Resistance-type flexible multifunctional sensor and preparation method and application thereof

Abstract

The invention discloses a resistive flexible multifunctional sensor and a preparation method and application thereof. The sensor comprises a bottom-layer flexible substrate, a resistance-type pressure sensitive layer, a second-layer flexible substrate, a third-layer flexible substrate, a resistance-type temperature sensitive layer and a top-layer flexible substrate which are sequentially arranged from bottom to top, and two sides of the upper surface of the resistance-type pressure sensitive layer are respectively connected with a double-sided conductive adhesive tape. A resistive humidity sensitive layer and a resistive ammonia gas sensitive layer are attached to the lower surface of the third flexible substrate side by side, notches are formed in the third flexible substrate and the top flexible substrate, and the notches penetrate through the third flexible substrate and the top flexible substrate and are arranged over the humidity sensitive layer and the ammonia gas sensitive layer. The sensor integrates four sensing functions of temperature, pressure, ammonia gas and humidity, and all sensitive layers are resistive, so that the number of lead interfaces of the sensor is remarkably reduced, and the design difficulty of a rear-end circuit is reduced.

Description

Technical Field

[0001] This invention relates to the field of flexible sensor technology, and more specifically, to a resistive flexible multifunctional sensor, its fabrication method, and its application. Background Technology

[0002] In recent years, with the rapid development of Internet of Things (IoT) technology, sensors, as sensing elements that provide real-time information, have been widely used in daily life and production practices, playing an indispensable role, especially in health monitoring, human-computer interaction and other fields.

[0003] Traditional sensors typically use silicon, glass, or rigid printed circuit boards (PCBs) as substrates and are fabricated using rigid materials such as metals, metal oxides, or semiconductors. While these sensors offer stable performance and mature manufacturing processes, their inherent rigidity and brittleness prevent them from maintaining a close and comfortable fit with human skin, organs, or other irregular, soft surfaces (such as textiles or robot joints). This results in inaccurate signal acquisition, low signal-to-noise ratios, and a tendency to detach or be damaged under dynamic bending, severely hindering their application in many emerging fields, such as continuous physiological signal monitoring (heart rate, blood pressure, respiration, sweat composition) attached to the skin, implantable medical devices, smart textiles, electronic skin, and soft robotic sensing systems that require interaction with the environment. Flexible sensors, using flexible materials as substrates, have emerged as a solution to address this challenge.

[0004] However, with the deepening of application demands, single-function flexible sensors are no longer sufficient to meet the multi-parameter sensing requirements in complex scenarios. For example, in health monitoring, it is often necessary to simultaneously acquire information such as pressure (e.g., pulse wave), temperature (body temperature), humidity (respiratory humidity, sweat), and specific biomarkers (e.g., ammonia, which reflects kidney metabolic function). Therefore, the development of multifunctional flexible sensors has been considered. However, in these sensors, as the number of sensing units increases, the ratio of the number of functions to the number of leads decreases, leading to increased device fabrication complexity, reduced space utilization, and increased difficulty in back-end circuit design. Therefore, it is urgent to solve the problems of existing sensors having limited functionality, numerous lead interfaces, and complex back-end processing circuits. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that existing flexible sensors have limited functions, a large number of leads, and complex device structures and back-end circuit designs. In order to overcome the above-mentioned defects of the prior art, the present invention provides a resistive flexible multifunctional sensor, its preparation method and application.

[0006] A first aspect of the present invention is to provide a resistive flexible multifunctional sensor, comprising, from bottom to top, a bottom flexible substrate, a resistive pressure-sensitive layer, a second flexible substrate, a third flexible substrate, a resistive temperature-sensitive layer, and a top flexible substrate. Double-sided conductive tape is connected to both sides of the upper surface of the resistive pressure-sensitive layer. A resistive humidity-sensitive layer and a resistive ammonia-sensitive layer are attached side-by-side to the lower surface of the third flexible substrate. A first metal film is provided at both ends of the resistive humidity-sensitive layer and at both ends of the resistive ammonia-sensitive layer. A first notch and a third notch are respectively formed on the third flexible substrate and the top flexible substrate, with the first and third notches positioned directly above the humidity-sensitive layer. A second notch and a fourth notch are also respectively formed on the third flexible substrate and the top flexible substrate, with the second and fourth notches positioned directly above the ammonia-sensitive layer. A second metal film is provided at both ends of the resistive temperature-sensitive layer.

[0007] Compared with existing technologies, this invention has the following advantages: It uses conductive tape as electrodes. When the pressure-sensitive layer is subjected to stress, its morphology deforms, causing a change in its resistance. The change in resistance across the pressure-sensitive layer reflects the change in external pressure. Changes in ambient ammonia and humidity can cause corresponding changes in the resistance of the sensitive layers. The change in resistance across the humidity-sensitive layer and the ammonia-sensitive layer reflects changes in the ambient humidity and ammonia levels. When the external temperature changes, the carrier transport within the temperature-sensitive layer changes, causing a corresponding change in its resistance. The change in resistance across the temperature-sensitive layer reflects the change in external temperature. Since all four sensitive layers use resistive sensors, the number and complexity of the leads are significantly reduced compared to pure capacitive sensors or capacitive-resistive hybrid sensors, while also reducing the complexity of the back-end processing circuitry. Resistive sensors, due to their natural affinity for DC signals, eliminate concerns about parasitic capacitance, allowing for extremely simple circuit design, easy integration with data acquisition systems, and support for multi-channel distributed measurement.

[0008] In one possible implementation, the bottom flexible substrate, the second flexible substrate, and the top flexible substrate are made of PDMS material, and the third flexible substrate is made of polyimide material. And / or, the resistive pressure-sensitive layer is made of amorphous carbon material, the resistive humidity-sensitive layer and the resistive ammonia-sensitive layer are made of polyaniline or polyaniline doped with organic molecules, and the resistive temperature-sensitive layer is made of platinum metal material. And / or, the double-sided conductive tape is a double-sided conductive copper tape. These materials are chosen because they offer good stability and conductivity.

[0009] In one possible implementation, the total thickness of the resistive flexible multifunctional sensor is 1mm-1.2mm.

[0010] In one possible implementation, the pressure-sensitive layer has a wrinkled morphology and a thickness of 800nm-1200nm.

[0011] In one possible implementation, the resistive temperature-sensitive layer has a serpentine structure with a thickness of 150nm-250nm and a linewidth of 150μm-250μm.

[0012] In one possible implementation, the thickness of the bottom flexible substrate is 400μm-600μm, the thickness of the second flexible substrate is 100μm-200μm, the thickness of the third flexible substrate is 100μm-200μm, and the thickness of the top flexible substrate is 200μm-400μm. These dimensional choices are preferred values ​​based on the material selection.

[0013] In one possible implementation, one strip of double-sided conductive tape is applied to each side of the upper surface of the resistive pressure-sensitive layer, completely covering both edges. Full edge coverage ensures better conductivity.

[0014] A second aspect of the present invention provides a method for manufacturing a resistive flexible multifunctional sensor, comprising the following steps: Step S1: Use magnetron sputtering to grow a resistive pressure-sensitive layer on the bottom flexible substrate, and connect double-sided conductive tape to the upper surface of the resistive pressure-sensitive layer. Step S2: Platinum metal is grown on the upper surface of the third flexible substrate using photolithography and electron beam to form a resistive temperature sensitive layer. A second metal thin film is sputtered at both ends of the resistive temperature sensitive layer using magnetron sputtering. Step S3: Use laser printing technology to cut out the first and second notches on the third flexible substrate. Attach the resistive humidity-sensitive layer and the resistive ammonia-sensitive layer to the lower surfaces of the first and second notches of the third flexible substrate, respectively. Use magnetron sputtering to sputter the second metal film at both ends of the resistive temperature-sensitive layer. Step S4: Prepare PDMS and curing agent by mass ratio (9~11):1 and spin coat them onto the resistive pressure sensitive layer obtained in step S1. Cure the layer to form a second flexible substrate. Then attach the third flexible substrate obtained in step S3 to the upper surface of the second flexible substrate. Step S5: Prepare PDMS and curing agent at a mass ratio of (9~11):1 and spin-coat the upper surface of the third flexible substrate obtained in step S4, and cure to form the top flexible substrate; Step S6: Hollow out the top flexible substrate at the first and second notches to form the third and fourth notches respectively, to obtain the resistive flexible multifunctional sensor.

[0015] In one possible implementation, the curing agent is Dow Corning SYLGARD 184.

[0016] A third aspect of the present invention provides an application of a resistive flexible multifunctional sensor in measuring temperature, pressure, humidity, and ammonia.

[0017] The beneficial effects of this invention are as follows: (1) The sensor of the present invention is a flexible multifunctional sensor based on the principle of all-resistive sensing, which can simultaneously detect temperature, pressure, humidity and ammonia.

[0018] (2) Because all sensors are resistive, the number and complexity of the device leads are reduced, as well as the complexity of the back-end processing circuit. The sensor significantly reduces the number of leads, simplifies the device structure and back-end circuit design, and is flexible enough to fit closely to flexible curved surfaces. The sensor can be used in conjunction with smart devices such as smartphones and smart bracelets to achieve real-time acquisition and analysis of relevant physiological indicators of the human body.

[0019] (3) The flexible multifunctional sensor provided by the present invention realizes the integrated design of four resistive sensors, which reduces the complex work of measuring with four different sensors, reduces workload, and shortens time cost.

[0020] (4) The flexible multifunctional sensor provided by the present invention realizes multiple functions of sensing through a simple resistance acquisition circuit, and improves the sensing accuracy of the device and reduces the data coupling between various physical quantities through temperature compensation. Attached Figure Description

[0021] Figure 1 This is an exploded view of the flexible multifunctional sensor constructed according to the present invention; Figure 2 This is a schematic diagram of a flexible multifunctional sensor constructed according to the present invention for measuring dynamic pressure and pressure response, where F represents the direction of pressure. Figure 3 This is a schematic diagram of the temperature-sensitive layer constructed according to the present invention for temperature measurement and temperature response; Figure 4 This is a schematic diagram of a humidity-sensitive layer constructed according to the present invention for humidity measurement and humidity response; Figure 5 This is a schematic diagram of an ammonia-sensitive layer constructed according to the present invention for ammonia measurement and ammonia response; Figure 6This is a schematic diagram of the flexible multifunctional sensor constructed according to the present invention used in electronic masks; Figure 7 This is a block diagram of the measurement procedure logic of the flexible multifunctional sensor constructed according to the present invention; Figure 8 This is an exploded view of the fabrication process of the multi-module flexible sensor constructed according to the present invention.

[0022] Explanation of reference numerals in the attached figures: 1. Bottom flexible substrate; 2. Pressure-sensitive layer; 3. Double-sided conductive tape; 4. Second flexible substrate; 5. Humidity-sensitive layer; 6. Ammonia-sensitive layer; 7. First metal film; 8. Third flexible substrate; 801. First notch; 802. Second notch; 9. Temperature-sensitive layer; 10. Second metal film; 11. Top flexible substrate; 1101. Third notch; 1102. Fourth notch. Detailed Implementation

[0023] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0024] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] Unless otherwise defined, all terms, symbols and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. All reagents and instruments used in this invention are commercially available.

[0026] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "inner," "outer," "front," "rear," "head," and "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0027] like Figure 1As shown, the present invention provides a resistive flexible multifunctional sensor: from bottom to top, it includes a bottom flexible substrate 1, a pressure-sensitive layer 2, a second flexible substrate 4, a third flexible substrate 8, a temperature-sensitive layer 9, and a top flexible substrate 11. The pressure-sensitive layer 2 is encapsulated by the bottom flexible substrate 1 and the second flexible substrate 4. A double-sided conductive tape 3 is attached to the upper surface of the pressure-sensitive layer 2 and extends beyond the bottom flexible substrate 1. A humidity-sensitive layer 5 and an ammonia-sensitive layer 6 are attached side by side to the lower surface of the third flexible substrate 8. The humidity-sensitive layer 5 and the ammonia-sensitive layer 6 are encapsulated by the second flexible substrate 4 and the third flexible substrate 8. The temperature-sensitive layer 9 is disposed on the top surface of the third flexible substrate 8 and encapsulated by the top flexible substrate 11. Notches are formed on both the third flexible substrate 8 and the top flexible substrate 11. The notches penetrate the third flexible substrate 8 and the top flexible substrate 11 and are located directly above the humidity-sensitive layer 5 and the ammonia-sensitive layer 6. Specifically, the notches include a first notch 801 and a second notch 802 disposed on the third flexible substrate, and a third notch 1101 and a fourth notch 1102 disposed on the top flexible substrate 11. The first notch 801 and the second notch 802 are disposed away from the temperature-sensitive layer 9. The first notch 801 and the third notch 1101 are disposed directly above the humidity-sensitive layer 5, and the second notch 802 and the fourth notch 1102 are disposed directly above the ammonia-sensitive layer 6.

[0028] The bottom flexible substrate 1, the second flexible substrate 4 and the top flexible substrate 11 are made of PDMS material, and the third flexible substrate 8 is made of polyimide material.

[0029] like Figure 1 As shown, to facilitate wire bonding, a first metal thin film 7 is formed by sputtering metal (such as Au, Cu, Ag) along the edges of the humidity-sensitive layer 5 and the ammonia-sensitive layer 6 using magnetron sputtering technology. Specifically, a first notch 801 and a second notch 802 are cut out on the third flexible substrate 8. Then, the first metal thin film 7 is sputtered on both sides of the first notch 801 and both sides of the second notch 802 to form electrodes. The humidity-sensitive layer 5 and the ammonia-sensitive layer 6 are then attached to the first notch 801 and the second notch 802, respectively. Additionally, before encapsulating the top flexible substrate 11, a second metal thin film 10 is sputtered along the edges of both ends of the temperature-sensitive layer 9 using magnetron sputtering technology to form electrodes. In use, silver paste is applied to the electrodes to form wires. Figure 3 a, Figure 4 a, Figure 5 The diagram of the lead wire in a is shown.

[0030] like Figure 2As shown in Figure a, the pressure-sensitive layer 2 is configured with a wrinkled morphology, and double-sided conductive tape 3 is used as an electrode. When the pressure-sensitive layer 2 is subjected to stress, its morphology deforms, causing a change in its resistance. The change in resistance at both ends of the pressure-sensitive layer 2 reflects the change in external pressure. Preferably, the pressure-sensitive layer 2 is made of amorphous carbon material, and commercially available amorphous carbon material can be used. The double-sided conductive tape 3 is made of double-sided conductive copper tape. The thickness of the pressure-sensitive layer 2 is 800nm-1200nm, and its length and width are bonded to the underlying flexible substrate 1. The double-sided conductive tape 3 is attached to the edge of the pressure-sensitive layer 2.

[0031] like Figure 3 As shown in Figure a, the temperature-sensitive layer 9 is made of a noble metal material and has a serpentine structure. A second metal thin film 10 is disposed at both ends of the temperature-sensitive layer 9. The thickness of the temperature-sensitive layer 9 is 150 nm-250 nm, and the linewidth is 150 μm-250 μm. The temperature-sensitive layer 9 is preferably made of platinum metal, and the second metal thin film 10 is also preferably platinum metal. When the external temperature changes, the carrier transport within the temperature-sensitive layer 9 changes, causing a corresponding change in its resistance. The change in resistance at both ends of the temperature-sensitive layer 9 reflects the change in external temperature. Therefore, the temperature-sensitive layer 9 should be made of a temperature-sensitive material, preferably platinum metal with good conductivity. Simultaneously, the serpentine structure design increases the sensitivity of temperature measurement and reduces the influence of strain on the temperature-sensitive layer 9.

[0032] like Figure 4 a and Figure 5 As shown in Figure a, the resistive humidity-sensitive layer 5 and the resistive ammonia-sensitive layer 6 are preferably made of polyaniline or polyaniline-doped with organic molecules. The humidity-sensitive layer 5 and the ammonia-sensitive layer 6 are bonded to the third flexible substrate 8 using a flip-chip method. A first metal film 7 is provided at both ends of both the humidity-sensitive layer 5 and the ammonia-sensitive layer 6. The first metal film 7 is preferably made of Au, Cu, or Ag metal. The third flexible substrate 8 and the top flexible substrate 11 have notches directly above the humidity-sensitive layer 5 and the ammonia-sensitive layer 6, allowing changes in ambient ammonia and humidity to cause changes in the resistance of the corresponding sensitive layers. By measuring the changes in resistance at both ends of the humidity-sensitive layer 5 and the ammonia-sensitive layer 6, changes in external humidity and ammonia levels can be detected. To better sense changes in ambient humidity and ammonia, two first metal films 7 on the humidity-sensitive layer 5 and two first metal films 7 on the ammonia-sensitive layer 6 are attached to the edges of the humidity-sensitive layer 5 and the ammonia-sensitive layer 6, respectively.

[0033] The thickness of the bottom flexible substrate 1 of the resistive flexible multifunctional sensor referred to in this invention is 400μm-600μm, the thickness of the second flexible substrate 4 is 100μm-200μm, the thickness of the third flexible substrate 8 is 100μm-200μm, the thickness of the top flexible substrate 11 is 200μm-400μm, and the total thickness of the resistive flexible multifunctional sensor is ultimately controlled to be 1mm-1.2mm.

[0034] like Figure 6 The diagram illustrates the application of the resistive flexible multifunctional sensor of this invention in an electronic mask. The electronic mask, equipped with the flexible multifunctional sensor, includes a pressure sensor to detect changes in human respiratory rate, a temperature sensor to monitor temperature changes in exhaled air, a humidity sensor to detect humidity changes in exhaled air, and an ammonia sensor to detect the ammonia content in exhaled air. Even when not worn, the electronic mask can detect ambient temperature and humidity. By monitoring changes in the resistance of each sensor and uploading the data via Bluetooth to a mobile phone or computer, real-time and comprehensive monitoring of human health indicators can be achieved.

[0035] Figure 7 The measurement program logic block diagram of the resistive flexible multifunctional sensor of the present invention is given. First, the resistance of the temperature-sensitive layer 9 is read, which is a function of temperature, and the current temperature is output. Then, the resistances of the pressure-sensitive layer 2, humidity-sensitive layer 5, and ammonia-sensitive layer 6 are measured sequentially, and their resistances are functions of pressure and temperature, humidity and temperature, and ammonia concentration and humidity, respectively. The temperature measured by the temperature sensor is used to compensate for the corresponding resistances, thereby outputting the current pressure, humidity, and ammonia concentration.

[0036] like Figure 8 The diagram shown is an exploded flowchart of the fabrication method of the resistive flexible multifunctional sensor of the present invention. The fabrication method includes the following steps: Part 1: Lower-level unit fabrication A bottom flexible substrate 1 is provided. Using magnetron sputtering technology with a graphite target as the target material, an amorphous carbon film with a wrinkled morphology is deposited on the surface of the flexible substrate to obtain a pressure-sensitive layer 2. Then, double-sided conductive tape 3 is applied to the surface of the amorphous carbon film at intervals to form two electrodes. PDMS and curing agent are spin-coated on the pressure-sensitive layer 2 in a ratio of (11~9):1 and cured to form a second flexible substrate 4. The second flexible substrate 4 is encapsulated with the bottom flexible substrate 1 with the amorphous carbon film deposited using PDMS encapsulation technology to complete the preparation of the lower unit.

[0037] Part Two: Upper-Level Unit Fabrication A third flexible substrate 8 is provided. A platinum thin film is deposited on the upper surface of the third flexible substrate 8 using photolithography and electron beam deposition to form a temperature-sensitive layer 9. Then, laser photolithography and electron beam deposition are used to cut out perforated structures at corresponding positions on the third flexible substrate 8, forming a first notch 801 and a second notch 802. Humidity-sensitive patches and ammonia-sensitive patches are then attached upside down onto the perforated first notch 801 and second notch 802 to form a humidity-sensitive layer 5 and an ammonia-sensitive layer 6. A second metal thin film 10 is sputtered onto both ends of the temperature-sensitive layer 9, and a first metal thin film 7 is sputtered onto both ends of the humidity-sensitive layer 5 and the ammonia-sensitive layer 6. Laser printing technology is used to cut out the top flexible substrate 11 at positions opposite the humidity-sensitive layer 5 and the ammonia-sensitive layer 6, forming a third notch 1101 and a fourth notch 1102. PDMS packaging technology is used to encapsulate the top flexible substrate 11 and the third flexible substrate 8 to complete the fabrication of the upper-layer unit. Finally, the upper-layer unit and the lower-layer unit are encapsulated to obtain the resistive flexible multifunctional sensor.

[0038] The present invention will be further described below with reference to specific embodiments.

[0039] Example 1 The first part, the fabrication of the lower-layer units, specifically includes: PDMS and curing agent Dow Corning SYLGARD 184 were mixed at a weight ratio of 10:1 and applied to a glass substrate. The mixture was then homogenized on a spin coater at a speed of 2000 rpm and cured in an oven at 60°C for 6 hours to obtain the bottom flexible substrate.

[0040] Amorphous carbon film was deposited on the surface of the flexible substrate using magnetron sputtering technology. The substrate was placed in a reaction chamber at a pressure of 0.7 Pa, and an inert gas was used as the sputtering gas. A graphite target was sputtered at a DC power of 1.1 kW to form the film. The sputtering gas flow rate was 55 sccm, the substrate rotation speed was 20 rpm, the deposition temperature was 23 °C, and the deposition time was 200 min. Double-sided copper tape was then attached to the surface of the amorphous carbon film to serve as an electrode.

[0041] PDMS and curing agent Dow Corning SYLGARD 184 were mixed at a weight ratio of 10:1 and coated onto an amorphous carbon film. The mixture was then cured in an oven at 60°C for 6 hours to obtain the second flexible substrate 4 and its encapsulation layer.

[0042] The second part, the fabrication of the upper-layer unit, specifically includes: A polyimide substrate was provided as the third flexible substrate 8. The polyimide substrate was treated with an ultrasonic cleaner for 5-10 minutes. LOR3A photoresist was coated onto the front side of the polyimide substrate using a spin coater. The spin coater was set to a speed of 600 rpm and an acceleration of 2000 rpm, held for 10 seconds, then the speed was increased to 4500 rpm and the acceleration to 2000 rpm, held for 60 seconds. After that, it was baked on a 170°C heating stage for 60 seconds. S1805 photoresist was then coated onto the polyimide substrate coated with LOR3A photoresist using a spin coater. The spin coater was set to a speed of 2000 rpm and an acceleration to 2000 rpm, held for 10 seconds, then the speed was increased to 6000 rpm and the acceleration to 2000 rpm, held for 60 seconds, and then baked on a 105°C heating stage for 60 seconds. Then, a serpentine pattern was etched onto the photoresist using a photolithography machine with an exposure time of 5.5 s and an exposure distance of 50 μm. Afterward, it was developed using a ZX238 for 45 s. Next, 10-20 nm of titanium and 100-200 nm of platinum were sequentially deposited onto the serpentine pattern using electron beam evaporation to obtain a temperature-sensitive layer 9 and a platinum second metal film 10 bonded to it. The prepared sample was then immersed in an NMP stripper at 90 °C for 15 minutes to remove the photoresist, resulting in a polyimide substrate with the temperature-sensitive layer 9.

[0043] LOR3A photoresist was coated onto the back side of a flexible polyimide substrate using a spin coater. The spin coater was set to a speed of 600 rpm and an acceleration of 2000 rpm for 10 seconds, followed by a speed of 4500 rpm and an acceleration of 2000 rpm for 60 seconds. The substrate was then baked on a 170°C heating stage for 60 seconds. Next, S1805 photoresist was coated onto the lower surface of the polyimide substrate coated with LOR3A photoresist using a spin coater. The spin coater was set to a speed of 2000 rpm and an acceleration of 2000 rpm for 10 seconds, followed by a speed of 6000 rpm and an acceleration of 2000 rpm for 60 seconds. The substrate was then baked on a 105°C heating stage for 60 seconds. Lead patterns were then etched onto the photoresist using a photolithography machine with an exposure time of 5.5 seconds and an exposure distance of 50 μm. The substrate was then developed using a ZX238 for 45 seconds. Then, Au first metal thin film 7 was sputtered on the lead pattern using magnetron sputtering as an electrode. Finally, the obtained sample was placed in NMP stripper at 90°C for 15 minutes to remove the photoresist.

[0044] A 1mm long and 1mm wide hollow pattern is engraved on the corresponding position of the polyimide substrate using laser engraving technology. The humidity-sensitive layer 5 and the ammonia-sensitive layer 6 are then bonded to the corresponding position on the back of the polyimide substrate using a flip-chip method, facing the hollow pattern. A humidity sensor is formed by combining the Au first metal film 7 on the edge of the humidity-sensitive layer 5, and an ammonia sensor is formed by combining the Au first metal film 7 on the edge of the ammonia-sensitive layer 6. A top flexible substrate 11 is used to encapsulate the humidity sensor and the ammonia sensor. PDMS and Dow Corning SYLGARD 184 curing agent are mixed at a weight ratio of 10:1 and applied to the upper surface of the polyimide substrate with the temperature-sensitive layer 9. The mixture is then homogenized on a spin coater at 2000 rpm and cured in a 60℃ oven for 6 hours to obtain the top flexible substrate 11 and its encapsulation layer. Hollow patterns are cut on the top flexible substrate 11 directly above the humidity sensor and the ammonia sensor. The encapsulation layer is then removed to obtain the lead wires.

[0045] Finally, PDMS and curing agent Dow Corning SYLGARD184 were mixed at a weight ratio of 10:1 and coated between the upper and lower units. After the upper and lower units were fixed and encapsulated, they were cured in an oven at 60°C for 6 hours to obtain an integral resistive flexible multifunctional sensor device.

[0046] The aforementioned overall resistive flexible multifunctional sensor device underwent relevant performance tests. For example... Figure 2 As shown in Figure a, a pressure in the F direction is applied to the surface of the device, and the voltage change of the pressure-sensitive layer 2 and the corresponding pressure response curve are measured within the stress range of 0-10 kPa. Figure 2 As shown in b, voltage changes are caused by resistance changes, thus illustrating that the pressure-sensitive layer 2 of this invention is a resistive sensor.

[0047] like Figure 3 As shown in Figure a, wires and instruments are connected to the two platinum leads of the temperature-sensitive layer 9 to form a circuit to test the resistance change of the temperature-sensitive layer 9, and then the temperature response curve is obtained as shown in Figure a. Figure 3 As shown in Figure b, it can be seen from the figure that the resistance changes are sensitive in the range of -20 to 80℃, the test accuracy is high, and it can well reflect the temperature changes of the test environment.

[0048] like Figure 4 As shown in Figure a, wires and instruments are connected to the two gold electrodes of the humidity-sensitive layer 5 to form a circuit to test the resistance change of the humidity-sensitive layer 5, and the response curve of the humidity-sensitive layer 5 to the sensitive source is obtained as shown in Figure a. Figure 4 As shown in Figure b, the response rate can reach 94% when the test time is over 1400s.

[0049] like Figure 5As shown in Figure a, wires and instruments are connected to the two gold electrodes of the ammonia gas sensitive layer 6 to form a circuit to test the resistance change of the ammonia gas sensitive layer 6, and the response curve of the ammonia gas sensitive layer 6 to the sensitive source is obtained as shown in Figure a. Figure 5 As shown in Figure b, it can be seen from the figure that a response can be obtained starting from an ammonia concentration of 15 ppb, indicating that the sensor prepared by this invention can effectively detect changes in ammonia concentration.

[0050] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A resistive flexible multifunctional sensor, characterized in that, The system comprises, from bottom to top, a bottom flexible substrate (1), a resistive pressure-sensitive layer (2), a second flexible substrate (4), a third flexible substrate (8), a resistive temperature-sensitive layer (9), and a top flexible substrate (11). The upper surface of the resistive pressure-sensitive layer (2) is connected to both sides with double-sided conductive tape (3). The lower surface of the third flexible substrate (8) is fitted with a resistive humidity-sensitive layer (5) and a resistive ammonia-sensitive layer (6). Both ends of the resistive humidity-sensitive layer (5) and the resistive ammonia-sensitive layer (6) are provided with a first metal film (7). The third... A first notch (801) and a third notch (1101) are respectively formed on the third flexible substrate (8) and the top flexible substrate (11). The first notch (801) and the third notch (1101) are located directly above the humidity-sensitive layer (5). A second notch (802) and a fourth notch (1102) are also formed on the third flexible substrate (8) and the top flexible substrate (11). The second notch (802) and the fourth notch (1102) are located directly above the ammonia-sensitive layer (6). A second metal thin film (10) is provided at both ends of the resistive temperature-sensitive layer (9).

2. The resistive flexible multifunctional sensor according to claim 1, characterized in that, The bottom flexible substrate (1), the second flexible substrate (4), and the top flexible substrate (11) are made of PDMS material, and the third flexible substrate (8) is made of polyimide material. And / or, the resistive pressure-sensitive layer (2) is made of amorphous carbon material, the resistive humidity-sensitive layer (5) is made of polyaniline or polyaniline-doped with organic molecules, the resistive ammonia-sensitive layer (6) is made of polyaniline or polyaniline-doped with organic molecules, and the resistive temperature-sensitive layer (9) is made of platinum metal material. And / or, the double-sided conductive tape (3) is a double-sided conductive copper tape.

3. The resistive flexible multifunctional sensor according to claim 2, characterized in that, The total thickness of the resistive flexible multifunctional sensor is 1mm-1.2mm.

4. The resistive flexible multifunctional sensor according to claim 3, characterized in that, The resistive pressure-sensitive layer (2) has a wrinkled morphology and a thickness of 800nm-1200nm.

5. The resistive flexible multifunctional sensor according to claim 3, characterized in that, The resistive temperature sensitive layer (9) has a serpentine structure with a thickness of 150nm-250nm and a linewidth of 150μm-250μm.

6. The resistive flexible multifunctional sensor according to claim 3, characterized in that, The thickness of the bottom flexible substrate (1) is 400μm-600μm, the thickness of the second flexible substrate (4) is 100μm-200μm, the thickness of the third flexible substrate (8) is 100μm-200μm, and the thickness of the top flexible substrate (11) is 200μm-400μm.

7. The resistive flexible multifunctional sensor according to claim 2, characterized in that, One strip of the double-sided conductive tape (3) is attached to each side of the upper surface of the resistive pressure sensitive layer (2), and both strips completely cover the edges of both sides.

8. The method for manufacturing a resistive flexible multifunctional sensor according to any one of claims 1-7, characterized in that, Includes the following steps: Step S1: Use magnetron sputtering to grow a resistive pressure sensitive layer (2) on the bottom flexible substrate (1), and connect double-sided conductive tape (3) to the upper surface of the resistive pressure sensitive layer (2). Step S2: Platinum metal is grown on the upper surface of the third flexible substrate (8) using photolithography and electron beam to form a resistive temperature sensitive layer (9), and a second metal thin film (10) is sputtered at both ends of the resistive temperature sensitive layer (9) using magnetron sputtering. Step S3: Use laser printing technology to cut out a first notch (801) and a second notch (802) on the third flexible substrate (8). Attach the resistive humidity-sensitive layer (5) and the resistive ammonia-sensitive layer (6) to the lower surfaces of the first notch (801) and the second notch (802) of the third flexible substrate (8), respectively. Use magnetron sputtering to sputter a first metal thin film (7) at both ends of the resistive humidity-sensitive layer (5) and the resistive ammonia-sensitive layer (6). Step S4: Prepare PDMS and curing agent by mass ratio (9~11):1 and spin coat them onto the resistive pressure sensitive layer (2) obtained in step S1. Cure to form the second flexible substrate (4). Then attach the third flexible substrate (8) obtained in step S3 to the upper surface of the second flexible substrate (4). Step S5: Prepare PDMS and curing agent by mass ratio (9~11):1 and spin coat them onto the upper surface of the third flexible substrate (8) obtained in step S4, and cure to form the top flexible substrate (11). Step S6: A third notch (1101) and a fourth notch (1102) are formed on the top flexible substrate (11) opposite to the first notch (801) and the second notch (802), respectively, to obtain the resistive flexible multifunctional sensor.

9. The manufacturing method according to claim 8, characterized in that, The curing agent is Dow Corning SYLGARD 184.

10. The application of a resistive flexible multifunctional sensor according to any one of claims 1-7 in measuring temperature, pressure, humidity and ammonia.

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