CN112326100B - Fluid pressure sensor based on micro-nano structure array surface and preparation method thereof - Google Patents
Fluid pressure sensor based on micro-nano structure array surface and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a fluid pressure sensor based on a micro-nano structure array surface and a preparation method thereof, belonging to the technical field of material science. The surface of the micro-strip nano-column composite structure array prepared by etching and other methods forms a plurality of stable passive valves with gradient threshold pressure in the trapezoidal micro-channel, so that the stability and the sensitivity of the fluid pressure sensor are greatly improved, the measuring range can reach 2-800 mbar, and the sensitivity can reach 16.71mbar‑1. The fluid pressure sensor can realize high-sensitivity measurement of the pressure value of fluid in various environments, the measurement result can be directly recorded by a camera of a mobile phone, and the detection cost is reduced.
Description
Technical Field
The invention belongs to the technical field of material science, and particularly relates to a fluid pressure sensor based on a micro-nano structure array surface and a preparation method thereof.
Background
The fluid pressure sensor is widely applied to the fields of wearable equipment, electronic skin, health care, microfluidics and the like (D. -H.Kim Science 2011,333, 838-. Capillary-assisted, electronically-sensed fluid pressure detectors for liquid column observation have been proposed in succession. The accuracy of the pressure sensor for observing the liquid column is low, the sensitivity of the capillary-assisted sensor is difficult to meet the measurement requirements of most of the applications at present, and the preparation cost of the electronic sensing detector is high.
The microchip can provide an efficient detection method for fluid pressure due to the advantages of small volume, low loss, high sensitivity, high detection speed and the like. The polymer emitting luminescence light under pressure environment is polymerized into the side channel of the microchip, thereby realizing the preparation of the microchip fluid pressure sensor, and the fluid pressure can be judged according to the color of the excitation light. However, this synthesis method is difficult to integrate into a complex device under test, and the polymer synthesis process and the test results are not reproducible well. In addition, an expensive excitation light detection device is required in the detection process, which greatly increases the pressure detection cost. Capillary valves in microchannels have also been used for fluid pressure sensing, but such valves have inaccurate threshold pressures and poor repeatability. In addition, the threshold pressure difference of the capillary valves with different dimensions is small, and the detection range is not wide. Therefore, such detection means are difficult to commercialize and cannot be widely applied to the fields of health care and the like. Therefore, the exploration of a high-sensitivity, low-cost, small-volume and visual fluid pressure sensor is a problem which needs to be solved urgently.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide a high-sensitivity and visual fluid pressure sensor based on a micro-nano structure array surface and a preparation method thereof. According to the invention, the nano-pillar array is embedded on the surface of the micron-sized strip array with the morphology arranged in parallel, the surface of the substrate is modified by a vapor deposition technology, and then the nano-pillar array is combined with a PDMS chip with a main fluid pore channel and a plurality of trapezoidal measurement pore channels to form the fluid pressure sensor. The whole preparation process of the fluid pressure sensor is simple to operate, the occupied area of the sensor is small, the detection sensitivity is high, and the detection result can be directly observed by naked eyes. Each hydrophobic microstrip nano-pillar composite structure on the substrate can form a passive valve in the trapezoidal measurement channel, and the threshold pressure (namely the maximum fluid pressure capable of being blocked) of the passive valve is inversely related to the length of the passive valve in the microchannel. By calculating and measuring the threshold pressure of the passive valve and designing and arranging the composite structure array, a valve gate array with the gradient of the threshold pressure rising can be formed in the trapezoidal measuring pore channel. When fluid flows through the main fluid pore channel, the fluid front ends driven by different pressures can stay in the composite structure array at different positions below the measuring pore channel. By comprehensively analyzing the position of the front end of the fluid in each trapezoidal measurement pore channel, high-sensitivity fluid pressure detection can be realized. The fluid pressure is measured mainly through the arrangement of the micro-strip nano-column composite structure and the regulation and control of a gas-liquid-solid three-phase line on the surface of the micro-strip nano-column composite structure, and the fluid measuring method has good repeatability and accuracy. The whole process does not need external complex circuit elements and auxiliary equipment, and the fluid pressure measurement result can be recorded and calculated by the function of the camera of the mobile phone, so that the preparation and running cost of the chip is effectively reduced.
The invention is realized by the following technical scheme:
a preparation method of a fluid pressure sensor based on a micro-nano structure array surface comprises the following specific steps:
(1) and processing the initial substrate on the surface of the micro-strip nano-column composite structure: placing the substrate in acetone for ultrasonic cleaning for three times, wherein each time lasts for 1-2min, then cleaning the substrate with absolute ethyl alcohol for three times, each time lasts for 1-2min, and then ultrasonically cleaning the substrate with deionized water until no organic solvent remains; then, carrying out acid oxidation treatment on the substrate (mixed solution of 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 7:3), then washing the substrate with deionized water until no acid solution exists, and storing the substrate in the deionized water for later use;
(2) cleaning the substrate obtained in the step (1) in an oxygen plasma cleaning machine for 5-10min to graft hydroxyl on the surface of the substrate, and then spin-coating a layer of photoresist on the surface of the substrate (the spin-coating condition is 1000-3000 rpm, 10-60 s, and the thickness of the photoresist film is 2-4 mu m); then placing the substrate under a micron-sized strip array mask plate for ultraviolet exposure for 10-30s, and then placing the substrate in a developing solution for soaking for 10-30s to obtain the photoresist surface of a micron-sized strip array pattern; placing the surface of the photoresist of the micron-sized strip array pattern in a cavity of a plasma etching machine, wherein the etching time is 2-20 min; placing the substrate in absolute ethyl alcohol for ultrasonic cleaning for 5-10min, and then using deionized water for ultrasonic cleaning for 5-10min to obtain the surface of the shape micron-scale strip array structure;
(3) placing the surface of the micron-sized strip array structure obtained in the step (2) in an oxygen plasma cleaning machine to clean for 5-10min to graft the surface of the micron-sized strip array structure into hydroxyl, then placing the substrate in a polydiallyldimethylammonium chloride solution with the mass fraction of 1-5% to soak for 2-10min, and ultrasonically cleaning for 2-5min by using deionized water to enable the surface of the substrate to have positive charges; then, placing the substrate in an electronegative metal nanoparticle solution to soak for 5-60min to obtain the surface of the microstrip adsorbed with the metal nanoparticles; placing the surface in a cavity of a plasma etching machine, etching for 10-120s, then soaking in a nano particle etching solution for 2-10min, and ultrasonically cleaning with deionized water for 1-3min to obtain a micro-strip nano-column composite structure surface; grafting a hydrophobic material on the surface of the composite structure by a vapor deposition method, so as to obtain a hydrophobic microstrip nano-pillar composite structure array on the surface of the substrate;
(4) placing a glass plate with a uniform chromium film and a photoresist layer under a micro-channel mask plate, exposing for 10-30s by an ultraviolet lamp, placing the photoresist layer at the lower layer and the chromium film at the upper layer, and then placing the glass plate in a developing solution to soak for 10-30s to obtain the glass surface with the chromium layer of the patterned photoresist; then, soaking the glass substrate in a chromium etching solution for 2-5min to remove the chromium layer on the surface, and obtaining the glass surface with the patterned chromium layer; placing the surface in glass etching solution (mass ratio HF: HNO)3：NH4F：H2Soaking the mixture in 25:23.5:9.35:450) for 20-120min to obtain a micro-channel mold; mixing Polydimethylsiloxane (PDMS) prepolymer and curing agent according to a mass ratio of 10: 0.8-1.0, vacuum degassing for 10-30min, pouring onto the surface of the microchip pore channel mold, and standing at 60-10 deg.CCuring for 3-10h in an oven at 0 ℃, and uncovering to obtain a PDMS microfluidic channel; and (4) bonding the obtained microfluidic pore channel and the surface of the micro-strip nano-column composite structure array prepared in the step (3) together at low temperature to obtain the fluid pressure sensor based on the surface of the micro-nano structure array.
The substrate used in the step (1) is a glass slide, a quartz plate, a monocrystalline silicon piece or a PDMS substrate.
The photoresist used in the step (2) is positive photoresist BP212-37s, BP212-45 or negative photoresist SU-8.
The micro strip mask plate used in the step (2) is a chromium layer patterning and film printing mask plate, wherein the micro strip pattern is formed by arranging a plurality of micron-sized line width parallel lines, and the number and the spacing of the micron lines are calculated according to needs and obtained by experimental measurement design.
In the steps (2) and (3), the etching pressure is 0-20mTorr, the etching temperature is 10-20 ℃, the etching substrate gas flow rate is 10-50sccm, the etching power is 0-400W (radio frequency) and 0-400W (inductively coupled plasma), and the etching gas is oxygen, trifluoromethane/sulfur hexafluoride, trifluoromethane/argon and other single gases or multi-component mixed gas.
The hydrophobic grafting material in the step (3) is 1H, 1H, 2H, 2H-per-fluoro octyl trichlorosilane (PFS) or trichloro octadecyl silane (OTS).
The nanoparticles used in step (3) are negatively charged, such as gold nanoparticles, silver nanoparticles or aluminum nanoparticles.
The etching liquid used in the step (3) is a corrosive liquid capable of consuming the nano particles, such as a gold etching liquid, a silver etching liquid or a chromium etching liquid.
The hydrophobic micro-strip nano-column composite structure array prepared in the step (3) has the strip height of 1-3 microns, the width of 10-30 microns and the distance of 10-40 microns, and micro-strips can form passive valves in pore channels; the nano-column is arranged on the micro-strip passive valve, the diameter of the nano-column cylinder is 100-500 nm, the height of the nano-column is 50-100 nm, the distance between the nano-columns is 100-150 nm, and the nano-column can form a compact micro-valve on the basis of the micro-strip passive valve.
The chromium etching solution used in the step (4) is a mixed solution of ammonium ceric nitrate and nitric acid with the volume ratio of 6%.
The micro-channel mask plate used in the step (4) is a chromium layer patterning and film printing mask plate, and the shape of the micro-channel is determined by the micro-channel mask plate.
And (4) bonding at low temperature, wherein the bonding time is not less than 2d, and the bonding temperature is not more than 60 ℃.
The micro-channel in the step (4) is composed of a straight channel and five trapezoidal channels, the trapezoidal channels are arranged on the side of the straight channel in parallel, the composite structure array is positioned below the trapezoidal channels, and each composite structure forms a passive valve in the trapezoidal measuring micro-channel. The number of micro-nano composite structures through which fluid flows in the five measuring channels, namely the number of the lattices of the strips through which the fluid flows, and the fluid pressure at the inlet of the straight channel have a good linear correlation relationship, so that the fluid pressure measurement can be realized by counting the number of the lattices through which the fluid flows, and the pressure sensing performance is realized by the micro-nano composite structures.
Compared with the prior art, the invention has the following advantages:
1. the preparation process is simple, a compact nano-column structure can be formed on the surface of the micro-strip nano-column composite structure array, so that a continuous micro valve is formed, the stability of a gas-liquid three-phase line at the front end of fluid on the surface of a traditional single strip passive valve is greatly enhanced by the composite surface, and the sensitivity and the stability of the fluid pressure sensor are ensured. The whole preparation process of the fluid pressure sensor does not need complex technology, and the processing difficulty of the pressure sensor is simplified to a greater extent.
2. The sensitivity of the sensor prepared by the invention can reach 16.7mbar-1Much higher than other types of fluid pressure sensors and the measurement results have outstanding repeatability.
3. The pressure sensor prepared by the invention has small floor area which is less than 4cm2The device is easy to carry and is suitable for measuring the fluid pressure under various conditions.
4. The sample amount required by the pressure sensor prepared by the invention is less than 1.3 mu L, and the detection cost of the sensor is further reduced.
5. The characterization of the measurement result of the pressure sensor prepared by the invention does not need complex detection equipment, the measurement result in the approximate range can be directly observed by naked eyes, and the magnitude of the fluid pressure can be accurately obtained by a camera carried by a mobile phone.
6. The prepared fluid pressure sensor can realize the measurement of multiple surface energies and various fluids, wherein the fluids comprise low-surface energy alcohol-water mixed liquor, blood, oil phase liquid and the like.
7. The pressure sensor prepared by the invention can be used for practical application, and in the case of the invention, a plurality of micro-channels with different shapes are designed and combined, so that the fluid pressure in the channels with different shapes and the fluid pressure in the channels with different shapes can be measured.
The preparation process is simple to operate, high-sensitivity visual fluid pressure detection can be realized by using cheap devices, the measuring range and the sensitivity of the pressure sensor can be adjusted according to needs, expensive energy input is not required in the operation process, the pressure sensor can be integrated with most experimental platforms, and the devices have good stability.
Drawings
FIG. 1: based on atomic force microscope photos and scanning electron microscope photos of the silicon strip nano-column composite structure array prepared in the embodiment 1-3;
wherein, a is atomic force microscope photo, b is scanning electron microscope photo;
in the figure, the distance between micron-sized strips is 20 microns, the height of the strips is 1.5 microns, the width of the strips is 15 microns, a plurality of nano columns are constructed on the micron-sized strips, the diameter of each cylinder is 100-500 nm, the height of each nano column is 50-100 nm, and the distance between the nano columns is 100-150 nm, and the dense micro-nano composite structure prepared by the method can form a gas-liquid three-phase line and a continuous micro valve with extremely stable threshold pressure in a micro channel, so that the accuracy of the fluid pressure sensor is greatly improved;
FIG. 2: based on the electron micrographs of the fluid pressure sensor prepared in example 4, there was a pressure drop in the flow of the fluid through the channels of the straight flow body, so that the fluid flowed through each of the bypass trapezoidal measurement channelsMeasuring the pressure at the inlet of the duct is gradually reduced; in the side trapezoid measuring pore channel, the threshold pressure of a passive valve array formed by the micro-nano composite structure array below the pore channel is gradually increased, and the fluid pressure value at the inlet of each measuring pore channel can be roughly estimated; the pressure at the inlet of the measuring channel is gradually reduced, so that the quantity of the liquid flowing through the valve in each measuring channel is gradually reduced, and the value of the pressure is found to have a good linear relation with the pressure of the fluid inlet by counting the sum of the quantities of the fluid flowing through the valves in the measuring channel. Therefore, the invention can accurately measure the inlet pressure of the fluid by statistically measuring the total lattice number of the fluid flowing through the pore canal, namely the valve number, thereby forming the fluid pressure sensor; (a) when the inlet fluid pressure is 80mbar, the total number of fluid flowing through the measuring orifice is 12; (b) the total number of fluid flow through the measurement orifice was 76 when the inlet fluid pressure was 145 mbar; (e) the number of the lattices through which fluid flows in the pore channel and the inlet pressure show good linear correlation, the number of the lattices is counted by a micro-nano composite structure through which the fluid flows, so that the pressure sensing performance is realized by the micro-nano composite structure, and as can be seen from the figure, the measuring range of the pressure sensor is 60-180 mbar, and the sensitivity is 0.94mbar-1。
FIG. 3: electron micrographs based on the fluid pressure sensor of different ranges and sensitivities prepared in example 5; (a) the threshold pressure of the passive valve can be increased by reducing the height of the pore channel, so that the maximum value and the minimum value of the measuring range of the sensor are increased, the threshold pressure difference between the micro-nano structure valves with different lengths is increased by reducing the height of the pore channel, the sensitivity of the sensor is reduced, the measuring range of the sensor with the pore channel height of 25 mu m is 85-270 mbar, and the sensitivity is 0.43mbar-1(ii) a (b) The small-spacing measurement pore channels reduce the distance and pressure drop between the measurement pore channels, so that the measurement range of the sensor is reduced, the sensitivity is increased, the measurement range of the sensor with the pore channel spacing of 200 mu m is 60-120 mbar, and the sensitivity is 1.89mbar-1(ii) a (c) Increasing the height of the orifice reduces the threshold pressure of the passive valve, thereby reducing the maximum and minimum range of the sensor, and increasing the height of the orifice simultaneously reduces the differenceThe threshold pressure difference between the valves with the length micro-nano structures increases the sensitivity of the sensor, the measuring range of the sensor with the pore channel height of 75 microns is 42-85 mbar, and the sensitivity is 2.13mbar-1(ii) a (d) The large-interval measurement pore channels increase the distance and pressure drop between the measurement pore channels, so that the measurement range of the sensor is enlarged, the sensitivity is reduced, the measurement range of the sensor with the pore channel interval of 800 micrometers is 60-220 mbar, and the sensitivity is 0.13-1.22 mbar-1(ii) a (e) The pressure sensors with different measuring ranges measure the linear correlation between the number of the pore grids and the inlet pressure;
FIG. 4: electron micrographs of fluid pressure sensors in different fluid environments based on the preparation of example 6; (a) the pressure drop among the measurement channels of the barrier-free channels is 12 grids; (b) the pressure drop among the measuring channels of the round barrier channels is 20 grids; (c) the pressure drop among the measurement channels of the triangular barrier channels is 24 grids; (d) the measured pressure drop between the channels of the square barrier channels was 29 grids; (e) the theoretical value and the measured value of the pressure drop of the barrier pores with different shapes are gradually increased, so that the barrier pores can block the flow of the fluid, and the trend of the theoretical value and the trend of the measured value are the same, which proves that the fluid pressure sensor prepared by the invention can be used for measuring the fluid pressure in different fluid environments.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to be limiting.
Example 1: preparation of hydrophilic substrates
The used substrate is a monocrystalline silicon wafer (100), the substrate is cut to be 2cm long and 1.5cm wide by a glass cutter, the substrate is sequentially placed in acetone, ethanol and deionized water for three times of ultrasonic treatment, each time lasts for 1-2min, then mixed solution (volume ratio is 7:3) of concentrated sulfuric acid with mass fraction of 98% and hydrogen peroxide with mass fraction of 30% is placed in a water bath, the water bath is heated to 120 ℃, and the water bath is kept for 5 hours, so that the hydrophilic substrate is obtained; and repeatedly ultrasonically washing the obtained substrate with deionized water for 5 times, wherein each time is 1-2min, and storing the substrate in the deionized water for later use.
Example 2: preparation of silicon micron-scale strip structure array
Cleaning a silicon wafer in an oxygen plasma cleaning machine for 5min, spin-coating a layer of photoresist on the surface of the silicon wafer (the spin-coating condition is 3000rpm and 60s), then placing a photoresist homogenizing substrate under a micron-scale strip array mask plate for ultraviolet exposure for 10s, and then placing the silicon wafer in a special developing solution for soaking for 30s to obtain the photoresist surface of the micron-scale strip array; placing the surface in a cavity of a plasma etching machine, etching for 10min (the etching pressure is 6mTorr, the etching temperature is 10 ℃, the etching power is RF 50W, and ICP is 100W), then placing the substrate in absolute ethyl alcohol, ultrasonically cleaning for 10min, removing residual photoresist on the surface, ultrasonically cleaning for 5min by using deionized water, and drying by using nitrogen to obtain the surface of the silicon micron-scale strip structure; according to the range and the sensitivity of the pressure to be measured, a corresponding micron-scale strip array mask is designed through calculation, and a plurality of strip arrays which are arranged in parallel are prepared by different masks and are respectively combined with the pore channels in the corresponding embodiments.
Example 3: preparation of silicon micro-strip nano-column composite structure array surface
Soaking the surface of the silicon micron-scale strip array structure obtained in the example 2 in a poly (diallyldimethylammonium chloride) solution with the mass fraction of 1% for 5min, and ultrasonically cleaning the surface of the substrate for 3 times and 2min each time by using deionized water to ensure that the surface of the substrate has positive charges; then placing the substrate in a gold nanoparticle solution with the average diameter of 50nm to be soaked for 5min to obtain the surface of the micro-strip adsorbed with the gold nanoparticles; placing the surface in a cavity of a plasma etching machine, etching for 60s (the etching pressure is 6mTorr, the etching temperature is 10 ℃, the etching power is 50W, and the ICP is 100W), soaking in a gold etching solution for 5min, then ultrasonically cleaning for 3min by deionized water to obtain a compact micro-strip nano-column composite structure surface, placing the surface in an oxygen plasma cleaning machine, cleaning for 5min to enable the surface of a substrate to be provided with hydroxyl, grafting 1H, 1H, 2H, 2H-fluorooctyl trichlorosilane on the surface of the substrate by a vapor deposition method, and obtaining a hydrophobic silicon micro-strip nano-column composite structure array surface; according to different micron-sized mask pattern arrangements in the embodiment 2, micro-nano composite structure array surfaces with different patterns and capable of being matched with microchip channels in various shapes can be obtained, the surface structures are compact nano-pillar arrays constructed on the surfaces of strip structure arrays arranged in parallel, the strip height is 1-3 micrometers, the width is 10-30 micrometers, and the distance is 10-40 micrometers; the diameter of the nano-column cylinder is 100-500 nm, the height of the nano-column is 50-100 nm, and the distance between the nano-columns is 100-150 nm.
Example 4: fluid pressure sensor preparation
Placing a glass plate with a uniform chromium film and a photoresist layer under a micro-channel mask plate consisting of trapezoidal and rectangular opaque film sheets, exposing for 10s by an ultraviolet lamp, and then placing a substrate in a developing solution to soak for 30s to obtain a patterned photoresist glass surface with a chromium layer; soaking in chromium etching solution for 5min, and placing the surface in glass etching solution (mass ratio HF: HNO)3：NH4F：H2Soaking in 25:23.5:9.35:450) for 30min to obtain a glass pore channel mold with a patterned morphology structure; mixing Polydimethylsiloxane (PDMS) prepolymer and curing agent according to a mass ratio of 10: 1, pouring the mixture onto the surface of a microchip channel mold after vacuum degassing for 30min, placing the microchip channel mold in an oven at the temperature of 60 ℃, curing for 10h, and lifting the microchip channel mold to obtain a PDMS microfluidic channel which consists of a straight channel and five trapezoidal measurement channels, wherein the measurement channels are connected to the sides of the straight channel, the height of the channel is 50 microns, the width of the channel is 60-400 microns, and the distance between the measurement channels is 400 microns; and (4) pressing the obtained microfluidic pore channel and the micro-strip nano-column composite structure array surface prepared in the step (3) together to obtain the fluid pressure sensor based on the micro-nano structure array surface, wherein the micro-strip array is positioned below the trapezoidal pore channel.
Example 5: preparation of fluid pressure sensor with different sensitivity and measuring range
Respectively placing a glass plate with a uniform chromium film and a photoresist layer under a pore mask plate composed of trapezoidal and rectangular opaque film sheets with different intervals, exposing for 10s by an ultraviolet lamp, changing the trapezoidal measurement pore interval to 200 and 800 μm, and then placing a substrate in a developing solution to soak for 30s to obtain patterned photoresist glass surfaces with different shapes and spiral chromium layers; soaking in chromium etching solution for 5min, and placing the surface on glassEtching solution (mass ratio HF: HNO)3：NH4F：H2O-25: 23.5:9.35:450) for 15 or 60min to obtain glass channel molds with different heights of patterned morphological structures, wherein the channel heights are respectively changed to 25 μm and 75 μm; mixing Polydimethylsiloxane (PDMS) prepolymer and curing agent according to a mass ratio of 10: 1, vacuum degassing for 30min, pouring the mixture on the surfaces of the microchip pore molds with the four different heights and the different shapes, placing the microchip pore molds in an oven at the temperature of 60 ℃, curing for 10h, and uncovering the microchip pore molds to obtain PDMS microfluidic pores with different heights and shapes; and (4) respectively pressing the obtained microfluidic pore channels and the micro-strip nano-column composite structure array surface prepared in the step (3) together to obtain the fluid pressure sensor based on the micro-nano structure array surface with different measuring ranges and sensitivities, wherein the micro-strip array is positioned below the trapezoidal pore channel.
Example 6: preparation of fluid pressure sensor under different fluid environments
Placing a glass plate with a uniform chromium film and a photoresist layer under a micro-channel mask plate with different barrier shapes, and exposing for 10s by an ultraviolet lamp, wherein the barrier channels are positioned in straight channels, and the barrier shapes are respectively circular, triangular and square; then, the substrate is placed in a developing solution to be soaked for 30s, and the patterned photoresist glass surface with different barrier shapes and the chromium layer is rotated is obtained; soaking in chromium etching solution for 5min, and placing the surface in glass etching solution (mass ratio HF: HNO)3：NH4F：H2Soaking in 25:23.5:9.35:450) for 30min to obtain a glass pore channel mold with a barrier morphology structure; mixing Polydimethylsiloxane (PDMS) prepolymer and curing agent according to a mass ratio of 10: 1, pouring the mixture onto the surface of a microchip pore channel mold with different barrier shapes after vacuum degassing for 30min, placing the mold in an oven at the temperature of 60 ℃, curing for 10h, and lifting the mold to obtain PDMS microfluidic pore channels with different barrier pore channels; and (4) pressing the micro-fluid pore and the micro-strip nano-column composite structure array surface prepared in the step (3) together to obtain the fluid pressure sensor based on the micro-nano structure array surface under different fluid environments, wherein the micro-strip array is positioned below the trapezoidal pore.
The preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (7)
1. A preparation method of a fluid pressure sensor based on a micro-nano structure array surface is characterized by comprising the following specific steps:
(1) and processing the initial substrate on the surface of the micro-strip nano-column composite structure: placing the substrate in acetone, ultrasonically cleaning for three times, each time for 1-2min, then cleaning for three times, each time for 1-2min, and then ultrasonically cleaning with deionized water until no organic solvent remains; then, carrying out acid oxidation treatment on the substrate, then washing the substrate by using deionized water until no acid liquid exists, and storing the substrate in the deionized water for later use;
(2) cleaning the substrate obtained in the step (1) in an oxygen plasma cleaning machine for 5-10min to graft hydroxyl on the surface of the substrate, and spin-coating a layer of photoresist on the surface of the substrate; then placing the substrate under a micron-scale strip array mask plate for ultraviolet exposure for 10-30s, and then placing the substrate in a developing solution for soaking for 10-30s to obtain the photoresist surface of a micron-scale strip array pattern; placing the photoresist surface of the obtained micron-scale strip array pattern in a cavity of a plasma etching machine, wherein the etching time is 2-20 min; placing the substrate in absolute ethyl alcohol for ultrasonic cleaning for 5-10min, and then ultrasonic cleaning with deionized water for 5-10min to obtain the surface of the shape micron-scale strip array structure;
(3) placing the surface of the micron-scale strip array structure obtained in the step (2) in an oxygen plasma cleaning machine to clean for 5-10min to graft the surface of the micron-scale strip array structure into hydroxyl, then placing the substrate in a polydiallyldimethylammonium chloride solution with the mass fraction of 1-5% to soak for 2-10min, and ultrasonically cleaning for 2-5min by using deionized water to enable the surface of the substrate to have positive charges; then, the substrate is placed in an electronegative nano particle solution to be soaked for 5-60min, and the surface of the micro-strip with the adsorbed compact nano particles is obtained; placing the surface of the micro-strip adsorbed with the dense nano-particles in a cavity of a plasma etching machine, etching for 10-120s, then soaking in a metal nano-particle etching solution for 2-10min, and ultrasonically cleaning with deionized water for 1-3min to obtain the surface of a micro-strip nano-column composite structure; grafting a hydrophobic material on the surface of the composite structure by a vapor deposition method, so as to obtain a hydrophobic microstrip nano-pillar composite structure array on the surface of the substrate;
(4) placing a glass plate with a uniform chromium film and a photoresist layer under a micro-channel mask plate, exposing for 10-30s by an ultraviolet lamp, placing the photoresist layer at the lower layer and the chromium film at the upper layer, and then placing the glass plate in a developing solution to soak for 10-30s to obtain the glass surface of the patterned photoresist with the chromium layer; then soaking the glass substrate in a chromium etching solution for 2-5min to remove the chromium layer on the surface to obtain the glass surface with the patterned chromium layer; placing the glass surface with the patterned chromium layer in a glass etching solution to be soaked for 20-120min to obtain a micro-channel mold; mixing polydimethylsiloxane prepolymer and curing agent according to the mass ratio of 10: 0.8-1.0, pouring the mixture onto the surface of a microchip pore channel mold after vacuum degassing for 10-30min, placing the microchip pore channel mold in an oven at the temperature of 60-100 ℃, curing for 3-10h, and uncovering the microchip pore channel to obtain a PDMS microfluidic pore channel; bonding the obtained microfluidic pore channel and the surface of the micro-strip nano-column composite structure array prepared in the step (3) together at low temperature to obtain the fluid pressure sensor based on the surface of the micro-strip nano-column composite structure array, namely realizing the preparation of the fluid pressure sensor through the design of a compact micro-nano composite structure;
the chromium etching solution used in the step (4) is a mixed solution of ammonium ceric nitrate and nitric acid according to the volume ratio of 6%;
the microchannel used in the step (4) is a microchip channel model formed by connecting trapezoidal, rectangular or polygonal shapes, and the size and the relative position of each shape are calculated according to the range of the pressure of the fluid to be measured and the sensitivity;
and (4) bonding at low temperature, wherein the bonding time is not less than 2d, and the bonding temperature is not more than 60 ℃.
2. The method for preparing a fluid pressure sensor based on the micro-nano structure array surface according to claim 1, wherein the substrate used in the step (1) is a glass slide, a quartz plate, a monocrystalline silicon plate or a PDMS substrate.
3. The method for preparing the fluid pressure sensor based on the micro-nano structure array surface according to claim 1, wherein the photoresist used in the step (2) is positive photoresist BP212-37s, BP212-45 or negative photoresist SU-8;
the micro strip mask plate used in the step (2) is a chromium layer patterning and film printing mask plate, wherein the micro strip pattern is formed by arranging a plurality of micron-sized line width parallel lines, and the number and the spacing of the micron lines are calculated according to needs and obtained by experimental measurement design.
4. The method for preparing the fluid pressure sensor based on the micro-nano structure array surface according to claim 1, wherein in the steps (2) and (3), the etching pressure is 0-20mTorr, the etching temperature is 10-20 ℃, the etching substrate gas flow rate is 10-50sccm, the etching power is 0-400W, the ICP is 0-400W, and the etching gas is oxygen, trifluoromethane/sulfur hexafluoride, trifluoromethane/argon single gas or multi-component mixed gas.
5. The method for preparing the fluid pressure sensor based on the micro-nano structure array surface according to claim 1, wherein the hydrophobic grafting material in the step (3) is 1H, 1H, 2H, 2H-per-fluoro octyl trichlorosilane (PFS) or trichloro-Octadecylsilane (OTS);
the nano particles used in the step (3) are negatively charged, such as gold nano particles, silver nano particles or aluminum nano particles;
the etching liquid used in the step (3) is corrosive liquid capable of reacting with the nano particles, such as gold etching liquid, silver etching liquid or aluminum etching liquid;
the hydrophobic micro-strip nano-column composite structure array prepared in the step (3) has strips with the height of 1-3 microns, the width of 10-30 microns and the distance of 10-40 microns, and micro-strips form passive valves in pore channels; the nano-column is arranged on the micro-strip passive valve, the diameter of the nano-column is 100-500 nm, the height of the nano-column is 50-100 nm, the distance between the nano-columns is 100-150 nm, and the compact nano-column forms a compact micro-valve on the basis of the micro-strip passive valve.
6. The method for preparing the fluid pressure sensor based on the micro-nano structure array surface according to claim 1, wherein the micro-channel in the step (4) is composed of a straight channel and five trapezoidal channels, the trapezoidal channels are arranged on the side of the straight channel in parallel, the composite structure array is positioned below the trapezoidal channels, and each composite structure forms a passive valve in the trapezoidal measuring micro-channel; the number of the micro-nano composite structures through which fluid flows in the five measuring channels, namely the number of valves through which the fluid flows, and the pressure of the fluid at the inlet of the straight channel have a good linear correlation relationship, so that the pressure of the fluid can be measured by counting the number of the valves through which the fluid flows, and the pressure sensing performance is realized by the micro-nano composite structures.
7. A fluid pressure sensor based on a micro-nano structure array surface is characterized by being prepared by the preparation method of the fluid pressure sensor based on the micro-nano structure array surface according to any one of claims 1 to 6.
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