Honeycomb-like flexible sensor, preparation method and application in wearable device

Abstract

The invention relates to the technical field of sensors, in particular to a honeycomb-imitated flexible sensor, a preparation method and application in wearable equipment, the honeycomb-imitated flexible sensor comprises two wires and a flexible sensing component, the flexible sensing component comprises at least two sensing units, and every two adjacent sensing units are stacked together layer by layer; hexagonal honeycomb holes are uniformly formed in the cross section of each sensing unit; each sensing unit comprises two hydrogel sensing pieces which are oppositely arranged; each hydrogel sensing piece comprises a conductive hydrogel plate, a plurality of supporting prismatic tables and a plurality of conductive prismatic tables; and the plurality of supporting prismatic tables and the plurality of conductive prismatic tables are uniformly arranged on the conductive hydrogel plate. The honeycomb-imitated flexible sensor has the advantages that the honeycomb-imitated flexible sensor can sense a high-speed impact event in real time, the transient force generated during impact and the position of the acting force are obtained, and accurate reference basis can be provided for further treatment of medical staff by obtaining injury information of a patient with mild cerebral concussion in time.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a honeycomb-like flexible sensor, a preparation method and an application in a wearable device. Background Art

[0002] Mild concussions are caused by impacts or severe vibrations to the head during sports such as skiing, football, and boxing, or in traffic accidents while cycling. Mild concussions have been recognized as a key risk factor for dementia, Alzheimer's disease, and other neurodegenerative diseases. According to statistics, approximately 42 million people worldwide suffer from mild concussions. Mild concussions usually do not lead to organic lesions, so traditional imaging techniques, such as magnetic resonance imaging, play a limited role in diagnosis, resulting in clinicians being able to make diagnoses based on their own experience and lacking objective and reliable diagnostic criteria or tools to assess the severity of patients.

[0003] With the development of wearable electronic devices, these devices that can achieve real-time sensing and information interaction based on objective data may become the most efficient and convenient health assessment tools. Many companies are trying to use the acceleration values ​​provided by wearable rigid sensors to identify the occurrence of mild concussions. However, the conditions that cause mild concussions are complex, including multiple factors such as the magnitude of external force and the location of action. Therefore, a detailed analysis of the intensity and location of the head impact is required, rather than relying on simple threshold alarms.

[0004] As an important component of wearable electronic devices, flexible sensing components can fit tightly to the surface of human skin, accurately monitor human movement and vital signs, and play an important role in health monitoring, disease diagnosis and treatment, and other fields. When flexible sensing components are used for the early diagnosis of mild concussion, they can sense high-speed impact events in real time and accurately capture the transient force generated by the impact and the specific location of the force. By obtaining detailed injury information of patients with mild concussion in a timely manner, flexible sensing components provide valuable reference for medical staff's subsequent treatment, helping to improve the accuracy of diagnosis and the effectiveness of treatment.

[0005] In recent years, conductive hydrogels have been widely used in sensing fields such as motion detection and respiratory monitoring due to their high water content, excellent mechanical properties and electrical properties. Although traditional petroleum-based hydrogel flexible sensing components have improved the mechanical properties of hydrogels to a certain extent, long-term contact may bring carcinogenic risks. Therefore, non-toxic and degradable natural polymer bio-based materials have become an ideal choice to replace petroleum-based materials. Summary of the invention

[0006] In view of this, the present invention aims to provide a honeycomb-like flexible sensor, a preparation method and its application in wearable devices. By extracting cellulose from corn stalks to prepare flexible sensing components, it can not only solve the problems of biocompatibility and degradability of flexible sensing components, but also reduce environmental pollution caused by straw burning and effectively improve resource utilization efficiency.

[0007] To achieve the above-mentioned purpose, the technical solution created by the present invention is implemented as follows: a honeycomb-like flexible sensor comprises two wires and a flexible sensing component, the flexible sensing component comprises at least two sensing units, and two adjacent sensing units are stacked together layer by layer; the cross section of each sensing unit is evenly provided with hexagonal honeycomb holes; the two wires are respectively connected to the flexible sensing component through conductive tapes; each sensing unit comprises two hydrogel sensing elements arranged opposite to each other; each hydrogel sensing element comprises a conductive hydrogel plate, a plurality of supporting prisms and a plurality of conductive prisms; the plurality of supporting prisms are evenly provided on the conductive hydrogel plate and are located at the opposite sides of the conductive hydrogel plate to form two rows of supporting prisms; the plurality of conductive prisms are evenly provided on the conductive hydrogel plate and are located between the two rows of supporting prisms; on the two oppositely arranged hydrogel sensing elements, the two opposite rows of supporting prisms abut against each other, and a gap is provided between the two opposite conductive prisms; on the two oppositely arranged hydrogel sensing elements, the two adjacent conductive prisms and the conductive prisms opposite to the two conductive prisms together constitute a hexagonal honeycomb hole.

[0008] Furthermore, the height of the conductive prism is smaller than the height of the supporting prism.

[0009] Furthermore, the cross-section of each conductive prism and the cross-section of each supporting prism are both trapezoidal, and the edges of each conductive prism and each supporting prism form an angle of 60° with the horizontal line.

[0010] A method for preparing a honeycomb-like flexible sensor, used to manufacture the above-mentioned honeycomb-like flexible sensor, comprises the following steps: S1: Extraction of corn stover cellulose; S2: preparation of nanofiber suspension; S3: preparing hydrogel ink; S4: 3D print at least 4 hydrogel sensing components; S5: Assemble the hydrogel sensing elements in step S4 into a flexible sensing component, and combine the flexible sensing component and the wire into a honeycomb-like flexible sensor.

[0011] Further, step S1 includes the following steps: S11: washing and drying the corn stalks, putting them into a grinder for crushing, and then collecting the corn stalk powder after passing through a sieve; S12: washing and filtering the corn stalk powder with deionized water, soaking the filtered corn stalk powder in anhydrous ethanol, filtering again, and drying the filtered corn stalk powder; S13: adding the corn stalk powder dried in step S12 into the sodium hydroxide solution to form a mixed solution of corn stalk powder and sodium hydroxide; S14: placing the corn stalk powder and the sodium hydroxide mixed solution into a microwave oven and heating them for a preset time, thereby breaking chemical bonds between molecules of the corn stalk powder by microwaves from the microwave oven; S15: lowering the temperature of the heated corn stalk powder and sodium hydroxide mixed solution to room temperature, washing with deionized water, filtering, and drying to obtain corn stalk powder with a neutral pH value; at the same time, dissolving the sodium chlorite solution in an aqueous glacial acetic acid solution to prepare a bleaching agent; S16: adding a bleaching agent to the corn stalk powder filtered in step S15, and heating it in a constant temperature water bath until a white precipitate appears; S17: The white precipitate obtained in step S16 is washed with deionized water and filtered to obtain white corn stalk powder with a neutral pH value, and the powder is placed in a drying oven for drying to obtain corn stalk cellulose.

[0012] Further, step S2 includes the following steps: S21: adding deionized water to the corn straw cellulose obtained in step S1 and stirring to obtain a corn straw cellulose solution; at the same time, adding tetramethylpiperidinium oxide and sodium bromide to the deionized water to form a catalyst solution.

[0013] S22: adding the catalyst solution into the corn straw cellulose solution to form a mixed solution of cellulose and the catalyst; then, adjusting the pH value of the mixed solution of cellulose and the catalyst to alkaline using a hydrochloric acid solution and a sodium hydroxide solution.

[0014] S23: adding sodium hypochlorite solution to the mixed solution of cellulose and catalyst to form an oxidized cellulose fiber suspension.

[0015] S24: The oxidized cellulose fiber suspension is centrifuged using a centrifuge, then washed with deionized water to become neutral and dried, and finally deionized water is added to obtain a nanofiber suspension through ultrasonic treatment.

[0016] Further, step S3 includes the following steps: S31: adding polyvinyl alcohol to the nanofiber suspension and heating it in an oil bath to obtain a hydrogel precursor solution; at the same time, preparing a dimethyl sulfoxide / PEDOT:PSS dispersion using dimethyl sulfoxide, deionized water and PEDOT:PSS conductive nanofibers; S32: The hydrogel precursor liquid and the dimethyl sulfoxide / PEDOT:PSS dispersion liquid are mixed according to a preset volume ratio, and placed in an ultrasonic cleaning machine for ultrasonic treatment to obtain a hydrogel ink.

[0017] Further, step S5 includes the following steps: S51: First, the hydrogel sensing elements obtained in step S4 are arranged opposite to each other and glued to form at least two sensing units; S52: Subsequently, at least two sensing units are stacked together layer by layer by gluing to form a flexible sensing component; S53: Finally, two wires are connected to the upper surface and the lower surface of the flexible sensing component respectively through conductive tape.

[0018] An application of a honeycomb-like flexible sensor in a wearable device is implemented based on the above-mentioned honeycomb-like flexible sensor, comprising a wearable device and at least one honeycomb-like flexible sensor; the wearable device is used to be worn on a user's body; and each honeycomb-like flexible sensor is arranged inside the wearable device.

[0019] Compared with the prior art, the invention can achieve the following beneficial effects: 1) The honeycomb-like flexible sensor of the present invention can sense high-speed impact events in real time, obtain the transient force generated during the impact and the position of the force, and provide accurate reference for further treatment of medical staff by timely obtaining injury information of patients with mild concussion.

[0020] 2) Extracting corn straw cellulose and applying it to the preparation of flexible sensing components can not only solve the problems of biocompatibility and degradability of flexible sensing components, but also reduce environmental pollution caused by straw burning and effectively improve resource utilization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings: Figure 1 is a schematic structural diagram of a honeycomb-like flexible sensor provided according to an embodiment of the present invention; Figure 2 is a schematic structural diagram of a honeycomb-like flexible sensor according to a first viewing angle provided by an embodiment of the present invention; Figure 3 yes Figure 2 A partial enlarged view of the hexagonal honeycomb holes at part A of the simulated honeycomb flexible sensor; Figure 4is a structural schematic diagram of an application of a honeycomb-like flexible sensor provided in an embodiment of the present invention in a wearable device; Figure 5 is a data graph of resistance change of each honeycomb-like flexible sensor when the left side of the helmet is impacted according to an embodiment of the present invention; Figure 6 is a data graph of resistance change of each honeycomb-like flexible sensor when the right side of the helmet is impacted according to an embodiment of the present invention; Figure 7 It is a data diagram of the resistance change of each honeycomb-like flexible sensor when the rear side of the helmet is impacted according to an embodiment of the present invention.

[0022] The reference numerals include: 1. wire; 2. flexible sensing component; 21. sensing unit; 211. hydrogel sensing element; 212. conductive hydrogel plate; 213. supporting prism; 214. conductive prism; 215. hexagonal honeycomb hole; 3. conductive tape; L1a. first imitation honeycomb flexible sensor; L1b. second imitation honeycomb flexible sensor; L1c. third imitation honeycomb flexible sensor; L1d. fourth imitation honeycomb flexible sensor; M1a. fifth imitation honeycomb flexible sensor; M1b. sixth imitation honeycomb flexible sensor; R1a. seventh imitation honeycomb flexible sensor; R1b. eighth imitation honeycomb flexible sensor; R1c. ninth imitation honeycomb flexible sensor; R1d. tenth imitation honeycomb flexible sensor. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0024] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0025] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0026] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0027] The present invention will be described in detail below with reference to the embodiments.

[0028] like Figures 1 to 3 As shown, a honeycomb-like flexible sensor includes two wires 1 and a flexible sensing component 2, wherein the flexible sensing component 2 includes at least two sensing units 21, and two adjacent sensing units 21 are stacked layer by layer. The cross section of each sensing unit 21 is evenly provided with hexagonal honeycomb holes 215. The two wires 1 are connected to the flexible sensing component 2 through conductive tapes 3, respectively.

[0029] In this embodiment, the two sensing units 21 are stacked together layer by layer by gluing.

[0030] Each sensing unit 21 includes two hydrogel sensing elements 211 arranged opposite to each other. Each hydrogel sensing element 211 includes a conductive hydrogel plate 212, a plurality of supporting prisms 213, and a plurality of conductive prisms 214. The plurality of supporting prisms 213 are evenly arranged on the conductive hydrogel plate 212 and are located at two opposite sides of the conductive hydrogel plate 212 to form two rows of supporting prisms 213. The plurality of conductive prisms 214 are evenly arranged on the conductive hydrogel plate 212 and are located between the two rows of supporting prisms 213. On the two oppositely arranged hydrogel sensing elements 211, a total of four rows of supporting prisms 213 on the two hydrogel sensing elements 211 are mutually abutted, and a gap is provided between the two opposite conductive prisms 214. On the two oppositely arranged hydrogel sensing elements 211, two adjacent conductive prisms 214 and the conductive prisms 214 opposite to the two adjacent conductive prisms 214 together form a hexagonal honeycomb hole 215.

[0031] In this embodiment, two oppositely disposed hydrogel sensing elements 211 are connected together by gluing.

[0032] Furthermore, the height of the conductive prism 214 is smaller than the height of the supporting prism 213 .

[0033] Furthermore, the cross-section of each conductive prism 214 and the cross-section of each supporting prism 213 are both trapezoidal, and the edges of each conductive prism 214 and each supporting prism 213 are at an angle of 60° to the horizontal line ( Figure 3 The horizontal line refers to a straight line parallel to the conductive hydrogel sheet 212.

[0034] The honeycomb structure has a unique hexagonal bionic structure with extraordinary mechanical advantages such as low density, high specific strength and stiffness, excellent energy absorption and load-bearing capacity. Experimental verification shows that under the same volume, the sensitivity of the flexible sensor with a honeycomb space structure is 2.24 times that of the triangular structure flexible sensor and 2.91 times that of the rectangular structure flexible sensor.

[0035] Therefore, in order to improve the sensitivity of the flexible sensing component 2, obtain excellent compression and bending resistance and ultra-light structural characteristics, the present invention selects a honeycomb structure as the spatial structure of the flexible sensing component 2. The applicant found that under the same pressure, when the angle between the side edges of the conductive prism 214 and the horizontal line is 60°, the deformation of the conductive prisms 214 that are in contact with each other due to mutual squeezing is the largest, thereby increasing the contact area between the surfaces of the conductive prisms 214 and forming more conductive paths. Therefore, selecting 60° as the angle between the conductive prism 214 and the horizontal line can significantly improve the detection sensitivity of the flexible sensing component 2 to pressure.

[0036] A method for preparing a honeycomb-like flexible sensor, used to manufacture the above-mentioned honeycomb-like flexible sensor, comprises the following steps: S1: extracting corn stalk cellulose; comprising the following steps: S11: Wash and dry the corn stalks, put them into a grinder for grinding, and then collect the corn stalk powder screened by a sieve.

[0037] In this embodiment, a 100-mesh screen is used to screen the crushed corn stalks, with the purpose of removing the larger particle size portion and retaining the screened corn stalk powder.

[0038] The crusher is a purchased part, model: XL-30C, manufacturer: Xulang Machinery Equipment Co., Ltd.

[0039] S12: Wash and filter the corn stalk powder with deionized water, repeat this process 2 to 3 times, then pour the filtered corn stalk powder into anhydrous ethanol and soak it for 10 minutes, filter the corn stalk powder again, and dry the corn stalk powder after filtering again. The purpose of washing with deionized water first is to remove water-soluble dust and soluble polysaccharides, and the purpose of soaking and washing with anhydrous ethanol is to remove residual water and water-insoluble fat-soluble substances such as oil stains in the stalk powder.

[0040] In this embodiment and the subsequent steps S15 to S17, steps S24, S31, and S32, the cleaning and ultrasonic treatment are all carried out by using an ultrasonic cleaning machine with a model number of JP-30 and a frequency of 25 Hz / 40 Hz produced by Shanghai Jipu Electronic Technology Co., Ltd. In addition, in this embodiment and the subsequent steps S15 to S17, the filtering step is carried out by using filter paper with a model number of 101 produced by Suzhou Baoweide Environmental Protection Technology Co., Ltd.

[0041] S13: Weigh 15 g of the corn stalk powder dried in step S12 and add it into 300 ml of a 12% by mass sodium hydroxide solution to form a mixed solution of corn stalk powder and sodium hydroxide.

[0042] The applicant found that as the mass fraction of the sodium hydroxide solution increased, the extraction rate of cellulose also increased. However, when the mass fraction exceeded 12%, the increase in the extraction rate was no longer significant. Therefore, from the perspective of cost saving and environmental protection, a 12% sodium hydroxide solution was selected as the optimal extraction condition.

[0043] S14: placing the corn stalk powder and the sodium hydroxide mixed solution into a microwave oven and heating them for a preset time, thereby breaking chemical bonds between molecules of the corn stalk powder by microwaves from the microwave oven.

[0044] In this embodiment, the power of the microwave oven is set to 595W, and the heating time is 10min. The applicant found that with the increase of microwave power, the chemical bonds between the molecules inside the corn stalks are broken more thoroughly, the removal rate of hemicellulose and lignin is higher, and the cellulose content finally obtained is higher. However, when the microwave power exceeds 595W, the rising trend of the cellulose extraction rate slows down significantly. From the perspective of cost saving, 595W is the optimal extraction power. At the same time, the applicant found that when the microwave treatment time does not exceed 10 minutes, microwave radiation promotes the breaking of chemical bonds between molecules, which is beneficial to the extraction of cellulose. However, when the microwave treatment time exceeds 10 minutes, the excessive microwave radiation time damages the structure of cellulose, resulting in a decrease in the cellulose extraction rate. Therefore, 10 minutes is selected as the optimal heating extraction time.

[0045] Corn straw cellulose is extracted using microwave-assisted method, which is an emerging technology for efficient extraction of corn straw cellulose. Its working principle is that microwave radiation can stimulate high-frequency vibrations of internal polar molecules, thereby strengthening the interaction between molecules and increasing the friction between molecules, thereby causing cell rupture. In corn straw, microwave radiation can destroy the hydrogen bonds between cellulose, hemicellulose and lignin in the cell wall, thereby effectively separating these components. Microwave-assisted extraction of corn straw cellulose has a higher extraction rate and can reduce the use of chemical reagents, which not only helps save costs, but is also of great significance for environmental protection.

[0046] S15: The temperature of the heated corn stalk powder and sodium hydroxide mixed solution is lowered to room temperature, and the corn stalk powder is washed with deionized water, filtered, and dried to obtain corn stalk powder with a neutral pH value. The drying is performed in a drying oven of model DZF-6210 produced by Honghua Instrument Equipment Co., Ltd. The drying temperature is 50° C. and the drying time is 12 hours.

[0047] At the same time, slowly pour pure glacial acetic acid into the sodium chlorite solution to prepare bleach.

[0048] In the present embodiment, 150ml of pure glacial acetic acid is slowly poured into 300ml of sodium chlorite solution with a concentration of 0.4mol / L to prepare a bleaching agent. The role of the sodium chlorite solution in the bleaching agent is to remove the lignin in the system. The applicant found that when the sodium chlorite concentration is controlled within the range of 0.1mol / L to 0.4mol / L, as its concentration increases, the extraction rate of cellulose gradually increases. However, when the concentration of the sodium chlorite solution exceeds 0.4mol / L, due to the excessively high concentration of sodium chlorite, part of the cellulose in the corn stalks will be dissolved, resulting in a decrease in the cellulose extraction rate. Therefore, 0.4mol / L is selected as the sodium chlorite solution concentration for optimal extraction.

[0049] S16: Add bleaching agent to the corn stalk powder filtered in step S15 and heat it in a constant temperature water bath at 75° C. for 1.5 hours until a white precipitate appears.

[0050] The applicant found that increasing the extraction temperature can improve the cellulose extraction rate, but too high a temperature reduces the solubility of lignin chlorate and inhibits the hydrolysis of lignin chlorate, resulting in a decrease in the cellulose content of the product. Therefore, the extraction temperature was set to 75°C.

[0051] In this embodiment, the volume ratio of the bleaching agent to the straw powder is 20:1.

[0052] S17: The white precipitate obtained in step S16 is washed with deionized water and filtered to obtain white corn straw powder with a neutral pH value, and the powder is placed in a drying oven for drying to obtain corn straw cellulose.

[0053] In this embodiment, the drying temperature of the drying box is 40° C. and the drying time is 12 hours. The drying box model is: DZF-6210, manufacturer: Honghua Instrument Equipment Co., Ltd.

[0054] S2: preparing a nanofiber suspension; comprising the following steps: S21: Deionized water is added to the corn straw cellulose obtained in step S1, and stirred with a stirrer to form a corn straw cellulose solution. At the same time, 64 mg of 2,2,6,6-tetramethylpiperidin-1-oxyl free radical and 400 mg of sodium bromide are added to 100 ml of deionized water to form a catalyst solution.

[0055] In this embodiment, 4 g of corn straw cellulose and 200 mL of deionized water were used for stirring, the stirring speed was 800 r / min, and the stirring time was 1 hour. The ratio of corn straw cellulose to deionized water is usually 1 g of corn straw cellulose to 50 mL of deionized water. The agitators in this embodiment and step S31 are all planetary agitators, model: DF-101D, and the stirring speed can be adjusted in the range of 0-2600 r / min, and the manufacturer: Gongyi Yuhua Instrument Co., Ltd.

[0056] S22: Add the catalyst solution to the corn straw cellulose solution to form a cellulose and catalyst mixed solution. The pH of the cellulose and catalyst mixed solution is about 7, and sodium hydroxide solution needs to be added to adjust the solution pH to about 10. If the pH of the mixed solution is less than 10, continue to drop a small amount of sodium hydroxide solution. If it is greater than 10, add hydrochloric acid solution to adjust the pH to 10.

[0057] In this embodiment, the pH value is 10. The alkaline environment can neutralize the acidic components in the cellulose, making the cellulose easier to extract. Using 2,2,6,6-tetramethylpiperidin-1-oxyl free radical as a catalyst helps prevent the aggregation of cellulose fibers, so that the cellulose fiber suspension has better stability.

[0058] S23: adding a sodium hypochlorite solution to the mixed solution of cellulose and the catalyst to form an oxidized cellulose fiber suspension.

[0059] In this embodiment, the total amount of sodium hypochlorite solution added is in the range of 8 ml to 28 ml, and 1.6 ml is added to the mixed solution of cellulose and catalyst at intervals of 10-15 minutes. If the pH value of the mixed solution of cellulose and catalyst is in the range of 10.5±0.1 15 minutes after the addition of sodium hypochlorite solution, 10 ml to 15 ml of anhydrous ethanol is then added to make the pH value of the cellulose fiber suspension less than 10, and the oxidation reaction of sodium hypochlorite is stopped.

[0060] The sodium hypochlorite solution is added to the cellulose fiber suspension, mainly to oxidize the cellulose fibers, so that the cellulose fibers are dispersed in water to form a stable suspension.

[0061] S24: The oxidized cellulose fiber suspension is placed in a centrifuge and centrifuged at a speed of 8000r / min for 10 minutes. After the centrifugation, the upper clear liquid is removed and the lower cellulose precipitate is retained. Next, the retained cellulose precipitate is washed with deionized water to neutralize and dry. The purpose of washing is to remove residual impurities and unreacted reagents attached to the cellulose fibers and make the cellulose fibers neutral. In order to ensure the washing effect, the above centrifugation and washing steps need to be repeated for a total of five times, and then dried to obtain the oxidized cellulose fibers. Finally, 8.3mL of deionized water is added to 0.7g of cellulose fibers, and ultrasonic treatment is performed for 1 hour with a power set to 1000W to further decompose the oxidized cellulose fibers into nanofibers. Through ultrasonic treatment, the oxidized cellulose fibers can be further decomposed into nano-scale fibers, and the final result is a nanofiber suspension.

[0062] Nanofibers are nanoscale materials extracted from cellulose. Compared with ordinary cellulose, nanofibers have many unique advantages. Nanofibers have a high specific surface area and excellent mechanical properties. These unique material properties give them significant advantages in making lightweight and high-strength materials, especially in the preparation of natural polymer composites. At the same time, nanofibers can entangle with other polymer chains due to their high aspect ratio to form more cross-linking sites, thus having great potential in improving the interfacial properties of composite materials. In addition, the biodegradable nature of nanofibers ensures that they will not cause long-term pollution to the environment after use. Compared with traditional petroleum-based materials, nanofibers have higher biocompatibility.

[0063] S3: preparing a hydrogel ink containing 7% by mass of straw nanofibers; comprising the following steps: S31: adding polyvinyl alcohol to the nanofiber suspension and heating it in an oil bath to obtain a hydrogel precursor; at the same time, preparing a dimethyl sulfoxide / PEDOT:PSS dispersion using dimethyl sulfoxide, deionized water and PEDOT:PSS conductive nanofibers.

[0064] In this embodiment, 1 g of polyvinyl alcohol was added to the nanofiber suspension and heated in an oil bath at 100° C. for 1 hour to obtain a hydrogel precursor solution. 1 mL of dimethyl sulfoxide, 8 mL of deionized water, and 1 mL of PEDOT:PSS conductive nanofiber were measured and the three mixed solutions were ultrasonically treated for 30 minutes using an ultrasonic cleaner to obtain a uniform dimethyl sulfoxide / PEDOT:PSS dispersion.

[0065] Polyvinyl alcohol is a water-soluble semi-crystalline polymer with excellent biocompatibility and solvent resistance, making it an ideal candidate material for the preparation of wearable flexible sensors. Both straw nanocellulose and polyvinyl alcohol contain a large number of hydroxyl groups, which can form a stable network structure through hydrogen bonding. In addition, the sodium carboxylate of straw nanofibers can also form hydrogen bonds with the hydroxyl groups of polyvinyl alcohol, thereby enhancing the stability of the hydrogel. This hydrogen bond network structure constitutes the basic framework of the hydrogel and gives it a certain mechanical strength.

[0066] The applicant found that when the mass percentage of straw nanofiber increased from 1% to 7%, the stress-strain and elastic modulus both increased by about 2 times. When the mass percentage of straw nanofiber increased from 8% to 20%, the mechanical properties of the hydrogel decreased. Therefore, when the mass percentage of straw nanofiber was selected to be 7%, the performance of the hydrogel ink was optimal.

[0067] Dimethyl sulfoxide is widely used in biology for cell cryopreservation because of its ability to interact with water molecules and lower the freezing point in the cell matrix. When dimethyl sulfoxide is introduced into the preparation of hydrogels, the antifreeze ability of the hydrogel can be improved. In addition to being a cryoprotectant, dimethyl sulfoxide is also beneficial to the gelation of polyvinyl alcohol and significantly improves the mechanical properties of the resulting organic hydrogel. PEDOT:PSS is a conductive polymer material that can withstand large strains, making it suitable for the manufacture of sensors that can be bent, stretched, or even twisted. At the same time, PEDOT:PSS has good electrical conductivity, and increasing the content of PEDOT:PSS can significantly increase the conductivity of the hydrogel, which is crucial for improving the sensitivity and response speed of the sensor.

[0068] S32: The hydrogel precursor solution and the dimethyl sulfoxide / PEDOT:PSS dispersion solution are mixed in a preset volume ratio (4:6), and placed in an ultrasonic cleaning machine for ultrasonic treatment for 2 hours to obtain a 3D printing hydrogel ink.

[0069] Increasing the PEDOT:PSS content can improve the conductivity of the hydrogel ink. However, with the increase of PEDOT:PSS content, the adhesion strength of the hydrogel ink gradually decreases. Considering the trade-off between printability, conductivity and adhesion, the hydrogel ink with a PEDOT:PSS mass percentage of 60% was selected as the printing material for constructing three-dimensional structures.

[0070] S4: 3D print at least 4 hydrogel sensing elements 211; In this embodiment, extrusion 3D printing technology is used to form the three-dimensional structure hydrogel sensor 211. The specific printing steps are as follows: S41: First, the hydrogel ink prepared in step 3 is transferred to the barrel of the 3D printer. In order to remove bubbles in the hydrogel ink and ensure that it flows smoothly, the 3D printer performs high-speed centrifugation. At the same time, in order to maintain the fluidity of the ink, the temperature of the barrel is set to 37°C. In this embodiment, the 3D printer is a multifunctional desktop biological 3D printer, model: Bio-architect®Sparrow, manufacturer: Genentech Biotechnology Co., Ltd.

[0071] S42: Next, the hydrogel sensor 211 model file is sliced ​​by the 3D printing slice software and imported into the 3D printer for printing. The air pressure of the 3D printer for extruding the printing material is 300 kPa, the diameter of the printer nozzle is selected to be 0.2 mm, the moving speed of the nozzle is 80 mm / min, and the speed of the nozzle for extruding the printing material is 0.3 ml / min.

[0072] The applicant found that in the range of lower printing pressure (50-250kpa) and smaller nozzle diameter (0.06-0.09mm), printing interruption or nozzle clogging is more common, while higher pressure range (450-500kPa) and larger nozzle diameter (0.25-0.54mm) will cause ink diffusion and shape deformation, so a more suitable printing pressure of 300Kpa and a more suitable nozzle diameter of 0.2mm are selected. If the nozzle moves too fast or the extrusion material speed is too slow, problems such as hydrogel line breakage and insufficient line height will occur. When the movement speed is too slow or the extrusion material speed is too fast, problems such as excessive hydrogel line width and gel accumulation will also occur, seriously affecting the molding effect. Therefore, the nozzle movement speed of 80mm / min and the extrusion material speed of 0.3ml / min are selected to avoid problems such as printing interruption, nozzle clogging, ink diffusion and shape deformation while ensuring a good molding effect.

[0073] S43: After the hydrogel sensor element 211 is completely printed, it is completely immersed in anhydrous ethanol for 1 hour to remove dimethyl sulfoxide. The rapid solvent exchange between dimethyl sulfoxide and anhydrous ethanol ensures that the shape of the hydrogel sensor element 211 does not collapse.

[0074] S44: Finally, the hydrogel sensor element 211 is taken out from the anhydrous ethanol and air-dried for 24 hours.

[0075] S5: The hydrogel sensing element 211 in step S4 is assembled into a honeycomb-like flexible sensor. The steps include: S51: First, the hydrogel sensing elements 211 obtained in step S4 are arranged opposite to each other and glued to form at least two sensing units 21. The supporting prisms 213 of the two hydrogel sensing elements 211 abut against each other, and a gap is provided between the two opposite conductive prisms.

[0076] S52 : Subsequently, at least two sensing units 21 are stacked together layer by layer by gluing to form a flexible sensing component 2 .

[0077] S53: Finally, the two wires 1 are connected to the upper surface and the lower surface of the flexible sensing component 2 respectively through the conductive tape 3, so as to measure the resistance change value output by the flexible sensing component 2.

[0078] When the honeycomb-like flexible sensor is not subjected to external pressure, the relatively arranged supporting prisms 213 in the flexible sensing component 2 are in contact with each other and play a supporting role, while the relatively arranged conductive prisms 214 are not in contact and do not form a conductive path. When the honeycomb-like flexible sensor is subjected to pressure, the flexible sensing component 2 is deformed, causing the relatively arranged conductive prisms 214 to contact each other and conduct electricity, thereby reducing the total resistance of the flexible sensing component 2. The more conductive prisms 214 that are in contact with each other, the smaller the total resistance of the honeycomb-like flexible sensor. The present invention adopts a two-layer superimposed structure. Under the same pressure, since the conductive prisms 214 between the two layers and inside each layer are likely to contact each other, more contact points are formed. This not only increases the number of conductive paths, but also makes the relative resistance change of the honeycomb-like flexible sensor more significant. This significant change in resistance is more easily captured by the detection system, thereby improving the sensitivity of the honeycomb-like flexible sensor to a certain extent.

[0079] An application of a honeycomb-like flexible sensor in a wearable device is implemented based on the honeycomb-like flexible sensor, and includes a wearable device and at least one honeycomb-like flexible sensor; the wearable device is used to be worn on a user's body; and each honeycomb-like flexible sensor is arranged inside the wearable device.

[0080] In this embodiment, the wearable device is a helmet. The helmet is provided with a group of simulated honeycomb flexible sensors that fit the left side, back of the head and right side of the head, and the simulated honeycomb flexible sensor groups are evenly distributed in the helmet. When a person wearing a helmet with simulated honeycomb flexible sensors falls or a traffic accident occurs during riding, causing the head to be hit, the simulated honeycomb flexible sensor is subjected to transient force and produces compression deformation. The greater the transient force, the greater the compression deformation of the simulated honeycomb flexible sensor, the more conductive prisms 214 that are in contact with each other, the larger the contact area, and the greater the resistance change generated. Therefore, the magnitude of the impact force on each part of the head can be divided according to the value of the output resistance change of each simulated honeycomb flexible sensor in the helmet. The position of the simulated honeycomb flexible sensor with the largest output resistance change value is the position that is hit the most, thereby assisting doctors to evaluate the degree of head injury and quickly find the most serious head injury position, so as to achieve the purpose of assisting the diagnosis and treatment of mild concussion.

[0081] The present invention is combined with Figures 4 to 7 The application of the honeycomb-like flexible sensor provided by the present invention in a wearable device is described with a specific embodiment.

[0082] like Figure 4The figure shows the distribution diagram of the simulated honeycomb flexible sensor array in the helmet, wherein the simulated honeycomb flexible sensor group that fits the left side of the head includes the first simulated honeycomb flexible sensor L1a, the second simulated honeycomb flexible sensor L1b, the third simulated honeycomb flexible sensor L1c and the fourth simulated honeycomb flexible sensor L1d. The simulated honeycomb flexible sensor group that fits the back of the head includes the fifth simulated honeycomb flexible sensor M1a and the sixth simulated honeycomb flexible sensor M1b. The simulated honeycomb flexible sensor group that fits the right side of the head includes the seventh simulated honeycomb flexible sensor R1a, the eighth simulated honeycomb flexible sensor R1b, the ninth simulated honeycomb flexible sensor R1c and the tenth simulated honeycomb flexible sensor R1d.

[0083] like Figures 5 to 7 As shown, when different parts of the helmet are hit, the simulated honeycomb flexible sensor group evenly distributed inside the helmet will generate a corresponding resistance change data graph. According to the resistance change data graph, the area of ​​the head that is hit the most can be quickly located, which is convenient for doctors to focus on treating this area. In addition, the resistance change at the maximum impact force that the human head can withstand can be set to a limit value. During competitions or daily training, athletes wear helmets containing simulated honeycomb flexible sensor groups. When the athlete's head is hit and the resistance change of a simulated honeycomb flexible sensor in the simulated honeycomb flexible sensor group exceeds the limit value, the training or competition can be suspended for timely treatment to prevent further damage.

[0084] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A honeycomb-like flexible sensor, characterized in that: It comprises two wires and a flexible sensing component, wherein the flexible sensing component comprises at least two sensing units, and two adjacent sensing units are stacked together layer by layer; the cross section of each sensing unit is evenly provided with hexagonal honeycomb holes; the two wires are respectively connected to the flexible sensing component through conductive tapes; Each of the sensing units comprises two hydrogel sensing elements arranged opposite to each other; each of the hydrogel sensing elements comprises a conductive hydrogel plate, a plurality of supporting prisms and a plurality of conductive prisms; the plurality of supporting prisms are evenly arranged on the conductive hydrogel plate and located at two opposite sides of the conductive hydrogel plate to form two rows of supporting prisms; the plurality of conductive prisms are evenly arranged on the conductive hydrogel plate and located between the two rows of supporting prisms; On the two oppositely arranged hydrogel sensing components, the two oppositely arranged rows of supporting prisms abut against each other, and a gap is arranged between the two oppositely arranged conductive prisms; on the two oppositely arranged hydrogel sensing components, the two adjacent conductive prisms and the conductive prisms opposite to the two conductive prisms together constitute a hexagonal honeycomb hole.

2. The honeycomb-like flexible sensor according to claim 1, characterized in that: The height of the conductive prism is smaller than the height of the supporting prism.

3. The honeycomb-like flexible sensor according to claim 1, characterized in that: The cross section of each of the conductive prisms and the cross section of each of the supporting prisms are both trapezoidal, and the edges of each of the conductive prisms and each of the supporting prisms form an angle of 60° with the horizontal line.

4. A method for preparing a honeycomb-like flexible sensor, used to manufacture the honeycomb-like flexible sensor according to any one of claims 1 to 3, characterized in that: The steps include: S1: Extraction of corn stover cellulose; S2: preparation of nanofiber suspension; S3: preparing hydrogel ink; S4: 3D printing at least 4 of the hydrogel sensing elements; S5: Assembling the hydrogel sensing element in step S4 into a flexible sensing component, and combining the flexible sensing component and the wire into a honeycomb-like flexible sensor.

5. The method for preparing a honeycomb-like flexible sensor according to claim 4, characterized in that: Step S1 includes the following steps: S11: washing and drying the corn stalks, putting them into a grinder for crushing, and then collecting the corn stalk powder after being sieved through a sieve; S12: washing and filtering the corn stalk powder with deionized water, soaking the filtered corn stalk powder in anhydrous ethanol, filtering again, and drying the filtered corn stalk powder; S13: adding the corn stalk powder dried in step S12 into the sodium hydroxide solution to form a mixed solution of corn stalk powder and sodium hydroxide; S14: placing the corn stalk powder and the sodium hydroxide mixed solution into a microwave oven and heating them for a preset time, thereby breaking chemical bonds between molecules of the corn stalk powder by microwaves from the microwave oven; S15: lowering the temperature of the heated corn stalk powder and sodium hydroxide mixed solution to room temperature, washing with deionized water, filtering, and drying to obtain corn stalk powder with a neutral pH value; at the same time, dissolving the sodium chlorite solution in an aqueous glacial acetic acid solution to prepare a bleaching agent; S16: adding the bleaching agent to the corn stalk powder filtered in step S15, and heating it in a constant temperature water bath until a white precipitate appears; S17: The white precipitate obtained in step S16 is washed with deionized water and filtered to obtain white corn stalk powder with a neutral pH value, and the powder is placed in a drying oven for drying to obtain corn stalk cellulose.

6. The method for preparing a honeycomb-like flexible sensor according to claim 4, characterized in that: Step S2 includes the following steps: S21: adding deionized water to the corn straw cellulose obtained in step S1 and stirring to obtain a corn straw cellulose solution; at the same time, adding tetramethylpiperidinium oxide and sodium bromide to the deionized water to form a catalyst solution; S22: adding the catalyst solution to the corn straw cellulose solution to form a cellulose and catalyst mixed solution; then, adjusting the pH value of the cellulose and catalyst mixed solution to alkaline using a hydrochloric acid solution and a sodium hydroxide solution; S23: adding a sodium hypochlorite solution to the mixed solution of cellulose and the catalyst to form an oxidized cellulose fiber suspension; S24: The oxidized cellulose fiber suspension is centrifuged using a centrifuge, then washed with deionized water to become neutral and dried, and finally deionized water is added to obtain a nanofiber suspension through ultrasonic treatment.

7. The method for preparing a honeycomb-like flexible sensor according to claim 4, characterized in that: Step S3 includes the following steps: S31: adding polyvinyl alcohol to the nanofiber suspension and heating it in an oil bath to obtain a hydrogel precursor solution; at the same time, preparing a dimethyl sulfoxide / PEDOT:PSS dispersion using dimethyl sulfoxide, deionized water and PEDOT:PSS conductive nanofibers; S32: The hydrogel precursor liquid and the dimethyl sulfoxide / PEDOT:PSS dispersion liquid are mixed according to a preset volume ratio, and placed in an ultrasonic cleaning machine for ultrasonic treatment to obtain a hydrogel ink.

8. The method for preparing a honeycomb-like flexible sensor according to claim 4, characterized in that: Step S5 includes the following steps: S51: First, the hydrogel sensing elements obtained in step S4 are arranged opposite to each other in pairs and glued together to form at least two sensing units; S52: Subsequently, at least two of the sensing units are stacked together layer by layer by gluing to form a flexible sensing component; S53: Finally, two wires are connected to the upper surface and the lower surface of the flexible sensing component respectively through conductive tape.

9. An application of a honeycomb-like flexible sensor in a wearable device, based on the honeycomb-like flexible sensor according to any one of claims 1 to 3, characterized in that: It comprises a wearable device and at least one honeycomb-like flexible sensor; the wearable device is used to be worn on a user's body; each of the honeycomb-like flexible sensors is arranged inside the wearable device.

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