclosure. The close-up view <NUM> illustrates the clamping bump <NUM> in contact with the membrane <NUM> at a location between the rings 126a and 126b. The applied pressure of the sensor die <NUM> onto the clamping bump <NUM> pushes on the membrane <NUM> such that the membrane compresses into the trenches 122a and 122b. The close-up view <NUM> also illustrates the glue stop trench <NUM>.

<FIG> is a schematic diagram of a side sectional view of a microfluidic chip <NUM> in accordance with embodiments of the present disclosure. The side sectional view <NUM> illustrates the opening <NUM> that exposes the microfluidic channel <NUM>. The side sectional view <NUM> illustrates the top surface <NUM>, the first intermediate surface <NUM> stepped down from the top surface <NUM>; and second intermediate surface <NUM> stepped down from the first intermediate surface <NUM>. The glue stop <NUM> is shown extending from the second intermediate surface <NUM> and surrounding the openings 710a and 710b. The second intermediate surface <NUM> also includes a clamping bump <NUM> surrounding each opening (e.g., opening 710a). A trench <NUM> (shown in <FIG>) can be between the clamping bump <NUM> and the glue stop <NUM>. The trench <NUM> can act as an additional glue stop for clamping the sensor die <NUM> onto microfluidic chip <NUM>.

<FIG> is a schematic diagram of a close-up view <NUM> of the microfluidic chip of <FIG> in accordance with embodiments of the present disclosure. As shown in <FIG>, the clamping bump <NUM> can be at a lower height than the glue stop <NUM>.

<FIG> is a schematic diagram of a side sectional view <NUM> of a sensor die <NUM> clamped to a microfluidic chip <NUM> in accordance with embodiments of the present disclosure. The sensor die <NUM> is placed onto the microfluidic chip <NUM> under an applied pressure. While under pressure, an adhesive <NUM> is applied to a gap between the first intermediate surface <NUM> and the second intermediate surface <NUM>. The adhesive <NUM> is cured under pressure. The sensors are aligned over the openings 710a and 710b. The clamping bump <NUM> contacts the membrane <NUM> in a location between rings 126a and 126b. The applied pressure can cause the membrane <NUM> to compress into the gripping trenches 122a and 122b. The glue stop <NUM> can contact the sensor die <NUM> due to the glue stop <NUM> height being taller than the clamping bump <NUM>. The contact made between the glue stop <NUM> and the sensor die <NUM> can further aide in preventing the adhesive <NUM> from contacting the membrane <NUM> or other parts of the sensor. Glue stop <NUM> can act as a spacer or hard stop for the sensor die <NUM>.

<FIG> is a schematic diagram of a close-up view <NUM> of a sensor die <NUM> clamped to the microfluidic chip <NUM> of <FIG> in accordance with embodiments of the present disclosure. The close-up view <NUM> illustrates the clamping bump <NUM> in contact with the membrane <NUM> at a location between the rings 126a and 126b. The applied pressure of the sensor die <NUM> onto the clamp <NUM> pushes on the membrane <NUM> such that the membrane compresses into the trenches 122a and 122b. The close-up view <NUM> also illustrates the glue stop trench <NUM>.

<FIG> is a schematic diagram of a side sectional view of a microfluidic chip <NUM> in accordance with embodiments of the present disclosure. The microfluidic chip <NUM> includes an opening <NUM> that exposes the microfluidic channel <NUM>. The side sectional view <NUM> illustrates the top surface <NUM>, the first intermediate surface <NUM> stepped down from the top surface <NUM>; and second intermediate surface <NUM> stepped down from the first intermediate surface <NUM>. The glue stop <NUM> is shown extending from the second intermediate surface <NUM> and surrounding the openings 810a and 810b. The second intermediate surface <NUM> also includes a clamping bump <NUM> surrounding each opening (e.g., opening 810a). The microfluidic chip <NUM> does not include a trench between the glue stop <NUM> and the clamping bump <NUM>.

<FIG> is a schematic diagram of a side sectional view <NUM> of a sensor die <NUM> clamped to a microfluidic chip <NUM> and electrically coupled to a printed circuit board <NUM> in accordance with embodiments of the present disclosure. Microfluidics chip <NUM> is similar to microfluidics chip <NUM> shown in <FIG>, but can also be similar to microfluidic chip <NUM> of <FIG> or microfluidic chip <NUM> of <FIG>. The sensor die <NUM> is clamped to the microfluidic chip <NUM> by an adhesive (such as adhesive substance <NUM> or adhesive substanct <NUM>) that is applied while the sensor die <NUM> is pushed down onto the microfluidic chip <NUM> and cured. A printed circuit board <NUM> can be adhered to the top surface <NUM> of the microfluidic chip <NUM> by an adhesive <NUM>. Adhesive <NUM> can be an adhesive tape, double sided tape, glue, or other known technique of affixing a rigid structure onto the microfluidic chip <NUM>. The printed circuit board <NUM> can include one or more contact pads <NUM> (shown in <FIG>) that are electrically connected to other circuit elements <NUM> (some of which are represented in <FIG>) through conductive traces (not shown). Each sensor <NUM> can be electrically connected to the printed circuit board <NUM> via wire bonds <NUM>. After wire bonding has been completed, an encapsulant <NUM> can be applied over at least a portion of the printed circuit board <NUM> to protect the wire bond <NUM> and to electrically insulate the contact pads. The encapsulant can be a UV-cured modified urethane.

<FIG> is a schematic diagram of a top-down view <NUM> of the sensor die clamped to a microfluidic chip and electrically coupled to a printed circuit board of <FIG> in accordance with embodiments of the present disclosure. <FIG> illustrates the sensor die <NUM> that includes sensor contacts <NUM>. Sensor contacts <NUM> are electrically connected to the ISE of the sensor through a via <NUM> (shown in <FIG>). The sensor contacts <NUM> are electrically connected to contact pads <NUM> on PCB <NUM> via wire bonds <NUM>. As shown, the PCB <NUM> can also include electrical components <NUM> that can perform various functions including applying bias to the sensor, detecting electrical signals from the sensor, and other functions.

<FIG> is a schematic diagram of a side sectional view <NUM> of a sensor die <NUM> clamped to a microfluidic chip <NUM> and secured to the microfluidic chip by screws <NUM> in accordance with embodiments of the present disclosure. A rigid structure <NUM> can be used to provide electrical connectivity between the sensor <NUM> and outside electronics, as well as to provide structural stability for securing the sensor die <NUM> to the microfluidic chip <NUM>. The rigid structure <NUM> can be a PCB, a metal surface, a polymer surface, etc. The microfluidic chip <NUM> and the rigid structure <NUM> can include through holes for receiving screws <NUM>, which are secured using a locking nut in this embodiment.

<FIG> is a schematic diagram of a top-down view <NUM> of a sensor die <NUM> clamped to a microfluidic chip <NUM> of <FIG> in accordance with embodiments of the present disclosure. <FIG> illustrates the rigid structure <NUM> to include contact pads <NUM> that can electrically connect contacts <NUM> on the sensor to outside electronics (e.g., electronics <NUM>) via a wire bond <NUM>. The screw <NUM> are shown to secure the rigid structure <NUM> to the microfluidic chip <NUM> with nuts.

Aspects described in this disclosure can employ thin-film fabrication techniques to create the sensor devices and structures described herein, and to achieve advantages that are described herein and that are readily apparent to those of skill in the art.

Advantages of the present disclosure are readily apparent. Advantages of using the through-silicon via to connect to the micro ion-selective electrode may include the following:.

Claim 1:
A microfluidic chip (<NUM>) comprising:
a microfluidics channel (<NUM>) in the microfluidic chip (<NUM>);
a top surface (<NUM>) and an intermediate surface (<NUM>), wherein the intermediate surface (<NUM>) is lower in height than the top surface (<NUM>);
an opening (<NUM>) in the intermediate surface (<NUM>) exposing the microfluidic channel (<NUM>);
a clamping bump (<NUM>) projecting from the intermediate surface (<NUM>) and surrounding the opening (<NUM>); and
a solid-state chemical sensor residing on a sensor die (<NUM>), at least a portion of the solid-state chemical sensor in contact with the clamping bump (<NUM>) of the microfluidic chip (<NUM>), the solid-state chemical sensor exposed to the microfluidics channel (<NUM>).