Electrical tracking of multiphase microfluidic flows

Abstract

Embodiments are provided for computer-implemented methods, systems, and devices for tracking multiphase flow in a microfluidic device. The embodiments include receiving a first reading from a first sensor of the microfluidic device, where the first reading represents detection of fluid at an interface between the fluid and the first sensor, and receiving a second reading from a second sensor of the microfluidic device using the processor, where the second reading represents detection of fluid at an interface between the fluid and the second sensor, the first sensor being positioned a distance from the second sensor. The embodiments also include calculating a flow rate of fluid in the microfluidic device based at least in part on a time difference between detection by the first sensor and detection by the second sensor and a distance between the first sensor and the second sensor.

Description

[Technical field]

[0001] The present invention relates generally to methods for fabricating microfluidic devices and the resulting structures, and more particularly to electrical tracking of multiphase flow in microfluidic devices. [Background technology]

[0002] Microfluidics involves the precise control and manipulation of small volumes of fluids that are typically limited to microscale channels and volumes typically in the sub-microliter range. Microfluidic devices often comprise microchannel circuits with multiple channels. The defining feature of microfluidics is due to the unique behavior that liquids exhibit at the microscale. Liquid flow in microfluidics is typically laminar. Volumes of less than one nanoliter can be achieved by fabricating structures with lateral dimensions in the micrometer range. Microfluidic devices generally refer to microfabricated devices used for the delivery, sampling, mixing, analysis, and administration of liquids. Summary of the Invention [Means for solving the problem]

[0003] An embodiment of the present invention is directed to a computer-implemented method for electrical tracking of multiphase flow in a microfluidic device. A non-limiting example of the computer-implemented method includes receiving, using a processor, a first reading from a first sensor of the microfluidic device, where the first reading represents detection of fluid at an interface between the fluid and the first sensor; receiving, using the processor, a second reading from a second sensor of the microfluidic device, where the second reading represents detection of fluid at an interface between the fluid and the second sensor, the first sensor being disposed at a distance from the second sensor; and calculating, using the processor, a flow rate of fluid in the microfluidic device based at least in part on a time difference between detection by the first sensor and detection by the second sensor and a distance between the first sensor and the second sensor.

[0004] An embodiment of the present invention is directed to a system for electrical tracking of multiphase flow in a microfluidic device. A non-limiting example of the system includes a processor and a memory coupled to the processor. The processor is configured to receive, using the processor, a first reading from a first sensor of the microfluidic device, where the first reading represents detection of a fluid at an interface between the fluid and the first sensor; receive, using the processor, a second reading from a second sensor of the microfluidic device, where the second reading represents detection of a fluid at an interface between the fluid and the second sensor, the first sensor being disposed at a distance from the second sensor; and calculate, using the processor, a flow rate of the fluid in the microfluidic device based at least in part on a time difference between detection by the first sensor and detection by the second sensor and a distance between the first sensor and the second sensor.

[0005] An embodiment of the present invention is directed to a method of fabricating a microfluidic device for electrical tracking of multiphase flow in the microfluidic device. A non-limiting example of fabricating the semiconductor device includes forming a first wafer with a first terminal of a first sensor and a first terminal of a second sensor; forming a second wafer with a second terminal of the first sensor and a second terminal of the second sensor; and bonding the first wafer to the second wafer, where the first terminal in the first wafer is aligned with the second terminal in the second wafer.

[0006] Additional technical features and advantages are realized through the techniques of the present invention. Embodiments and aspects of the present invention are described in detail herein and are considered a part of the claimed subject matter. For a better understanding, please refer to the detailed description and drawings.

[0007] The particular subject matter of the exclusive rights claimed herein is particularly pointed out and distinctly claimed in the claims at the conclusion of this specification. The foregoing and other features and advantages of embodiments of the present invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 shows a top view and a cross-sectional view along line AA of a microfluidic structure after processing operations according to one or more embodiments of the present invention. [Diagram 2] FIG. 2 shows a top view and a cross-sectional view along line AA of a microfluidic structure after processing operations according to one or more embodiments of the present invention. [Diagram 3] FIG. 3 shows a top view and a cross-sectional view along line AA of a microfluidic structure after processing operations according to one or more embodiments of the present invention. [Figure 4] FIG. 4 shows a top view and a cross-sectional view along line AA of a microfluidic structure after processing operations according to one or more embodiments of the present invention. [Diagram 5]FIG. 5 shows a top view and a cross-sectional view along line AA of a microfluidic structure after processing operations according to one or more embodiments of the present invention. [Figure 6] FIG. 6 shows a top view and a cross-sectional view along line AA of a microfluidic structure after processing operations according to one or more embodiments of the present invention. [Figure 7] FIG. 7 shows a top view and a cross-sectional view along line AA of a microfluidic structure after processing operations according to one or more embodiments of the present invention. [Figure 8] FIG. 8 illustrates a microfluidic device according to one or more embodiments of the invention. [Figure 9] FIG. 9 illustrates another microfluidic device in accordance with one or more embodiments of the invention. [Figure 10] FIG. 10 illustrates a different microfluidic device according to one or more embodiments of the present invention. [Figure 11] FIG. 11 illustrates another microfluidic device in accordance with one or more embodiments of the invention. [Figure 12] FIG. 12 illustrates a microfluidic device according to one or more embodiments of the present invention. [Figure 13] FIG. 13 shows a flow diagram illustrating a method of making a microfluidic device in accordance with one or more embodiments of the present invention. [Figure 14] FIG. 14 shows a flow diagram illustrating a method for tracking multiphase fluids in microfluidics in accordance with one or more embodiments of the present invention. [Figure 15] FIG. 15 shows a block diagram illustrating one example of a processing system for implementing the teachings herein.

[0009] The figures depicted herein are exemplary. There may be many variations in the figures or the operations described therein without departing from the scope of the present invention. For example, operations may be performed in a different order, or operations may be added, deleted, or modified. Also, the word "connected" and variations thereof are intended to describe having a communication path between two elements, and do not imply that the elements are directly connected with no intervening elements / connections between them. All of these variations are considered part of this specification.

[0010] In the accompanying drawings and the following detailed description of the described embodiments, various elements illustrated in the drawings are labeled with two or three digit reference numbers. With few exceptions, the leftmost digit of each reference number corresponds to the drawing in which the element is first shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] For the sake of brevity, conventional techniques associated with semiconductor device and integrated circuit (IC) fabrication may or may not be described in detail herein. Moreover, various tasks and process steps described herein may be incorporated into a more comprehensive procedure or process having additional steps or functions not described in detail herein. In particular, because the various steps in the manufacture of semiconductor devices and semiconductor-based ICs are well known, for the sake of brevity, many conventional steps will only be briefly mentioned herein or will be omitted entirely without providing details of the well-known processes.

[0012] Turning now to an overview of the technology more specifically related to the present invention, microfluidic devices have a user chip interface and a closed flow path. The closed flow path facilitates the integration of functional elements (e.g., heaters, mixers, pumps, UV detectors, valves, etc.) into one device while minimizing problems related to leakage and evaporation. Analysis of liquid samples often requires a series of steps (e.g., filtration, dissolving reagents, heating, washing, signal reading, etc.). The inclusion of multiple channels on a single device increases the footprint of the device and therefore its manufacturing cost.

[0013] Optical methods can be used to track multiphase transitions in known microfluidic devices, but this requires the microfluidic device to be made from a material that is transparent to light. Optical detection is also diffraction limited, requiring optical contrast between the phases or the use of fluorescent particles to track the flow.

[0014] Turning now to a summary of aspects of the invention, one or more embodiments of the invention address the above-mentioned shortcomings of the prior art by providing a microfluidic device having an electrical sensor integrated therein. In embodiments of the invention, the integrated electrical sensor is constructed and arranged to enable the microfluidic device to track a fluid-liquid interface as a function of time, which can further obtain spatially resolved and time-dependent information of the position of each phase in a multi-phase system and be used for flow tracking. In some embodiments of the invention, the electrical sensor is a capacitance sensor configured to measure capacitance, and each fluid flowing through the microfluidic device can exhibit different dielectric properties that can be measured by its effect on the capacitance that can be measured by one or more capacitance sensors. In embodiments of the invention, the electrical sensor is embedded within the channel wall to enable measurement of the electrical properties of the fluid as a function of time, which allows tracking of the movement of the fluid-liquid interface.

[0015] A method according to an embodiment of the invention can include measuring capacitance as a function of time at different points of the microfluidic device while a multiphase (immiscible) flow is established. The capacitance signal is monitored for an abrupt change that reflects the passage of an interface between two terminals. Using the distance between the sensors (which is known) and the time it takes for the fluid interface to pass the different sensors, various figures-of-merit can be calculated, including but not limited to, interfacial displacement rate, channel saturation, and fluid wettability.

[0016] In one or more embodiments of the present invention, the frequency at which the capacitance is measured can be tuned to a desired value / range. The frequency can be adjusted to increase the contrast in capacitance between the fluid phases to be measured. The frequency can also be adjusted to increase the sampling rate and capture higher interfacial velocities.

[0017] Turning now to a more detailed description of aspects of the invention, Figure 1 illustrates a top view and cross-sectional line AA view of structure 100 after an initial set of fabrication operations to form a final microfluidic device according to one or more embodiments of the invention. In an embodiment of the invention, known fabrication operations are used to form and pattern a hard mask 104 on oxide layer 102 of structure 100. As best seen in the top view, the pattern in hard mask 104 includes openings 106 that expose portions of oxide layer 102.

[0018] In some embodiments of the present invention, the hard mask 104 can include an oxygen-containing layer, such as a silicon oxide (SiO2) layer or a silicon oxynitride (SiON) layer; a layer that is substantially free of oxygen, such as a silicon nitride (SiN) layer or a silicon carbide (SiC) layer; or a composite dielectric film that is substantially free of oxygen. In some embodiments of the present invention, the hard mask 104 can be formed only from tantalum nitride (TaN).

[0019] FIG. 2 shows a top view and a cross-sectional view along line AA of the structure 100 after processing operations according to one or more embodiments of the present invention. As shown in FIG. 2, the hard mask 104 (shown in FIG. 1) has been removed. However, prior to removing the hard mask 104, an oxide etch was performed to etch through the exposed portions of the oxide layer 102 and form trenches that are billeted with metal to form contacts 202. In accordance with an embodiment of the present invention, each of the contacts 202 will function as a first terminal of a two terminal sensor to be formed. The contacts 202 can include any suitable conductive material, such as metal (e.g., tungsten, titanium, tantalum, ruthenium, zirconium, cobalt, copper, aluminum, platinum), conductive metal compound material (e.g., tantalum nitride, titanium nitride, tantalum carbide, titanium carbide, titanium aluminum carbide, tungsten silicide, tungsten nitride, cobalt silicide, nickel silicide), conductive carbon, or any suitable combination of these materials. In some embodiments of the present invention, contact 202 comprises copper, cobalt, or tungsten. The conductive material used to form contact 202 may further comprise dopants that are incorporated during or after deposition. In some embodiments of the present invention, contact 202 may comprise barrier metal liners (not shown). In one or more embodiments of the present invention, after the conductive material that forms contact 202 is deposited, chemical-mechanical planarization (CMP) is performed on structure 100 to remove excess conductive material and planarize structure 100 to the levels shown.

[0020] 3 shows a top view and a cross-sectional view along line AA of the structure 100 after processing operations according to one or more embodiments of the present invention. As shown in FIG. 3, an additional oxide layer 302 has been deposited on the top surface of the oxide layer 102. In one or more embodiments of the present invention, the oxide layer 302 can be the same material as the oxide layer 102. Any known method of forming the oxide layer 302 can be utilized, such as chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), atomic layer deposition (ALD), flowable CVD, spin-on dielectric, or physical vapor deposition (PVD).

[0021] With further reference to FIG. 3, a hard mask 304 is formed over oxide layer 302 and patterned to include openings that expose one or more portions of a top surface of the underlying oxide layer 302.

[0022] FIG. 4 shows a top view and a cross-sectional view along line AA of the structure 100 after processing operations according to one or more embodiments of the present invention. As shown in FIG. 4, the hard mask 304 has been removed. However, before removing the hard mask 304 (as shown in FIG. 3), the portion of the oxide layer 302 not covered by the hard mask 304 is etched to form an opening in the oxide layer 302. The opening in the oxide layer 302 is filled with metal to form the bottom terminal 402 of the two terminal sensor to be formed. In an embodiment of the present invention, the hard mask 304 can be removed by applying a CMP that planarizes the structure 100 to the level shown in FIG. 4. The bottom terminal 402 is formed on the contact 202.

[0023] 5 shows a top view and a cross-sectional view along line AA of structure 100 after processing operations in accordance with one or more embodiments of the present invention. As shown in FIG. 5, an oxide layer 502 is deposited on oxide layer 302 and bottom terminal 402 of structure 100. In one or more embodiments of the present invention, oxide layer 502 is the same material as oxide layer 302 or oxide layer 102 or a combination thereof. Any known method of forming oxide layer 502 can be utilized.

[0024] 5, a hard mask 504 is formed on the oxide layer 502. Any manner of forming the hard mask 504 can be used. A top view of the structure 100 shows that the hard mask 504 is patterned to expose a portion of the top surface of the oxide layer 502. An oxide etchant is applied to the structure 100 to etch the portions of the oxide layer 502 not covered by the hard mask 504 to form microchannels 602 in the oxide layer 502.

[0025] 6 shows a top view and a cross-sectional view along line AA of the structure 100 after processing operations in accordance with one or more embodiments of the present invention. As shown in FIG. 6, after an oxide etch is performed to form a microchannel 602 in the structure 100, the hard mask 504 (shown in FIG. 5) is removed, thereby forming a first wafer 604 including the microchannel 602. As shown, the first wafer 604 also includes the oxide layer 102, the contact 202, the bottom terminal 402, the oxide layer 302, and the microchannel 602.

[0026] FIG. 7 shows a top view and a cross-sectional view along line AA of the structure 100 after processing operations according to one or more embodiments of the present invention. As shown in FIG. 7, a complementary wafer 702 is formed and is similar to the first wafer 604 shown in FIG. 6. The complementary wafer 702 includes an oxide layer 704, contacts 708 for the top terminals 710 of the two terminal sensors to be formed, and an oxide layer 706. In one or more embodiments of the present invention, the complementary wafer 702 is formed without elements corresponding to the microchannels 602 and includes top terminals 710 corresponding to each of the bottom terminals 402 of the sensors formed in the first wafer 604. As shown in FIG. 7, the top terminals 710 of the complementary wafer 702 are aligned with the bottom terminals 402 of the first wafer 604. The complementary wafer 702 is bonded to the first wafer 604 to complete the formation of the structure 100 to form a microfluidic device. As shown, the oxide layer 706 of the complementary wafer 702 is bonded to the microchannel 602 of the first wafer 604. It should be understood that the bonding process can be performed using any of the known techniques. In a non-limiting example, the microfluidic device is formed with two sensors, where each sensor includes a top terminal and a bottom terminal that measure capacitance as fluid flows through the microchannel, although it should be understood that any number of sensors can be included to obtain operational measurements.

[0027] FIG. 8 shows a configuration 800 for monitoring multiphase flow within a cross section of a microchannel in accordance with one or more embodiments of the present invention. The microchannel includes, in this non-limiting example, two sensors. Each sensor includes a top terminal and a bottom terminal and is used to measure the capacitance of a fluid. The movement of the fluid can be tracked within the microfluidic device and interfaces between fluids can be monitored. A first sensor 802 includes a first terminal 802A and a second terminal 802B, which correspond to the bottom terminal 402 and the top terminal 710 of FIG. 7, respectively. A second sensor 804 includes a first terminal 804A and a second terminal 804B. It should be understood that any number of sensors can be incorporated into the microfluidic device to track multiphase fluid flow.

[0028] The distance L between the two sensors (capacitors) is known. The distance L can be selected for the desired application during fabrication of the microfluidic device. In this non-limiting example, the distance L is ∼1 mm. The distance L between the sensors divided by the time difference at which the fluid interface is detected between the first sensor 802 and the second sensor 804 gives the average interfacial displacement velocity U of the fluid in the microchannel, i.e., figures-of-merit.

[0029] As shown in Figure 8, the sensors (shown in Figure 7) are embedded within the walls of the microchannel, and each sensor has a top terminal and a bottom terminal, and the microchannel contains a first fluid (Fluid 1) and a second fluid (Fluid 2), where the first fluid (Fluid 1) and the second fluid form a fluid interface.

[0030] Also shown in Figure 8 are graphs of responses for the first sensor 802 and the second sensor 804. The graphs represent capacitance on the Y-axis and units of time on the X-axis. Graphs are shown for inlet and outlet responses detecting fluids flowing in the microchannel where the interface between the fluids provides a change in capacitance. The first graph shows that the change in capacitance is proportional to the time t 入 The second graph shows the change in capacitance as detected by the first sensor over time t 出 denotes the time detected by the second sensor.

[0031] By using the time information and the distance L information, the interface displacement velocity U in the microchannel can be calculated. It should be understood that the sensor is connected to a processor or computing unit (e.g., as shown in FIG. 15, described below) to process the signals. The interface displacement velocity U can be calculated by Equation 1 below.

number

[0032] 9 shows another configuration of a system 900 for tracking multiphase flow in a microfluidic device in accordance with one or more embodiments of the present invention. The system 900 includes a series of sensors positioned at different positions xi along the direction of fluid flow. Each sensor has two terminals, a top terminal and a bottom terminal, and functions as a capacitor to detect the capacitance as the fluid passes through them. A first sensor at position x1 has terminals 902A and 902B, a second sensor at position x2 has terminals 904A and 904B, a third sensor at position x3 has terminals 906A and 906B, and a fourth sensor at position x4 has terminals 908A and 908B.

[0033] By calculating the percentage of the total length traveled by the interface between the fluids, the saturation (S) of the invading fluid (Fluid 1) can be determined. The interfacial velocity (U) and saturation (S) can be calculated using Equations 2 and 3 below, respectively.

number

number

[0034] As shown in the series of graphs in Figure 9, the time at which each sensor 902, 904, 906 and 908 detects a change in capacitance of the multiphase flow is shown. By measuring the capacitance between the top and bottom terminals of each sensor as a function of time, the movement of the fluid-fluid interface within the channel can be tracked. The series of graphs shows that a first sensor 902 detects a change in capacitance, followed by a second sensor 904, a third sensor 906 and a fourth sensor 908. By analyzing a fraction or portion of the microchannel, the saturation of the microchannel can be determined.

[0035] Figure 10 shows a different embodiment of the invention with multiple sensors 1, 2, 3, 4 and 5 arranged in parallel across the microchannel of the device. As shown in Figure 10, the sensor positions across the microchannel are known and can be used to determine the shape of the fluid interface as described below. Each sensor has two terminals, a top terminal (shown in Figure 10) and a bottom terminal (not shown), and functions as a capacitor to detect the capacitance as the fluid passes through these terminals.

[0036] By using an architecture such as that shown in Figure 10, the shape of the fluid-fluid interface can be determined, which provides information about the wettability of the invading fluid. If the innermost sensor 3 detects a change in capacitance after the outermost sensors 1 and 5, then the fluid 1 is wetting the surface.

number

number

[0037] FIG. 11 shows another embodiment of the invention including a network 1100 of connected microchannels filled with at least two fluids (first fluid 1102, second fluid 1104) that support multiphase flow. As shown, multiple measurements can be taken at different locations within the network of multiple microchannels. As shown, each segment of the network 1100 can be equipped with a pair of sensors, e.g., sensor 1106 and sensor 1108, to detect the inlet and outlet of fluids through the segment of the network 1100 of interest. FIG. 12 shows a network 1200 for a different embodiment of the invention, where the region of interest not only has a two-dimensional (xy) network of connected microchannels, but is stacked vertically (z) as well as connected bypass-through vertical channels. As shown in FIG. 12, each segment of the network 1200 may include a pair of sensors, such as sensor 1206 and sensor 1208, that detect the inlet and outlet of a fluid through the segment, where each sensor 1206 and 1208 detects a fluid interface between a first fluid 1202 and a second fluid 1204.

[0038] 13 shows a flow chart of a method 1300 of fabricating the microfluidic device according to one or more embodiments of the invention. The microfluidic device can include a device, such as the device shown in FIG. 7. The method 1300 begins at block 1302 and proceeds to block 1304, which provides for forming a first wafer including a first terminal of a first sensor and a first terminal of a second sensor. As shown in FIG. 6, the first terminal includes contact 202 and plate 402. The first wafer also includes microchannels of the microfluidic device for transporting fluid.

[0039] Block 1306 forms a second wafer with a second terminal of the first sensor and a second terminal of the second sensor. As shown in FIG. 7, a complementary wafer 702 is formed with the second terminals corresponding to the first terminals. The second terminals include contacts and plates similar to the contacts and plates formed in the first wafer.

[0040] Block 1308 bonds the first wafer to the second wafer, where the first terminals of the first wafer are aligned with the second terminals of the second wafer. Method 1300 ends at block 1310. Method 1300 is not intended to be limited by the steps shown in Figure 13. It should be understood that different steps or different sequences of steps can be used to fabricate the microfluidic device.

[0041] FIG. 14 shows a flow chart of a method 1400 for performing electrical tracking of multiphase flow in a microfluidic device. Method 1400 can be performed by any of the microfluidic devices and processing systems shown in FIGS. 7-10, such as the processing system shown in FIG. 15. Method 1400 begins at block 1402 and proceeds to block 1404 which provides for receiving, using a processor, a first reading from a first sensor of the microfluidic device, where the first reading represents detection of fluid at an interface between the fluid and the first sensor. When a fluid interface between a first fluid and a second fluid passes the first sensor, a capacitance changes and is detected by the first sensor. The time at which the first sensor senses the fluid can be recorded.

[0042] Block 1406 receives a second reading from a second sensor of the microfluidic device using the processor, where the second reading represents a detection of a fluid at an interface between the fluid and the second sensor, the first sensor being disposed at a distance from the second sensor. As the fluid interface between the first fluid and the second fluid continues to flow through the microchannel, the fluid interface passes the second sensor. The second sensor measures a change in capacitance, and the time of the detection can be recorded.

[0043] Block 1408 calculates the flow rate of the fluid in the microfluidic device based at least in part on the time difference between the detection by the first sensor and the detection by the second sensor and the distance between the first sensor and the second sensor. The (volumetric) flow rate can be calculated by dividing the flow rate by the cross-sectional area of ​​the channel. In one or more embodiments of the invention, the calculation is performed by a processor, which is described below with reference to FIG. 15. A calculation such as that shown in Equation 1 above is performed to obtain the interface displacement rate. In other embodiments of the invention, multiple sensors are arranged in parallel or in series to obtain figures-of-merit, such as the wettability of the fluid or the saturation of the channel. The resulting calculation can be performed in real time to control the flow of the fluid by providing signals to pumps, regulators, etc. Method 1400 ends at block 1410. Method 1400 is not intended to be limited by the steps shown in FIG. 14. It should be understood that different steps or different sequences of steps can be used to perform tracking of the fluid interface in the microfluidic device.

[0044] Referring to FIG. 15, one embodiment of a processing system 1500 for implementing the teachings herein is shown. In this embodiment, the system 1500 has one or more central processing units (processors) 101a, 101b, 101c, etc. (collectively or generally referred to as one or more processors 101). In one embodiment, each processor 101 may comprise a reduced instruction set computer (RISC) microprocessor. The processors 101 are connected to a system memory 114 and various other components via a system bus 113. A read only memory (ROM) 122 is connected to the system bus 113 and may comprise a basic input / output system (BIOS) that controls certain basic functions of the system 100.

[0045] FIG. 15 further shows an input / output (I / O) adapter 107 and a network adapter 126 coupled to the system bus 113. The I / O adapter 107 may be a small computer system interface (SCSI) adapter that communicates with a hard disk 103, a tape storage drive 105, or any other similar component or combination thereof. The I / O adapter 107, the hard disk 103, and the tape storage drive 105 are collectively referred to herein as a mass storage device 124. An operating system 120 for executing on the processing system 100 may be stored on the mass storage device 124. The network adapter 126 interconnects the bus 113 with an external network 116, allowing the data processing system 1500 to communicate with other such systems. A screen (e.g., a display monitor) 115 is connected to the system bus 113 by a display adapter 112, which may include a graphics adapter and a video controller for improving the performance of graphics-intensive applications. In one embodiment, adapters 107, 126, and 112 may be connected to one or more I / O buses that are connected to system bus 113 through an intermediate bus bridge (not shown). Suitable I / O buses for connecting peripheral devices, such as hard disk controllers, network adapters, and graphics adapters, typically include common protocols, such as Peripheral Component Interconnect (PCI). Additional input / output devices are shown connected to system bus 113 through user interface adapter 108 and display adapter 112. Keyboard 109, mouse 110, and speakers 111 are all interconnected to bus 113 through user interface adapter 108, which may include, for example, a super I / O chip that integrates multiple device adapters into a single integrated circuit.

[0046] In an exemplary embodiment, processing system 1500 includes a graphics processing unit 130. Graphics processing unit 130 is a specialized electronic circuit designed to manipulate and modify memory to accelerate the creation of images in a frame buffer intended for output to a display. In general, graphics processing unit 130 has a highly parallel structure that makes it very efficient at manipulating computer graphics and image processing, as well as being more effective than a general purpose CPU for algorithms in which the processing of large blocks of data is performed in parallel.

[0047] Thus, as configured in Figure 15, system 1500 includes processing capability in the form of processor 101, memory capability, such as those described above including system memory 114 and mass storage device 124, input means, such as those described above including keyboard 109 and mouse 110, and output means, such as those described above including speaker 111 and display 115. In one embodiment, a portion of system memory 114 and mass storage device 124 collectively store an operating system for coordinating the functioning of the various components illustrated in Figure 15.

[0048] The present invention may be a system, method, or computer program product or computer program, or combination thereof, at any level of technical detail that may be integrated. The computer program product may include one or more computer readable storage media having computer readable program instructions for causing a processor to perform aspects of the present invention.

[0049] The computer readable storage medium can be a tangible device capable of holding and storing instructions for use by an instruction execution device. The computer readable storage medium can be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination thereof. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as a punch card or a ridge structure in a groove in which instructions are recorded, or any suitable combination thereof. As used herein, a computer-readable storage medium should not be construed as a transitory signal per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission medium (e.g., light pulses passing through a fiber optic cable), or electrical signals transmitted over electrical wires.

[0050] The computer readable program instructions described herein can be downloaded from a computer readable storage medium to an individual computing device / processing device or to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, or a wireless network, or a combination thereof. The network may be comprised of copper transmission cables, optical transmission fiber, wireless transmission, routers, firewalls, switches, gateway computers, or edge servers, or a combination thereof. A network adapter card or network interface in each computing device / processing device receives the computer readable program instructions from the network and transfers the computer readable program instructions to the individual computing device / processing device for storage in a computer readable storage medium.

[0051] The computer readable program instructions for carrying out the operations of the present invention may be either assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, configuration data for an integrated circuit, or source or object code written in any combination of one or more programming languages, such as object-oriented programming languages, e.g., Smalltalk, C++, and the like, conventional procedural programming languages ​​(e.g., the "C" programming language or similar programming languages). The computer readable program instructions may be executed entirely on the user's computer, partially on the user's computer, partially on the user's computer as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer via any kind of network, such as a local area network (LAN) or a wide area network (WAN), or the connection may be to an external computer (e.g., through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), may execute computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry to perform aspects of the invention.

[0052] Aspects of the present invention are described herein with reference to flowchart illustrations or block diagrams, or combinations thereof, of methods, apparatus (systems), and computer program products or computer programs according to embodiments of the present invention. It will be understood that each block of the flowchart illustrations or block diagrams, or combinations thereof, and combinations of blocks in the flowchart illustrations or block diagrams, or combinations thereof, can be implemented by computer readable program instructions.

[0053] These computer readable program instructions may be provided to a processor of a computer or other programmable data processing apparatus such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate means for implementing the functions / operations specified in one or more blocks of the flowchart illustrations or block diagrams, or combinations thereof, to produce a machine. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer programmable data processing apparatus or other device, or combinations thereof, to function in a particular manner, such that a computer readable storage medium having stored thereon includes an article of manufacture including instructions that implement aspects of the functions / operations specified in one or more blocks of the flowchart illustrations or block diagrams, or combinations thereof.

[0054] The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device such that the instructions, which execute on a computer, other programmable data processing apparatus, or other device, implement the functions / acts identified in one or more blocks of the flowchart illustrations or block diagrams, or combinations thereof, to cause the computer, other programmable apparatus, or other device to perform a series of operational steps to generate a computer-implemented process.

[0055] The flowchart diagrams and block diagrams in the drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products or computer programs according to various embodiments of the present invention. In this regard, each block in the flowchart diagrams or block diagrams may represent a module, segment, or portion of an instruction, which includes one or more executable instructions for implementing one or more specified logical functions. In some alternative implementations, the functions shown in the blocks may occur out of the order shown in the drawings. For example, two blocks shown in succession may actually be accomplished as one step performed simultaneously, substantially simultaneously, partially or fully in a time-overlapping manner, depending on the functions involved, or the blocks may be performed in the reverse order. It should be noted that each block of the block diagrams or flowchart diagrams or combinations thereof, as well as combinations of multiple blocks of the block diagrams or flowchart diagrams or combinations thereof, may be implemented by a special purpose hardware-based system that performs the specified functions or operations, or may execute a combination of special purpose hardware and computer instructions.

[0056] The description of various embodiments of the present invention has been presented for illustrative purposes and is not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terms used in this specification have been selected to best explain the principles of the embodiments, practical applications, or technical improvements to the technology found in the market, or to enable those skilled in the art to understand the embodiments disclosed herein.

[0057] The techniques of the embodiments of the present invention described herein, in contrast to existing architectures, do not require advanced optical measurement equipment (high resolution, high sensitivity microscopes) to directly visualize and evaluate the fluid flow. In addition, the techniques described herein provide very high integration density (3D integration), can be scaled up to the nanoscale, and are compatible with standard semiconductor technology processes.

[0058] Various embodiments of the present invention are described herein with reference to the associated drawings. Alternative embodiments may be devised without departing from the scope of the present invention. In the following description and drawings, various connections and positional relationships (e.g., above, below, adjacent, etc.) are described between multiple elements, but those skilled in the art will recognize that many of the positional relationships described herein are orientation independent, as long as the described functionality is maintained even when the orientation is changed. These connections or positional relationships or combinations thereof can be direct or indirect, unless otherwise specified, and the present invention is not intended to be limited in this respect. Thus, connections of entities can refer to either direct or indirect coupling, and positional relationships between entities can be direct or indirect positional relationships. As an example of an indirect positional relationship, reference herein to forming layer "A" on layer "B" encompasses the situation where one or more intermediate layers (e.g., layer "C") are between layers "A" and "B," as long as the relative properties and functionality of layers "A" and "B" are not substantially changed by the one or more intermediate layers.

[0059] The following definitions and abbreviations should be used for interpretation of the claims and the specification. As used herein, the words "comprise," "includes," "includes," "including," "has," "having," "containing," or "containing" or any other variation thereof are intended to cover a non-exclusive inclusion. For example, a composition, mixture, process, method, article, or device consisting of a list of elements is not necessarily limited to only those elements, but can include other elements not expressly listed or elements inherent to such composition, mixture, process, method, article, or device.

[0060] Additionally, the word "exemplary" is used herein to mean "e.g., serving as an example or illustration." Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms "at least one" and "one or more" are understood to include any integer number greater than or equal to one, i.e., 1, 2, 3, 4, etc. The term "multiple" is understood to include any integer number greater than or equal to two, i.e., 2, 3, 4, 5, etc. The term "connected" can include indirect and direct "connected."

[0061] References herein to "one embodiment," "an embodiment," "an exemplary embodiment," and the like indicate that the described embodiment may include a particular feature, structure, or characteristic, but that all embodiments may or may not include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one of ordinary skill in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[0062] For purposes of the following description, the terms "above," "below," "right," "left," "vertical," "horizontal," "top," "bottom," and their derivatives shall refer to the described structures and methods as oriented in the depicted figures. The terms "overlying," "on," "located on," or "located on top of" mean that a first element, e.g., a first structure, is above a second element, e.g., a second structure, and that an intervening element, e.g., an interface structure, may be present between the first element and the second element. The term "direct contact" means that a first element, e.g., a first structure, and a second element, e.g., a second structure, are connected at the interface of the two elements without an intermediate conductive, insulating, or semiconducting layer.

[0063] Spatially relative terms, such as "below," "under," "lower than," "on top of," and the like, may be used herein for ease of description to describe the relationship of an element or feature to one or more other elements or features as illustrated in the figures. It will be understood that these spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, an element described as "below" or "below" the other element or feature would then be oriented "above" the other element or feature. Thus, the term "below" can encompass both an above and below orientation. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptions used herein will be interpreted accordingly.

[0064] For example, the phrase "selective to," e.g., "a first element selective to a second element," means that the first element is etched and the second element can function as an etch stop.

[0065] The words "about," "substantially," "approximately," and variations thereof are intended to encompass the degree of error associated with the measurement of a particular quantity based on equipment available at the time of filing this application. For example, "about" can encompass a range of ±8%, 5%, or 2% of a given value.

[0066] The term "conformal" (eg, conformal layer) means that the thickness of a layer is substantially the same on all surfaces or that the thickness varies by less than 15% of the nominal thickness of the layer.

[0067] As previously noted herein, for the sake of brevity, conventional techniques associated with semiconductor device and integrated circuit (IC) fabrication may or may not be described in detail herein. However, by way of background, a more general description of a semiconductor device fabrication process that may be utilized in implementing one or more embodiments of the present invention will now be provided. While the specific fabrication operations used in implementing one or more embodiments of the present invention may be individually known, the described combination of operations and / or resulting structures of the present invention are unique. Thus, the unique combination of operations described in connection with the fabrication of semiconductor devices in accordance with the present invention utilizes a variety of individually known physical and chemical processes performed on a semiconductor (e.g., silicon) substrate, some of which are described in the immediately following paragraphs.

[0068] Generally, the various processes for forming the microchips that will be included in an IC are divided into four general categories: deposition, removal / etching, semiconductor doping, and patterning / lithography. Deposition is any process that grows, coats, or otherwise transfers material onto a wafer. Available techniques include physical vapor deposition (PVD), chemical vapor deposition (CVD), electrochemical deposition (ECD), molecular beam epitaxy (MBE), and more recently atomic layer deposition (ALD), among others. Removal / etching is any process that removes material from the wafer. Examples include etching processes (either wet or dry) and chemical-mechanical planarization (CMP), among others. Semiconductor doping is the alteration of electrical properties, for example by doping the source and drain of a transistor, typically by diffusion or by ion implantation, or a combination thereof. These doping steps are then performed by furnace annealing or by rapid thermal annealing (RTA). Annealing serves to activate the implanted dopants. Films, both conductive (e.g., polysilicon, aluminum, copper, etc.) and insulators (e.g., various forms of silicon dioxide and silicon nitride, etc.), are used to connect and separate the transistors and their components. Selective doping of various regions of a semiconductor substrate allows the conductivity of the substrate to be changed by the application of a voltage. By creating a structure of these various components, millions of transistors can be built and wired together to form the complex circuits of modern microelectronic devices.Semiconductor lithography is the creation of a three-dimensional relief image or pattern on a semiconductor substrate and then transferring the pattern to the substrate. In semiconductor lithography, the pattern is formed by a light-sensitive polymer called photoresist. The lithography and etching pattern transfer steps are repeated many times to build the complex structures that make up the transistors and the many interconnects that connect the millions of transistors in a circuit. Each pattern printed on the wafer is aligned with the previously created pattern, and conductors, insulators, and selectively doped regions are slowly built up to form the final device.

[0069] The flow charts and block diagrams in the drawings illustrate possible implementations of a manufacturing or operating method or combination thereof according to various embodiments of the present invention. Various functions / operations of the method are represented in the flow charts by blocks. In some alternative embodiments, the functions noted in the blocks may occur out of the order depicted in the drawings. For example, two blocks shown in succession may in fact be executed substantially simultaneously, or the blocks may be executed in the reverse order in some cases, depending on the functionality involved.

[0070] The description of various embodiments of the present invention is presented for illustrative purposes and is not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terms used in this specification have been selected to best explain the principles of the embodiments, practical applications, or technical improvements to the technology found in the market, or to enable those skilled in the art to understand the embodiments disclosed herein.

Claims

1. 1. A computer-implemented method for tracking a fluid in a microfluidic device, comprising: a processor receiving a first reading from a first sensor of the microfluidic device, where the first reading represents a detection of fluid at an interface between the fluid and the first sensor; the processor receiving a second reading from a second sensor of the microfluidic device, where the second reading represents a detection of a fluid at an interface between the fluid and the second sensor, the first sensor being disposed at a distance from the second sensor; and the processor calculating a flow rate of fluid in the microfluidic device based at least in part on a time difference between detection by the first sensor and detection by the second sensor and a distance between the first sensor and the second sensor. Including, the method further comprising detecting the fluid using an additional sensor, the first sensor, the second sensor and the additional sensor being aligned in parallel. The method.

2. The computer-implemented method of claim 1 , wherein the time difference is measured between detection at the first sensor and detection at the second sensor.

3. The computer-implemented method of claim 1 or 2, wherein the first sensor and the second sensor are embedded within the microfluidic device.

4. 4. The computer-implemented method of claim 1, wherein the first sensor and the second sensor are configured to detect a change in capacitance caused by the fluid flowing through the microfluidic device.

5. The computer-implemented method of claim 1 , wherein detecting the fluid comprises detecting a center portion of the fluid and an edge portion of the fluid to determine a wettability of the fluid.

6. 1. A computer-implemented system for tracking multiphase flow in a microfluidic device for tracking fluid in the microfluidic device, comprising: A processor; and A memory coupled to the processor wherein the processor: receiving a first reading from a first sensor of the microfluidic device, where the first reading represents a detection of fluid at an interface between the fluid and the first sensor; receiving a second reading from a second sensor of the microfluidic device, the second reading representing a detection of a fluid at an interface between the fluid and the second sensor; and calculating a flow rate of fluid in the microfluidic device based at least in part on a time difference between detection by the first sensor and detection by the second sensor and a distance between the first sensor and the second sensor; It is structured as follows: the processor is further configured to detect the fluid using an additional sensor, wherein the first sensor, the second sensor, and the additional sensor are aligned in parallel. The system.

7. The system of claim 6 , wherein the time difference is measured between detection at the first sensor and detection at the second sensor.

8. The system of claim 6 or 7, wherein the first sensor and the second sensor are embedded within the microfluidic device.

9. The system of any one of claims 6 to 8, wherein the first sensor and the second sensor are configured to detect a change in capacitance caused by the fluid flowing through the microfluidic device.

10. The system of claim 6 , wherein detecting the fluid comprises detecting a center portion of the fluid and an edge portion of the fluid to determine a wettability of the fluid.

11. A computer program causing a computer to carry out the method according to any one of claims 1 to 5.

12. A computer-readable storage medium having the computer program according to claim 11 recorded thereon.

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