CN109954526B

CN109954526B - Microfluidic device and manufacturing method thereof

Info

Publication number: CN109954526B
Application number: CN201910323839.1A
Authority: CN
Inventors: 宋晓欣; 张锋; 刘文渠; 吕志军; 董立文; 崔钊; 王利波; 孟德天; 姚琪
Original assignee: BOE Technology Group Co Ltd
Current assignee: BOE Technology Group Co Ltd
Priority date: 2019-04-22
Filing date: 2019-04-22
Publication date: 2021-12-03
Anticipated expiration: 2039-04-22
Also published as: CN109954526A

Abstract

The invention discloses a microfluidic device and a manufacturing method thereof, relates to the technical field of microfluidics, and aims to solve the problem that the accuracy of a detection result of a liquid drop to be detected by the conventional microfluidic device is poor. The microfluidic device comprises a TFT back plate, a microfluidic driving unit, a piezoelectric transduction unit and a hydrophobic layer; the TFT backboard comprises a first thin film transistor and a second thin film transistor; the microfluidic driving unit and the piezoelectric transduction unit are arranged on the TFT back plate, the orthographic projection of the microfluidic driving unit on the TFT back plate and the orthographic projection of the piezoelectric transduction unit on the TFT back plate are arranged in a staggered mode, the microfluidic driving unit is electrically connected with the first thin film transistor, and the piezoelectric transduction unit is electrically connected with the second thin film transistor; the hydrophobic layer covers the microfluidic driving unit. The invention can be used for detecting biochemical samples and the like.

Description

Microfluidic device and manufacturing method thereof

Technical Field

The invention relates to the technical field of microfluidics, in particular to a microfluidic device and a manufacturing method thereof.

Background

The digital microfluidic technology can integrate basic operation units of sample preparation, reaction, separation, detection and the like in the processes of biological, chemical and medical analysis on a micron-scale chip and automatically complete the whole analysis process. Because the method can reduce the cost, has the advantages of short detection time, high sensitivity and the like, and has great prospect in the fields of biology, chemistry, medicine and the like.

A microfluidic device in the related art, as shown in fig. 1, includes a microfluidic unit 01, an optical unit 02, and a detection unit 03, where the microfluidic unit 01 has a fluid channel 04, and the optical unit 02 is configured to emit a light beam to the fluid channel 04; the detection unit 03 includes a substrate 031 and a plurality of photosensors 032 disposed on the substrate 031. When in use, the light emitted from the optical unit 02 passes through the liquid in the fluid channel 04 and then irradiates the photoelectric sensor 032, and the position, concentration, composition and other information of the liquid droplet in the fluid channel 04 can be obtained by detecting the electric signal emitted from the photoelectric sensor 032.

However, in the detection process, the photosensor 032 is easily affected by ambient stray light (e.g., ambient light or stray light reflected by other objects such as liquid drops from the optical unit 02), so that the accuracy of the detection result is affected.

Disclosure of Invention

The embodiment of the invention provides a microfluidic device and a manufacturing method thereof, which are used for solving the problem that the existing microfluidic device has poor accuracy in detection results of liquid drops to be detected.

In order to achieve the above object, in a first aspect, an embodiment of the present invention provides a microfluidic device, including a TFT back plate, a microfluidic driving unit, a piezoelectric transducing unit, and a hydrophobic layer; the TFT backboard comprises a first thin film transistor and a second thin film transistor; the microfluidic driving unit and the piezoelectric transduction unit are arranged on the TFT backboard, the orthographic projection of the microfluidic driving unit on the TFT backboard and the orthographic projection of the piezoelectric transduction unit on the TFT backboard are arranged in a staggered mode, the microfluidic driving unit is electrically connected with the first thin film transistor, and the piezoelectric transduction unit is electrically connected with the second thin film transistor; the hydrophobic layer covers the microfluidic driving unit.

Further, the piezoelectric transduction unit and the microfluidic driving unit are located on the same TFT back plate, and the piezoelectric transduction unit and the microfluidic driving unit are covered by the hydrophobic layer.

Furthermore, the piezoelectric transduction unit comprises a first flat layer, a first electrode, a first piezoelectric medium layer and a second electrode, wherein the first flat layer is arranged on the TFT backboard, the first flat layer is provided with a cavity, the first electrode is arranged on the first flat layer and is electrically connected with the second thin film transistor, the first piezoelectric medium layer covers the first electrode, the second electrode is arranged on the first piezoelectric medium layer, the first electrode covers the cavity, the second electrode is arranged on the positive projection on the TFT backboard, and the hydrophobic layer covers the first piezoelectric medium layer and covers the second electrode.

Further, in a direction perpendicular to a thickness direction of the TFT backplane, a size of the cavity is d, a wavelength of the acoustic wave emitted by the piezoelectric transduction unit is λ, and d and λ satisfy: d is less than or equal to lambda/2.

Further, the number of the cavities is plural.

Further, the distance between two adjacent cavities is b, the wavelength of the sound wave emitted by the piezoelectric transduction unit is λ, and b and λ satisfy: b is less than or equal to lambda/2.

Furthermore, the cavity penetrates through the first flat layer along a first direction, so that the first flat layer forms a bridge structure, and the first direction is a direction perpendicular to the thickness direction of the TFT back plate; the size range of the cavity is 0.5 mm-0.8 mm along the thickness direction of the TFT back plate.

Furthermore, the micro-fluidic driving unit comprises a driving electrode and a second piezoelectric medium layer, the driving electrode is arranged on the TFT backboard and is electrically connected with the first thin film transistor, the second piezoelectric medium layer is arranged on the TFT backboard and covers the driving electrode, and the hydrophobic layer covers the second piezoelectric medium layer.

Furthermore, the microfluidic driving unit further comprises a second flat layer, the second flat layer is arranged on the TFT backplane, the driving electrode is arranged on the second flat layer, the second flat layer and the first flat layer are located on the same layer, the driving electrode and the first electrode are located on the same layer, and the second piezoelectric medium layer and the first piezoelectric medium layer are located on the same layer.

Furthermore, the microfluidic driving unit further comprises a first bonding layer, and the first bonding layer is arranged between the second piezoelectric medium layer and the hydrophobic layer.

Still further, the piezoelectric transduction unit further includes a second adhesive layer disposed between the first piezoelectric medium layer and the hydrophobic layer.

In a second aspect, embodiments of the present invention provide a method for manufacturing a microfluidic device according to some embodiments of the first aspect, including the following steps: providing a TFT backboard; forming a micro-fluidic driving unit and a piezoelectric transduction unit on the TFT back plate; and forming a hydrophobic layer to cover the microfluidic driving unit and the piezoelectric transduction unit.

Further, forming a piezoelectric transduction unit on the TFT backplane, comprising the steps of: forming a first flat layer having a cavity on the TFT backplane; forming a first electrode on the first planarization layer; wherein the first electrode is electrically connected to the second thin film transistor; forming a first piezoelectric medium layer on the first flat layer to cover the first electrode; forming a second electrode on the first piezoelectric medium layer; wherein orthographic projections of the second electrode, the cavity and the first electrode on the TFT backboard are overlapped.

Further, forming a first flat layer having a cavity on the TFT backplane includes: forming a sacrificial layer on the TFT backplane; forming the first flat layer on the TFT backplane to cover the sacrificial layer; the sacrificial layer penetrates through the first flat layer along a first direction, and the first direction is a direction perpendicular to the thickness direction of the TFT back plate; etching away the sacrificial layer to form the cavity.

Further, forming a microfluidic driving unit on the TFT backplane, comprising: forming a driving electrode on the TFT backplane; wherein the driving electrode is electrically connected to the first thin film transistor; and forming a second piezoelectric medium layer on the TFT backboard to cover the driving electrode.

According to the microfluidic device and the manufacturing method thereof provided by the embodiment of the invention, the position, concentration and other information of the liquid drop are detected through the ultrasonic wave emitted by the piezoelectric transduction unit, the wavelength of the ultrasonic wave is short, diffraction is not easy to occur when the ultrasonic wave is irradiated on the tiny liquid drop, and the piezoelectric transduction unit can accurately sense the position, concentration and other information of the tiny liquid drop through the reflected ultrasonic wave, so that the accuracy of a detection result is ensured.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural view of a microfluidic device in the related art;

fig. 2 is a top view (without a cover plate) of a microfluidic device in some embodiments of the invention;

FIG. 3 is a cross-sectional view A-A of FIG. 2;

fig. 4 is a schematic diagram of a microfluidic device structure in some embodiments of the invention (the microfluidic driving unit and the piezoelectric transducing unit are not on the same TFT backplane);

FIG. 5 is a schematic view of the structure of a microfluidic device in some embodiments of the present invention (without a cover plate, with a cavity opened in the substrate base plate of the TFT backplane);

fig. 6 is a schematic view of the structure of a microfluidic device according to some embodiments of the present invention (without a cover plate, with a plurality of cavities in the piezoelectric transducing unit);

FIG. 7 is a schematic view of a microfluidic device structure (with a cover plate) in some embodiments of the invention;

FIG. 8 is a process diagram (cross-sectional view) of the fabrication of a cavity for a piezoelectric transducing unit in some embodiments of the present invention;

FIG. 9 is a process diagram (top view) of the fabrication of a cavity for a piezoelectric transducing element in some embodiments of the present invention;

fig. 10 is a flow chart of the fabrication of a microfluidic device in an embodiment of the present invention;

fig. 11 is a flow chart of a process for fabricating a piezoelectric transducing unit of a microfluidic device in an embodiment of the present invention;

FIG. 12 is a flow chart illustrating the fabrication of a cavity of a piezoelectric transducing element in an embodiment of the present invention;

fig. 13 is a flow chart illustrating a process of manufacturing a microfluidic driving unit of the microfluidic device according to the embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.

The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In a first aspect, an embodiment of the present invention provides a microfluidic device, as shown in fig. 2 and fig. 3, including a TFT (Thin Film Transistor) back plate 1, a microfluidic driving unit 2, a piezoelectric transduction unit 3, and a hydrophobic layer 4; the TFT backplane 1 includes a first thin film transistor 11 and a second thin film transistor 12; the microfluidic driving unit 2 and the piezoelectric transduction unit 3 are both arranged on the TFT backboard 1, the orthographic projection of the microfluidic driving unit 2 on the TFT backboard 1 and the orthographic projection of the piezoelectric transduction unit 3 on the TFT backboard 1 are arranged in a staggered manner, the microfluidic driving unit 2 is electrically connected with the first thin film transistor 11, and the piezoelectric transduction unit 3 is electrically connected with the second thin film transistor 12; the hydrophobic layer 4 covers the microfluidic drive unit 2.

When the microfluidic device is used, a liquid drop to be detected is placed on a fluid channel on the hydrophobic layer 4, then the microfluidic driving unit 2 drives the liquid drop to be detected to move along a preset path under the control of the first thin film transistor 11, and meanwhile, the piezoelectric transduction unit 3 is used for detecting information such as the position and the concentration of the liquid drop to be detected. The detection principle of the piezoelectric transducing unit 3 is as follows: the piezoelectric transduction unit 3 can be powered on under the control of the second thin film transistor 12, the first piezoelectric medium layer 33 generates mechanical vibration (the mechanical vibration has a certain time sequence) under the action of an electric field, the piezoelectric layer generates mechanical vibration to generate ultrasonic waves to be transmitted to a fluid channel on the hydrophobic layer 4, if a liquid drop to be detected moves to the position, the liquid drop can reflect the ultrasonic waves to the first piezoelectric medium layer 33 to enable the piezoelectric layer to vibrate, the mechanical vibration is reversely converted into an electric signal to be output by utilizing the inverse piezoelectric effect of the first piezoelectric medium layer 33, and therefore information such as the position, concentration and the like of the liquid drop to be detected can be detected by detecting the electric signal output by the piezoelectric transduction unit 3.

The orthographic projection of the microfluidic driving unit 2 on the TFT back plate 1 and the orthographic projection of the piezoelectric transduction unit 3 on the TFT back plate 1 are arranged in a staggered mode, so that blocking and attenuation of ultrasonic waves emitted by the microfluidic driving unit 2 on the piezoelectric transduction unit 3 can be avoided, and the ultrasonic waves can be transmitted to a fluid channel on the hydrophobic layer 4 to sense liquid drops to be detected.

The micro-fluidic device provided by the embodiment of the invention detects information such as the position and concentration of a liquid drop through the ultrasonic waves emitted by the piezoelectric transduction unit 3, because the wavelength of the ultrasonic waves is short, diffraction is not easy to occur when the ultrasonic waves are irradiated on the tiny liquid drop, and the piezoelectric transduction unit 3 can accurately sense the information such as the position and concentration of the tiny liquid drop through the reflected ultrasonic waves, so that the accuracy of a detection result is ensured.

In the above embodiment, the piezoelectric transduction unit 3 and the microfluidic driving unit 2 are not arranged at unique positions, for example, the piezoelectric transduction unit 3 and the microfluidic driving unit 2 may be integrated on the same TFT backplane 1, as shown in fig. 3, the piezoelectric transduction unit 3 and the microfluidic driving unit 2 are located on the same TFT backplane 1, and the hydrophobic layer 4 covers both the piezoelectric transduction unit 3 and the microfluidic driving unit 2. In addition, the piezoelectric transduction unit 3 and the microfluidic driving unit 2 may also be respectively disposed on different TFT backplates 1, as shown in fig. 4, the TFT backplane 1 includes a first TFT backplane 13 and a second TFT backplane 14 that are stacked, the first TFT backplane 13 includes a first thin film transistor 11, the second TFT backplane 14 includes a second thin film transistor 12, the microfluidic driving unit 2 is disposed on the first TFT backplane 13, and the piezoelectric transduction unit 3 is disposed on the second TFT backplane 14 and located between the first TFT backplane 13 and the second TFT backplane 14. Compared with the piezoelectric transduction unit 3 and the microfluidic driving unit 2 which are respectively arranged on different TFT back plates 1, the piezoelectric transduction unit 3 and the microfluidic driving unit 2 are integrated on the same TFT back plate 1, so that the use of one TFT back plate 1 can be reduced, the structure of the microfluidic device is simpler and more compact, the assembling procedures of the microfluidic device can be reduced, the assembling difficulty of the microfluidic device is reduced, the occupied space of the microfluidic device can be reduced, and the miniaturization of the microfluidic device is facilitated.

The structure of the piezoelectric transducer unit 3 is not exclusive, and may be, for example, the following structure: as shown in fig. 3, the piezoelectric transduction unit 3 includes a first flat layer 31, a first electrode 32, a first piezoelectric medium layer 33, and a second electrode 34, the first flat layer 31 is disposed on the TFT backplate 1, the first flat layer 31 has a cavity 311, the first electrode 32 is disposed on the first flat layer 31 and electrically connected to the second thin film transistor 12, the first piezoelectric medium layer 33 covers the first electrode 32, the second electrode 34 is disposed on the first piezoelectric medium layer 33, orthographic projections of the first electrode 32, the cavity 311, and the second electrode 34 on the TFT backplate 1 are overlapped, and the hydrophobic layer 4 covers the first piezoelectric medium layer 33 and covers the second electrode 34. In addition, the piezoelectric transducer unit 3 may have the following structure: as shown in fig. 5, the piezoelectric transduction unit 3 includes a first electrode 32, a first piezoelectric medium layer 33, and a second electrode 34, a cavity 311 is formed on the substrate 15 of the TFT backplate 1, the first electrode 32 is disposed on the TFT backplate 1 and electrically connected to the second thin film transistor 12, the first piezoelectric medium layer 33 covers the first electrode 32, the second electrode 34 is disposed on the first piezoelectric medium layer 33, orthographic projections of the first electrode 32, the cavity 311, and the second electrode 34 on the TFT backplate 1 are overlapped, and the hydrophobic layer 4 covers the first piezoelectric medium layer 33 and covers the second electrode 34. Compared with the embodiment that the cavity 311 in the piezoelectric transduction unit 3 is arranged on the substrate base plate 15 of the TFT backplate 1, in the embodiment shown in fig. 3, the piezoelectric transduction unit 3 is provided with the cavity 311, that is, the first flat layer 31 is provided with the cavity 311, so that the process implementation difficulty is low when the piezoelectric transduction unit 3 is manufactured, the process can be completed through etching and other processes, and the substrate base plate 15 of the TFT backplate 1 is prevented from being damaged. Meanwhile, the cavity 311 is arranged on the first flat layer 31, and the distance between the cavity 311 and the first piezoelectric medium layer 33 is short, so that ultrasonic waves generated by vibration of the first piezoelectric medium layer 33 can be easily transmitted into the cavity 311 to be gathered in the cavity 311, the directivity of the ultrasonic waves is increased, the divergence of the ultrasonic waves is better prevented, the signal-to-noise ratio can be increased, the position of a liquid drop to be detected can be more accurately detected, and the detection sensitivity of the piezoelectric transduction unit 3 is improved.

As shown in fig. 3, the directivity of the piezoelectric transducer element 3 is correlated with the wavelengths λ and d (the size of the cavity 311 in the direction perpendicular to the thickness direction of the TFT backplane 1) of the emitted acoustic wave. As shown in the following formula, when d is much smaller than λ, the sound wave has no significant directivity; and when d tends towards lambda, the sound wave shows increasingly stronger directivity; when d is much larger than λ, the sound wave exhibits strong directivity. From this, it is understood that the larger d is, the stronger the directivity of the ultrasonic wave is, and the higher the sensitivity of the piezoelectric transducer unit 3 is; however, the piezoelectric transducer unit 3 with a larger d value generally has more side lobes in the directional diagram, and more side lobes are not beneficial to the concentration of the ultrasonic wave capability, and the attenuation is increased, so that the propagation distance of the ultrasonic wave is reduced. The research shows that when d and lambda satisfy: when d is less than or equal to lambda/2, the directivity of the sound wave emitted by the piezoelectric transduction unit 3 can be ensured, and the number of side lobes can be reduced well, so that the attenuation degree of the ultrasonic wave can be reduced, and the propagation distance of the ultrasonic wave can be increased.

In the formula: d (theta) is a directivity function; j. the design is a square₁Is a Bessel function of order 1; k is wave number, k is 2 pi/lambda; a is the radius of the sound source; d is the sound source diameter, d is 2 a; λ is the acoustic wavelength.

In the piezoelectric transducer unit 3, the number of the cavities 311 may be one (as shown in fig. 3) or plural (as shown in fig. 5). When the piezoelectric transducing unit 3 has a plurality of cavities 311 as compared with one cavity 311, the number of main lobes of the acoustic wave emitted from the piezoelectric transducing unit 3 can be increased, and the increase in the number of main lobes can increase the density of the main lobes, so that the accuracy of the position detection of the liquid droplet by the piezoelectric transducing unit 3 can be improved.

It should be noted that: the lobe with the maximum radiation intensity in the directional diagram of the acoustic wave emitted by the piezoelectric transduction unit 3 is called a main lobe, and the rest lobes are called side lobes or side lobes.

In order to reduce the number of side lobes in the acoustic wave emitted by the piezoelectric transducer unit 3, as shown in (c) of fig. 8, the distance between two adjacent cavities 311 is b, and b and λ satisfy: b is less than or equal to lambda/2. Because the value of d can be limited by the value of b, when b is less than or equal to lambda/2, d can be less than or equal to lambda/2, thereby not only ensuring the directivity of the sound wave emitted by the piezoelectric transduction unit 3, but also well reducing the number of side lobes, further reducing the attenuation degree of the ultrasonic wave and improving the propagation distance of the ultrasonic wave.

The frequency of the sound waves emitted by the piezoelectric transduction unit 3 is not too high, and if the frequency is too high, the ultrasonic waves are quickly attenuated in the air and can cause damage to human bodies, so that the frequency of the sound waves emitted by the piezoelectric transduction unit 3 can be between 25 and 40kHz, and the wavelength lambda can be calculated to be 8.5mm to 13.6 mm; thus, from the relationship of b, d and λ, one can obtain: the value of b is 4.2mm and the value of d is 4 mm.

In the process of manufacturing the piezoelectric transducer unit 3, the cavity 311 is formed by etching, and the specific process is as follows: as shown in fig. 8 (a) and fig. 9 (a), a sacrificial layer 36 is provided on the TFT backplane 1; as shown in fig. 8 (b) and fig. 9 (b), the first flat layer 31 is covered on the sacrificial layer 36 so that the sacrificial layer 36 penetrates the first flat layer 31 in a first direction X, which is one direction perpendicular to the thickness direction of the TFT backplane 1; as shown in (c) in fig. 8 and (c) in fig. 9, the sacrificial layer 36 is etched away to form a cavity 311. Since the sacrificial layer 36 penetrates the first planarization layer 31 in the first direction X, the cavity 311 is formed to penetrate the first planarization layer 31 in the first direction X, so that the first planarization layer 31 forms a bridge structure.

As shown in fig. 8 (c), the size h of the cavity 311 in the thickness direction of the TFT backplane 1 is an important parameter (i.e., the size of the sacrificial layer 36 in the thickness direction of the TFT backplane 1), and if h is too small, the flow of the etching solution is not smooth when the sacrificial layer 36 is etched, and the etching effect on the sacrificial layer 36 is not good; if h is too large, the first planarization layer 31 on the cavity 311 is easily broken; researches show that when the range of h is 0.5 mm-0.8 mm, the sacrificial layer 36 can be etched better, and the first flat layer 31 on the cavity 311 can be prevented from being broken.

In the piezoelectric transducer unit 3, as shown in fig. 8 (c), the first planarization layer 31 may be an organic planarization layer or an inorganic planarization layer. The organic planarization layer has greater hardness and better mechanical properties than the inorganic planarization layer, so that the first planarization layer 31 above the cavity 311 can be made less prone to fracture.

In the microfluidic device provided in the embodiment of the present invention, the structure of the microfluidic driving unit 2 is not unique, and may be, for example, the following structure: as shown in fig. 3, the microfluidic driving unit 2 includes a driving electrode 21 and a second piezoelectric medium layer 22, the driving electrode 21 is disposed on the TFT backplane 1 and electrically connected to the first thin film transistor 11, the second piezoelectric medium layer 22 is disposed on the TFT backplane 1 and covers the driving electrode 21, and the hydrophobic layer 4 covers the second piezoelectric medium layer 22. In addition, the microfluidic driving unit 2 may have the following structure: the second piezoelectric medium layer 22 in the microfluidic drive unit 2 shown in fig. 3 is replaced by an inorganic medium layer, such as a SiNx medium layer. Compared with an inorganic dielectric layer, the piezoelectric dielectric layer is adopted in the embodiment shown in fig. 3, and the dielectric constant of the piezoelectric dielectric layer is large, so that the charge density of the capacitor can be improved, and the driving voltage of the driving electrode 21 can be reduced, and the output voltage of the first thin film transistor 11 on the TFT backplane 1 does not need to be designed to be as high, so that the first thin film transistor 11 manufactured by the existing manufacturing process (such as LTPS and Oxide process) can meet the requirement, and the manufacturing difficulty of the TFT backplane 1 can be greatly reduced.

In the embodiment using the piezoelectric medium layer, the positional relationship between the microfluidic driving unit 2 and each film layer of the piezoelectric transduction unit 3 is not unique, and may be as follows: as shown in fig. 3, the microfluidic driving unit 2 further includes a second flat layer 23, the second flat layer 23 is disposed on the TFT backplane 1, the driving electrode 21 is disposed on the second flat layer 23, the second flat layer 23 and the first flat layer 31 are located on the same layer, the driving electrode 21 and the first electrode 32 are located on the same layer, and the second piezoelectric medium layer 22 and the first piezoelectric medium layer 33 are located on the same layer. In addition, the following may be mentioned: the second flat layer 23 is located at a different layer from the first flat layer 31, the driving electrode 21 is located at a different layer from the first electrode 32, and the second piezoelectric medium layer 22 is located at a different layer from the first piezoelectric medium layer 33. Compared with the latter structure, in the former structure, the second flat layer 23 and the first flat layer 31 are located on the same layer, the driving electrode 21 and the first electrode 32 are located on the same layer, and the second piezoelectric medium layer 22 and the first piezoelectric medium layer 33 are located on the same layer, so that the second flat layer 23, the first flat layer 31, the driving electrode 21, the first electrode 32, the second piezoelectric medium layer 22 and the first piezoelectric medium layer 33 can be completed through one process, thereby greatly simplifying the manufacturing processes of the microfluidic driving unit 2 and the piezoelectric transduction unit 3, and further being beneficial to reducing the manufacturing cost.

In the micro-fluidic device provided by the embodiment of the invention, the first piezoelectric medium layer 33 and the second piezoelectric medium layer 22 can be PVDF layers, PVDF is a novel piezoelectric polymer material, and the micro-fluidic device has the advantages of high piezoelectric constant, low density, good flexibility, wide frequency response, low acoustic impedance, high sensitivity and good stability, can be divided into any shape and size, and has little influence on the vibration response of a system when being processed into a film to be used as a sensor.

In the microfluidic driving unit 2, in order to make the second piezoelectric medium layer 22 and the hydrophobic layer 4 be combined more tightly, as shown in fig. 3, the microfluidic driving unit 2 further includes a first adhesive layer 24, and the first adhesive layer 24 is disposed between the second piezoelectric medium layer 22 and the hydrophobic layer 4. By arranging the first adhesive layer 24, the second piezoelectric medium layer 22 and the hydrophobic layer 4 are bonded more tightly, so that Poor plating (such as surface Coating, Spin or Slot Coating) caused by the loose bonding between the second piezoelectric medium layer 22 and the hydrophobic layer 4 can be avoided.

In the piezoelectric transducer unit 3, in order to make the first piezoelectric medium layer 33 and the hydrophobic layer 4 be bonded more tightly, as shown in fig. 3, the piezoelectric transducer unit 3 further includes a second adhesive layer 35, and the second adhesive layer 35 is disposed between the first piezoelectric medium layer 33 and the hydrophobic layer 4. By arranging the second adhesive layer 35, the first piezoelectric medium layer 33 and the hydrophobic layer 4 are bonded more tightly, so that Poor plating (such as surface Coating, Spin or Slot Coating) caused by the loose bonding between the first piezoelectric medium layer 33 and the hydrophobic layer 4 can be avoided.

As shown in fig. 3, the first adhesive layer 24 and the second adhesive layer 35 may be provided in the same layer.

As shown in fig. 6 and 7, the microfluidic device provided in the embodiment of the present invention may further include a cover plate 5, where the cover plate 5 is disposed opposite to the hydrophobic layer 4 to form a fluid channel 6 between the cover plate 5 and the hydrophobic layer 4, a common electrode 7 covers a surface of one side of the cover plate 5 close to the hydrophobic layer 4, and a second hydrophobic layer 8 covers the common electrode 7. By providing the cover plate 5 and the second hydrophobic layer 8, the liquid drop can simultaneously contact the hydrophobic layer 4 and the second hydrophobic layer 8, and the liquid drop can move more easily, so that the driving voltage on the driving electrode 21 can be greatly reduced, for example, the driving voltage on the driving electrode 21 can be reduced to be lower than 40V.

In the microfluidic device provided by the embodiment of the invention, as shown in fig. 2, the number of the piezoelectric transduction units 3 and the number of the microfluidic driving units 2 are multiple, and the multiple piezoelectric transduction units and the multiple microfluidic driving units 2 are arranged in an array.

In a second aspect, embodiments of the present invention provide a method for manufacturing a microfluidic device as described in some embodiments of the first aspect, including the following steps: as shown in figure 10 of the drawings,

s1, as shown in fig. 3, providing a TFT backplane 1;

the TFT backplane 1 may be manufactured by the following steps: providing a base substrate 15; a Gate (GA), a gate insulating layer (GI), an Active layer (Active layer), a source drain metal layer (SD layer), and a passivation layer (PVX layer) are respectively prepared on the substrate 15.

The TFT backplane 1 may be an oxide TFT (oxide TFT) backplane, a low temperature multi-channel silicon TFT (ltps TFT) backplane, or an amorphous silicon TFT (a-Si TFT) backplane, which is not specifically limited herein;

when the TFT backplane 1 is an oxide TFT backplane 1, the TFT on the TFT backplane 1 may be an Etch Stop Layer (ESL), a back channel etch layer (BCE), or a Coplanar layer (copanar), and is not limited herein.

S2, as shown in fig. 3, forming a microfluidic driving unit 2 and a piezoelectric transduction unit 3 on the TFT backplane 1;

the microfluidic driving unit 2 and the piezoelectric transduction unit 3 may be formed on the TFT back plate 1 at the same time, or the microfluidic driving unit 2 and the piezoelectric transduction unit 3 may be formed in sequence, which is not limited herein.

S3, as shown in fig. 3, a hydrophobic layer 4(Teflon) is formed to cover the microfluidic driving unit 2 and the piezoelectric transducing unit 3.

The technical problems solved and the technical effects achieved by the method for manufacturing a microfluidic device according to the embodiments of the present invention are the same as the technical problems solved and the technical effects achieved by the microfluidic device in the first aspect.

In the above method for manufacturing a microfluidic device, the step of forming the piezoelectric transduction unit 3 on the TFT backplane 1 may include: as shown in figure 11 of the drawings,

s211, as shown in fig. 3, forming a first planarization layer 31 having a cavity 311 on the TFT backplane 1;

the first planarization layer 31 may be an organic planarization layer or an inorganic planarization layer, but when the first planarization layer 31 is an organic planarization layer, the mechanical property is better, and the first planarization layer 31 above the cavity 311 can be better prevented from being broken.

S212, as shown in fig. 3, forming a first electrode 32 on the first planarization layer 31; wherein the first electrode 32 is electrically connected to the second thin film transistor 12;

the material of the first electrode 32 may be Mo, but is not limited thereto, and other metal materials may also be used; the first electrode 32 may be formed by a sputtering process and may have a thickness of 2200A.

S213, as shown in fig. 3, forming a first piezoelectric medium layer 33 on the first planarization layer 31 to cover the first electrode 32;

the material of the first piezoelectric medium layer 33 may be polyvinylidene fluoride (PVDF), or a vinylidene fluoride copolymer (PVDF-TrFE), which is not specifically limited herein;

when the material of the first piezoelectric medium layer 33 is polyvinylidene fluoride (PVDF), the coating may be performed according to the following process parameters: spin-coating at a rotation speed of 500rpm for 30s to form a polyvinylidene fluoride layer with a thickness of 20um, pre-drying the polyvinylidene fluoride layer at 135 ℃ for 15min, and then crystallizing and polarizing the polyvinylidene fluoride layer to form a first piezoelectric medium layer 33.

S214, as shown in fig. 3, forming a second electrode 34 on the first piezoelectric medium layer 33;

wherein, the orthographic projections of the second electrode 34, the cavity 311 and the first electrode 32 on the TFT back plate 1 are overlapped; the material of the second electrode 34 may be ITO (indium tin oxide), and the thickness of the second electrode 34 may be 700A.

In the piezoelectric transduction unit 3 prepared by the method, the cavity 311 is located on the first flat layer 31, so that the difficulty in process implementation is low when the piezoelectric transduction unit 3 is manufactured, and the cavity 311 can be manufactured by processes such as etching and the like, so that the cavity 311 does not need to be manufactured on the substrate base plate 15 of the TFT backplate 1 (as shown in fig. 5), and the substrate base plate 15 of the TFT backplate 1 can be prevented from being damaged.

In the above step S211, the first planarization layer 31 having the cavity 311 may be formed by: as shown in figure 12 of the drawings,

s2111, as shown in fig. 8 (a) and fig. 9 (a), forming a sacrificial layer 36 on the TFT backplane 1;

the width d of the sacrificial layer 36 is 4mm, the height thereof is 0.5mm, and the size of the sacrificial layer 36 is adapted to the size of the cavity 311; the sacrificial layer 36 may be formed by: forming a sacrificial film on the TFT backplane 1, and then forming a sacrificial layer 36 through a patterning process (such as a photolithography process); the material of the sacrificial layer 36 may be Mo.

S2112, as shown in fig. 8 (b) and fig. 9 (b), forming a first flat layer 31 on the TFT backplane 1 to cover the sacrifice layer 36;

wherein, along a first direction X, the sacrificial layer 36 is disposed through the first flat layer 31, and the first direction X is a direction perpendicular to the thickness direction of the TFT backplane 1; that is: in the first direction X, the dimension m of the first planarization layer 31 is smaller than the dimension n of the sacrificial layer 36;

m can be 3.5-3.8 mm; n may be 4 mm. This is provided to facilitate the etching of the sacrificial layer 36 by the etching liquid from both sides of the first planarization layer 31;

the first planarization layer 31 may be cured at 230 c for 1h after formation.

S2113, as shown in (c) in fig. 8 and (c) in fig. 9, the sacrifice layer 36 is etched away to form the cavity 311.

Wherein, the sacrificial layer 36 may be etched for 100s by using the TRI400 to etch away the sacrificial layer 36, forming the bridge type first planarization layer 31. Then coating Resin2 layer for flattening, and curing for 1h at 230 ℃. A cavity 311 structure is prepared.

After the cavity 311 is formed, a planarization layer may be further formed on the first planarization layer 31 for better planarization; the flat layer can be cured at 230 deg.C for 1h after formation.

The above is a manufacturing method of the first flat layer 31 having the cavity 311, and in addition, a film having the cavity 311 may be separately manufactured on the first flat layer 31 having the cavity 311, and then the film is attached to the TFT backplane 1 to form the first flat layer 31.

The method for manufacturing the microfluidic device provided by the embodiment of the invention is to form the microfluidic driving unit 2 on the TFT backboard 1, and the method can comprise the following steps: as shown in figure 13 of the drawings, in which,

s221, as shown in fig. 3, forming a driving electrode 21 on the TFT backplane 1;

wherein, the driving electrode 21 is electrically connected with the first thin film transistor 11; the material of the driving electrode 21 may be Mo, and the driving electrode 21 may be formed by a sputtering process and may have a thickness of 2200A.

S222, as shown in fig. 3, forming a second piezoelectric medium layer 22 on the TFT backplane 1 to cover the driving electrode 21;

the material of the second piezoelectric medium layer 22 may be polyvinylidene fluoride (PVDF), or a vinylidene fluoride copolymer (PVDF-TrFE), which is not specifically limited herein;

when the material of the second piezoelectric medium layer 22 is polyvinylidene fluoride (PVDF), the coating may be performed according to the following process parameters: and spin-coating at a rotation speed of 500rpm for 30s to form a polyvinylidene fluoride layer with a thickness of 20um, pre-drying the polyvinylidene fluoride layer at 135 ℃ for 15min, and crystallizing and polarizing the polyvinylidene fluoride layer after the pre-drying to form the second piezoelectric medium layer 22.

In step S222, the second piezoelectric medium layer 22 may be used to replace an inorganic medium layer (such as a SiNx medium layer), but the second piezoelectric medium layer 22 is adopted, and since the dielectric constant of the second piezoelectric medium layer 22 is large, the charge density of the capacitor can be increased, so that the driving voltage of the driving electrode 21 can be reduced, and thus the output voltage of the first thin film transistor 11 on the TFT backplane 1 does not need to be designed to be as high, so that the first thin film transistor 11 manufactured by the existing manufacturing process (such as LTPS and Oxide process) can meet the requirement, and the manufacturing difficulty of the TFT backplane 1 can be greatly reduced.

In the above method for manufacturing the micro-fluidic driving unit 2, as shown in fig. 3, the driving electrode 21 and the first electrode 32 may be formed in one step, and the second piezoelectric medium layer 22 and the first piezoelectric medium layer 33 may be formed in one step, so that the manufacturing steps of the micro-fluidic driving unit 2 and the piezoelectric transduction unit 3 can be greatly simplified, and the manufacturing cost can be further reduced.

In the above method for manufacturing the microfluidic driving unit 2, as shown in fig. 3, before the driving electrode 21 is formed, the second planarization layer 23 may be formed on the TFT backplane 1, and the driving electrode 21 covers the second planarization layer 23. The second planarization layer 23 may be disposed in one process with the first planarization layer 31. By providing the second planarization layer 23, it is ensured that the driving electrode 21 and the first electrode 32 are located on the same layer, so as to facilitate the fabrication of the driving electrode 21 and the first electrode 32.

In the above method for manufacturing the microfluidic driving unit 2, as shown in fig. 3, after the second piezoelectric medium layer 22 is formed and before the hydrophobic layer 4 is formed, the first adhesive layer 24 may be formed on the second piezoelectric medium layer 22, so that the second piezoelectric medium layer 22 and the hydrophobic layer 4 are more tightly bonded, and poor plating caused by the loose bonding between the second piezoelectric medium layer 22 and the hydrophobic layer 4 is avoided.

Wherein the first adhesive layer 24 may be spin-coated at 1300rpm for 30s to form a thickness of 0.4 um.

In the method for manufacturing the piezoelectric transduction unit 3, after the first piezoelectric medium layer 33 is formed, the second adhesive layer 35 may be formed on the first piezoelectric medium layer 33, so that the first piezoelectric medium layer 33 and the hydrophobic layer 4 may be more tightly combined, and poor plating caused by the loose combination of the first piezoelectric medium layer 33 and the hydrophobic layer 4 is avoided.

Wherein, as shown in fig. 3, the second electrode 34 may be formed on the second adhesive layer 35; the second adhesive layer 35 may be spin-coated at 1300rpm for 30s to form a thickness of 0.4 um.

In the above method for manufacturing the piezoelectric transduction unit 3, as shown in fig. 3, the second adhesive layer 35 and the first adhesive layer 24 can be formed through one process, so that the manufacturing processes of the microfluidic driving unit 2 and the piezoelectric transduction unit 3 can be greatly simplified, and the manufacturing cost can be further reduced.

The features of the embodiment of the method for manufacturing a microfluidic device that are the same as or similar to those of the embodiment of the product of the microfluidic device may specifically refer to the description of the embodiment of the product of the microfluidic device, and are not repeated herein.

In the description herein, particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A microfluidic device is characterized by comprising a TFT back plate, a microfluidic driving unit, a piezoelectric transduction unit and a hydrophobic layer;

the TFT backboard comprises a first thin film transistor and a second thin film transistor;

the microfluidic driving unit and the piezoelectric transduction unit are arranged on the TFT backboard, the orthographic projection of the microfluidic driving unit on the TFT backboard and the orthographic projection of the piezoelectric transduction unit on the TFT backboard are arranged in a staggered mode, the microfluidic driving unit is electrically connected with the first thin film transistor, and the piezoelectric transduction unit is electrically connected with the second thin film transistor;

the piezoelectric transduction unit and the microfluidic driving unit are positioned on the same TFT back plate, and the piezoelectric transduction unit and the microfluidic driving unit are both covered by the hydrophobic layer;

the micro-fluidic driving unit comprises a driving electrode and a second piezoelectric medium layer, the driving electrode is arranged on the TFT backboard and is electrically connected with the first thin film transistor, the second piezoelectric medium layer is arranged on the TFT backboard and covers the driving electrode, and the hydrophobic layer covers the second piezoelectric medium layer;

the piezoelectric transduction unit comprises a first flat layer, a first electrode, a first piezoelectric medium layer and a second electrode, the first flat layer is arranged on the TFT backboard, the first flat layer is provided with a cavity, the first electrode is arranged on the first flat layer and is electrically connected with the second thin film transistor, the first piezoelectric medium layer covers the first electrode, the second electrode is arranged on the first piezoelectric medium layer, the orthographic projection of the first electrode on the TFT backboard covers the cavity and the orthographic projection of the second electrode on the TFT backboard, and the hydrophobic layer covers the first piezoelectric medium layer and covers the second electrode;

the micro-fluidic driving unit further comprises a second flat layer, the second flat layer is arranged on the TFT backboard, the driving electrode is arranged on the second flat layer, the second flat layer and the first flat layer are located on the same layer, the driving electrode and the first electrode are located on the same layer, and the second piezoelectric medium layer and the first piezoelectric medium layer are located on the same layer.

2. The microfluidic device according to claim 1, wherein the size of the cavity in a direction perpendicular to the thickness direction of the TFT backplane is d, the wavelength of the sound wave emitted by the piezoelectric transduction unit is λ, and d and λ satisfy: d is less than or equal to lambda/2.

3. The microfluidic device according to claim 1, wherein the number of the cavities is plural.

4. The microfluidic device according to claim 3, wherein the distance between two adjacent cavities is b, the wavelength of the sound wave emitted by the piezoelectric transduction unit is λ, and b and λ satisfy: b is less than or equal to lambda/2.

5. The microfluidic device according to claim 1, wherein the cavity is disposed through the first planar layer along a first direction, the first direction being one direction perpendicular to a thickness direction of the TFT backplane, such that the first planar layer forms a bridge-type structure; the size range of the cavity is 0.5 mm-0.8 mm along the thickness direction of the TFT back plate.

6. The microfluidic device according to claim 1, wherein the microfluidic driving unit further comprises a first adhesive layer disposed between the second piezoelectric medium layer and the hydrophobic layer.

7. The microfluidic device according to any of claims 2 to 5, wherein the piezoelectric transduction unit further comprises a second adhesive layer disposed between the first piezoelectric medium layer and the hydrophobic layer.

8. A method of manufacturing a microfluidic device according to claim 1, comprising the steps of:

providing a TFT backboard;

forming a micro-fluidic driving unit and a piezoelectric transduction unit on the TFT back plate;

forming a hydrophobic layer to cover the microfluidic driving unit and the piezoelectric transduction unit;

forming a piezoelectric transduction unit on the TFT backboard, comprising the steps of:

forming a first flat layer having a cavity on the TFT backplane;

forming a first electrode on the first planarization layer; wherein the first electrode is electrically connected to the second thin film transistor;

forming a first piezoelectric medium layer on the first flat layer to cover the first electrode;

forming a second electrode on the first piezoelectric medium layer; wherein an orthographic projection of the first electrode on the TFT backplane covers the cavity and an orthographic projection of the second electrode on the TFT backplane;

forming a microfluidic driving unit on the TFT backplane, comprising:

forming a driving electrode on the TFT backplane; wherein the driving electrode is electrically connected to the first thin film transistor;

forming a second piezoelectric medium layer on the TFT backboard to cover the driving electrode;

the second flat layer and the first flat layer are located on the same layer, the driving electrode and the first electrode are located on the same layer, and the second piezoelectric medium layer and the first piezoelectric medium layer are located on the same layer.

9. The method for manufacturing a microfluidic device according to claim 8, wherein forming a first flat layer having a cavity on the TFT backplane comprises:

forming a sacrificial layer on the TFT backplane;

forming the first flat layer on the TFT backplane to cover the sacrificial layer; the sacrificial layer penetrates through the first flat layer along a first direction, and the first direction is a direction perpendicular to the thickness direction of the TFT back plate;

etching away the sacrificial layer to form the cavity.