Devices and methods for flow control in microfluidic systems

Abstract

Microfluidic devices and methods for controlling the flow of cells or particles in a microfluidic channel are disclosed. The microfluidic device may include a substrate having an outlet channel. The microfluidic device may also include a microfluidic channel disposed on the substrate such that an outlet of the microfluidic channel is disposed above the outlet channel. The microfluidic device may further include a set of piezoelectric actuators disposed above the outlet channel and adjacent to the outlet, the set of piezoelectric actuators configured to eject a portion of fluid from the microfluidic channel through the outlet.

Description

[Technical Field]

[0001] Priority and Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 406,851, filed September 15, 2022, entitled "Thin film PZT actuator located in the microfluidic channel," which is incorporated by reference in its entirety.

[0002] FIELD OF THE INVENTION This application relates generally to controlling the flow of cells or particles, and more particularly to controlling the flow of cells or particles in microfluidic channels. [Background technology]

[0003] Conventional techniques for controlling the flow of cells or particles in microfluidic devices rely on external flow systems (e.g., using components located outside the microfluidic device). However, such external flow control systems typically do not provide precise control of the fluid dynamics in the microfluidic device for reliable cell capture, localization, and analysis, resulting in more complex and less cost-effective systems. These and other challenges associated with external flow control systems have limited the throughput for processing cells or particles using microfluidic devices. Summary of the Invention

[0004] As discussed above, controlled flow is a challenging problem in microfluidic devices. Some systems use external pumps for crude flow control. Some systems attach piezoelectric disks to induce flow or attach piezoelectric MEMS devices to drive flow. However, cellular fluid dynamics are difficult to control using each of these approaches (e.g., due to a lack of process control and / or precision). Described herein are devices and methods for flow control in microfluidic devices or systems. Such devices and methods may address challenges associated with conventional devices and methods for flow control in microfluidic devices or systems.

[0005] For example, a single-cell particle sensing system (e.g., for bacteria / viruses) is described with integrated electrodes and an inertial piezoelectric pump (forming a laminar flow field for the single cell). The piezoelectric pump vibration can generate displacements and acoustic waves that control the local inertial motion of the particle (e.g., in the x, y, and z planes) with submicron-level control. Additionally, the piezoelectric material (e.g., lead zirconate titanate (PZT)) can be positioned to protect it from any mechanical contact during processing or operation.

[0006] According to some embodiments, a microfluidic device includes: (i) a substrate having an outlet channel; (ii) a microfluidic channel disposed on the substrate such that an outlet of the microfluidic channel is disposed above the outlet channel; and (iii) a set of piezoelectric actuators disposed above the outlet channel and adjacent to the outlet, the set of piezoelectric actuators configured to expel a portion of fluid from the microfluidic channel through the outlet.

[0007] According to some embodiments, a method includes (i) feeding a plurality of particles through a microfluidic channel having an outlet disposed above the outlet channel; (ii) manipulating the particles flowing through the microfluidic channel using an electric field with a set of electrodes; and (iii) ejecting a portion of the fluid in the microfluidic channel using a set of piezoelectric actuators disposed above the outlet channel adjacent to the outlet.

[0008] According to some embodiments, a method of constructing a microfluidic device includes (i) disposing a set of piezoelectric actuators on a substrate, (ii) disposing a passivation layer on the set of piezoelectric actuators, (iii) forming an outlet channel by removing a portion of the substrate below the set of piezoelectric actuators, (iv) disposing a polymer layer on an optical layer (e.g., a glass substrate), (v) forming a microfluidic inlet by removing a portion of the optical layer, and (vi) forming a microfluidic channel between the microfluidic inlet and outlet channel by bonding the optical layer to the substrate via the polymer layer.

[0009] Thus, the disclosed devices and methods relate to flow and ejection technologies implemented within or as part of microfluidic devices, enabling controlled flow of cells or particles within microfluidic channels based on electro-hydro-dynamic (EHD) displacement using piezoelectric actuators and electrodes. Such controlled flow provides reliable cell capture, localization, and analysis. The disclosed devices and methods may replace or complement conventional devices and methods.

[0010] The features and advantages described herein are not necessarily all-inclusive, and in particular, some additional features and advantages will be apparent to those skilled in the art upon consideration of the drawings, specification, and claims provided in this disclosure. Furthermore, it should be noted that the language used herein has been chosen primarily for ease of reading and instructional purposes, and not necessarily to limit or restrict the subject matter described herein. [Brief explanation of the drawings]

[0011] In order that the present disclosure may be more fully understood, a more particular description may be made by reference to features of various embodiments, some of which are illustrated in the accompanying drawings. However, the accompanying drawings only illustrate relevant features of the present disclosure and therefore should not be considered as necessarily limiting, since the description may recognize other useful features, as those skilled in the art will understand upon reading the present disclosure. [Figure 1A] FIG. 1 shows a top view of an exemplary microfluidic device according to some embodiments. [Figure 1B] 1 illustrates a plan view of an exemplary piezoelectric film according to some embodiments. [Figure 2A] FIG. 1B shows a cross-sectional view of the microfluidic device of FIG. 1A, according to some embodiments. [Figure 2B] FIG. 1B shows another cross-sectional view of the microfluidic device of FIG. 1A, according to some embodiments. [Figure 2C] 1 illustrates a cross-sectional view of an exemplary piezoelectric actuator, according to some embodiments. [Figure 3A] 1B illustrates an exemplary manufacturing process for the microfluidic device of FIG. 1A, according to some embodiments. [Figure 3B] 1B illustrates an exemplary manufacturing process for the microfluidic device of FIG. 1A, according to some embodiments. [Figure 3C] 1B illustrates an exemplary manufacturing process for the microfluidic device of FIG. 1A, according to some embodiments. [Figure 4]FIG. 1 is a block diagram illustrating exemplary electrical components for a microfluidic device according to some embodiments. [Figure 5A] FIG. 1 is a flow diagram illustrating an exemplary method for controlling the flow of cells or particles in a microfluidic channel, according to some embodiments. [Figure 5B] FIG. 1 is a flow diagram illustrating an exemplary method for fabricating a microfluidic device, according to some embodiments.

[0012] In accordance with common practice, the various features illustrated in the drawings are not necessarily drawn to scale and like reference numerals may be used to refer to like features throughout the specification and drawings. DETAILED DESCRIPTION OF THE INVENTION

[0013] Reference will now be made to embodiments, examples of which are illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the various described embodiments. However, it will be apparent to those skilled in the art that the various described embodiments may be practiced without these specific details. In other instances, methods, procedures, components, circuits, and networks that are well known to those skilled in the art have not been described in detail so as not to unnecessarily obscure aspects of the embodiments.

[0014] The microfluidic devices described herein allow for electrical and / or optical sensing of one or more cells (or other particles). The microfluidic aspects of the devices allow for precise flow control (e.g., using electrodes and / or piezoelectric components). Piezoelectric components (e.g., piezoelectric layers) with exit ports (e.g., nozzles) allow for direct ejection (e.g., jetting) of cells (e.g., after they have been processed).

[0015] The microfluidic devices described herein can improve design flexibility and address a wider design space by utilizing the placement of piezoelectric materials. For example, small (e.g., less than 20 μm) to large (e.g., greater than 200 μm) piezoelectric structures can be designed and used, thereby providing a wider range of performance attributes. In addition, the piezoelectric films described herein can improve processing (e.g., ease and reproducibility). For example, the piezoelectric film can be disposed between a silicon-on-insulator (SOI) handle layer and a glass top layer and encapsulated in a passivation material (e.g., a dielectric material) to prevent exposure to mechanical stress. For example, this film can be formed by selectively etching the SOI. This can also enable easier wafer handling. The devices described herein can also improve packaging flexibility and / or robustness (improving yield) by mechanically protecting the piezoelectric actuators and piezoelectric film.

[0016] 1A shows a plan view of a microfluidic device 100, according to some embodiments. The device 100 includes a fluidic channel 102 (e.g., a microfluidic channel) formed on a substrate. In some embodiments, the fluidic channel 102 is formed by bonding a first substrate having a depression, recess, or notch to a second substrate such that the fluidic channel 102 is provided between the first and second substrates. The device 100 of FIG. 1A also includes openings (apertures) 110-1 through 110-8 for electrodes, bonding pads, and / or circuitry.

[0017] Fluidic channel 102 has an inlet 103 and an outlet 107. The locations of inlet 103 and outlet 107 shown for fluidic channel 102 in FIG. 1A are merely examples. Inlet 103 and outlet 107 may be located at other locations along the length of fluidic channel 102 or device 100. In some embodiments, length L1 of fluidic channel 102 (e.g., measured from inlet 103 to outlet 107) is in the range of 1 mm to 50 mm (e.g., 15 mm). In some embodiments, width W1 of microfluidic device 100 is in the range of 0.2 mm to 5 mm (e.g., 0.7 mm). In some embodiments, the width of fluidic channel 102 (e.g., at a representative portion such as sensing region 102-A, which may be the narrowest portion) is configured based on the size of the particles to be analyzed. For example, for cell measurements, the width of fluidic channel 102 can be configured according to the size of the cells so that only a single cell is detected at a time. In some embodiments, fluidic channel 102 includes one or more portions having different respective widths. For example, the fluidic channel 102 may include a portion having a (protruding) shape that is larger than the width of the sensing region 102-A. Similarly, the fluidic channel 102 may include one or more portions having a width that is smaller than the width of the sensing region 102-A. In some embodiments, the wider the fluidic channel 102, the slower the velocity of particles flowing through the corresponding portion of that fluidic channel 102 (e.g., if the fluidic channel 102 has a uniform height). Thus, for example, a wider portion may be used to reduce the velocity of particles (e.g., immobilize the particles), thereby allowing more time for analyzing the particles.

[0018] Device 100 also includes an input region 104 for receiving a sample fluid having particles (e.g., cells) at an inlet port as input to device 100 and for supplying the sample fluid from the inlet port to fluidic channel 102 via inlet 103. In some embodiments, device 100 includes a set of piezoelectric actuators in input region 104 (e.g., around inlet 103). The shape and size of input region 104 in FIG. 1A are merely exemplary. Device 100 further includes an output region 106 for collecting at least a portion of the sample fluid from fluidic channel 102 and for ejecting or delivering the portion of the sample fluid through outlet 107 (e.g., a nozzle) for further processing or analysis. The shape and size of output region 106 in FIG. 1A are merely exemplary. In some embodiments, output region 106 includes a set of piezoelectric actuators positioned adjacent to outlet 107 to eject a portion of the fluid in fluidic channel 102. In some embodiments, the set of piezoelectric actuators includes one or more piezoelectric actuators (e.g., piezoelectric micro-electro-mechanical system (MEMS) actuators). In some embodiments, the set of piezoelectric actuators includes two or more piezoelectric actuators. In some embodiments, device 100 includes an actuation circuit electrically connected to the set of piezoelectric actuators. In some embodiments, in response to application of an electrical signal from the actuation circuit, the set of piezoelectric actuators generates vibrations that generate displacements and acoustic waves, thereby controlling the local inertial motion of particles within fluidic channel 102 in the three-dimensional x, y, and z planes with submicron-level control. In some embodiments, the set of piezoelectric actuators induces laminar flow from input region 104 toward outlet 107.

[0019] Device 100 includes a set of electrodes 108 (e.g., an electrode pair). The set of electrodes 108 can be used to charge particles so that they can be manipulated using an electric field as they flow through fluidic channel 102. In some embodiments, the distance between a pair of electrodes is configured so that only a single cell at a time is manipulated using the electric field. In some embodiments, device 100 includes a driver circuit (e.g., driver circuit 440 described with respect to FIG. 4) electrically connected to one or more of the electrodes. In some embodiments, the driver circuit is configured to generate an electrical signal in the megahertz and gigahertz frequency range. In some embodiments, the frequency of the electrical signal supplied to the electrodes depends on one or more types of particles to be analyzed using device 100.

[0020] In some embodiments, device 100 includes a second array of piezoelectric actuators, one or more electrode (pairs), and / or a third array of piezoelectric actuators. In some embodiments, the second array of piezoelectric actuators is disposed adjacent to inlet 103 to induce laminar flow from inlet 103 toward outlet 107. In some embodiments, the second array of piezoelectric actuators is configured for mixing and / or separation of an input sample. In some embodiments, the second array of piezoelectric actuators is disposed between inlet 103 and outlet 107. For example, the second array of piezoelectric actuators may be disposed laterally between inlet 103 and outlet 107 (e.g., inlet 103 may be disposed in an upstream region of the microfluidic channel, outlet 107 may be disposed in a downstream region of the microfluidic channel, and the second array of piezoelectric actuators may be disposed in a midstream region of the microfluidic channel). In some embodiments, the third array of piezoelectric actuators is disposed between inlet 103 and outlet 107. Like the first array of piezoelectric actuators, in some embodiments, the second and third arrays of piezoelectric actuators each include one or more piezoelectric actuators (e.g., piezoelectric microelectromechanical systems (MEMS) actuators).

[0021] In some embodiments, device 100 includes two or more output regions, and electrodes 108 operate to direct different types of particles toward the different output regions. In some embodiments, each output region has an outlet port and a set of piezoelectric actuators. In some embodiments, different portions of the sample fluid from inlet 103 (e.g., each portion corresponding to a particular cell or cell type) are deflected toward a corresponding output region. Thus, each different portion of the sample fluid is collected at and ejected from a corresponding output region. Deflection of different portions of the sample fluid can be achieved, for example, by vibration and displacement caused by activation of a piezoelectric actuator.

[0022] In some embodiments, in response to application of an electrical signal from the actuation circuit, the second array of piezoelectric actuators generates vibrations that generate displacements and acoustic waves that cause mixing and separation of the sample fluid and control the local inertial motion of the particles to induce laminar flow within the fluidic channel 102. In some configurations, the sample fluid flows through the fluidic channel 102 at a rate of 1 μL / min to 1 mL / min. In some embodiments, when activated using an appropriate electrical signal from the actuation circuit, the third array of piezoelectric actuators is configured to deflect charged particles (manipulated using an electric field generated by one or more electrode pairs) to specific output regions. In some embodiments, the one or more electrode pairs charge the particles so that they can be manipulated using an electric field as they flow through the fluidic channel 102.

[0023] In some embodiments, one or more electrode pairs detect electrical signals of particles (e.g., cells) flowing through the microfluidic channel 102 adjacent to the one or more electrode pairs. In some embodiments, a drive circuit is electrically connected to the electrodes and configured to generate electrical signals in the megahertz and gigahertz frequency range. In some embodiments, the drive circuit is configured to generate electrical signals having voltages in the range of 1 volt to 100 volts. In some embodiments, the drive circuit is configured to generate electrical signals having pulses in the range of 1 μs to 20 μs. In some embodiments, the pulses are sawtooth pulses, square pulses, or sinusoidal pulses. In some embodiments, the device 100 includes readout circuitry (e.g., the drive / readout circuitry 440 described with respect to FIG. 4 ) electrically connected to the one or more electrodes. In some embodiments, the readout circuitry receives electrical signals from the one or more electrodes and relays the electrical signals (with or without processing, such as filtering) to one or more processors of the device 100 or to one or more processors operatively connected to the device 100.

[0024] In some embodiments, one or more electrode pairs provide an electric field to induce the movement (e.g., deflection) of charged particles (e.g., particles charged by other electrode pairs). For example, the electric field provided by one or more electrode pairs may induce the direct movement of charged particles by providing a potential difference. As another example, the electric field provided by one or more electrode pairs may be used to control the position, rotation, and / or acceleration of charged particles. Additionally or alternatively, the electric field provided by one or more electrode pairs may induce electrohydrodynamic flow of a fluid (e.g., when the fluid includes a dielectric medium).

[0025] In some embodiments, each particle may pass near one or more electrode pairs for a period of 0.1 to 100 milliseconds, hi some embodiments, each particle may pass near one or more second electrode pairs for a period of 0.1 to 100 milliseconds.

[0026] In some embodiments, the separation distance between the electrode pairs and the distance between the first and second electrodes are configured based on one or more types of particles to be analyzed using device 100. In some embodiments, the particle processing rate in microfluidic device 100 is between 100 particles / minute and 1 million particles / minute.

[0027] In some embodiments, the electrodes are disposed on the same substrate as each other and / or the piezoelectric component, hi some embodiments, electrode pairs are disposed on different substrates (e.g., one electrode of the electrode pair is disposed on a bottom substrate and the other electrode of the electrode pair is disposed on a top substrate).

[0028] 1A is merely an example. The set of electrodes 108 and the position of the sensing region 102-A may vary along the length of the channel. For example, to obtain accurate impedance measurements, it may be beneficial to balance the lengths of the "sensing" zone electrodes (e.g., the length and width of the electrodes from the sensing region 102-A to pad 110-1 and the other pad 110-3 may be the same).

[0029] FIG. 1B illustrates a plan view of a piezoelectric film 152, according to some embodiments. The piezoelectric film 152 is disposed within the output region 106 (e.g., over the output channels) shown in FIG. 1A. As described in more detail below, the piezoelectric film 152 can include a substrate 209 (e.g., a buried oxide layer and / or a device layer), a passivation layer, and a piezoelectric material (e.g., PZT). In some embodiments, the piezoelectric material is polyvinylidene fluoride, gallium phosphate, bismuth sodium titanate, lead zirconate titanate, quartz, berlinite (AlPO), sucrose (table sugar), Rochelle salt, topaz, tourmaline group minerals, lead titanate (PbTiO), langasite (LaGaSiO), gallium orthophosphate (GaPO), lithium niobate (LiNbO), lithium tantalate (LiTaO), any of the perovskite-containing family of ceramics, tantalum oxide (TaO), or the like. Examples of suitable ferrites include tungsten bronze, potassium niobate (KNbO3), sodium tungstate (Na2WO3), Ba2NaNb5O5, Pb2KNb5O15, potassium sodium niobate ((K,Na)NbO3) (e.g., NKN or KNN), bismuth ferrite (BiFeO3), sodium niobate (NaNbO3), barium titanate (BaTiO3), bismuth titanate (Bi4Ti3O12), sodium bismuth titanate (NaBi(TiO3)2), zinc blende, GaN, InN, AlN, and ZnO.

[0030] Piezoelectric membrane 152 includes outlet 107 (e.g., a nozzle) for channel 102. FIG. 1B also shows electrical pathway 154 and corresponding contact 158 ​​(e.g., coupled to a first electrode) and electrical pathway 156 and corresponding contact 160 (e.g., coupled to a second electrode). The first electrode and second electrode may be coupled to one or more piezoelectric layers to actuate the piezoelectric material and eject fluid through outlet 107. In some embodiments, outlet 107 has a diameter of less than 200 μm (e.g., 30, 60, or 120 μm). In some embodiments, piezoelectric member 152 has a diameter in the range of 200 μm to 1500 μm (e.g., 300, 600, or 1200 μm).

[0031] FIG. 2A illustrates a cross-sectional view of a microfluidic device 100 along the A-A' direction, according to some embodiments. As shown in FIG. 2A, the device 100 includes an optical layer 202 (e.g., made of glass) having an inlet channel 214. The optical layer 202 is bonded to a substrate 209 via an adhesive layer 204. The adhesive layer 204 includes a microfluidic channel 220 (e.g., the microfluidic channel 102). In the example of FIG. 2A, the substrate 209 includes a handle layer 212, a buried oxide (BOX) layer 210 (e.g., made of SiO), and a device layer 208. In some embodiments, the device layer 208 has a thickness in the range of 1 μm to 5 μm. In some embodiments, the handle layer 212 has a thickness in the range of 200 μm to 600 μm.

[0032] According to some embodiments, the outlet channel 216 is provided in the substrate 209 (eg, etched into the handle layer 212). According to some embodiments, outlet 218 (e.g., outlet 107) is provided in substrate 209 (e.g., through box layer 210 and device layer 208). Passivation layer 206 (e.g., a sealing layer) is coupled to substrate 209. Device 100 includes a bottom electrode 224, a top electrode 230, and a piezoelectric layer 228 (e.g., surrounding outlet 218). The device further includes a contact 226 coupled to bottom electrode 224 and a contact 238 coupled to top electrode 230. Passivation layer 206 separates electrodes 224 and 230 and piezoelectric layer 228 from channel 220. According to some embodiments, electrodes 222 are disposed within channel 220. The number and location of electrodes 222 in FIG. 2A are merely examples. In some embodiments, electrodes 222 have a thickness in the range of 0.01 μm to 2 μm. Other embodiments may include a different number of electrodes and / or different arrangements of electrodes.

[0033] In some embodiments, the channel 220 is provided by the optical layer 202, the adhesive layer 204, and the device layer 208. In some embodiments, the channel 220 has a height of 10 microns to 1 mm (e.g., 10 microns, 20 microns, 30 microns, 40 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, 200 microns, 300 microns, 400 microns, 500 microns, 600 microns, 700 microns, 800 microns, 900 microns, or 1 mm, or within a range between any two of the foregoing values). In some embodiments, the optical layer 202 has a thickness of 5 microns to 2 mm (e.g., 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns, 20 microns, 30 microns, 40 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, 200 microns, 300 microns, 400 microns, 500 microns, 600 microns, 700 microns, 800 microns, 900 microns, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, or 2 mm, or a range between any two of the foregoing values). In some embodiments, the substrate 209 is 500 microns thick. In some embodiments, the inlet 103 is provided in the substrate 209 (e.g., in addition to or as an alternative to being provided in the optical layer 202).

[0034] In some embodiments, adhesive layer 204 is disposed between optical layer 202 and substrate 209 (e.g., between optical layer 202 and device layer 208). In some embodiments, adhesive layer 204 is comprised of a polymer. Examples of polymers and organic materials include polyvinylidene fluoride (PVDF) and its copolymers, polyamides, and paralym-C, polyimides and polyvinylidene chloride (PVDC), and diphenylalanine peptide nanotubes (PNT).

[0035] In some embodiments, adhesive layer 204 is adapted and / or arranged to bond optical layer 202 (e.g., a first substrate) and substrate 209 (e.g., a second substrate) to one another. For example, if adhesive layer 204 is not included, optical layer 202 may not bond to substrate 209. In some embodiments, adhesive layer 204 is comprised of a photosensitive material. For example, photosensitive adhesive layer 204 can provide definition, such as width, height, and curvature, of fluidic channel 220 (e.g., improve the signal-to-noise ratio (SNR) for single-cell sensing). In some embodiments, adhesive layer 204 is adapted and / or arranged to provide stress relief to device 100 (e.g., to prevent stress cracking when the chip is assembled into a package). In some embodiments, adhesive layer 204 is cured / hardened (e.g., subjected to multiple stages of curing / hardening). In some embodiments, adhesive layer 204 is exposed to a temperature above the transition temperature of the adhesive layer (e.g., 150 degrees Celsius), causing the adhesive layer to harden and bond optical layer 202 (e.g., glass) to substrate 209 (e.g., silicon). In some embodiments, adhesive layer 204 is comprised of a liquid or dry film. Adhesive layer 204 may be a negative or positive photoresist. In some embodiments, adhesive layer 204 is comprised of an epoxy (e.g., bisphenol A) and / or polyimide with a photoinitiator (e.g., added to drive cross-linking based on the wavelength of light).

[0036] In some embodiments, piezoelectric layer 228 has a thickness of 0.1 microns to 100 microns (e.g., 0.1 microns, 0.5 microns, 1 micron, 2 microns, 5 microns, 10 microns, 20 microns, 30 microns, 40 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, or 100 microns, or a range between any two of the foregoing values). In some embodiments, piezoelectric layer 228 is disposed on a silicon-on-insulator (SOI) layer. In some embodiments, the silicon-on-insulator (SOI) layer is connected to one or more of the contacts (e.g., contact 226).

[0037] 2B illustrates a cross-sectional view of microfluidic device 100 along the B-B′ direction, according to some embodiments. As shown in FIG. 2B, conductive layer 252 is coupled to contact 238 (e.g., corresponding to electrical pathway 154 and contact 158 ​​in FIG. 1B ), and conductive layer 250 is coupled to contact 226 (e.g., corresponding to electrical pathway 156 and contact 160 in FIG. 1B ). In some embodiments, conductive layer 250 and conductive layer 252 are each composed of a conductive material (e.g., copper, aluminum, gold, or platinum). In some embodiments, a respective bond pad is coupled to conductive layer 250 and conductive layer 252. In some embodiments, electrode 224 and electrode 230 are each composed of a conductive material (e.g., copper, aluminum, gold, or platinum).

[0038] FIG. 2C illustrates a cross-sectional view of a piezoelectric actuator 231, according to some embodiments. The piezoelectric actuator 231 includes a bottom electrode 224, a piezoelectric layer 228, and a top electrode 230. In some embodiments, the piezoelectric layer 228 is composed of PZT and has a thickness in the range of 0.1 μm to 10 μm (e.g., 2 μm). In some embodiments, the bottom electrode 224 and / or the top electrode 230 are composed of strontium oxide (SR0) and / or titanium. In some embodiments, the bottom electrode 224 and / or the top electrode 230 have a thickness in the range of 100 Å to 500 Å. FIG. 2C includes a cross-section 260 illustrating a portion of the device layer 208, the top electrode 230, the bottom electrode 224, and the piezoelectric layer 228. The cross-section 260 also includes a layer 262 (e.g., a resist layer).

[0039] 3A-3C illustrate an exemplary fabrication process for the microfluidic device of FIG. 1A , according to some embodiments. FIG. 3A illustrates optical layer 202 (e.g., a glass substrate). FIG. 3B illustrates adhesion layer 204 applied to optical layer 202 (as portions 204-1 and 204-2). In some embodiments, adhesion layer 204 is a polymer fluid layer. In some embodiments, adhesion layer 204 is applied via polymer spin-coating and patterning (e.g., to form access to fluid channels and bond pads). In some embodiments, the spin-coat has a thickness in the range of 10 μm to 100 μm (e.g., 50 μm). FIG. 3C illustrates access channels (e.g., inlet channel 214) formed in optical layer 202 (e.g., via a laser drilling and / or etching process). In some embodiments, a laser drilling process is used to form the inlets and / or outlets. In some embodiments, a laser drilling process is used to etch the bond pad(s).

[0040] FIG. 4 is a block diagram illustrating exemplary electrical components for a microfluidic device, according to some embodiments. In some embodiments, the device (e.g., device 100) includes one or more processors 402 and a memory 404. In some embodiments, the memory 404 includes instructions for execution by the one or more processors 402. In some embodiments, the stored instructions include instructions for providing actuation signals to one or more piezoelectric actuators (e.g., piezoelectric actuator 231). In some embodiments, the actuation signals for the different piezoelectric actuators are configured such that each of the piezoelectric actuators generates vibrations at a different frequency. For example, one or more of the piezoelectric actuators may operate at a frequency in a range of 1 kHz to 100 kHz, e.g., based on a desired flow rate. In some embodiments, the stored instructions include instructions for providing an actuation signal to one or more of the electrodes 222 to charge particles flowing through the fluidic channel 220, thereby enabling the particles to be manipulated using an electric field. In some embodiments, the device also includes an electrical interface 406 connected to the one or more processors 402 and the memory 404. In some embodiments, the device further includes an actuation circuit 430 connected to one or more piezoelectric actuators 401, such as piezoelectric actuator 231. For example, the actuation circuit 430 sends an electrical signal to the piezoelectric actuator to initiate actuation of the piezoelectric actuator.

[0041] In some embodiments, the device further includes a driver circuit 440 coupled to one or more electrodes 405, such as electrode 222, electrode 224, and / or electrode 230. For example, the driver circuit 440 sends electrical signals to the one or more electrodes to generate an electric field using the one or more electrodes to charge particles flowing through the fluidic channel. In some embodiments, the device further includes a readout circuit (e.g., driver / readout circuit 440) connected to the one or more electrodes 405. The readout circuit receives the electrical signals from the one or more electrodes 405 and provides the electrical signals (with or without processing) to one or more processors 402 via an electrical interface 406.

[0042] In some embodiments, the device further includes a measurement / analysis circuit 450 connected to one or more electrodes 452. In some embodiments, the measurement / analysis circuit 450 is configured to detect particle impedance of particles in the microfluidic channel (e.g., channel 220). In some embodiments, the measurement / analysis circuit 450 is connected to the actuation circuit 430 and informs the actuation circuit 430 how to actuate the piezoelectric actuator (e.g., based on the impedance measurements). In some embodiments, the actuation circuit 430 is configured to adjust the actuation (e.g., adjust the frequency and / or magnitude) of the one or more piezoelectric actuators based on particle analysis results from the measurement / analysis circuit 450. In some embodiments, one or more electrodes are shared between electrode(s) 405 and electrode(s) 452.

[0043] 5A is a flow diagram illustrating a method 500 of controlling the flow of cells or particles in a microfluidic channel, according to some embodiments. In some embodiments, method 500 is performed in a microfluidic device (e.g., device 100).

[0044] The method 500 includes providing 502 a plurality of particles through a microfluidic channel (e.g., channel 220) having an outlet (e.g., outlet 218) disposed above an outlet channel (e.g., outlet channel 216). For example, a sample fluid having particles (e.g., cells) is provided into a fluidic channel 102 having an inlet 103 and an outlet 107.

[0045] In some embodiments, the method 500 includes inducing laminar flow from an inlet to an outlet of the microfluidic channel using a first set of piezoelectric actuators. For example, the first set of piezoelectric actuators may induce laminar flow from the inlet 103 to the outlet 107 of the fluidic channel 102. As an example, the first set of piezoelectric actuators may be positioned adjacent to the inlet 103 to induce laminar flow from the inlet 103 to the outlet 107 of the fluidic channel 102. The first set of piezoelectric actuators may be activated or actuated based on an actuation signal from the one or more processors 402.

[0046] Method 500 includes measuring 504 (e.g., via measurement / analysis circuitry 450) the impedance of a plurality of particles flowing through the microfluidic channel. In various embodiments, the impedance is measured before and / or after manipulating the particles. In some embodiments, the impedance is measured using a second set of electrodes (e.g., electrode(s) 452). In some embodiments, method 500 includes measuring one or more properties of the particles flowing through the microfluidic channel.

[0047] Method 500 includes manipulating 506 particles flowing through the microfluidic channel with an electric field using a set of electrodes (e.g., electrode 222 and / or electrode 405). For example, charging the particles allows the particles flowing through the microfluidic channel to be manipulated with an electric field. As an example, when activated, the set of electrodes (e.g., at least a subset of electrodes 222) charges particles flowing through the fluidic channel such that the particles flowing through the fluidic channel can be manipulated with an electric field.

[0048] In some embodiments, the method 500 includes providing an actuation signal to one or more electrode pairs to charge particles flowing through the microfluidic channel. For example, the one or more processors 402 provide an actuation signal to the electrodes 222 so that particles in the fluidic channel 220 can be manipulated using an electric field.

[0049] In some embodiments, the method 500 includes ejecting (508) a portion of the fluid in the microfluidic channel using a set of piezoelectric actuators (e.g., piezoelectric actuators 231) positioned adjacent to the outlet and above the outlet channel. For example, when activated or actuated, the piezoelectric actuators 231 cause displacement and vibration to eject a portion of the fluid in the fluidic channel 220 through the outlet 218. In some embodiments, the method 500 includes providing an actuation signal to the set of piezoelectric actuators, for example, from one or more processors 402. In some embodiments, the set of piezoelectric actuators and the outlet are sized to eject particles having diameters in the range of 100 nm to 100 μm. In some embodiments, the method further includes inducing laminar flow from the inlet to the outlet of the microfluidic channel using a second set of piezoelectric actuators. In some embodiments, the actuation signal for the set of piezoelectric actuators is generated to generate a vibration frequency in the actuators based on the fluid composition (e.g., particle size and / or concentration) in the microfluidic channel. For example, the actuators are configured to vibrate to eject only one cell at a time.

[0050] FIG. 5B is a flow diagram illustrating a method 550 for fabricating a microfluidic device, according to some embodiments.

[0051] The method 550 includes disposing 552 a set of piezoelectric actuators (e.g., piezoelectric actuators 231) on a substrate (e.g., substrate 209). In some embodiments, the substrate includes a device layer (e.g., having a thickness of 1 to 5 μm), a BOX layer (e.g., having a thickness in the range of 0.5 to 5 μm), and a handle layer (e.g., having a thickness in the range of 400 μm to 500 μm).

[0052] The method 550 also includes disposing 554 a passivation layer (e.g., passivation layer 206) over the set of piezoelectric actuators. In some embodiments, the passivation layer has a thickness in the range of 0.01 μm to 1 μm. In some embodiments, the passivation layer is an encapsulation layer. In some embodiments, disposing the passivation layer includes depositing silicon nitride. In some embodiments, the passivation layer is composed of silicon nitride, silicon carbide, SiO made from TEOS or silazane, aluminum nitride, aluminum oxide, and / or a photosensitive polymer. In some embodiments, the thickness of the passivation layer is based on the thickness of the set of piezoelectric actuators and / or the desired piezoelectric vibration properties.

[0053] In some embodiments, the method 550 includes patterning and etching the passivation layer to place / form electrode contacts.

[0054] The method 550 also includes forming an outlet channel (e.g., outlet channel 216) by removing a portion of the substrate below the set of piezoelectric actuators (556). In some embodiments, the method 550 includes patterning and etching the device layer and the BOX layer to form an outlet (e.g., a nozzle). In some embodiments, the handle layer for the SOI is etched through to provide a "tunnel" through which the droplet can drain (e.g., bypassing / avoiding any "thin wafer handling" processes, including dicing).

[0055] In some embodiments, method 550 includes outlet (nozzle) formation. For example, nozzle formation is performed by a multi-step etching process. For example, a first step forms a backside that stops on the SOI layer (e.g., a selective DRIE etch that also provides an outlet membrane). In this example, a second etch is performed from the top side and penetrates through the SOI layer. In some embodiments, the SOI wafer is not thinned. Instead, holes are made in areas of the membrane to allow droplet ejection, thereby improving wafer handling, improving yield, and / or allowing more design space for larger piezoelectric actuators and / or membranes.

[0056] The method 550 also includes bonding (558) a polymer layer (e.g., adhesive layer 204) to the optical layer (e.g., optical layer 202). For example, FIG. 3B shows adhesive layer 204 disposed on optical layer 202. In some embodiments, the optical layer is a glass substrate (e.g., having a thickness in the range of 200 μm to 700 μm (e.g., 500 μm)). In some embodiments, the polymer layer is spin-coated, exposed, and developed to form microfluidic channels. In some embodiments, bond pads are exposed to allow access to the electrodes. In some embodiments, the optical layer enables hybrid optical-electrical sensing.

[0057] The method 550 also includes forming 560 a microfluidic inlet (e.g., inlet channel 214) by removing a portion of the optical layer. For example, FIG. 3C shows an inlet channel 214 formed in the optical layer 202. In some embodiments, the optical layer is laser drilled to form the inlet (and / or other holes for electrical contacts).

[0058] The method 550 also includes forming 562 a microfluidic channel (e.g., channel 220) between the microfluidic inlet and outlet channels by bonding the optical layer to the substrate via the polymer layer. In some embodiments, the optical layer and polymer layer are aligned and bonded to a silicon device wafer.

[0059] Some embodiments include arranging piezoelectric (e.g., PZT) actuators and nozzles within the SOI-polymer-glass hybrid structure. Some embodiments include a piezoelectric actuator configuration applied to a microfluidic channel. Some embodiments include an electrode array for sensing cells or particles arranged on the same layer as the actuator electrodes, which can improve device fabrication, processing, and interconnection. Thus, a high-throughput, high-reproducibility single-cell processing system with integrated inertial flow, sorting, and delivery for cell post-processing is disclosed. The PZT structure can drive the actuation and delivery of droplets containing particles, cells, and / or therapeutic agents through nozzles built within the PZT stack itself. Droplet ejection can be achieved through a "large via" fabricated in the handle layer of the SOI wafer.

[0060] In light of the above disclosure, specific embodiments are described below.

[0061] (A1) In one aspect, some embodiments include a microfluidic device (e.g., microfluidic device 100) including: (i) a substrate (e.g., substrate 209) having an outlet channel (e.g., outlet channel 216); (ii) a microfluidic channel (e.g., microfluidic channel 220) disposed on the substrate such that an outlet (e.g., outlet 218) of the microfluidic channel is disposed above the outlet channel; and (iii) a set of piezoelectric actuators (e.g., piezoelectric layer 228) disposed above the outlet channel and adjacent to the outlet, the set of piezoelectric actuators configured to eject a portion of fluid from the microfluidic channel through the outlet. In some embodiments, the set of piezoelectric actuators consists of one piezoelectric actuator. As an example, the substrate can be a silicon-on-insulator (SOI) substrate. The set of piezoelectric actuators can be composed of lead zirconate titanate (PZT). In some embodiments, the piezoelectric actuators have a thickness in the range of 0.1 μm to 5 μm. In some embodiments, the outlet has a diameter in the range of 20 μm to 150 μm. In one example, the microfluidic channel extends over a substrate, and the outlet channel is formed through the thickness of the substrate. In some embodiments, the outlet comprises a hole, the hole being formed through the thickness of the set of piezoelectric actuators and completely surrounded within the edge of the set of piezoelectric actuators. In some embodiments, fluid is configured to exit the microfluidic channel through the outlet hole. In some embodiments, the set of piezoelectric actuators is attached to a polymer layer. In some embodiments, the set of piezoelectric actuators is protected by an insulator to prevent contact with the conductive fluid. In some embodiments, the set of piezoelectric actuators has a diameter in the range of 100 μm to 300 μm.

[0062] (A2) In some embodiments of A1, the outlet comprises a hole, the hole being formed through the thickness of the set of piezoelectric actuators and being surrounded by the set of piezoelectric actuators.

[0063] (A3) In some embodiments of A1 or A2, the set of piezoelectric actuators is disposed on a membrane above the outlet channel. In various embodiments, the membrane is disposed above, below, or otherwise adjacent to the outlet channel. For example, the membrane can be comprised of a thin layer of substrate (e.g., having a thickness in the range of 1 μm to 5 μm). In some embodiments, the membrane separates the outlet channel from a corresponding portion of the microfluidic channel. As an example, the membrane can include portions of the BOX layer 210 and device layer 208 disposed above the outlet channel 216 (as shown in FIG. 2A).

[0064] (A4) In some embodiments of any of A1 through A3, the microfluidic device further includes a passivation layer (e.g., a sealing layer) disposed between the set of piezoelectric actuators and the microfluidic channel. For example, the passivation layer (e.g., passivation layer 206) may be composed of nitride. In some embodiments, the passivation layer has a thickness in the range of 0.01 μm to 1 μm. Exemplary passivation materials include silicon nitride, silicon carbide, SiO2, aluminum nitride, aluminum oxide, and photosensitive polymers.

[0065] (A5) In some embodiments of any of A1 through A4, the microfluidic device further includes a first electrode (e.g., upper electrode 230) and a second electrode (e.g., lower electrode 224), the first electrode and the second electrode configured to provide actuation signals to a set of piezoelectric actuators, the set of piezoelectric actuators disposed between the first electrode and the second electrode. For example, the first electrode and the second electrode may be composed of gold (Au). In some embodiments, each of the first electrode and the second electrode has a thickness in the range of 0.05 μm to 2 μm.

[0066] (A6) In some embodiments of any of A1 through A5, the microfluidic device further includes an optical layer (e.g., optical layer 202), and the microfluidic channel is disposed between the optical layer and the substrate. For example, the optical layer may be comprised of glass. In some embodiments, the optical layer includes a passivation layer. In some embodiments, a non-optical top layer is used in place of optical layer 202. In some embodiments, the optical layer includes a top layer. In some embodiments, the optical layer is comprised of a transparent and / or translucent material.

[0067] (A7) In some embodiments of any of A1 through A6, the microfluidic device further includes a polymer layer (e.g., adhesion layer 204) that provides at least a portion of the microfluidic channel. In some embodiments, the polymer layer adheres the substrate to the optical layer. In some embodiments, a non-polymeric adhesion layer is used in place of the polymer layer.

[0068] (A8) In some embodiments of any of A1 to A7, the microfluidic device further includes one or more electrodes (e.g., electrode 222), the one or more electrodes disposed adjacent to the microfluidic channel and configured to apply an electric field to the fluid. In some embodiments, the one or more electrodes have a thickness in the range of 0.01 μm to 1 μm. In some embodiments, the set of piezoelectric actuators and the one or more electrodes are disposed on the same layer (e.g., disposed on passivation layer 206).

[0069] (A9) In some embodiments of any of A1 through A8, the substrate includes a silicon base layer (e.g., handle layer 212) and a buried oxide (BOX) layer (e.g., BOX layer 210), where the BOX layer separates the microfluidic channels from the silicon base layer. For example, the BOX layer separates the silicon base layer from the device layer. By way of example, the silicon base layer may have a thickness in the range of 200 μm to 600 μm, and the device layer may have a thickness in the range of 1 μm to 5 μm.

[0070] (A10) In some embodiments of any of A1 to A9, the microfluidic device further comprises a second set of piezoelectric actuators disposed adjacent to the inlet of the microfluidic channel, hi some embodiments, a third set of piezoelectric actuators disposed between the inlet and the outlet.

[0071] (A11) In some embodiments of any of A1 through A10, the microfluidic device further includes control circuitry (e.g., processor(s) 402, actuation circuitry 430, electrical interface 406, and / or drive / readout circuitry 440), the control circuitry electrically connected to the set of piezoelectric actuators and configured to provide actuation signals to the set of piezoelectric actuators. In some embodiments, the control circuitry is further configured to provide activation signals to one or more electrodes to selectively charge particles flowing through the microfluidic channel.

[0072] (B1) In another aspect, some embodiments include a method (e.g., method 500) that includes: (i) providing a plurality of particles through a microfluidic channel having an outlet disposed above an outlet channel; (ii) measuring the impedance of the particles flowing through the microfluidic channel (e.g., via measurement / analysis circuitry 450); (iii) using a set of electrodes to manipulate the particles flowing through the microfluidic channel using an electric field (e.g., via drive / readout circuitry 440); and (iv) ejecting a portion of the fluid in the microfluidic channel using a set of piezoelectric actuators disposed above the outlet channel adjacent to the outlet. In some embodiments, the set of piezoelectric actuators and the outlet are sized to eject particles having diameters in the range of 100 nm to 100 μm. In some embodiments, the method further includes inducing a laminar flow from the inlet to the outlet of the microfluidic channel using a second set of piezoelectric actuators. In various embodiments, the impedance of the particles flowing through the microfluidic channel is measured before, during, or after manipulating the particles. In some embodiments, the particles flowing through the microfluidic channel are manipulated based on the measured impedance.

[0073] (B2) In some embodiments of B1, the method further includes providing actuation signals to the set of piezoelectric actuators (e.g., via actuation circuitry 430) and providing electrical signals to the set of electrodes (e.g., via drive / readout circuitry 440). In some embodiments, the actuation signals for the set of piezoelectric actuators are generated to produce vibration frequencies in the actuators based on the fluid composition (e.g., particle size and / or concentration) in the microfluidic channel. For example, the actuators are configured to vibrate to eject only one cell at a time.

[0074] (B3) In some embodiments of B1 or B2, the method further includes providing an actuation signal (e.g., from actuation circuitry 430) to the first array of piezoelectric actuators (e.g., via electrical interface 406).

[0075] (C1) In another aspect, some embodiments include a method, the method including: (i) disposing a set of piezoelectric actuators (e.g., piezoelectric actuator 231) on a substrate (e.g., substrate 209); (ii) disposing a passivation layer (e.g., passivation layer 206) on the set of piezoelectric actuators; (iii) forming an outlet channel (e.g., outlet channel 216) by removing a portion of the substrate below the set of piezoelectric actuators; (iv) bonding a polymer layer (e.g., adhesion layer 204) to an optical layer (e.g., optical layer 202); (v) forming a microfluidic inlet (e.g., inlet channel 214) by removing a portion of the optical layer; and (vi) forming a microfluidic channel (e.g., channel 220) between the microfluidic inlet and outlet channels by bonding the optical layer to the substrate via the polymer layer. In some embodiments, the polymer layer has a thickness in the range of 20 μm to 100 μm. In some embodiments, the microfluidic channel includes a sensor region (e.g., region 102-A) between the inlet and outlet. In some embodiments, the microfluidic channel is shaped to narrow in the sensor region. In some embodiments, bonding the optical layer to the substrate via the polymer layer includes adhering the polymer layer to a passivation layer. In some embodiments, bonding the optical layer to the substrate includes applying pressure and heat to the polymer layer to form a laminate composite structure. In some embodiments, the polymer layer is bonded to the substrate and / or passivation layer before the polymer layer is bonded to the optical layer. In some embodiments, the polymer layer is bonded to the optical layer before the polymer layer is bonded to the substrate and / or passivation layer. In some embodiments, forming the microfluidic inlet includes etching the optical layer. For example, laser drilling the optical layer to form the inlet. In some embodiments, the optical layer is a glass substrate. In some embodiments, the optical layer is at least semi-transparent to enable optical sensing of the microfluidic channel. For example, piezoelectric structure and performance can be monitored through the optical layer.

[0076] In some embodiments, forming the microfluidic inlet includes removing a portion of the substrate (e.g., the inlet is formed through the substrate in place of the optical layer). In some embodiments, the polymer layer is configured to converge the channels into the sensing region to enable a high signal-to-noise ratio (SNR) for broad-spectrum, high-frequency sensing, and then diverge the channels to align with the exhaust actuation zone design.

[0077] In some embodiments, a polymer microfluidic layer is spin-coated or laminated onto glass, and then the polymer layer is exposed and developed. It is then aligned to the sensors and piezoelectric actuators on the silicon. It is then fully baked under pressure to form a laminated composite structure.

[0078] (C2) In some embodiments of C1, the substrate comprises a BOX layer (e.g., BOX layer 210) separating a base layer (e.g., handle layer 212) and a device layer (e.g., device layer 208), and the set of piezoelectric actuators is disposed on the device layer. For example, the base layer may have a thickness of 450 μm, the BOX layer may have a thickness of 1 μm, and the device layer may have a thickness of 3 μm.

[0079] (C3) In some embodiments of C1 or C2, disposing the set of piezoelectric actuators includes (i) depositing a bottom electrode layer (e.g., bottom electrode 224) on the substrate, (ii) depositing a piezoelectric material (e.g., piezoelectric layer 228) on the bottom electrode layer, and (iii) depositing a top electrode layer (e.g., top electrode 230) on the piezoelectric material. In some embodiments, disposing the set of piezoelectric actuators further includes etching an electrode pattern into the top electrode layer, etching an actuator pattern into the piezoelectric material, and etching an electrode pattern into the bottom electrode layer.

[0080] (C4) In some embodiments of any of C1 to C3, forming the outlet channel includes forming a microfluidic outlet (e.g., outlet 218), wherein the diameter of the microfluidic outlet is smaller than the diameter of the outlet channel. For example, the microfluidic outlet may have a diameter of 50 μm or less, and the outlet channel may have a diameter of 300 μm or more.

[0081] (C5) In some embodiments of any of C1 to C4, bonding the polymer layer to the optical layer includes applying a polymer spin coat to the optical layer. For example, the polymer may be applied in a pattern using a mask. In some embodiments, the polymer layer is spin coated, exposed, and developed to form microfluidic channels. In some embodiments, the polymer layer is laminated onto the optical layer.

[0082] (C6) In some embodiments of any of C1 to C5, disposing a passivation layer on the set of piezoelectric actuators includes depositing a passivation layer. By way of example, the passivation layer has a thickness in the range of 0.01 μm to 1 μm.

[0083] (C7) In some embodiments of any of C1 to C6, the method further includes disposing a set of electrodes (e.g., electrode 222) within or adjacent to the microfluidic channel. In some embodiments, disposing the set of electrodes includes patterning and etching the passivation layer.

[0084] Terms such as "first," "second," and the like may be used herein to describe various elements, but it should be understood that these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first array can be referred to as a second array, and similarly, a second array can be referred to as a first array, without departing from the scope of the various described embodiments. Although the first array and the second array are both arrays, they are not the same array.

[0085] The terminology used in the description of embodiments herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the claims. In the description and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It will also be understood that the term "and / or" herein refers to and includes any and all possible combinations of one or more of the associated listed items. It will also be understood that the terms "comprises" and / or "comprising" herein specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0086] The foregoing description has been described with reference to specific embodiments for purposes of explanation. However, the illustrative description above is not intended to be exhaustive or to limit the scope of the claims to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. The embodiments have been chosen and described to best explain the principles of the various described embodiments and their practical applications, thereby enabling others skilled in the art to best utilize the principles and various described embodiments, with various modifications suited to the particular uses contemplated.

Claims

1. a substrate having an outlet channel; a microfluidic channel disposed on the substrate such that an outlet of the microfluidic channel is disposed over at least a portion of the outlet channel; a set of piezoelectric actuators disposed above the outlet channel and adjacent to the outlet, the set of piezoelectric actuators configured to eject a portion of fluid from the microfluidic channel through the outlet; A microfluidic device comprising:

2. 10. The microfluidic device of claim 1, wherein the outlet comprises a hole formed through a thickness of the set of piezoelectric actuators and surrounded by the set of piezoelectric actuators.

3. The microfluidic device of claim 1 or 2, wherein the set of piezoelectric actuators is disposed on a membrane above the outlet channel.

4. The microfluidic device of any one of claims 1 to 3, further comprising a passivation layer disposed between the set of piezoelectric actuators and the microfluidic channel.

5. 5. The microfluidic device of claim 1, further comprising a first electrode and a second electrode, the first electrode and the second electrode configured to provide actuation signals to the set of piezoelectric actuators, the set of piezoelectric actuators being disposed between the first electrode and the second electrode.

6. The microfluidic device according to any one of claims 1 to 5, further comprising an optical layer, the microfluidic channel being disposed between the optical layer and the substrate.

7. The microfluidic device of any one of claims 1 to 6, further comprising a polymer layer that provides at least a portion of the microfluidic channel.

8. 8. The microfluidic device of claim 1, further comprising one or more electrodes disposed adjacent to the microfluidic channel and configured to apply an electric field to the fluid.

9. 9. The microfluidic device of claim 1, wherein the substrate comprises a silicon base layer and a buried oxide (BOX) layer, the BOX layer separating the microfluidic channel from the silicon base layer.

10. The microfluidic device of any one of claims 1 to 9, further comprising a second set of piezoelectric actuators positioned adjacent to the inlets of the microfluidic channels.

11. 11. The microfluidic device of claim 1, further comprising a control circuit electrically connected to the set of piezoelectric actuators and configured to provide actuation signals to the set of piezoelectric actuators.

12. providing a plurality of particles through a microfluidic channel having an outlet disposed over at least a portion of the outlet channel; manipulating the particles flowing through the microfluidic channel using an electric field with a set of electrodes; ejecting a portion of fluid in the microfluidic channel using a set of piezoelectric actuators positioned above the outlet channel adjacent to the outlet; A method comprising:

13. providing actuation signals to the set of piezoelectric actuators; providing an actuation signal to the set of electrodes; The method of claim 12 further comprising:

14. 1. A method of constructing a microfluidic device, comprising: disposing a set of piezoelectric actuators on a substrate; disposing a passivation layer over the set of piezoelectric actuators; forming an outlet channel by removing a portion of the substrate below the set of piezoelectric actuators; bonding the polymer layer to the optical layer; forming a microfluidic inlet by removing a portion of the optical layer; forming a microfluidic channel between the microfluidic inlet and outlet channels by bonding the optical layer to the substrate via the polymer layer; A method comprising:

15. The method of claim 14 , wherein the substrate comprises a BOX layer separating a base layer and a device layer, and the set of piezoelectric actuators is disposed on the device layer.

16. disposing the set of piezoelectric actuators; depositing a lower electrode layer on the substrate; depositing a piezoelectric material on the lower electrode layer; depositing a top electrode layer on the piezoelectric material; Including, 16. The method of claim 14 or 15.

17. 17. The method of any one of claims 14 to 16, wherein forming the outlet channel comprises forming a microfluidic outlet, wherein a diameter of the microfluidic outlet is smaller than a diameter of the outlet channel.

18. The method of any one of claims 14 to 17, wherein disposing the polymer layer on the optical layer comprises applying a polymer spin coat onto the optical layer.

19. The method of any one of claims 14 to 18, wherein disposing the passivation layer on the set of piezoelectric actuators comprises depositing the passivation layer.

20. The method of any one of claims 14 to 19, further comprising disposing a set of electrodes within or adjacent to the microfluidic channel.

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