Touch sensing protrusion based on piezoelectric gel and preparation method of touch sensing protrusion

Abstract

The invention discloses a tactile sensing protrusion based on piezoelectric gel and a preparation method of the tactile sensing protrusion. The preparation method comprises the following steps: converting a pressure signal into an electrical signal by using the piezoelectric gel; the piezoelectric gel has the advantages of sensitive response, biocompatibility and obvious piezoelectric signals, and can effectively convert instantaneous pressure signals into voltage signals; by regulating and controlling the concentration of LiTFSI, the piezoelectric gel can have different transient response characteristics to pressure, and can be selected according to different application scenes; the first transistor is provided with a large memory window and has a high-sensitivity pressure signal-electric signal conversion function, and an instantaneous pressure signal can be converted into a current signal to be output, so that subsequent processing is facilitated; the second transistor has transconductance as high as 104, and can accurately collect and amplify piezoelectric signals generated by the first transistor; simple processes such as evaporation and spin coating are adopted in the manufacturing process, large-area manufacturing is easy, the yield is high, and commercialized application is easy.

Description

Technical Field

[0001] The present invention relates to the field of transistors and sensor technology, and in particular to a tactile sensing synapse based on piezoelectric gel and a preparation method thereof. Background Art

[0002] Organic Electrochemical Transistor (OECT) has received extensive attention in the field of bioelectronics due to its unique characteristics and excellent performance. OECT uses organic semiconductors as channel materials, which can not only conduct electrons but also ions, making it an ideal bridge for the conversion of ion signals and electrical signals. Its high transconductance characteristics enable it to effectively amplify weak signals. At the same time, it has the advantages of low driving voltage and high biocompatibility, making it of important application value in biomedical sensors, neural interfaces and flexible electronic devices. In addition, since the characteristics of OECT in ion-electron mixed conduction are similar to the working mechanism of biological neurons, it also shows great potential in simulating biological nervous systems and developing bionic devices.

[0003] Pressure sensors are an indispensable part of modern electronic technology and are widely used in medical monitoring, artificial intelligence, robotics, wearable devices and other fields. They are especially important in the development of bionic electronic skin. Bionic electronic skin can sense external pressure, vibration, touch and other information by imitating the mechanical perception function of human skin, providing strong technical support for the development of flexible electronics and artificial intelligence. However, existing pressure sensing technology often faces the difficult trade-off between sensitivity, resolution and dynamic response capability. How to further improve the performance of sensors is still an important direction for current technological development.

[0004] Therefore, it is necessary to develop a tactile sensing synapse based on piezoelectric gel and a preparation method thereof to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to design a tactile sensing synapse based on piezoelectric gel and a preparation method thereof in order to solve the above problems.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions: A tactile perception synapse based on piezoelectric gel includes a first transistor and a second transistor, wherein the first source and the first gate of the first transistor, and the second source and the second gate of the second transistor are all arranged on a substrate, a first semiconductor is arranged above the first source, a first drain is arranged above the first semiconductor, a second semiconductor is arranged above the second source, a second drain is arranged above the second semiconductor, the second gate is connected to the first drain, a piezoelectric gel is arranged between the first gate and the first source; and an ionic liquid gel is arranged between the first gate and the channel, and between the second gate and the channel.

[0007] The method for preparing a tactile sensing synapse based on piezoelectric gel comprises the following steps: Step 1: Drying the cleaned substrate; Step 2: Using a mask method to evaporate a bottom electrode of a specific shape on the dried substrate, the bottom electrode includes a first source electrode, a first gate electrode, a second source electrode, and a second gate electrode; Step 3: Spin-coating a semiconductor material doped with a photocrosslinker on a silicon wafer, followed by exposure and cleaning by a mask method to obtain a patterned semiconductor region; Step 4: using a mask method to evaporate a top electrode, the top electrode includes a first drain electrode and a second drain electrode; Step 5: Adding Ag or AgCl dispersion to the first gate and the second gate, followed by annealing to form Ag or AgCl gates; Step 6: dripping ionic liquid gel between the first gate and the second gate and the channel respectively, dripping piezoelectric gel between the first gate and the first source, and performing photocuring; Step 7: Package the device.

[0008] Preferably, the thickness of the semiconductor material is 200-500 nm.

[0009] Preferably, the top electrode is gold with a thickness of 80 nm.

[0010] Preferably, the piezoelectric gel is prepared by mixing PVDF-HFP, LiTFSI and polypropylene carbonate and by a casting method.

[0011] Preferably, the semiconductor material is at least one of Pg2T-T, gdpp-g2t, pedot:pss, and BBL.

[0012] Preferably, the cross-linking agent is PEGDA.

[0013] The beneficial effects of the present invention are: In the present invention, piezoelectric gel is used to convert pressure signals into electrical signals. Piezoelectric gel has the advantages of sensitive response, biocompatibility, and obvious piezoelectric signals, and can effectively convert instantaneous pressure signals into voltage signals.

[0014] In the present invention, by adjusting the concentration of LiTFSI, the piezoelectric gel can have different transient response characteristics to pressure, and can be selected according to different application scenarios.

[0015] In the present invention, the first transistor has a large memory window and a high-sensitivity pressure signal-electrical signal conversion function, which can convert the instantaneous pressure signal into a current signal output, facilitating subsequent processing.

[0016] In the present invention, the second transistor has a transconductance as high as 104, and can accurately collect and amplify the piezoelectric signal generated by the first transistor.

[0017] In the present invention, the manufacturing process uses simple processes such as evaporation and spin coating, which are easy to manufacture on a large scale, have a high yield rate, and are easy to commercialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the tactile sensing synapse based on piezoelectric gel in the present invention; Figure 2 is a transfer curve of the first transistor in the present invention; Figure 3 is a transfer curve of the second transistor in the present invention; Figure 4 is the output response of pressing the gate region of the first transistor in the present invention; Figure 5 The output response of pressing the channel region of the first transistor in the present invention; Figure 6 Schematic diagram of the output response of the first transistor under periodic pressure in the channel region of the present invention. Schematic diagram of the output response of applying periodic force in the channel region of transistor 1; A is time-pressure; B is time-output current.

[0019] Explanation of the numbers in the accompanying drawings: 1-second transistor, 2-substrate, 3-second source, 4-second semiconductor, 5-second drain, 6-second gate, 7-ionic liquid gel, 8-first transistor, 9-first source, 10-first semiconductor, 11-first drain, 12-first gate, 13-piezoelectric gel. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0023] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use, or are directions or positional relationships commonly understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0024] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0025] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms such as "setting" and "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings.

[0027] like Figure 1As shown, a tactile perception synapse based on piezoelectric gel includes a first transistor 8 and a second transistor 1. The first source 11 and the first gate 12 of the first transistor 8, and the second source 3 and the second gate 6 of the second transistor 1 are all arranged on a substrate 2. The first semiconductor 10 is arranged above the first source 9, and the first drain 11 is arranged above the first semiconductor 10. The second semiconductor 4 is arranged above the second source 3, and the second drain 5 is arranged above the second semiconductor 4. The second gate 6 is connected to the first drain 11, and a piezoelectric gel 13 is arranged between the first gate 12 and the first source 9; and an ionic liquid gel 7 is arranged between the first gate 12 and the channel, and between the second gate 6 and the channel.

[0028] The method for preparing a tactile sensing synapse based on piezoelectric gel comprises the following steps: Step 1: Drying the cleaned substrate; Step 2: Using a mask method to evaporate a bottom electrode of a specific shape on the dried substrate, the bottom electrode includes a first source electrode, a first gate electrode, a second source electrode, and a second gate electrode; Step 3: Spin-coating a semiconductor material doped with a photocrosslinker on a silicon wafer, followed by exposure and cleaning by a mask method to obtain a patterned semiconductor region; Step 4: using a mask method to evaporate a top electrode, the top electrode includes a first drain electrode and a second drain electrode; Step 5: Adding Ag or AgCl dispersion to the first gate and the second gate, followed by annealing to form Ag or AgCl gates; Step 6: dripping ionic liquid gel between the first gate and the second gate and the channel respectively, dripping piezoelectric gel between the first gate and the first source, and performing photocuring; Step 7: Package the device.

[0029] The bottom electrode is 3nm thick chromium and 80nm gold, the semiconductor layer is 200-500nm thick, the top electrode is 80nm thick gold, and the piezoelectric gel is fixed to a 10mm×3mm×1mm rectangular block (length×width×height) through the PDMS well.

[0030] The piezoelectric gel is made by mixing PVDF-HFP, LiTFSI, and polypropylene carbonate and casting into a specific shape.

[0031] The electrodes are prepared by evaporation using a metal mask with a pattern. This process has the advantages of simple operation process, adjustable electrode thickness, uniform film formation, etc., which can ensure the yield rate in mass production. In order to enhance the adhesion strength between gold and silicon substrate, a certain thickness of chromium is evaporated at the bottom of the gold electrode as a transition layer.

[0032] The semiconductor layer adopts an organic polymer material with good transmission characteristics, good chemical stability and low threshold voltage, such as one or more combinations of Pg2T-T, gdpp-g2t, pedot:pss, BBL, etc. The organic semiconductor layer material of the present invention is preferably Pg2T-T.

[0033] The gate of the transistor is made by dripping Ag / AgCl slurry and annealing it at an appropriate temperature. The silver / silver chloride gate has a lower chemical potential than gold, which can make the gate voltage more effective in driving ions in the electrolyte and reduce the threshold voltage.

[0034] The cross-linking agent of the semiconductor layer is PEGDA, which can undergo a polymerization reaction under 280nm ultraviolet light to solidify the organic semiconductor material and form a specific semiconductor pattern.

[0035] Example 1 The steps of preparing the tactile sensing synapse based on piezoelectric gel are as follows: Step 1: ultrasonically clean the silicon substrate using detergent, deionized water, and isopropyl alcohol, and then dry it; Step 2: On the dried silicon substrate, use a metal mask with a specific pattern to evaporate a 3nm thick Cr transition layer and 80nm of gold as a bottom electrode.

[0036] Step 3: The silicon wafer with the evaporated bottom electrode is subjected to ultraviolet irradiation treatment for 10 minutes to enhance the hydrophilicity of the silicon wafer and ensure the adhesion of the semiconductor layer on the silicon wafer.

[0037] Step 4: Spin coating the organic semiconductor solution on the silicon substrate after UV treatment at a speed of 3000 rpm. In the present invention, Pg2T-T is dissolved in chloroform at a concentration of 10 mg / ml to form a solution, and DA is dissolved in chloroform at a concentration of 20 mg / ml to form a solution, and then mixed at a volume ratio of 2:1. After the spin coating is completed, 280nm ultraviolet light is used to expose through the mask for 140 seconds, and then the undeveloped part is cleaned with chloroform, leaving the patterned semiconductor layer.

[0038] Step 5: Using a metal mask with a specific pattern, evaporate gold with a thickness of 50 nm and 80 nm as the top electrode.

[0039] Step 6: Add Ag / AgCl slurry to the gates of the first transistor and the second transistor, and anneal at 60 degrees Celsius for 10 minutes.

[0040] Step 7: Add electrolyte gel between the Ag / AgCl gate and the organic semiconductor of the second transistor and place it at room temperature to dry naturally. To prepare the electrolyte gel, first dissolve PVDF-co-HFP in acetone at 12.5wt / wt%, and then mix [EMIM][TFSI] and PVDF-co-HFP at a volume ratio of 9:1. Figure 3 As shown, the second transistor has more than 10 5 On / off ratio and high transconductance of nearly 0.2S.

[0041] Step 7: The piezoelectric gel was in situ cast between the gate of the first transistor and the organic semiconductor through the PDMS well and allowed to dry naturally at room temperature. To prepare the piezoelectric gel, LiTFSI was dissolved in propylene carbonate at 3 mol / L; PVDF-co-HFP was dissolved in acetone at 7.5 wt / wt%, and then 5 mL of the LiTFSI solution was mixed with 33.3 g of PVDF-co-HFP.

[0042] Example 2 The difference from Example 1 is that in step 7, LiTFSI is dissolved in propylene carbonate at 2 mol / L.

[0043] Example 3 The difference from Example 1 is that in step 7, LiTFSI is dissolved in propylene carbonate at 1 mol / L.

[0044] Example 4 The difference from Example 1 is that in step 7, LiTFSI is dissolved in propylene carbonate at 0.5 mol / L.

[0045] First, a piezoelectric gel with a length of 10 mm, a width of 3 mm, and a thickness of 1 mm was cast to test its piezoelectric effect. Different pressures were applied to the piezoelectric gel using weights. The pressed area was connected to the positive electrode of the test table, and the non-pressed area was connected to the test table to measure the output voltage of the piezoelectric gel as shown in Table 1:

[0046] Subsequently, a piezoelectric gel with a length of 10 mm, a width of 3 mm, and a thickness of 1 mm was cast in the electrolyte region of the first transistor. The transfer curve of the first transistor was measured as follows: Figure 2 shown.

[0047] During the test, the source of the first transistor is connected to a 0.5V power supply, the gate of the first transistor is connected to a 0.4V power supply, the drain is left empty, the source of the second transistor is connected to a 0.5V power supply, and the drain of the second transistor is grounded.

[0048] The following tests were performed on Example 1: A pressure of 4N and a duration of 0.1s is applied to the channel region of the first transistor, and the change of the drain current output by the second transistor is observed as follows: Figure 4 As shown, a significant pressure-induced current output phenomenon was observed, and as the pressure was removed, the drain current was still higher than the initial state.

[0049] A pressure of 4N and a duration of 0.1s is applied to the channel region of the first transistor, and the change of the drain current output by the second transistor is observed as follows: Figure 5 As shown, a significant pressure-induced change in current output was observed, and as the pressure was removed, the drain current was still lower than the initial state.

[0050] A sinusoidal pressure of 0-4N and a period of 5s is applied to the electrolyte region of the first transistor, and the drain current output of the second transistor is observed to change as follows: Figure 6 As shown, the output current of the second transistor continues to decrease with the effect of periodic pressure.

[0051] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A tactile sensing synapse based on piezoelectric gel, characterized in that: The invention comprises a first transistor and a second transistor, wherein the first source and the first gate of the first transistor, and the second source and the second gate of the second transistor are all arranged on a substrate, the first semiconductor is arranged above the first source, the first drain is arranged above the first semiconductor, the second semiconductor is arranged above the second source, the second drain is arranged above the second semiconductor, the second gate is connected to the first drain, a piezoelectric gel is arranged between the first gate and the first source, and an ionic liquid gel is arranged between the first gate and the channel, and between the second gate and the channel.

2. The method for preparing a tactile sensing synapse based on piezoelectric gel according to claim 1, characterized in that: The following steps are involved: Step 1: Drying the cleaned substrate; Step 2: Using a mask method to evaporate a bottom electrode of a specific shape on the dried substrate, the bottom electrode includes a first source electrode, a first gate electrode, a second source electrode, and a second gate electrode; Step 3: Spin-coating a semiconductor material doped with a photocrosslinker on a silicon wafer, followed by exposure and cleaning by a mask method to obtain a patterned semiconductor region; Step 4: using a mask method to evaporate a top electrode, the top electrode includes a first drain electrode and a second drain electrode; Step 5: Dropping Ag or AgCl dispersion on the first gate and the second gate, followed by annealing to form Ag or AgCl gates; Step 6: dripping ionic liquid gel between the first gate and the second gate and the channel respectively, dripping piezoelectric gel between the first gate and the first source, and performing photocuring; Step 7: Package the device.

3. The method for preparing a tactile sensing synapse based on piezoelectric gel according to claim 2, characterized in that: The thickness of the semiconductor material is 200-500nm.

4. The method for preparing a tactile sensing synapse based on piezoelectric gel according to claim 2, characterized in that: The top electrode is gold with a thickness of 80 nm.

5. The method for preparing a tactile sensing synapse based on piezoelectric gel according to claim 2, characterized in that: The piezoelectric gel is prepared by mixing PVDF-HFP, LiTFSI, and polypropylene carbonate through a casting method.

6. The method for preparing a tactile sensing synapse based on piezoelectric gel according to claim 2, characterized in that: The semiconductor material is at least one of Pg2T-T, gdpp-g2t, pedot:pss, and BBL.

7. The method for preparing a tactile sensing synapse based on piezoelectric gel according to claim 2, characterized in that: The cross-linking agent was PEGDA.

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