Organic electrochemical transistor-based temperature sensor and method of manufacturing the same

Abstract

The application discloses a temperature sensor based on an organic electrochemical transistor and a preparation method thereof. The temperature sensor comprises a substrate, a source electrode and a drain electrode arranged on the substrate, a PEDOT:PSS organic semiconductor thin film layer as a channel coated on the source electrode and the drain electrode, an electrolyte arranged on the PEDOT:PSS organic semiconductor thin film layer, and a gate electrode in contact with the electrolyte. The preparation method of the temperature sensor comprises the following steps: preparing a PEDOT:PSS mixed solution; cleaning the substrate, performing surface coating pretreatment, and then preparing the source electrode and the drain electrode on the surface of the substrate; spin-coating the PEDOT:PSS mixed solution on the surface of the source electrode and the drain electrode to obtain an organic semiconductor thin film layer channel; dropping the electrolyte on the organic semiconductor thin film layer channel, and contacting the gate electrode with the electrolyte to obtain the temperature sensor based on the organic electrochemical transistor. The application can realize real-time and accurate monitoring of body temperature.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biochemical sensors, and particularly relates to a temperature sensor based on an organic electrochemical transistor and a preparation method thereof. BACKGROUND

[0002] Among many physical indicators related to human health, body temperature is the first symptom of many diseases. The diagnosis and treatment of many diseases in clinical practice rely on the monitoring of body temperature. Through abnormal changes in body temperature, diseases can be discovered in time, and early diagnosis and treatment can greatly reduce the risk of death and disability. The mercury thermometer currently used in clinical practice can only monitor instantaneous body temperature, which can easily lead to the loss of the best diagnosis and treatment time, resulting in high mortality and disability rate. Therefore, body temperature monitoring is of great significance, and there is an urgent need for a body temperature sensor that can be accurately monitored in real time.

[0003] In recent years, flexible wearable sensors for body temperature monitoring have attracted widespread attention from researchers. Chen et al. (Sci. Rep., 2015, 5: 11505) transferred body temperature sensitive metal films (Au and Cr) to a porous structure of a semi-permeable membrane substrate to prepare a super flexible body temperature sensor. The sensor has excellent air permeability, water resistance and biocompatibility, and can be used for all-weather measurement of underarm body temperature. The temperature coefficient of resistance (TCR) is 0.278% ° / C, and the skin surface temperature change caused by flowing air and water droplets can be accurately measured. Lin et al. (Adv. Mater., 2021, 2107309) designed a hydrogen bond crosslinking network based on carboxylated styrene-butadiene rubber (XSBR) and hydrophilic sericin (SS) non-covalent modification of carbon nanotubes (CNTs), and made a thermal resistance type body temperature sensor. The sensor has an electrical conductivity of 0.071 S / m, and the TCR can reach 1.636% / °C. Most of the current body temperature sensors are resistance type sensors based on Au, AgNW, CNTs and other thermal sensitive materials, which have high resistance sensitivity (the TCR in the current reported research is as high as 9.2% / °C), meeting the needs of monitoring small temperature changes. However, the device mostly only has a few tens of microamperes or even nanometer level current (10 -9 ~10 -5 A), the current sensitivity is low (the highest value in the current reported research is only 7.14 μA / °C), and a complex circuit and large precision instrument are needed for monitoring, which is not conducive to future wearable applications. At the same time, the nonlinear relationship between resistance and body temperature makes the sensitivity in the high temperature range low and the detection range small. Therefore, it is very important to improve the current and linearity for the research of body temperature sensors, and it is urgent to develop new sensing mechanisms.

[0004] Organic electrochemical transistors (OECT) with PEDOT:PSS as a typical material is an ion-electronic device that penetrates the semiconductor and modulates the transistor channel electrical characteristics, which belongs to the electrolyte gate-controlled transistor, and was invented by Wrighton and his colleagues in 1984. Due to the advantages of simple structure, high electronic / ionic conductivity, good biocompatibility, stable operation in water environment, easy combination with flexible substrate, etc., it is widely used in the research of biosensors, such as ion detection, metabolite detection, pathogen detection and electro-physiological signal monitoring, etc. The source-drain current of the organic electrochemical transistor has good linearity with the effective gate voltage and temperature, and can output milliamperes of current (10 -3 A) at low operating voltage, which has the potential to realize high sensitivity, large current and good linearity of temperature sensor, and there is no research on temperature sensor based on organic electrochemical transistor, and this field still needs to be explored. SUMMARY

[0005] The present application aims to solve the problems in the prior art, and provides a temperature sensor based on an organic electrochemical transistor and a preparation method thereof, which realizes real-time and accurate monitoring of human body temperature by testing the change of current, and has high sensitivity, good linearity, simple testing, fast response speed and stable performance.

[0006] In order to achieve the above-mentioned purpose, the present application has the following technical solutions:

[0007] A temperature sensor based on an organic electrochemical transistor, comprising a substrate, and a source electrode and a drain electrode arranged on the substrate, a PEDOT:PSS organic semiconductor thin film layer as a channel is coated on the source electrode and the drain electrode, an electrolyte is arranged on the PEDOT:PSS organic semiconductor thin film layer, and the electrolyte is in contact with a gate electrode.

[0008] As a preferred solution, the substrate is made of glass, polymer flexible material or silicon wafer.

[0009] As a preferred solution, the preparation electrode of the source electrode and the drain electrode comprises an Au electrode or a Pt electrode.

[0010] As a preferred solution, the electrolyte uses 10 -4 M~10 -1 M NaCl aqueous solution.

[0011] As a preferred solution, the preparation electrode of the gate electrode comprises an Ag / AgCl electrode, an Au electrode or a Pt electrode.

[0012] As a preferred solution, the length of the drain electrode is 3-5 mm, the width is 1-2 mm, and the thickness is 50-100 nm; the length of the source electrode is 3-5 mm, the width is 1-2 mm, and the thickness is 50-100 nm; the length of the PEDOT:PSS organic semiconductor thin film layer is 0.1-1 mm, the width is 3-5 mm, and the thickness is 300-600 nm.

[0013] As a preferred solution, the drain electrode current I DS The calculation is performed according to the following formula:

[0014]

[0015] In the formula, W is the channel width, i.e. the width of the PEDOT:PSS organic semiconductor thin film layer; L is the channel length, i.e. the length of the PEDOT:PSS organic semiconductor thin film layer; d is the thickness of the PEDOT:PSS organic semiconductor thin film layer; μ is the hole mobility; C* is the volume capacitance; V P is the pinch-off voltage; is the effective gate voltage; V DS is the source-drain voltage;

[0016]

[0017]

[0018] In the formula, C G is the gate capacitance, C C is the channel capacitance, V G is the gate voltage, is the initial solution potential, and γ is the capacitance proportionality coefficient;

[0019] The solution potential is modified by introducing the redox reaction in the solution and the electric field shielding effect caused by the PSS anions in the channel, and the solution potential expression is modified as follows:

[0020]

[0021] In the formula, is the modified solution potential, k B is the Boltzmann constant, T is the temperature, q is the elementary charge, c is the electrolyte concentration, z is the number of electrons transferred in the reaction process, and N PSS is the PSS anion concentration;

[0022] The effective gate voltage The calculation is performed according to the following formula:

[0023]

[0024]

[0025] Channel current as a function of effective gate voltage is calculated as follows:

[0026]

[0027]

[0028] where g m is the transconductance;

[0029] The sensitivity is adjusted by regulating the cation valence z, the electrolyte concentration c, the PSS anion concentration N PSS and the capacitance scaling factor γ.

[0030] A preparation method of the organic electrochemical transistor-based temperature sensor, comprising the following steps:

[0031] The PEDOT:PSS aqueous solution is mixed with ethylene glycol, 3- glycidoxypropyltrimethoxysilane and dodecylbenzenesulfonic acid, and stirred uniformly to obtain a PEDOT:PSS mixed solution;

[0032] The substrate is cleaned, surface coating pretreatment is performed, and a source electrode and a drain electrode are prepared on the surface of the substrate;

[0033] The PEDOT:PSS mixed solution is spin-coated on the surface of the source electrode and the drain electrode to obtain an organic semiconductor thin film layer channel;

[0034] An electrolyte is added dropwise on the organic semiconductor thin film layer channel, the gate electrode is contacted with the electrolyte, and the organic electrochemical transistor-based temperature sensor is obtained.

[0035] As a preferred solution, in the step of mixing the PEDOT:PSS aqueous solution with ethylene glycol, 3-glycidoxypropyltrimethoxysilane and dodecylbenzenesulfonic acid, the volume ratio of ethylene glycol, 3-glycidoxypropyltrimethoxysilane and dodecylbenzenesulfonic acid in the PEDOT:PSS aqueous solution is 5%, 4% and 0.1%, respectively.

[0036] As a preferred solution, the substrate is cleaned by being sequentially subjected to ultrasonic cleaning in soapy water, deionized water, acetone and isopropanol twice, and then dried by a nitrogen gun;

[0037] The step of performing surface coating pretreatment is that the substrate is treated by ultraviolet ozone or plasma for 5-20 minutes;

[0038] The method of preparing the source electrode and the drain electrode on the surface of the substrate includes vacuum thermal evaporation, magnetron sputtering or vapor deposition;

[0039] In the step of spin-coating the PEDOT:PSS mixed solution on the surface of the source electrode and the drain electrode, the spin-coating rotation speed is 1000 r / min-5000 r / min, the spin-coating time is 10 s-60 s, and the thickness of the obtained organic semiconductor thin film layer is 300 nm-600 nm.

[0040] Compared with the prior art, the present application has at least the following beneficial effects:

[0041] The present application proposes a brand-new temperature sensing mechanism based on an organic electrochemical transistor, which is different from the previous resistance temperature sensing. The temperature sensing mechanism proposed by the present application is derived from the linear shift of the effective gate voltage of the device caused by temperature, and due to the existence of transconductance, a slight change in temperature can cause a huge change in current. Therefore, the organic electrochemical transistor temperature sensor based on the present application has the unique advantages of high current sensitivity, large basic current, and good linear relationship between voltage and temperature. The present application first proposes the use of an organic electrochemical transistor for a temperature sensor. Due to its high current sensitivity, it can monitor the current without complex circuits and large precision instruments. In addition, the organic electronic material used has high ion / electron conductivity, and has the advantage of stable operation in an electrolyte such as an aqueous solution, so that the temperature sensor based on the organic electrochemical transistor of the present application has the characteristics of simple testing, fast response speed, stable and reversible temperature change, etc. The real-time and accurate monitoring of human body temperature can be realized by testing the change of the current. The brand-new temperature sensing mechanism proposed by the present application reveals that the temperature change sensitivity of the electrochemical biosensor can be further adjusted by adjusting the valence state of the electrolyte cation of the organic electrochemical transistor, the electrolyte concentration, the type of gate electrode, and the test voltage, so that the device works in the state of maximum temperature change sensitivity. The temperature sensor based on the organic electrochemical transistor of the present application has a simple structure and preparation process, and can be attached to the surface of the human body skin. It has a wide application prospect in predicting the cognitive state of the human body to the thermal environment and the early diagnosis of diseases, and is beneficial to mass production. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a structural diagram of the organic semiconductor thin film material PEDOT:PSS of the embodiment of the present application;

[0043] Figure 2 is a schematic diagram of the temperature sensor structure and testing method based on the organic electrochemical transistor of the embodiment of the present application;

[0044] Figure 3 is a temperature change transfer characteristic curve of the embodiment of the present application in 10 -1 M NaCl aqueous solution;

[0045] Figure 4 is a temperature change transfer characteristic curve of the embodiment of the present application in 10 -1Time response curve diagram of variable temperature in M NaCl aqueous solution;

[0046] Figure 5 is a variable temperature transfer characteristic curve diagram of the embodiment of the present application in 10 -1.5 Time response curve diagram of variable temperature in M NaCl aqueous solution;

[0047] Figure 6 is a variable temperature transfer characteristic curve diagram of the embodiment of the present application in 10 -1.5 Time response curve diagram of variable temperature in M NaCl aqueous solution;

[0048] Figure 7 is a variable temperature transfer characteristic curve diagram of the embodiment of the present application in 10 -2 Time response curve diagram of variable temperature in M NaCl aqueous solution;

[0049] Figure 8 is a variable temperature transfer characteristic curve diagram of the embodiment of the present application in 10 -2 Time response curve diagram of variable temperature in M NaCl aqueous solution;

[0050] Figure 9 is a variable temperature voltage offset of the embodiment of the present application in different concentrations of NaCl aqueous solution;

[0051] Figure 10 is a variable temperature current real-time change diagram of the embodiment of the present application in 10 -2 M NaCl aqueous solution;

[0052] Figure 11 is a variable temperature current and estimated temperature linear relationship diagram of the embodiment of the present application in 10 -2 M NaCl aqueous solution;

[0053] Figure 12 is a variable temperature transfer characteristic curve diagram of the embodiment of the present application in 10 -2 M NaCl aqueous solution;

[0054] Figure 13 is a variable temperature transfer characteristic curve diagram of the embodiment of the present application in 10 -2 Time response curve diagram of variable temperature in M NaCl aqueous solution;

[0055] Figure 14 is a variable temperature current real-time change diagram of the embodiment of the present application in 10 -2 M NaCl aqueous solution;

[0056] Figure 15 is a variable temperature current and estimated temperature linear relationship diagram of the embodiment of the present application in 10 -2 M NaCl aqueous solution. DETAILED DESCRIPTION

[0057] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments.

[0058] The organic electrochemical transistor-based temperature sensor according to the embodiment of the application comprises a substrate, a source electrode and a drain electrode arranged on the substrate, and a PEDOT:PSS organic semiconductor thin film layer as a channel coated on the source electrode and the drain electrode, and an electrolyte arranged on the PEDOT:PSS organic semiconductor thin film layer, and the electrolyte is in contact with a gate electrode.

[0059] In a possible implementation, the substrate can be made of glass, a polymer flexible material or a silicon wafer.

[0060] In a possible implementation, the prepared electrodes of the source electrode and the drain electrode can be Au electrodes or Pt electrodes.

[0061] In a possible implementation, the electrolyte can be 10 -4 M ~ 10 -1 M NaCl aqueous solution, or one of other various liquid or solid electrolytes.

[0062] In a possible implementation, the prepared electrode of the gate electrode can be an Ag / AgCl electrode, an Au electrode or a Pt electrode.

[0063] In a possible implementation, the length of the drain electrode is 3mm-5mm, the width is 1mm-2mm, and the thickness is 50nm-100nm; the length of the source electrode is 3mm-5mm, the width is 1mm-2mm, and the thickness is 50nm-100nm; the length of the PEDOT:PSS organic semiconductor thin film layer is 0.5mm-1mm, the width is 3mm-5mm, and the thickness is 300nm-600nm.

[0064] The drain current I of the organic electrochemical transistor-based temperature sensor according to the embodiment of the application is DS Depending on geometric and physical device parameters, the calculation is performed according to the following formula:

[0065]

[0066] In the formula, W is the channel width, i.e. the width of the PEDOT:PSS organic semiconductor thin film layer; L is the channel length, i.e. the length of the PEDOT:PSS organic semiconductor thin film layer; d is the thickness of the PEDOT:PSS organic semiconductor thin film layer; μ is the hole mobility; C* is the bulk capacitance; V P is the pinch-off voltage; is the effective gate voltage; V DS is the source-drain voltage;

[0067] The geometric and physical device parameters are quantities independent of the electrolyte concentration, while the effective gate voltage V The effective gate voltage will change with other factors such as the concentration of electrolyte The calculation expression is as follows:

[0068]

[0069]

[0070] In the formula, C G is the gate capacitance, C C is the channel capacitance, V G is the gate voltage, is the initial solution potential, and γ is the capacitance proportionality coefficient.

[0071] The solution potential is modified by introducing the redox reaction in the solution and the electric field shielding effect of PSS anions in the channel, and the solution potential expression is modified as follows:

[0072]

[0073] In the formula, is the modified solution potential, k B is the Boltzmann constant, T is the temperature, q is the basic charge, c is the electrolyte concentration, z is the number of electrons transferred in the reaction process (the number of valence states of cations), and N PSS is the PSS anion concentration.

[0074] The effective gate voltage is calculated as follows:

[0075]

[0076]

[0077] The channel current changes with the effective gate voltage and is calculated as follows:

[0078]

[0079]

[0080] In the formula, g m is the transconductance; in the PEDOT:PSS organic electrochemical transistor, due to the existence of the transconductance g m , a slight change in the gate voltage can also cause a large change in the current, so a larger temperature response can be achieved; the temperature will cause a linear shift of the effective gate voltage, thereby causing a change in the current, and the voltage, current and temperature have a linear relationship; by adjusting the cation valence z, the electrolyte concentration c, and the PSS anion concentration N PSSand the sensitivity is adjusted by the capacitance proportional coefficient γ. Therefore, the new temperature sensing mechanism based on PEDOT:PSS organic electrochemical transistors can realize temperature sensing with high sensitivity, large current and good linear relationship.

[0081] Example 1

[0082] This embodiment relates to a preparation method of a PEDOT:PSS organic electrochemical transistor with a glass substrate and Au source and drain electrodes, and the specific steps are as follows:

[0083] a) 500 μl of PEDOT:PSS aqueous solution (PH1000), 25 μl of ethylene glycol (EG), 20 μl of 3-glycidoxypropyltrimethoxysilane (GOP S) and 0.5 μl of dodecylbenzenesulfonic acid (DBSA) are taken with a pipette respectively, mixed, stirred on a magnetic stirrer for more than 2 h, and prepared for use; the structure of PEDOT:PSS is shown in Figure 1 .

[0084] b) The glass substrate is ultrasonically cleaned in soapy water, deionized water, acetone and isopropanol twice, and each cleaning lasts for 30 min.

[0085] c) After the substrate is blown dry with a nitrogen gun, the surface is further treated with ultraviolet ozone for 15 min.

[0086] d) The source and drain electrodes are prepared on the clean glass substrate by vacuum thermal evaporation with a mask. First, 5 nm of Cr is deposited as an adhesion layer at a rate of 0.01 nm / s to enhance the bonding force of the upper layer of Au to the glass substrate, then 10 nm of Au is deposited at a rate of 0.01 nm / s, and then 40 nm of Au is deposited at a rate of 0.1 nm / s, and finally the thickness of the source and drain electrodes is 55 nm.

[0087] e) The PEDOT:PSS mixed solution is taken off the magnetic stirrer, 18 μL of the solution is taken with a pipette, and the solution is spin-coated on the surface of the source and drain electrodes at a speed of 2000 r / min by using a solution spin-coating method, the spin-coating time is 1 min, and the thickness of the organic semiconductor thin film is controlled to be 450 nm.

[0088] f) The thin film on the organic electrochemical transistor except the channel is wiped off with a cotton swab soaked with deionized water to avoid excessive off-state current.

[0089] g) The sample is annealed on a hot stage at 120°C for 10 min to prepare a device structure as shown in Figure 2 , and the thickness of the PEDOT:PSS organic semiconductor thin film layer is 450 nm.

[0090] h) The current response of the PEDOT:PSS organic electrochemical transistor to temperature change is tested, and the test structure is as shown inFigure 2 As shown, the specific method for temperature variation testing is as follows.

[0091] 1) Prepare NaCl aqueous solutions of different concentrations for later use.

[0092] 2) Place the PEDOT:PSS organic electrochemical transistor on a hot plate with precisely controlled temperature, and then... -1 A NaCl aqueous solution was added dropwise to the device channel as an electrolyte, and an Ag / AgCl electrode was used as the gate electrode and in contact with the electrolyte. The transfer characteristic curves of the organic electrochemical transistor were obtained at different temperatures by changing the hot-stage temperature (I...). DS -V G ) and time response curve (I DS -Time), such as Figure 3 and Figure 4 As shown, when the temperature rises from 22.1℃ to 40.1℃, the voltage offset can reach 2.30mV / ℃; when the gate voltage is 0.2V, the channel current drops from -1.29mA to -1.93mA, the sensitivity is 34.4μA / ℃, and the relative channel current change is 2.69% / ℃; when the gate voltage is 0V, the channel current drops from -4.21mA to -5.28mA, the sensitivity is 59.4μA / ℃, and the relative channel current change is 1.41% / ℃.

[0093] 3) Place the PEDOT:PSS organic electrochemical transistor on a hot plate where the temperature can be precisely controlled, and then... -1.5 An aqueous solution of MNaCl was added dropwise to the device channel as an electrolyte, and an Ag / AgCl electrode was used as the gate electrode and in contact with the electrolyte. The Ig of the organic electrochemical transistor was obtained by changing the hot-stage temperature at different temperatures. DS -V G and I DS -Time curve, such as Figure 5 and Figure 6 As shown, when the temperature rises from 22.2℃ to 41.0℃, the voltage offset reaches 3.74mV / ℃; when the gate voltage is 0.2V, the channel current drops from -2.68mA to -4.19mA, with a sensitivity of 75.6μA / ℃ and a relative channel current change of 2.81% / ℃; when the gate voltage is 0V, the channel current drops from -5.78mA to -7.39mA, with a sensitivity of 88.1μA / ℃ and a relative channel current change of 1.53% / ℃.

[0094] 4) Place the PEDOT:PSS organic electrochemical transistor on a hot plate where the temperature can be precisely controlled, and then... -2 An aqueous NaCl solution was added dropwise to the device channel as an electrolyte, and an Ag / AgCl electrode served as the gate electrode and was in contact with the electrolyte. The Ig of the organic electrochemical transistor was obtained by changing the hot-stage temperature at different temperatures.DS -V G and I DS -Time curve, such as Figure 7 and Figure 8 As shown, when the temperature rises from 24.9℃ to 41.0℃, the voltage offset reaches 4.82mV / ℃; when the gate voltage is 0.2V, the channel current drops from -2.00mA to -3.07mA, the sensitivity is 64.8μA / ℃, and the relative channel current change is 3.24% / ℃; when the gate voltage is 0V, the channel current drops from -4.85mA to -6.30mA, the sensitivity is 90.3μA / ℃, and the relative channel current change is 1.86% / ℃.

[0095] 5) By integrating the temperature-varying test data of PEDOT:PSS organic electrochemical transistors using NaCl aqueous solutions of different concentrations as electrolytes, it can be concluded that within a certain concentration range, the lower the electrolyte concentration, the greater the temperature-varying voltage deviation of the device. Figure 9 As shown.

[0096] Example 2

[0097] This embodiment relates to the real-time current response of a PEDOT:PSS organic electrochemical transistor to rapidly changing temperatures. The fabrication method of the PEDOT:PSS organic electrochemical transistor is as described in Example 1, and the specific method for real-time temperature monitoring is as follows:

[0098] a) Prepare 10 -2 M NaCl aqueous solution, a portion of the solution is placed at room temperature, and the other portion is placed on a hot plate with precise temperature control, and the solution temperature is controlled at 50℃, for later use.

[0099] b) Place the PEDOT:PSS organic electrochemical transistor on the probe stage and allow it to stand at room temperature for 10 minutes. -2 An aqueous solution of NaCl was added dropwise to the device channel as an electrolyte. An Ag / AgCl electrode served as the gate electrode and was in contact with the electrolyte. The initial temperature was 20.7°C. To rapidly change the device channel temperature, several drops of 50°C NaCl aqueous solution were added dropwise to the device channel using a pipette or syringe. -2 An aqueous solution of MNaCl was used, and the current-time curve of the organic electrochemical transistor at a gate voltage of 0V was measured, as shown in the figure. Figure 10 As shown, arrows 1-6 represent adding 1-6 drops of 50°C electrolyte to the channel, respectively. When the 50°C electrolyte is added to the channel, the channel temperature changes instantaneously, and the device current responds rapidly after 0.08 seconds. Furthermore, as heat dissipates, the device current returns to its initial room temperature value after a period of time, demonstrating good reversibility. The more 50°C electrolyte added, the greater the device response, such as... Figure 11As shown, the estimated current sensitivity of the device is approximately 24.4 μA / ℃. The PEDOT:PSS organic electrochemical transistor exhibits a rapid response and excellent sensitivity during temperature changes, demonstrating superior performance in real-time and accurate temperature monitoring.

[0100] Example 3

[0101] This embodiment relates to a method for fabricating a PEDOT:PSS organic electrochemical transistor using PDMS as a substrate and Au as the source and drain electrodes. The specific steps are as follows:

[0102] a) Use a pipette to take 500 μl of PH1000, 25 μl of EG, 20 μl of GOPS and 0.5 μl of DBSA respectively, mix them, and stir on a magnetic stirrer for more than 2 hours.

[0103] b) The glass substrate was ultrasonically cleaned twice in sequence with soapy water, deionized water, acetone and isopropanol, each time for 30 minutes.

[0104] c) After drying the glass substrate with a nitrogen gun, further treat the surface with ultraviolet ozone for 5 minutes.

[0105] d) Cut the purchased PDMS with a thickness of 100 μm into appropriate sizes, soak it in chlorobenzene (CB) for 5 min, then wash it in isopropanol (IPA) for 30 s to remove the PDMS with low crosslinking degree, and then dry the PDMS substrate with a nitrogen gun and adhere it to the glass substrate.

[0106] e) Treat the PDMS substrate surface with ultraviolet ozone for 15 min.

[0107] f) The source and drain electrodes were fabricated on a clean flexible PDMS substrate using mask vacuum thermal evaporation. First, 5 nm of Cr was deposited as an adhesion layer at 0.01 nm / s to enhance the adhesion between the upper gold layer and the flexible substrate. Then, 10 nm of Au was deposited at 0.01 nm / s, followed by 40 nm of Au at 0.1 nm / s. The final thickness of the source and drain electrodes was 55 nm.

[0108] g) Remove the above PEDOT:PSS mixed solution from the magnetic stirrer, take 18 μL of the solution with a pipette, and spin-coat the solution onto the source and drain surfaces at a speed of 2000 r / min using the solution spin-coating method. The spin-coating time is 1 min, and the thickness of the organic semiconductor film is controlled to be 450 nm.

[0109] h) Use a cotton swab soaked in deionized water to wipe away the thin film on the organic electrochemical transistor except for the channel to avoid excessive off-state current.

[0110] i) Anneal the sample on a hot plate at 120°C for 10 min to prepare the sample as shown in the image. Figure 2 The device structure shown has a PEDOT:PSS organic semiconductor thin film layer with a thickness of 450 nm.

[0111] j) The specific methods for testing the current response of flexible PEDOT:PSS organic electrochemical transistors to temperature changes, including variable temperature testing and real-time temperature monitoring, are as follows:

[0112] 1) Prepare 10 -2 M NaCl aqueous solution, for later use.

[0113] 2) Place the flexible PEDOT:PSS organic electrochemical transistor on a hot stage where the temperature can be precisely controlled, and then place 10 - 2 An aqueous solution of MNaCl was added dropwise to the device channel as an electrolyte, and an Ag / AgCl electrode served as the gate electrode and was in contact with the electrolyte. The Ig of the flexible organic electrochemical transistor was obtained by changing the hot-stage temperature at different temperatures. DS -V G and I DS -Time curve, such as Figure 12 and Figure 13 As shown, when the temperature rises from 31.2℃ to 46.5℃, the voltage offset reaches 4.81mV / ℃; when the gate voltage is 0.2V, the channel current drops from -1.84mA to -2.41mA, with a sensitivity of 35.9μA / ℃ and a relative channel current change of 1.95% / ℃; when the gate voltage is 0V, the channel current drops from -3.51mA to -4.13mA, with a sensitivity of 38.9μA / ℃ and a relative channel current change of 1.11% / ℃.

[0114] 3) Separate the flexible PEDOT:PSS organic electrochemical transistor from the bottom glass substrate, place it on a hot stage with precise temperature control, and then place 10 -2 A NaCl aqueous solution was added dropwise to the device channel as an electrolyte, and an Ag / AgCl electrode served as the gate electrode and was in contact with the electrolyte. The hot-stage temperature was rapidly changed to obtain the current-time curve of the organic electrochemical transistor at a gate voltage of -0.2V, as shown below. Figure 14 As shown, the arrows indicate temperature changes. When the temperature increases from 25.0℃ to 37.7℃, the device current maintains a good linear relationship with temperature, and the device sensitivity is 1.2μA / ℃. Due to the inevitable microcracks that form between the Au electrode and the PEDOT:PSS film during separation from the glass substrate, interface damage occurs, leading to a significant decrease in the device's base current and sensitivity. To clarify the effect of the base current on the device's temperature-dependent response, the current I... DS The relationship with temperature is converted into relative current I. DSThe relationship between / I0 and temperature, such as Figure 15 As shown, the channel current changes by 1.80% per degree Celsius, which is similar to the aforementioned performance, indicating that the flexible device still has excellent temperature sensing capabilities.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A temperature sensor based on an organic electrochemical transistor, characterized in that: The device includes a substrate, and a source and a drain disposed on the substrate. A PEDOT:PSS organic semiconductor thin film layer is coated on the source and the drain as a channel. An electrolyte is disposed on the PEDOT:PSS organic semiconductor thin film layer and the electrolyte is in contact with the gate. Drain current Calculate according to the following formula: In the formula, W This refers to the channel width, which is the width of the PEDOT:PSS organic semiconductor thin film layer. L This refers to the channel length, which is the length of the PEDOT:PSS organic semiconductor thin film layer. d The thickness of the PEDOT:PSS organic semiconductor thin film layer; μ Hole mobility; C * indicates volume capacitance; V P This is the pinch-off voltage; Effective gate voltage; Source-drain voltage; In the formula, Gate capacitance, Channel capacitance, Gate voltage, The initial electrolyte potential, This is the capacitance proportionality coefficient; Introduced redox reactions in electrolytes and in the channel PSS The electric field shielding effect brought by anions is used to correct the electrolyte potential, and the electrolyte potential expression is corrected as follows: In the formula, To correct the electrolyte potential, k B Boltzmann's constant, T For temperature, q For elementary charge, c Electrolyte concentration, z This represents the number of electrons transferred during the reaction. N PSS for PSS Anion concentration; Effective gate voltage Calculate according to the following formula: Channel current varies with effective gate voltage The change is calculated using the following formula: In the formula, For transconductance; By adjusting the cation valence state z and electrolyte concentration c , PSS Anion concentration N PSS and capacitance proportionality coefficient Achieve sensitivity adjustment; The source and drain electrodes include Au electrodes or Pt electrodes; The electrolyte uses 10 -4 M~10 -1 NaCl aqueous solution of M; The electrode used to fabricate the gate includes an Ag / AgCl electrode, an Au electrode, or a Pt electrode.

2. The temperature sensor based on organic electrochemical transistors according to claim 1, characterized in that: The substrate is made of glass, a flexible polymer material, or a silicon wafer.

3. The temperature sensor based on organic electrochemical transistors according to claim 1, characterized in that: The drain electrode has a length of 3mm to 5mm, a width of 1mm to 2mm, and a thickness of 50nm to 100nm; the source electrode has a length of 3mm to 5mm, a width of 1mm to 2mm, and a thickness of 50nm to 100nm; the PEDOT:PSS organic semiconductor thin film layer has a length of 0.1mm to 1mm, a width of 3mm to 5mm, and a thickness of 300nm to 600nm.

4. A method for fabricating a temperature sensor based on an organic electrochemical transistor as described in any one of claims 1-3, characterized in that, Includes the following steps: PEDOT:PSS aqueous solution was mixed with ethylene glycol, 3-epoxypropyltrimethoxysilane and dodecylbenzenesulfonic acid and stirred until homogeneous to obtain PEDOT:PSS mixed solution; The substrate is cleaned, and a surface coating pretreatment is performed. Then, the source and drain electrodes are fabricated on the substrate surface. A PEDOT:PSS mixed solution was spin-coated onto the surfaces of the source and drain electrodes to obtain an organic semiconductor thin film channel. An electrolyte is dropped onto the channel of an organic semiconductor thin film layer, and the gate is brought into contact with the electrolyte to obtain a temperature sensor based on an organic electrochemical transistor.

5. The preparation method according to claim 4, characterized in that, In the step of mixing the PEDOT:PSS aqueous solution with ethylene glycol, 3-epoxypropyltrimethoxysilane and dodecylbenzenesulfonic acid, the volume ratios of ethylene glycol, 3-epoxypropyltrimethoxysilane and dodecylbenzenesulfonic acid in the PEDOT:PSS aqueous solution are 5%, 4% and 0.1%, respectively.

6. The preparation method according to claim 4, characterized in that, The method for cleaning the substrate is as follows: the substrate is ultrasonically cleaned twice in sequence with soapy water, deionized water, acetone and isopropanol, and then dried with a nitrogen gun. The step of performing surface coating pretreatment is as follows: treat the substrate with ultraviolet ozone or plasma for 5 min to 20 min. Methods for fabricating source and drain electrodes on substrate surfaces include vacuum thermal evaporation, magnetron sputtering, or vapor deposition. In the step of spin-coating the PEDOT:PSS mixed solution onto the surfaces of the source and drain electrodes, the spin-coating speed is 1000 r / min to 5000 r / min, the spin-coating time is 10 s to 60 s, and the thickness of the resulting organic semiconductor thin film layer is 300 nm to 600 nm.

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