An attachable flexible temperature sensor and a preparation method and application thereof

Abstract

The application provides a wearable flexible temperature sensor, a preparation method and application thereof. The temperature sensor comprises a substrate, a semiconductor layer and an electrolyte layer in sequence; an electrode is further included in the temperature sensor; and the electrolyte in the electrolyte layer is a gel electrolyte. The temperature sensor has an ion gel gated electrochemical transistor sensor with adjustable sensing sensitivity, and based on the adjustable controllability of the property change and ion migration behavior caused by the phase transition of the temperature-dependent ion gel layer, the temperature sensing response with adjustable temperature sensitive area, high sensitivity and fast response is developed, and the application research of the wearable flexible temperature electronic sensor is successfully promoted.

Description

Technical Field

[0001] This invention belongs to the field of flexible electronic sensors and smart wearable technology, and relates to an attachable flexible temperature sensor, its preparation method and application. Background Technology

[0002] With the development of the times, wearable devices themed around smart interconnection and big health have received widespread attention. The development of wearable devices requires electronic sensors to perceive human physical and physiological signals, and they need to be thin, flexible, and conformally contactable with the skin (Lou Z, Chen S, Wang L, et al. Nano Energy, 2017, 38:28-35). Furthermore, constructing wearable devices with temperature sensing capabilities plays a crucial role in detecting body temperature and sensing ambient temperature.

[0003] Organic electronic sensors are devices that convert physical or physiological signals into electrical signals, and are widely used in fields such as medical health, industrial production, and national defense. One type of organic field-effect transistor (OFET), which uses organic semiconductors as the active layer, has signal conversion and signal amplification capabilities (Rivnay J. et al., Nature Reviews Materials, 2018, 3(2): 1-14), and also has advantages such as solution-processability, intrinsic flexibility, and easy integration, providing a good carrier for wearable flexible temperature sensing devices. However, traditional OFETs consume a lot of power, while organic electrochemical transistors with liquid electrolytes as insulating layers suffer from problems such as poor stability, slow temperature response speed, and low response sensitivity. Furthermore, the mechanism of adjusting the sensitive region of temperature response as needed is not well understood. Therefore, constructing reliable, low-power temperature sensing transistors still faces challenges. Summary of the Invention

[0004] To address the shortcomings of current technologies, this invention proposes a class of ion-gel gated electrochemical transistor sensors with tunable sensing sensitivity. Based on the tunable property changes and ion migration behavior caused by temperature-dependent phase transitions in the ion-gel layer, a highly sensitive and fast-responding temperature sensing response with a tunable temperature-sensitive region has been developed, successfully advancing the application research of wearable flexible temperature electronic sensing. Specifically, this invention provides the following technical solution:

[0005] A temperature sensor is provided, comprising a substrate, a semiconductor layer, and an electrolyte layer in sequence; the temperature sensor also includes electrodes; wherein the electrolyte in the electrolyte layer is a gel electrolyte.

[0006] According to an embodiment of the present invention, the temperature sensor is preferably a flexible temperature sensor.

[0007] According to an embodiment of the invention, the temperature sensor is attachable; specifically, it is suitable for use as a sensor in wearable devices.

[0008] According to an embodiment of the present invention, the semiconductor layer is an organic semiconductor layer. Specifically, the organic semiconductor may include at least one or a mixture of two or more semiconductors selected from polythiophene semiconductors, pyrrolopyrrole semiconductors, or naphthalimide semiconductors. Preferably, the semiconductor layer includes at least one selected from PEDOT:PSS, PBTTT, P3HT, DPP2T-TT, P(g2T-TT), and PgBTTT.

[0009] According to an embodiment of the present invention, the thickness of the semiconductor layer can be 10-1000 nm, preferably 20-100 nm, for example 50 nm.

[0010] According to an embodiment of the present invention, the gel material in the gel electrolyte is selected from at least one of eutectic gel, ionogel, hydrogel, iono-liquid crystal elastomer, or a composite gel including the above gel materials.

[0011] Preferably, the eutectic gel is selected from at least one of the following: choline chloride and polyvinyl alcohol (PVA) and polyacrylic acid (PAA) composite eutectic gel, choline chloride and polyacrylamide (PAAM) eutectic gel, ethylene glycol (EG) and ZnCl2 and cellulose acetate eutectic gel.

[0012] Preferably, the ionic gel comprises an ionic liquid and a polymer, wherein the ionic liquid has a mass content of 10-50 wt%, for example, 50 wt%. Further, the ionic liquid is selected from ionic liquids known in the art, such as [EMIM][TFSI]. Further, the polymer is selected from polymethyl methacrylate (PMMA), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), and polyethylene oxide (PEO). Exemplarily, the ionic gel is selected from at least one of [EMIM][TFSI] / PMMA, [EMIM][TFSI] / PVDF-HFP, [EMIM][TFSI] / PEO, etc.

[0013] Preferably, the hydrogel is selected from at least one of polyacrylamide gel, polyamide gel, sodium alginate, and gelatin.

[0014] Preferably, the ionic liquid crystal elastomer is selected from at least one of azobenzene liquid crystal elastomers, polysiloxane liquid crystal elastomers, and cholesteric liquid crystal elastomers.

[0015] Preferably, the composite gel comprises an inorganic non-metallic material and a gel material selected from at least one of eutectic gels, ionogels, hydrogels, and ion-liquid crystal elastomers. Further, the inorganic non-metallic material comprises at least one of graphene and carbon nanotubes.

[0016] According to an embodiment of the present invention, the thickness of the electrolyte layer can be 1-5000 μm, preferably 1-50 μm, for example, 5 μm. The inventors have found that when the thickness of the electrolyte layer is too thick (e.g., greater than 5000 μm), the sensor response speed is slow, and the sensor performance is difficult to stabilize and repeat.

[0017] According to an embodiment of the present invention, the electrode includes a source electrode, a drain electrode, and a gate electrode, wherein the source electrode, drain electrode, and gate electrode are disposed independently on the surface of the same layer or different layers.

[0018] According to an embodiment of the present invention, the substrate is selected from rigid substrates and / or flexible substrates, preferably flexible substrates.

[0019] Preferably, the rigid substrate is selected from at least one of glass substrates, Si / SiO2 substrates, etc. Preferably, the flexible substrate is selected from at least one of PI film, PET film, PDMS film, etc.

[0020] According to an embodiment of the present invention, the thickness of the substrate is not specifically limited, and a thickness known in the art can be used.

[0021] According to embodiments of the present invention, the source electrode, drain electrode, and gate electrode are made of the same or different materials, and are independently selected from at least one of metals, alloys, metal oxides, electrochemical electrodes, semiconductor electrodes, conductive polymers, and inorganic conductive materials. Preferably, the source electrode, drain electrode, and gate electrode are all made of different materials. Preferably, the source electrode and drain electrode are made of the same material, but different from the gate electrode. Exemplarily, the source electrode and drain electrode are selected from metals, and the gate electrode is a combination of an inorganic conductive material and a semiconductor electrode.

[0022] Preferably, the metal is selected from at least one of gold, silver, chromium, aluminum, and copper. Preferably, the alloy is selected from at least one of platinum alloys, magnesium-aluminum alloys, and titanium alloys. Preferably, the metal oxide is selected from at least one of indium tin oxide, manganese dioxide, and ruthenium dioxide. Preferably, the electrochemical electrode is selected from at least one of platinum-carbon electrodes, calomel electrodes, and silver / silver chloride electrodes. Preferably, the semiconductor electrode is selected from inorganic electrodes and / or organic electrodes, such as at least one of doped inorganic silicon electrodes, organic semiconductors (poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid)PEDOT:PSS, P(g2T-TT) optopolymers, etc. Preferably, the conductive polymer is selected from at least one of polypyrrole and polyaniline. Preferably, the inorganic conductive material is selected from at least one of carbon nanotubes, graphene, and conductive carbon paste.

[0023] For example, the source electrode and drain electrode are made of chromium and / or gold, and the gate electrode is made of gold.

[0024] According to an embodiment of the present invention, the source electrode and the drain electrode are disposed on the same surface of the same layer, for example, on the surface of the substrate or the same surface of the semiconductor layer, preferably between the substrate and the semiconductor layer, or between the semiconductor layer and the electrolyte layer. Preferably, the source electrode and the drain electrode can be parallel plate electrodes or interdigitated electrodes. Further, the distance between the source electrode and the drain electrode is 5 μm-1000 μm, preferably 5-100 μm, for example 20 μm, 30 μm, 40 μm, or 50 μm. Preferably, the thickness of the source electrode and the drain electrode is the same or different, independently selected from 10-1000 nm, preferably 10-100 nm, for example 20 nm, 30 nm, 40 nm, or 50 nm.

[0025] According to an embodiment of the present invention, the gate electrode may be disposed on the surface of the substrate, the surface of the semiconductor layer, or the surface of the electrolyte layer, preferably on the surface of the substrate or the surface of the electrolyte layer. Preferably, the thickness of the gate electrode is 10-1000 nm, more preferably 10-100 nm, for example 20 nm, 30 nm, 40 nm, or 50 nm.

[0026] In this invention, the substrate, semiconductor layer, electrolyte layer, and electrode are selected from materials that are flexible and stretchable, thereby giving the temperature sensor a flexible and attachable performance.

[0027] The present invention also provides a method for preparing the above-mentioned temperature sensor, wherein the preparation method includes at least the step of setting a gel electrolyte layer.

[0028] According to an embodiment of the present invention, the step of setting the gel electrolyte layer specifically includes:

[0029] The raw materials for forming the gel electrolyte layer are prepared and the electrolyte layer is obtained by at least one of the following methods: photocoupling, spin coating / drop coating, casting, spraying or 3D printing, etc.

[0030] According to an embodiment of the present invention, the preparation method specifically includes:

[0031] A source electrode and a drain electrode are respectively disposed on the surface of a substrate, followed by the sequential placement of a semiconductor layer, a gel electrolyte layer, and a gate electrode to obtain the temperature sensor;

[0032] Alternatively, a source electrode, a drain electrode, and a gate electrode can be respectively disposed on the substrate surface, followed by the sequential deposition of a semiconductor layer and a gel electrolyte layer to obtain the temperature sensor.

[0033] According to an embodiment of the present invention, the substrate can be cleaned using known methods.

[0034] According to an embodiment of the present invention, the method for forming a source electrode and a drain electrode on a substrate surface specifically involves fabricating the source electrode and the drain electrode on the substrate using a vacuum thermal deposition method. Preferably, the vacuum thermal deposition method can be performed under conditions known in the art, as long as the source electrode and the drain electrode can be obtained.

[0035] According to an embodiment of the present invention, the semiconductor layer can be prepared by any one of the following processes: spin coating, drop coating, shear stretching, vapor deposition, and roll-to-roll printing.

[0036] According to an embodiment of the present invention, the gate electrode can be prepared by at least one of the following methods: lamination (e.g., laminating flexible metal electrodes), shear stretching, spin coating (e.g., spin coating semiconductors), deposition, spraying (e.g., spraying inorganic non-metallic conductive materials), vapor deposition (e.g., vapor deposition of metals or alloys), and 3D printing.

[0037] According to an embodiment of the present invention, the semiconductor layer and / or electrolyte layer may further undergo annealing. Preferably, the annealing conditions are: annealing at or above 50°C for at least 10 minutes, for example, annealing at 50-100°C for 10-60 minutes.

[0038] According to an exemplary embodiment of the present invention, the specific steps of the preparation method are as follows:

[0039] (1) The source electrode and the drain electrode were fabricated on a flexible substrate by vacuum thermal deposition.

[0040] (2) An organic semiconductor layer is prepared on the surface of a flexible substrate with source and drain electrodes by spin coating and then annealed.

[0041] (3) An electrolyte layer is deposited on the surface of the organic semiconductor layer and then annealed.

[0042] (4) A gate electrode is prepared on the surface of the electrolyte layer by lamination, wherein the material of the gate electrode is a gold-plated PI thin film and spin-coated P(g2T-TT) semiconductor.

[0043] The present invention also provides applications of the above-described temperature sensor, such as in wearable devices.

[0044] The present invention also provides a wearable device comprising the temperature sensor described above.

[0045] The beneficial effects of this invention are:

[0046] 1. This invention provides an electronic sensor with temperature sensing capabilities, making it particularly suitable for wearable devices. Specifically, this invention proposes a class of ion-gel gated electrochemical transistor sensors with tunable sensing sensitivity. Based on the tunability of property changes and ion migration behavior caused by temperature-dependent phase transitions in the ion gel layer, a temperature sensing response with tunable temperature-sensitive region, high sensitivity, and fast response has been developed, successfully advancing the application research of wearable flexible temperature electronic sensors. This invention provides a temperature sensor based on the effect of temperature on the ion dynamics of the device, which influences the device's electrical performance. The temperature sensor can also be used to study temperature dependence relationships.

[0047] 2. Specifically, this invention selects an organic semiconductor whose mobility is greatly affected by temperature as the semiconductor layer and a gel electrolyte whose ionic conductivity is greatly affected by temperature as the electrolyte layer, thereby achieving real-time temperature monitoring. Furthermore, based on the flexible and stretchable properties of the substrate, semiconductor, gel, and gate materials, a flexible and attachable temperature sensor is realized.

[0048] 3. The sensor provided by this invention utilizes the amplification capability of transistors to achieve high sensitivity and high signal-to-noise ratio detection of temperature, thus realizing high-resolution temperature detection.

[0049] 4. This invention provides a method for assembling a flexible wearable temperature sensor, promoting the development of the wearable field. Attached Figure Description

[0050] Figure 1 The diagram shows the structure of a temperature sensor, where a is a schematic diagram of a temperature sensor with a top grid structure; and b is a schematic diagram of a temperature sensor with a side grid structure.

[0051] Figure 2 This is the molecular structural formula of the material used in the embodiments of the present invention.

[0052] Figure 3The following is a performance test of the temperature sensor with an ionic liquid concentration of 50% in Example 1 at room temperature, where a is the transfer characteristic curve and b is the output characteristic curve of the corresponding electronic device.

[0053] Figure 4 The temperature response performance of the temperature sensor prepared in Example 1 of the present invention is shown in (a); the current-temperature response relationship of the temperature sensor is shown in (b); and the temperature sensitivity range of the temperature sensor is shown in (c).

[0054] Figure 5 The real-time monitoring curves (a) and (b) of the response time monitoring results at different temperatures for the temperature sensor with an ion concentration of 50% prepared in Example 1 of this invention are shown.

[0055] Figure 6 This is a schematic diagram of the flexible temperature sensor prepared in Embodiment 2 of the present invention.

[0056] Figure 7 Example 2 illustrates the time-based monitoring of temperature signals from ice, tweezers, and fingers in practical applications. Detailed Implementation

[0057] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0058] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0059] Example 1

[0060] The structure of the temperature sensor prepared in Example 1 is as follows: Figure 1 As shown, the materials used are as follows Figure 2 As shown, by adjusting the proportion of ionic liquid in the electrolyte layer to regulate the glass transition temperature of the ionogel, a class of temperature sensors with tunable temperature sensitivity, high temperature sensitivity, and fast response speed has been developed. The following describes the fabrication process. Figure 1 The specific steps for fabricating the temperature sensor with the top grid structure shown in Figure a are as follows:

[0061] (1) A P(g2T-TT) organic semiconductor solution with a concentration of 7.5 mg / mL was prepared using chloroform as a solvent and stirred at room temperature for 5 h to prepare the semiconductor active layer; P(g2T-TT) is a high-performance semiconductor, and its structure is shown in the figure below. Figure 2 As shown.

[0062] (2) PMMA gel was dissolved in butyl acetate at a concentration of 180 mg / mL. After stirring at 80 °C for 24 h, ionic liquids [EMIM][TFSI] were added to obtain gel electrolytes, which were used to prepare electrolyte layers. The concentration ratios of the ionic liquids were 30%, 35%, 40%, 45%, 50%, and 55%, respectively.

[0063] (3) The glass substrate was ultrasonically cleaned with secondary water, ethanol solvent, and acetone solvent at a power of 60W. After being purged with nitrogen, a patterned metal mask was attached. Vacuum thermal deposition technology was used to sequentially vapor-deposit 5nm Cr and 25nm Au on the glass substrate as source and drain electrodes, forming a Cr-Au electrode with a thickness of 30nm.

[0064] (4) After ultrasonicating the glass substrate with the Cr-Au electrode deposited, it is purged with nitrogen and then the P(g2T-TT) organic semiconductor solution from step (1) is spin-coated onto the glass substrate to obtain a semiconductor layer with a thickness of 50 nm.

[0065] (5) The organic semiconductor layer was annealed at 65°C for 10 min, the semiconductor mask was made using PDMS, and the semiconductor thin film was patterned using plasma.

[0066] (6) Spin-coat the six gel electrolytes from step (2) onto the surface of the organic semiconductor layer from step (5) to obtain an electrolyte layer with a thickness of 5 μm, and anneal it in a vacuum oven at 50 °C for 30 minutes.

[0067] (7) Gold is deposited to a flexible PI film with a thickness of 50 μm and P(g2T-TT) is spin-coated to obtain a gate electrode. After annealing, the electrodes are laminated onto the surface of the electrolyte layer in step (6) to obtain six temperature sensors with different temperature sensitivity ranges. The concentrations of ionic liquids in the gel electrolytes corresponding to the electrolyte layers are 30%, 35%, 40%, 45%, 50%, and 55%, respectively.

[0068] This embodiment fabricated a temperature sensor with good amplification capability. Taking a device with a 50% ionic liquid concentration as an example, its transfer curve and output curve at room temperature were measured. See details below. Figure 3 .

[0069] The six temperature sensors in this embodiment exhibit temperature dependence; see [link to documentation]. Figure 4 a; the response of current to temperature is shown in section a. Figure 4 In section b, the region where the current changes most with temperature is taken as the temperature-sensitive range; see details below. Figure 4 c.

[0070] The temperature sensor in this embodiment can be used to monitor temperature changes in real time and rapidly. Taking a device with an ion concentration of 50% as an example, the current change from 30°C to 80°C is shown. (See [link]). Figure 5 For details on response time at different temperatures, please refer to section a. Figure 5 b.

[0071] Example 2

[0072] The temperature sensor prepared in this embodiment is basically the same as in Embodiment 1, except that the ion concentration in step (2) is 50%, and the only difference is that the substrate in step (3) is a 50nm flexible PI substrate; other conditions are the same as in Embodiment 1. Figure 6 As shown, this embodiment constructs a flexible, attachable temperature sensor; Figure 7 This is a real-time monitoring curve of the current change of the temperature sensor in this embodiment when touched by objects of different temperatures.

[0073] The exemplary embodiments of the present invention have been described above. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A temperature sensor, characterized in that, The temperature sensor comprises a substrate, a semiconductor layer, and an electrolyte layer in sequence; the temperature sensor also includes electrodes; wherein the electrolyte in the electrolyte layer is a gel electrolyte.

2. The temperature sensor according to claim 1, characterized in that, The temperature sensor is a flexible temperature sensor.

3. The temperature sensor according to claim 1 or 2, characterized in that, The semiconductor layer is an organic semiconductor layer; And / or, the thickness of the semiconductor layer is 10-1000 nm.

4. The temperature sensor according to any one of claims 1-3, characterized in that, The gel material in the gel electrolyte is selected from at least one of eutectic gel, ionic gel, hydrogel, ionic liquid crystal elastomer, or a composite gel including the above gel materials; And / or, the thickness of the electrolyte layer is 1-5000 μm.

5. The temperature sensor according to claim 4, characterized in that, The eutectic gel is selected from at least one of the following: choline chloride and polyvinyl alcohol (PVA) and polyacrylic acid (PAA) composite eutectic gel, choline chloride and polyacrylamide (PAAM) eutectic gel, ethylene glycol (EG) and ZnCl2 and cellulose acetate eutectic gel; And / or, the ionic gel comprises an ionic liquid and a polymer selected from polymethyl methacrylate (PMMA), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), and polyethylene oxide (PEO); And / or, the hydrogel is selected from at least one of polyacrylamide gel, polyamide gel, sodium alginate, and gelatin; And / or, the ionic liquid crystal elastomer is selected from at least one of azobenzene liquid crystal elastomers, polysiloxane liquid crystal elastomers, and cholesteric liquid crystal elastomers; And / or, the composite gel comprises an inorganic non-metallic material and a gel material selected from at least one of eutectic gels, ionogels, hydrogels, and iono-liquid crystal elastomers.

6. The temperature sensor according to any one of claims 1-5, characterized in that, The electrode includes a source electrode, a drain electrode, and a gate electrode, which are independently disposed on the surface of the same layer or different layers.

7. A method for preparing a temperature sensor according to any one of claims 1-6, characterized in that, The preparation method includes at least the step of setting a gel electrolyte layer.

8. The preparation method according to claim 7, characterized in that, The step of setting the gel electrolyte layer specifically includes: The raw materials for forming the gel electrolyte layer are prepared by at least one of the following methods: photocoupling, spin coating / drop coating, casting, spraying or 3D printing.

9. The application of the temperature sensor according to any one of claims 1-6 in a wearable device.

10. A wearable device comprising the temperature sensor according to any one of claims 1-6.

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