A flexible pressure sensor for human motion / voice detection and its preparation method and application

Abstract

The present invention belongs to the technical field of flexible strain sensors, and specifically relates to a flexible pressure sensor for human motion / voice detection and its preparation method and application. It is composed of MoS2 / HEC / PU sponge, electrode and PI tape encapsulation layer, with polyurethane sponge as elastic substrate, MoS2 / HEC coating as conductive sensing layer, the electrode is fixed to the upper and lower surfaces of MoS2 / HEC / PU sponge by conductive silver paste, and PI tape is pasted on both sides of the electrode to make the electrode more fixed and insulated from the outside, and the electrode is a flexible conductive silver-plated tape. The flexible pressure sensor has the advantages of high sensitivity and rapid response to wide range pressure detection, which can not only be used for human motion signal monitoring, but also the flexible pressure sensor can be combined with machine learning algorithm to realize voice recognition through laryngeal movement, and has important application value in assisting the voice of the voiceless, voice auxiliary output system, human health evaluation, human-computer interaction, electronic skin and other aspects.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible strain sensors, and in particular relates to a flexible pressure sensor for human motion / voice detection and a preparation method and application thereof. Background Art

[0002] With the development of technologies such as the Internet of Things, intelligent robots, and health monitoring, flexible pressure sensors have received more and more attention as core devices for perception. Pressure sensors can sense pressure signals and convert them into electrical signals according to certain rules. In the face of more and more special signals and special environments, higher requirements are placed on pressure sensors. Traditional pressure sensors based on single crystal silicon, metals, metal oxide films, and nitride materials have inherent rigidity and brittleness, and their flexibility and strain range are very limited, which cannot meet people's requirements. Flexible pressure sensors can not only detect pressure, but also overcome the shortcomings of traditional pressure sensors, and have the characteristics of flexibility, ductility, bendability, and wearability. According to different sensing mechanisms, flexible pressure sensors can be divided into resistive, capacitive, piezoelectric, and triboelectric types. Among them, piezoresistive flexible pressure sensors are widely used due to their easy signal acquisition, simple manufacturing, and low cost, and have broad development prospects.

[0003] At present, many flexible pressure sensors with excellent performance have been developed. They use flexible substrates and new nanomaterials (MXene, carbon nanotubes) with high sensitivity, rapid response, wide detection range and other characteristics. However, there are still problems such as the inability to balance high sensitivity and wide detection range of pressure sensors, poor stability, serious drift, complicated manufacturing process, and high cost. This leads to huge challenges for flexible pressure sensors in practical applications.

[0004] Flexible pressure sensors have broad application potential in wearable devices, human-computer interaction, medical rehabilitation and other fields. For example, flexible pressure sensors are attached to the surface of the human body or clothing, and signals are collected and processed through portable devices and wireless transmission technology. Flexible pressure sensors are then used to detect human motion and physiological signals, and the detection results are used to achieve interaction with robots. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method for preparing and applying a flexible pressure sensor for human motion / voice detection, thereby realizing human motion signal detection and voice detection through laryngeal movement.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a flexible pressure sensor for human motion / voice detection, composed of a MoS2 / HEC / PU sponge, an electrode and a PI tape encapsulation layer, with a polyurethane sponge as an elastic substrate and a MoS2 / HEC coating as a conductive sensing layer. The electrode is fixed to the upper and lower surfaces of the MoS2 / HEC / PU sponge by conductive silver paste, and PI tape is pasted on both sides of the electrode to make the electrode more fixed and insulated from the outside world. The electrode is a flexible conductive silver-plated tape.

[0007] Furthermore, the MoS2 / HEC / PU sponge is obtained by dipping a PU sponge with a MoS2 / HEC solution and then drying it, and the MoS2 / HEC solution is obtained by mixing a MoS2 solution and a HEC solution in a volume ratio of 1:1; the MoS2 nanosheets contact each other to form a conductive path, and the HEC improves the adhesion strength of the coating on the polyurethane sponge.

[0008] Furthermore, the sensing principle of the sensor is:

[0009] The sensor has a porous structure and meets the requirements of low pressure sensitivity and wide detection range. When the sensor is subjected to a small pressure, the sponge skeleton bends, causing microcracks in the conductive sensing coating on it, which in turn causes the conductive path to break. Therefore, the current of the sensor decreases. Further increase in applied pressure causes the sponge skeleton to bend more significantly, and contact occurs between the skeletons, which causes the number of conductive paths added in the sensor to increase rapidly, causing the current to increase rapidly. As the applied pressure continues to increase, the contact area between the sponge skeletons increases until the skeletons are fully in contact. After the applied pressure is unloaded, the flexible sensor relies on the inherent elasticity of the PU sponge to return to its initial state.

[0010] A method for preparing a flexible pressure sensor for human motion / voice detection, the preparation steps comprising:

[0011] (1) Add HEC powder to deionized water and stir it magnetically to completely dissolve it to obtain a transparent HEC solution;

[0012] (2) adding sodium molybdate dihydrate and thioacetamide to deionized water, and then adding oxalic acid to the mixed solution after magnetic stirring, and then magnetic stirring to obtain a mixed solution; placing the obtained mixed solution in a high-pressure reactor, reacting it in an environment of 200° C. for 24 hours, and obtaining MoS2 by a hydrothermal method, washing the obtained MoS2 several times to remove impurities, and dispersing it in water to obtain a pure MoS2 suspension;

[0013] (3) mixing the HEC solution and the MoS2 suspension to obtain a MoS2 / HEC solution;

[0014] (4) washing the PU sponge with deionized water and anhydrous ethanol to remove impurities on the sponge surface, then immersing the cleaned and dried PU sponge in a MoS2 / HEC solution for 4 h, drying it in an environment of 50°C, and repeating the above process to completely dip-coat the PU sponge skeleton with the MoS2 / HEC coating to obtain a MoS2 / HEC sponge;

[0015] (5) Then, the electrodes were fixed to the two ends of the MoS2 / HEC sponge using conductive silver paste and encapsulated with polyimide (PI) tape to obtain the MoS2 / HEC / PU sponge pressure sensor.

[0016] Furthermore,

[0017] In (1) above, the concentration of the HEC solution is 0.02 mg / mL.

[0018] Furthermore,

[0019] In said (2), the mass ratio of sodium molybdate dihydrate, thioacetamide and oxalic acid is 5:6:3;

[0020] The washing method in (2) is to remove impurities by centrifugal washing with deionized water and ethanol three times each, with a rotation speed of 6000 r / min and a single washing time of 10 min.

[0021] Furthermore,

[0022] The volume ratio of the HEC solution to the MoS2 suspension in (3) is 1:1;

[0023] An application of a flexible pressure sensor for human motion / voice detection,

[0024] The sensors are applied to bend detection of knuckles, wrists, elbows and knees, as well as for step detection, touch detection and generating Morse code.

[0025] An application of a flexible pressure sensor for human motion / voice detection,

[0026] The flexible pressure sensor is used in a pressure sensing array, which is composed of 9 MoS2 / HEC / PU sponge pressure sensors arranged in a 3×3 form, and can detect the spatial distribution and amplitude of external pressure;

[0027] The flexible pressure sensor is used for data acquisition, data preprocessing algorithm, and support vector machine algorithm is used for signal classification and recognition.

[0028] Furthermore,

[0029] The flexible pressure sensor is worn on the neck to collect signals of throat movements during speaking and convert them into resistance signals. During the test, the flexible pressure sensor fits tightly against the neck.

[0030] The data preprocessing algorithm includes data filtering, data normalization, and feature extraction, wherein the feature extraction uses fast Fourier transform (STFT) to extract the characteristics of the signal in the time domain and frequency domain;

[0031] The support vector machine algorithm is used as a multi-classification algorithm. The data preprocessing result, i.e., the feature data extracted from each signal, is used as the input of the support vector machine algorithm, and the speech classification result is used as the output of the support vector machine algorithm. Grid search is used to select the parameter penalty coefficient "C" and kernel function radius "g" of the support vector machine to improve the accuracy of machine learning recognition.

[0032] The invention discloses a flexible pressure sensor for human motion / voice detection and its preparation method and application. The invention uses a polyurethane (PU) sponge with good mechanical properties as a flexible substrate and a MoS2 / HEC (molybdenum disulfide / hydroxyethyl cellulose) composite material as a conductive layer of the pressure sensor. The MoS2 / HEC / PU sponge flexible pressure sensor is prepared by a simple and easy-to-operate repeated dip coating method. The obtained sensor has a high sensitivity (0.746 kPa -1 ), wide detection range (0-250kPa), short response / recovery time (120ms / 120ms) and repeatability of more than 1200 cycles. The present invention detects speech by detecting laryngeal movement through a flexible pressure sensor, and recognizes the detection results through a machine learning algorithm, showing important application potential in assisting the voiceless, speech-assisted output systems, human health evaluation, human-computer interaction, and electronic skin. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a diagram of the preparation process of the MoS2 / HEC / PU sponge flexible pressure sensor according to an embodiment of the present invention;

[0034] Figure 2 a is a photo of the MoS2 / HEC / PU sponge flexible pressure sensor according to an embodiment of the present invention;

[0035] Figure 2 b is a schematic diagram of the structure of a sponge flexible pressure sensor according to an embodiment of the present invention;

[0036] Figure 3 a, b are SEM images of PU sponge according to an embodiment of the present invention;

[0037] Figure 3c, d are SEM images of MoS2 / HEC / PU sponge according to the embodiment of the present invention;

[0038] Figure 4 a is the X-ray diffraction (XRD) diagram of MoS2, HEC, and MoS2 / HEC in the embodiment of the present invention;

[0039] Figure 4 b is the FT-IR spectra of MoS2, HEC, and MoS2 / HEC in the embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of the changes in the internal microstructure of the MoS2 / HEC / PU sponge pressure sensor during the pressure application process according to an embodiment of the present invention;

[0041] Figure 6 a is the stress-strain curve of the PU sponge of the embodiment of the present invention at 10%, 20%, 40%, 60%, and 80% strain;

[0042] Figure 6 b is a comparison of stress-strain curves of MoS2 / HEC / PU sponge and PU sponge at 80% strain in the embodiment of the present invention;

[0043] Figure 6 c is the effect of the number of dip-coatings on the resistance of the MoS2 / PU sponge pressure sensor and the MoS2 / HEC / PU sponge flexible pressure sensor according to the embodiment of the present invention;

[0044] Figure 6 d is the change of current with pressure of the MoS2 / HEC / PU sponge pressure sensor according to the embodiment of the present invention;

[0045] Figure 6 e is the current-voltage curve of the MoS2 / HEC / PU sponge pressure sensor of the embodiment of the present invention under the pressure of 0kPa, 20kPa, 40kPa, 60kPa, 80kPa and 100kPa;

[0046] Figure 6 f is the response time and recovery time of the MoS2 / HEC / PU sponge pressure sensor according to the embodiment of the present invention;

[0047] Figure 6 g is the change of current of the MoS2 / HEC / PU sponge pressure sensor in the pressure range of 10 kPa to 50 kPa according to the embodiment of the present invention;

[0048] Figure 6 h is the current response of the MoS2 / HEC / PU sponge pressure sensor of the embodiment of the present invention at frequencies of 0.04 Hz, 0.09 Hz, 0.13 Hz, 0.17 Hz, 0.24 Hz, and 0.39 Hz;

[0049] Figure 6 i is the stability of the MoS2 / HEC / PU sponge pressure sensor in 1200 loading-unloading pressure cycles according to the embodiment of the present invention;

[0050] Figure 7 a is the part of the human body wearing the MoS2 / HEC / PU sponge pressure sensor according to the embodiment of the present invention;

[0051] Figure 7 be is the current change of the MoS2 / HEC / PU sponge pressure sensor when detecting the bending of human fingers, wrists, elbows and knees in the embodiment of the present invention;

[0052] Figure 7 f is the MoS2 / HEC / PU sponge pressure sensor of the present invention installed on the sole, and its current changes when walking;

[0053] Figure 7 g is the MoS2 / HEC / PU sponge pressure sensor of the embodiment of the present invention worn on the wrist to identify "light touch", "heavy touch" and "holding";

[0054] Figure 7 h is the word "pressure" expressed in the form of Morse code by pressing the sensor in the embodiment of the present invention;

[0055] Figure 8 a is a schematic diagram of the structure of a pressure sensing array according to an embodiment of the present invention;

[0056] Figure 8 b is a photo of a pressure sensing array according to an embodiment of the present invention;

[0057] Fig. 9 a is a photo of the pressure sensing array of the embodiment of the present invention being pressed by three fingers;

[0058] Fig. 9 b is the current response when the pressure sensing array of the embodiment of the present invention is pressed by three fingers;

[0059] Fig. 9 c is a photo of a rubber stopper placed on the pressure sensing array according to an embodiment of the present invention;

[0060] Fig. 9 d is the current response when a rubber plug is placed on the pressure sensing array of the embodiment of the present invention;

[0061] Fig. 9 e is a schematic diagram of pressing sensors on a pressure sensing array in sequence to write the number “2” according to an embodiment of the present invention;

[0062] Fig. 9f is the current change of each sensor when the number "2" is written through the pressure sensing array in the embodiment of the present invention;

[0063] Fig.10 When the numbers "1", "3", "4", "5", "6", "7", "8", and "9" are written through the pressure sensing array in the embodiment of the present invention, the current changes of each sensor;

[0064] Fig.11 a is the response waveform obtained by the MoS2 / HEC / PU sponge pressure sensor when the volunteer says the words "help", "food", "I", "need", "one", "water", and "wonderful" in the embodiment of the present invention;

[0065] Fig.11 b is a schematic diagram of the process of performing speech recognition through the MoS2 / HEC / PU sponge pressure sensor signal in an embodiment of the present invention;

[0066] Fig.11 c is a schematic diagram of a support vector machine algorithm according to an embodiment of the present invention;

[0067] Fig.11 d is the confusion matrix of the predicted categories and actual categories of the training set according to the embodiment of the present invention;

[0068] Fig.11 e is the confusion matrix of the predicted categories and actual categories of the test set according to the embodiment of the present invention;

[0069] Fig.12 The sensor response waveform corresponding to the volunteer repeating "Help", "Food", "I", "Need", "One", "Water", and "Wonderful" ten times in the embodiment of the present invention;

[0070] Fig.13 The figure is a detailed flow chart of the speech recognition algorithm according to the embodiment of the present invention. DETAILED DESCRIPTION

[0071] The specific implementation manner will be further described below in conjunction with the accompanying drawings.

[0072] The reagents and instruments in the following examples are all conventional experimental reagents and instruments.

[0073] Embodiment 1:

[0074] A flexible pressure sensor for human motion / voice detection, the sensor uses polyurethane sponge as an elastic substrate and MoS2 / HEC coating as a conductive sensing layer. The pressure detection range of the flexible pressure sensor is 0-250kPa and the sensitivity is 0.746kPa -1, response / recovery time is 120ms / 120ms, with excellent selectivity, repeatability and stability.

[0075] A method for preparing a flexible pressure sensor for human motion / voice detection, the preparation process diagram is as follows Figure 1 As shown, follow these steps:

[0076] (1) 0.2 g of HEC powder was added to 20 mL of deionized water and the HEC powder was completely dissolved in the deionized water by magnetic stirring for 12 h to obtain a transparent HEC solution (0.02 mg / mL).

[0077] (2) 0.5 g of sodium molybdate dihydrate and 0.6 g of thioacetamide were added to 40 mL of deionized water, and the mixed solution was magnetically stirred for 0.5 h. Then, 0.3 g of oxalic acid powder was added to the mixed solution, and the mixed solution was magnetically stirred for another 0.5 h to obtain a mixed solution.

[0078] (3) The mixed solution obtained in step (2) is placed in a high-pressure reactor and reacted at 200° C. for 24 hours to obtain a MoS2 nanosheet suspension.

[0079] (4) The MoS2 nanosheet suspension obtained in step (3) was washed 3 times with deionized water and ethanol by centrifugation (the rotation speed was 6000 r / min, and the single washing time was 10 min to remove impurities, and finally a pure MoS2 nanosheet suspension was obtained.

[0080] (5) After mixing the HEC solution obtained in step (1) and the pure MoS2 nanosheet suspension obtained in step (3), stirring for 10 minutes and ultrasonically oscillating for 20 minutes to obtain a uniform MoS2 / HEC solution.

[0081] (6) The MoS2 / HEC solution was dip-coated onto a polyurethane sponge and dried at 50°C for 5 h to obtain a MoS2 / HEC sensing coating.

[0082] (7) The PU sponge purchased from Lishui Yunchuang Sponge Products Co., Ltd. was cut into 1.5 cm × 1.5 cm × 1.5 cm size, and then the PU sponge was washed with deionized water and anhydrous ethanol to remove impurities on the sponge surface. The cleaned and dried PU sponge was then immersed in the MoS2 / HEC solution, immersed for 4 h and dried in an environment of 50 °C, and the above process was repeated to completely dip-coat the MoS2 / HEC coating on the PU sponge skeleton to obtain a MoS2 / HEC sponge.

[0083] (8) Then, the electrodes are fixed to the two ends of the MoS2 / HEC sponge using conductive silver paste. After being encapsulated with polyimide (PI) tape, the fabrication of the MoS2 / HEC / PU sponge pressure sensor is completed. The actual picture and structural schematic diagram of the prepared flexible pressure sensor are shown in Figure 2 As shown in Figure 2, the MoS2 / HEC / PU sponge pressure sensor includes MoS2 / HEC / PU sponge, electrodes and PI tape.

[0084] The above-mentioned MoS2 / HEC sensing coating can be firmly attached to the sponge skeleton to form a conductive path, and produce microcracks when subjected to pressure, making the flexible pressure sensor more sensitive to tiny pressures.

[0085] Characterization and analysis of MoS2 / HEC / PU sponge flexible pressure sensor:

[0086] Scanning electron microscopy (SEM, Hitachi S-4800) was used to characterize the structural morphology of MoS2 / HEC / PU sponge pressure sensor. X-ray diffraction (XRD, Rigaku D / Max 2500PC) was used to obtain the X-ray diffraction patterns of MoS2, HEC, and MoS2 / HEC. The functional groups of MoS2, HEC, and MoS2 / HEC were characterized by FT-IR (NEXUS).

[0087] SEM images of PU sponge at different magnifications are shown in Figure 2. Figure 3 As shown in a and b. The PU sponge has a 3D porous structure with a pore diameter of 100-500μm and a smooth skeleton. The PU sponge after dip-coating with MoS2 / HEC solution still has a 3D porous structure, while the surface of the sponge skeleton becomes rough, which indicates that the porous structure is successfully retained during the preparation of the sensor and the MoS2 / HEC conductive layer is constructed on the sponge skeleton. Figure 3 c, d. In addition, XRD studies were performed to confirm the successful preparation of the material. Figure 4 As shown in a, the XRD pattern of MoS2 has characteristic diffraction peaks at 2θ=9.24°, 33.17°, 34.74°, and 58.08°, corresponding to the (002), (100), (103), and (110) crystal planes, respectively, proving the successful preparation of MoS2. The XRD pattern of HEC has a characteristic diffraction peak at 2θ=20.16°, indicating the typical semi-crystalline nature of the polymer. The XRD pattern of MoS2 / HEC contains the characteristic diffraction peaks of MoS2 and HEC, proving the successful preparation of the MoS2 / HEC composite material. Figure 4 b shows the FT-IR spectra of MoS2, HEC and MoS2 / HEC. -1The absorption bands observed at 590 cm are related to the bending and stretching vibrations of OH, which originate from water molecules absorbed by the material. -1 The band at 1397cm is caused by the stretching vibration of the Mo-S bond. -1 The band observed at 600 cm -1 Above absorption band (1123cm -1 ) may be due to the sulfate groups generated by the oxidation of MoS2 surface. In the FT-IR spectrum of HEC, the -1 The absorption band is assigned to the stretching vibration of CH in the CH2 group. The bending vibration of O appears at 1636 cm -1 .1418cm -1 The band belongs to the stretching vibration of -COC-. Located at 1330cm -1 The absorption peak is related to the CH bending vibration of primary alcohol (-CHOH-). 1061cm -1 The vibration band at is assigned to CO stretching vibration. The FT-IR spectrum of MoS2 / HEC contains all the characteristic peaks of MoS2 and HEC, which further proves the successful preparation of MoS2 / HEC.

[0088] Sensing principle of MoS2 / HEC / PU sponge flexible pressure sensor:

[0089] The designed sensor has a porous structure, which meets the requirements of low pressure sensitivity and wide detection range. The sensitive mechanism diagram of the sensor with this structure is shown in Figure 5 When the MoS2 / HEC / PU sponge sensor is subjected to a small pressure, the sponge skeleton bends, causing microcracks in the conductive layer on it, which in turn leads to the breakage of the conductive path ( Figure 5 b). As a result, the current of the sensor decreases. Then, further increase in applied pressure causes the sponge skeleton to bend more significantly, and contact occurs between the skeletons. At this point, the number of additional conductive paths in the sensor increases rapidly, causing the current to increase rapidly. As the applied pressure continues to increase, the contact area between the sponge skeletons increases until the skeletons are fully in contact ( Figure 5 c). After the applied pressure is unloaded, the MoS2 / HEC / PU sponge flexible sensor recovers to its initial state relying on the inherent elasticity of the PU sponge.

[0090] Mechanical properties of MoS2 / HEC / PU sponge flexible pressure sensor:

[0091] Figure 6a shows the stress change of the PU sponge when the strain is gradually increased from 0% to 10%, 20%, 40%, 80% and then released. As the applied pressure increases, the pressure increases as the PU sponge is squeezed. When the sensor is compressed to 80%, its stress reaches 14.98 kPa. The PU sponge did not undergo plastic deformation during the experiment, indicating that it is suitable for flexible pressure sensors. Figure 6 b shows the stress-strain curves of MoS2 / HEC / PU sponge and PU sponge under 80% compressive strain. The elastic modulus of MoS2 / HEC / PU sponge is 39.47 kPa, which is increased compared with that of PU sponge.

[0092] Sensing characteristics of MoS2 / HEC / PU sponge flexible pressure sensor:

[0093] Figure 6 c indicates that the sensor resistance is stable after being immersed for 4 times, so the sensors of the present invention are immersed for 4 times unless otherwise specified.

[0094] The sensitivity of the pressure sensor is an important performance parameter. The sensitivity (S) of the MoS2 / HEC / PU sponge pressure sensor is defined as follows: S = (ΔI / I0) / ΔP, where ΔP is the change in applied pressure, I0 and ΔI are the initial current and current change, respectively. Figure 6 d shows that within the range of 0-250kPa, the sensitivity of the MoS2 / HEC / PU sponge pressure sensor can be divided into three regions. In the low pressure range of 0-4.5kPa, the sensitivity S1 is 0.042kPa -1 In the medium pressure range of 4.5-50kPa, the sensitivity S2 is 0.293kPa -1 In the high pressure range of 45-250kPa, the sensitivity S3 is 0.746kPa -1 .

[0095] Figure 6 e) The MoS2 / HEC / PU sponge sensor has good ohmic connection in the range of 0-100 kPa and good static pressure stability, which is the advantage of the present invention.

[0096] Figure 6 f shows that the response time of MoS2 / HEC / PU sponge to the applied pressure is 120ms, and the recovery time is 120ms. The fast response and recovery are beneficial to the application of sensors in practical monitoring.

[0097] The MoS2 / HEC / PU sponge pressure sensor was repeatedly subjected to pressures of 10, 20, 30, 40 and 50 kPa. Figure 6 g shows that the sensor exhibits different reliable current responses to different pressures.

[0098] Figure 6 h shows that the sensor has a stable response to the same pressure in the frequency range of 0.04-0.39 Hz.

[0099] Figure 6 i shows the current change curve of the sensor after 1200 loading-unloading cycles at a pressure of 20 kPa. There is no obvious change in the current response curve when comparing the several cycles at the beginning (upper inset) and the end (lower inset) of the stability test, indicating that the sensor has excellent durability.

[0100] Embodiment 2:

[0101] The invention discloses an application of a flexible pressure sensor for monitoring human motion.

[0102] Figure 7 a shows that the MoS2 / HEC / PU sponge sensor can be installed on different parts of the human body, including fingers, wrists, elbows, and knees for human motion monitoring.

[0103] Figure 7 b shows the response of the sensor current to the finger bending angle. When the angle increases from 0° to 150°, the sensor current shows a clear and discernible change, indicating that the flexible pressure sensor of the present invention can detect the finger bending angle.

[0104] Figure 7 c, d, and e illustrate that the sensor has a stable response to wrist, elbow, and knee flexion and immediate recovery, indicating that it can record the flexion and straightness of joints during physical exercise.

[0105] Figure 7 f shows that sensors placed on the soles of shoes can record the number of steps during walking by sensing pressure changes.

[0106] In addition, the pressure sensor has the ability to simulate human skin touch. The MoS2 / HEC / PU sponge pressure sensor worn on the wrist can clearly distinguish between light touch, heavy touch and wrist grip, such as Figure 7 As shown in g.

[0107] and, Figure 7 h shows the word “pressure” expressed in Morse code by pressing the sensor, demonstrating that the sensor can achieve information transmission.

[0108] Embodiment 3:

[0109] A pressure sensing array consisting of 9 MoS2 / HEC / PU sponge pressure sensors arranged in a 3×3 pattern can detect the spatial distribution and amplitude of external pressure. The sensing array is made on a PI film substrate, and each sensor in the array is a sensing pixel. The sensors are connected individually to reduce interference between sensors. Figure 8 a shows a photograph of the sensor array, Figure 8 b shows the structural schematic diagram of the sensor array.

[0110] The ability of the pressure sensing array to detect pressure distribution was verified by finger compression and placement of a rubber stopper. Fig. 9 a shows a three-finger press sensing array. Fig. 9 b shows the response of the pressure sensing array. From the test results, it can be seen that the pressure applied by the middle finger is the largest, and the pressure applied by the ring finger is the smallest. When the rubber plug is placed on the sensing array ( Fig. 9 c), the response of the sensor array is as follows Fig. 9 As shown in Figure d, due to the uniform mass distribution of the rubber plug, the four sensing pixels show almost the same response. In addition, by pressing the sensing array regularly with a finger, the current of the sensing array changes accordingly. Fig. 9 e shows the pressing order of the number "2", Fig. 9 f shows the current change of each sensing pixel during the pressing process. Similarly, the pressing sequence of the numbers “1”, “3”, “4”, “5”, “6”, “7”, “8” and “9” and the response of the sensing array are shown in Fig.10 Displayed in.

[0111] Embodiment 4:

[0112] A method for detecting speech through laryngeal movements.

[0113] The movement of the laryngeal muscles is closely related to the spoken speech, so there is hope to recognize speech by detecting laryngeal movement, which is also expected to help the voiceless "speak". The MoS2 / HEC / PU sponge flexible pressure sensor is used to detect the laryngeal movement when speaking different words, and the machine learning algorithm is used to classify and recognize the sensor signal. The MoS2 / HEC / PU sponge flexible pressure sensor is installed on the neck to collect the laryngeal movement signal of the volunteer's speech. Fig.11 a shows the response waveforms obtained by the sensor corresponding to the words "Help", "Food", "I", "Need", "One", "Water", "Wonderful", etc. The response waveforms of most words have obvious unique features, while the sensor signals of some words have similar features, such as "I" and "One". In addition, Fig.12As shown, the sensor signals of the ten repetitions are almost the same, indicating that the sensor has good repeatability. In order to distinguish different signals, a machine learning algorithm is used to classify them. Fig.11 b illustrates a flow chart of speech recognition, including data collection, output preprocessing, feature extraction, model training and result prediction. First, the laryngeal movement was tested for 50 cycles when speaking seven words, forming a data set containing 350 sets of samples. Subsequently, the collected sensor signals were filtered and normalized, and their features in the time domain and frequency domain were extracted by fast Fourier transform (STFT). The feature vector of each sample is used as the input of the classification algorithm. The support vector machine (SVM) classification algorithm is used to determine which type the signal belongs to and output the result of speech prediction. In machine learning, 70% of the data (245 sets) are randomly selected for training, and the other 30% of the data (105 sets) are used for testing. In addition, grid search is used to select the parameter penalty coefficient "C" and kernel function radius "g" of SVM to improve the accuracy of machine learning recognition. The detailed speech recognition flow chart is shown in Fig.13 . Finally, the recognition accuracy of the training data set is 100% ( Fig.11 c), the recognition accuracy of the test data set is 97.14% ( Fig.11 d). This shows the feasibility of the MoS2 / HEC / PU sponge flexible pressure sensor assisted by the support vector machine algorithm in detecting laryngeal muscle movement and performing speech recognition, as well as its huge application potential in medical health and human-computer interaction.

[0114] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable ordinary technicians in the field to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made based on the essence of the content of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a flexible pressure sensor for human motion / voice detection, wherein the flexible pressure sensor is composed of a MoS2 / HEC / PU sponge, an electrode and a PI tape encapsulation layer, wherein the PU sponge is used as an elastic substrate, and the MoS2 / HEC coating is used as a conductive sensing layer. The electrode is fixed to the upper and lower surfaces of the MoS2 / HEC / PU sponge by conductive silver paste, and PI tape is pasted to both sides of the electrode to make the electrode more fixed and insulated from the outside. The electrode is a flexible conductive silver-plated tape, and is characterized in that: The preparation steps include: (1) Add HEC powder to deionized water and stir it magnetically to completely dissolve it to obtain a transparent HEC solution; (2) adding sodium molybdate dihydrate and thioacetamide to deionized water, and then adding oxalic acid to the mixed solution after magnetic stirring, and then magnetic stirring to obtain a mixed solution; placing the obtained mixed solution in a high-pressure reactor, reacting it in an environment of 200° C. for 24 hours, and obtaining MoS2 by a hydrothermal method, washing the obtained MoS2 several times to remove impurities, and dispersing it in water to obtain a pure MoS2 suspension; (3) mixing the HEC solution and the MoS2 suspension to obtain a MoS2 / HEC solution; (4) washing the PU sponge with deionized water and anhydrous ethanol to remove impurities on the surface of the PU sponge, then immersing the cleaned and dried PU sponge in a MoS2 / HEC solution for 4 h, drying it in an environment of 50°C, and repeating the above process to completely dip-coat the PU sponge with the MoS2 / HEC coating to obtain a MoS2 / HEC / PU sponge; (5) Then, the electrodes were fixed to the two ends of the MoS2 / HEC / PU sponge using conductive silver paste and encapsulated with PI tape to obtain a flexible pressure sensor.

2. The method for preparing the flexible pressure sensor according to claim 1, characterized in that: In (1) above, the concentration of the HEC solution is 0.02 mg / mL.

3. The method for preparing the flexible pressure sensor according to claim 1, characterized in that: In said (2), the mass ratio of sodium molybdate dihydrate, thioacetamide and oxalic acid is 5:6:3; The washing method in (2) is to remove impurities by centrifugal washing with deionized water and ethanol three times each, with a rotation speed of 6000 r / min and a single washing time of 10 minutes.

4. The method for preparing the flexible pressure sensor according to claim 1, characterized in that: The volume ratio of the HEC solution to the MoS2 suspension in (3) is 1:

1.

5. An application of a flexible pressure sensor for human motion / voice detection, wherein the flexible pressure sensor is prepared by the method according to any one of claims 1 to 4, characterized in that: The flexible pressure sensor is applied to bend detection of finger joints, wrist joints, elbow joints and knee joints, as well as for step detection, touch detection and generation of Morse code.

6. An application of a flexible pressure sensor for human motion / voice detection, wherein the flexible pressure sensor is prepared by the method according to any one of claims 1 to 4, characterized in that: The flexible pressure sensor is used in a pressure sensing array, which is composed of 9 MoS2 / HEC / PU sponge pressure sensors arranged in a 3×3 form, and can detect the spatial distribution and amplitude of external pressure; The flexible pressure sensor is used for data collection, and the data preprocessing algorithm and the support vector machine algorithm are used for signal classification and recognition.

7. The application of the flexible pressure sensor according to claim 6, characterized in that: The flexible pressure sensor is worn on the neck to collect signals of throat movements during speaking and convert them into resistance signals. During the test, the flexible pressure sensor fits tightly against the neck. The data preprocessing algorithm includes data filtering, data normalization, and feature extraction, wherein the feature extraction uses fast Fourier transform (STFT) to extract the characteristics of the signal in the time domain and frequency domain; The support vector machine algorithm is used as a multi-classification algorithm. The data preprocessing result, i.e., the feature data extracted from each signal, is used as the input of the support vector machine algorithm, and the speech classification result is used as the output of the support vector machine algorithm. Grid search is used to select the parameter penalty coefficient "C" and kernel function radius "g" of the support vector machine to improve the accuracy of machine learning recognition.

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