Tunable memristor-based flexible stress sensor and preparation method thereof
By preparing a memristor-based stress sensor on a flexible substrate, using memristor characteristics and asymmetric electrode-dielectric layer design, the problem of contradiction between sensitivity and range of traditional stress sensors is solved, and the tunability of sensitivity and range is achieved, and the application scenarios are expanded.
Patent Information
- Application Number
- CN202510529031.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-25
- Publication Date
- 2025-07-25
AI Technical Summary
Traditional stress sensors have contradictions in sensitivity and range, and the rigid substrate preparation process is complex and costly, limiting their application in wearable devices and mechanical moving parts.
A memristor-based stress sensor is prepared on a flexible substrate, and the resistance value is tunable through the memristor characteristics. The memristor device is prepared using photolithography and magnetron sputtering processes. Combined with asymmetric electrode-dielectric layer design, the bidirectional tunability of the stress sensor's sensitivity and range are achieved.
Simplifies the preparation process, reduces costs, and broadens the application of stress sensors in wearable and mechanically mobile parts, providing more accurate and reliable stress measurement results.
Smart Images
Figure CN120379527A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electronic devices, and particularly relates to a method for preparing a flexible stress sensor based on a memristor and a preparation method thereof. Background Art
[0002] A stress sensor is a device for measuring the stress suffered by an object, and is widely used in the fields of structural health monitoring, biomedical engineering, aerospace, etc. Traditional stress sensors are mainly based on technologies such as resistive strain gauges, piezoelectric elements or fiber optic sensors. However, these sensors have limitations in some aspects, such as sensitivity, range, stability, cost or manufacturing process, etc. The existing problems are as follows: For piezoresistive stress sensors, the sensitivity and range are a pair of contradictions. High-sensitivity stress sensors usually correspond to small ranges, and large ranges restrict the sensitivity of stress sensors. It is difficult to use one stress sensor to achieve tests with different sensitivity ranges, resulting in high costs of stress sensors in practical applications.
[0003] Currently, piezoresistive stress sensors are usually prepared by micro-nano processing technology on a rigid substrate to manufacture MEMS devices. This process flow is complex and costly, and the rigid substrate restricts the configuration of stress sensors in wearable devices and mechanical moving parts, which all limit the further development of stress sensors. Summary of the Invention
[0004] In order to solve the above two problems, the present invention discloses a tunable flexible stress sensor based on a memristor. A memristive device made of a material with piezoresistive characteristics is prepared on a flexible substrate. The piezoresistive characteristics are used to achieve stress sensing, and the memristive characteristics are used to achieve tunability of the resistance value. By adjusting the turn-on voltage of the device, the piezoresistive range of the device can be adjusted bidirectionally from small to large and from large to small, realizing a flexible tunable stress sensor that can be used for multiple purposes.
[0005] Platinum and silver electrodes make it easier for the memristor to form conductive filaments in the energized state, and molybdenum disulfide makes it easier for the memristor to change from the on state to the high-resistance state. A tunable flexible stress sensor based on a memristor, the memristor uses a flexible material as a carrier, and includes a PDMS layer, a metal Ni layer, a metal Pt layer, a MoS2 layer, a TiO2 layer, a metal Ag layer, and a TiN layer arranged in sequence from bottom to top.
[0006] Furthermore, the memristor adopts a structure of platinum-molybdenum disulfide-titanium dioxide-silver. Platinum and silver electrodes make it easier for the memristor to form conductive filaments in the energized state, and molybdenum disulfide makes it easier for the memristor to change from the on state to the high-resistance state.
[0007] Furthermore, a nickel layer is plated as an adhesion layer before plating the bottom electrode platinum layer. The adhesion layer makes the platinum electrode not easy to fall off.
[0008] Further, in the present invention, the sizes of the MoS2 layer and the TiO2 layer are larger than those of the bottom electrode Pt layer and the top electrode Ag layer, so as to prevent the situation of short circuit caused by the contact between the upper and lower electrodes during the preparation process.
[0009] Further, the titanium nitride layer is deposited on the upper electrode silver layer to play an anti-oxidation role.
[0010] Further, when powered on, before and after the formation of the conductive filament, due to the stress effect, the on-resistance and off-resistance of the memristor will change, and the magnitude of the stress can be obtained through the resistance value.
[0011] The present invention uses optical lithography and PVD magnetron sputtering processes to prepare a stress sensor based on a memristor, and designs reasonable process steps, including the shape of the lithography mask.
[0012] The method for preparing a flexible stress sensor based on a memristor according to the present invention includes the following steps: The first step: Pour 16 g of high-transparency optical potting adhesive (A) and 1.6 g of high-transparency optical potting adhesive (B) into a mold and stir well using a magnetic stirrer; The second step: Place the mold in a forced-air drying oven at 90 °C for baking for 0.5 h, and perform demolding treatment after baking to obtain a PDMS substrate.
[0013] The third step: Spin-coat a photoresist on the surface of the PDMS substrate, and then use optical lithography technology to define a 20 μm × 5 μm long rectangle on the spin-coated photoresist layer.
[0014] The fourth step: Use magnetron sputtering technology to sputter 20 nm of metallic nickel and 40 nm of metallic foil on the defined pattern respectively, then place the PDMS substrate in an acetone solution for ultrasonic treatment, and then place the PDMS substrate in absolute ethanol and ultrapure water for cleaning in sequence to remove the residual photoresist; obtain a metallic Ni layer and a metallic Pt layer.
[0015] The fifth step: Spin-coat a photoresist on the surface of the PDMS substrate, and then use optical lithography technology to define a 10 μm × 10 μm square on the spin-coated photoresist layer.
[0016] The sixth step: Use magnetron sputtering technology to sputter 5 nm of MoS2 and 15 nm of TiO2 on the defined pattern respectively, then place the PDMS substrate in an acetone solution for ultrasonic treatment, and then place the PDMS substrate in absolute ethanol and ultrapure water for cleaning in sequence to remove the residual photoresist; obtain a MoS2 layer and a TiO2 layer.
[0017] Step 7: Spin-coat photoresist on the surface of the PDMS substrate, and then use optical lithography technology to define a 20 μm × 5 μm square on the spin-coated photoresist layer.
[0018] Step 8: Sputter 100 nm of Ag and 5 nm of TiN on the defined pattern by magnetron sputtering technology, then place the PDMS substrate in an acetone solution for ultrasonic treatment, and then place the PDMS substrate in anhydrous ethanol and ultrapure water for cleaning in turn to remove the residual photoresist; a metal Ag layer and a TiN layer are obtained.
[0019] Advantages of the present invention: 1. The preparation process of the flexible stress sensor based on memristor prepared by the present invention is simple, only using two processes, namely photolithography process and magnetron sputtering coating process. The operation is simple and it is easy to scale up production. At the same time, the unique properties of the memristor enable the sensor to dynamically adjust according to different stress levels, so as to provide more accurate and reliable measurement results. The flexible stress sensor has a simple structure and good sensitivity. In addition, it has strong environmental adaptability and can be used in multiple fields.
[0020] 2. Based on the piezoresistive characteristic sensor, the present invention designs a memristor structure, utilizes the memristive characteristic of the device, adjusts the size of the conductive filament through the turn-on voltage, and then regulates the size of the resistance value, so as to realize the range adjustment of the stress sensor based on the piezoresistive effect, and finally realize the sensitivity and range switching of the stress sensor.
[0021] 3. A memristive device with piezoresistive characteristic materials is prepared on a flexible substrate. The piezoresistive characteristic realizes stress sensing, and the memristive characteristic realizes the tunability of the resistance value. By adjusting the turn-on voltage of the device, the piezoresistive range of the device can be adjusted bidirectionally from small to large and from large to small, realizing a flexible tunable stress sensor with multiple functions.
[0022] 4. Metal Ni has excellent adhesion, high conductivity and low contact resistance, which can reduce signal transmission loss. Metal Pt has an extremely low resistivity, which can effectively reduce the ohmic consumption of the electrode itself. MoS2 as a blocking layer makes it easier for the memristor to change from the low resistance state to the high resistance state. TiO2 has an excellent switching ratio, and the sensor based on TiO2 can achieve a wide range. Metal Ag has unique ion migration characteristics and low voltage, making the sensor have high sensitivity and wide range.
[0023] 5. This asymmetric electrode-dielectric layer design (the bottom electrode and the top electrode are 20 μm × 5 μm, and the dielectric layer is 5 μm × 5 μm) realizes electric field concentration by reducing the area of the dielectric layer, significantly reduces the operating voltage and increases the switching ratio; the large-size electrode extension part enhances the heat dissipation capacity and mechanical stress buffering, optimizing the thermal stability and flexible reliability; at the same time, the electrode covering the edge of the dielectric layer can suppress leakage current, improve the contact resistance and current uniformity, and the size difference provides a process tolerance space, facilitating high-density cross-array integration.
[0024] The present invention prepares a stress sensor based on the piezoresistive effect on a flexible substrate. The flexible substrate realizes the combination of the mechanical freedom degree of the stress sensor device and the piezoresistive effect. After being flexibly bent, based on the piezoresistive effect, an electrical signal can be directly obtained to obtain stress parameters, avoiding complex MEMS processes, greatly simplifying the process flow and cost, and broadening the application of the stress sensor in wearable scenarios and mechanical activity part scenarios.
[0025] Based on the piezoresistive characteristic sensor, the present invention designs a memristor structure. By utilizing the memristive characteristic of the device, through the turn-on voltage, the size of the conductive filament is adjusted, and then the size of the resistance value is regulated to realize the range adjustment of the stress sensor based on the piezoresistive effect, and finally the sensitivity and range switching of the stress sensor are realized. Brief Description of the Drawings
[0026] Figure 1 Side view of the flexible stress sensor based on the memristor.
[0027] Figure 2 Top view of the flexible stress sensor based on the memristor.
[0028] In the figure: PDMS layer 1, metal Ni layer 2, bottom electrode Pt layer 3, MoS2 layer 4, TiO2 layer 5, top electrode Ag layer 6, TiN layer 7.
[0029] Figure 3 Process flow chart of the flexible stress sensor based on the memristor.
[0030] Figure 4 It is a hysteresis curve diagram under the action of a voltage of 1.5 V. Among them, Figure (a) is the hysteresis curves of different stresses with a turn-on voltage of 1.5 V in the standard coordinate system; Figure (b) is the hysteresis curves of different stresses with a turn-on voltage of 1.5 V in the logarithmic coordinate system; among them, A1, A2, and A3 are the hysteresis curves obtained by the same device under different stresses at a turn-on voltage of 1.5 V.
[0031] Figure 5It is a hysteresis curve diagram under the action of a voltage of 1.8 V; among them, Figure (a) is the hysteresis curves of different stresses with an opening voltage of 1.8 V in the standard coordinate system; Figure (b) is the hysteresis curves of different stresses with an opening voltage of 1.8 V in the logarithmic coordinate system. Among them, A1, A2, and A3 are the hysteresis curves obtained by the same device under different stresses at an opening voltage of 1.8 V. Detailed implementation mode
[0032] The following further clarifies the present invention in conjunction with the attached drawings and the detailed implementation mode. It should be understood that the following detailed implementation mode is only used to illustrate the present invention and not to limit the scope of the present invention. It should be noted that the terms "front", "rear", "left", "right", "up" and "down" used in the following description refer to the directions in the attached drawings, and the terms "inside" and "outside" respectively refer to the directions towards or away from the geometric center of a specific component. Embodiment
[0033] This embodiment uses a flexible material as a carrier, including a PDMS layer, a metal Ni layer, a bottom electrode Pt layer, a MoS2 layer, a TiO2 layer, a top electrode Ag layer, and a TiN layer arranged in sequence from bottom to top.
[0034] The method for preparing the stress sensor based on the memristor of the present invention takes the preparation of the upper and lower electrodes of 20 μm×5 μm and the dielectric layer of 10 μm×10 μm as an example, and the preparation process is as follows: The first step: Pour 16 g of high-transparency optical potting adhesive (A) and 1.6 g of high-transparency optical potting adhesive (B) into the mold and stir well using a magnetic stirrer; The second step: Place the mold in a forced-air drying oven at 90°C and bake for 0.5 h. After baking, perform a demolding process to obtain a PDMS substrate.
[0035] The third step: After the PDMS substrate is ultrasonically cleaned (for 5 min) in acetone, absolute ethanol, and ultrapure water in sequence, then blow it dry with nitrogen; Use a spin coater to first spin coat photoresist on the surface of the silicon substrate with an insulating layer at a rotation speed of 600 revolutions per minute for 9 seconds, and then spin coat photoresist at a rotation speed of 4000 revolutions per minute for 40 seconds. Then use optical lithography technology to define the lower electrode pattern on the spin-coated photoresist layer, and the model of the lithography machine is MA6.
[0036] The fourth step: Use magnetron sputtering technology to sputter 20 nm of metal nickel and 40 nm of metal foil on the defined pattern respectively, then place the PDMS substrate in an acetone solution for ultrasonic treatment, and then place the PDMS substrate in absolute ethanol and ultrapure water for cleaning in sequence to remove the residual photoresist; Obtain a metal Ni layer and a metal Pt layer.
[0037] Step 5: After drying with nitrogen, use a spin coater to spin coat photoresist on the surface of the silicon substrate with an insulating layer. First, spin coat at a speed of 600 revolutions per minute for 9 seconds, and then spin coat at a speed of 4000 revolutions per minute for 40 seconds. Then, use optical lithography technology to define the dielectric layer pattern on the spin-coated photoresist layer; Step 6: Use magnetron sputtering technology to sputter 5 nm of MoS2 and 15 nm of TiO2 on the defined pattern respectively. Then, put the PDMS substrate into an acetone solution for ultrasonic treatment, and then put the PDMS substrate into anhydrous ethanol and ultrapure water in sequence for cleaning to remove the residual photoresist; obtain the MoS2 layer and the TiO2 layer.
[0038] Step 7: After drying with nitrogen, use a spin coater to spin coat photoresist on the surface of the silicon substrate with an insulating layer. First, spin coat at a speed of 600 revolutions per minute for 9 seconds, and then spin coat at a speed of 4000 revolutions per minute for 40 seconds. Then, use optical lithography technology to define the upper electrode pattern on the spin-coated photoresist layer.
[0039] Step 8: Use magnetron sputtering technology to sputter 100 nm of Ag and 5 nm of TiN on the defined pattern respectively. Then, put the PDMS substrate into an acetone solution for ultrasonic treatment, and then put the PDMS substrate into anhydrous ethanol and ultrapure water in sequence for cleaning to remove the residual photoresist; obtain the metal Ag layer and the TiN layer.
[0040] Combined with the product of Example 1, Figure 4 It is a hysteresis curve diagram under the action of a voltage of 1.5 V. Among them, Figure (a) is the hysteresis curves of different stresses with an opening voltage of 1.5 V in the standard coordinate system; Figure (b) is the hysteresis curves of different stresses with an opening voltage of 1.5 V in the logarithmic coordinate system. Among them, A1, A2, and A3 are the hysteresis curves obtained by the same device under different stresses at an opening voltage of 1.5 V. From the currently measured hysteresis curves, it can be obtained that when the stress increases, the resistance value of the device decreases at an opening voltage of 1.5 V.
[0041] Figure 5 It is a hysteresis curve diagram under the action of a voltage of 1.8 V; among them, Figure (a) is the hysteresis curves of different stresses with an opening voltage of 1.8 V in the standard coordinate system; Figure (b) is the hysteresis curves of different stresses with an opening voltage of 1.8 V in the logarithmic coordinate system. Among them, A1, A2, and A3 are the hysteresis curves obtained by the same device under different stresses at an opening voltage of 1.8 V. From the obtained hysteresis curves, we can conclude that when the stress increases, the resistance value of the device decreases at an opening voltage of 1.8 V.
[0042] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.
Claims
1. An adjustable memristor-based flexible stress sensor, characterized in that, The memristor uses a flexible material as the substrate, including a PDMS layer (1), a metal Ni layer (2), a bottom electrode Pt layer (3), a MoS2 layer (4), a TiO2 layer (5), a top electrode Ag layer (6), and a TiN layer (7) sequentially arranged from bottom to top; based on the piezoresistive and memristive characteristics of the composite material, by adjusting the turn-on voltage of the device, the resistance value of the measured device will change, and then the piezoresistive range of the device can be tuned, broadening the stress sensing range based on the piezoresistive effect.
2. The tunable memristor-based flexible stress sensor according to claim 1, wherein The sizes of the MoS2 layer (4) and the TiO2 layer (5) are larger than those of the bottom electrode Pt layer (3) and the top electrode Ag layer (6).
3. The tunable memristor-based flexible stress sensor according to claim 1, wherein After being powered on, the memristor will show an on-state resistance and an off-state resistance.
4. The tunable memristor-based flexible stress sensor according to claim 1, wherein The structure of platinum-molybdenum disulfide-titanium dioxide-silver is adopted.
5. The tunable memristor-based flexible stress sensor according to claim 4, wherein Before plating the bottom electrode Pt (3), a metal Ni layer (2) is plated first as an adhesion layer, so that the bottom electrode Pt (3) is not easily detached.
6. A preparation method of a tunable memristor-based flexible stress sensor, characterized in that: A flexible substrate is adopted, and the method includes the following steps: The first step: Pour 16 g of high-transparency optical potting adhesive (A) and 1.6 g of high-transparency optical potting adhesive (B) into the mold and stir well using a magnetic stirrer; The second step: Place the mold in a forced-air drying oven at 90 °C and bake for 0.5 h. After baking, perform a demolding process to obtain the PDMS substrate (1); The third step: Spin-coat photoresist on the surface of the PDMS substrate (1), and then use optical lithography technology to define a 20 μm × 5 μm long rectangle on the spin-coated photoresist layer; The fourth step: Use magnetron sputtering technology to sputter 20 nm of metal nickel and 40 nm of metal foil on the defined pattern respectively, then place the PDMS substrate in an acetone solution for ultrasonic treatment, and then place the PDMS substrate in anhydrous ethanol and ultrapure water for cleaning in sequence to remove the residual photoresist; obtain the metal Ni layer (2) and the metal Pt layer (3); The fifth step: Spin-coat photoresist on the surface of the PDMS substrate (1), and then use optical lithography technology to define a 5 μm × 5 μm square on the spin-coated photoresist layer; The sixth step: Use magnetron sputtering technology to sputter 5 nm of MoS2 and 15 nm of TiO2 on the defined pattern respectively, then place the PDMS substrate in an acetone solution for ultrasonic treatment, and then place the PDMS substrate in anhydrous ethanol and ultrapure water for cleaning in sequence to remove the residual photoresist; obtain the MoS2 layer (4) and the TiO2 layer (5); The seventh step: Spin-coat photoresist on the surface of the PDMS substrate (1), and then use optical lithography technology to define a 20 μm × 5 μm square on the spin-coated photoresist layer; The eighth step: Use magnetron sputtering technology to sputter 100 nm of Ag and 5 nm of TiN on the defined pattern respectively, then place the PDMS substrate in an acetone solution for ultrasonic treatment, and then place the PDMS substrate in anhydrous ethanol and ultrapure water for cleaning in sequence to remove the residual photoresist; obtain the metal Ag layer (6) and the TiN layer (7).