A flexible pressure sensor based on bacterial cellulose and textiles and a preparation method thereof

Abstract

The present invention relates to the technical field of wearable intelligent flexible sensors. The present invention discloses a flexible pressure sensor based on bacterial cellulose and textiles and a preparation method thereof. The flexible pressure sensor is a bacterial cellulose network carrying conductive nanofillers that are directionally attached to the upper and lower surfaces and vertical warp fibers of a compressible textile. The present invention adds fiber-producing bacteria, conductive nanofillers, and compressible textiles to a culture medium of fiber-producing bacteria, and cultures them at a certain temperature for a period of time to obtain a textile-based hydrogel; the textile-based hydrogel is sterilized, washed, and freeze-dried to obtain the flexible pressure sensor. The flexible pressure sensor achieves a breakthrough in bacterial cellulose-based pressure sensors from a two-dimensional sheet film structure to a three-dimensional structure, can obtain a larger compression working range without sacrificing sensitivity, and has high skin compliance.

Description

Technical Field

[0001] The present invention relates to the technical field of wearable intelligent flexible sensors, and in particular to a flexible pressure sensor based on bacterial cellulose and textiles and a preparation method thereof. Background Art

[0002] The development of wearable intelligent flexible sensor devices that can sensitively detect physical and biological signals without significant impact on the environment is of great significance for their applications in electronic skin, health monitoring and other fields. Current flexible pressure sensors are usually made by depositing sensing materials on the surface of flexible substrates or encapsulating them into flexible substrates. Therefore, the working range in practical applications mainly depends on the compressibility of flexible materials. However, flexible substrates have strong hysteresis effects and it is difficult to respond to compression recovery in time, which has a great impact on the sensitivity of the sensor. In addition, the mechanical flexibility, environmental degradability and interface adaptability of pressure sensors with skin are equally important for the application of smart wearables.

[0003] Bacterial cellulose (BC), as a potential biomass resource, has a unique three-dimensional nano-network structure and abundant hydrogen bonds, and can adhere to conductive materials like "spider silk" to form a sensing network. However, bacterial cellulose-based sensors are always prepared into sheet-like films by physical coating or chemical grafting. Although the production process is simplified, bacterial cellulose-based pressure sensors in the state of two-dimensional thin film sheets are generally insensitive to pressure signals and have very limited compressibility. In particular, the BC film prepared by direct drying has a dense stacking structure and has almost no compressibility. For example, the invention patent CN109734842B discloses a transparent conductive flexible bacterial cellulose composite material and a preparation method thereof. First, the bacterial cellulose hydrogel is treated with sodium hydroxide, then immersed in acrylic acid, and finally polymerized and cured in a photopolymerized low eutectic solvent using ultraviolet light to obtain the transparent conductive flexible bacterial cellulose composite material. For example, the invention patent with patent number CN 115060397 A provides a method for preparing a graphene / bacterial cellulose-based wearable wireless pressure sensor, firstly, the graphene and bacterial cellulose are freeze-dried separately, then mixed and ultrasonically dispersed to obtain a dispersion, the dispersion is vacuum filtered and cut to obtain a sheet of graphene / bacterial cellulose conductive material, and finally the dispersion is placed between the filtered sheet conductive layers to obtain the graphene / bacterial cellulose-based wearable wireless pressure sensor. Since traditional bacterial cellulose-based sensors rely on the inherent resistance change of the sensing material and the deformation range of bacterial cellulose, it is difficult to strike a balance between high sensitivity and sufficient working range. In addition, the bacterial cellulose-based pressure sensors in the two-dimensional film state after drying have a certain rigidity and brittleness, which makes them less skin-compatible and limits their use in smart wearables. Summary of the invention

[0004] The purpose of the present invention is to propose a flexible pressure sensor based on bacterial cellulose and textiles and a preparation method thereof in view of the above-mentioned deficiencies of the prior art. The problem that the sensitivity and working range of the existing sensor devices are difficult to balance, the pressure-strain working range is small, the adaptability to soft interfaces such as skin is poor, and the degradation pressure caused to the environment after disposal is solved. The flexible pressure sensor achieves a breakthrough in the bacterial cellulose-based pressure sensor from a two-dimensional sheet film structure to a three-dimensional structure, can obtain a larger compression working range without sacrificing sensitivity, and has high skin compliance.

[0005] The invention discloses a flexible pressure sensor based on bacterial cellulose and textiles. The flexible pressure sensor is a bacterial cellulose network carrying conductive nanofillers which are directionally attached to the upper and lower surfaces and vertical warp fibers of the compressible textiles.

[0006] Furthermore, the conductive nanofiller includes one or more of polypyrrole, gold nanoparticles, silver nanoparticles, silver nanowires, vanadium dioxide, graphene oxide, Mxene, and carbon nanotubes.

[0007] Furthermore, the compressible textile is a polyester fiber textile; the raw material of the polyester fiber textile includes polyester fiber; and\or the raw material of the polyester fiber textile also includes polyurethane fiber.

[0008] Furthermore, the compressible textile is a three-dimensional spacer fabric.

[0009] A method for preparing the above flexible pressure sensor comprises adding fiber-producing bacteria, conductive nanofillers, and compressible textiles into a culture medium of fiber-producing bacteria, culturing at a certain temperature for a period of time to obtain a textile-based hydrogel; sterilizing and washing the textile-based hydrogel, and then freeze-drying it to obtain the flexible pressure sensor.

[0010] Furthermore, the culture medium is HS culture medium, including glucose, yeast extract, peptone, citric acid, disodium hydrogen phosphate dodecahydrate, and deionized water.

[0011] Furthermore, the fiber-producing bacteria is Acetobacter xylinum (also known as Gluconacetobacter xylinum) of the genus Acetobacter.

[0012] Furthermore, the mass of the conductive nanofiller is 0.1wt% to 0.4wt% of the mass of the culture medium.

[0013] Furthermore, the textile-based hydrogel was obtained by culturing at 30° C. for 5-7 days.

[0014] Further, the culture medium is sterilized in a high temperature and high pressure sterilizer for use; and\or, the textile-based hydrogel is sterilized by boiling with a sodium hydroxide aqueous solution, and then washed with deionized water until neutral.

[0015] Furthermore, the size of the compressible textile is 15×15 mm to 25×25 mm.

[0016] The present invention utilizes the in-situ fermentation technology of bacterial cellulose, and adds conductive fillers during the culture process to form a three-dimensional nano-conductive network. The problem of low sensor sensitivity is solved through the contact and separation process of the three-dimensional conductive network. In order to increase the working range of the bacterial cellulose nano-conductive network, textiles with super strong compression recovery ability are added during the culture process as the skeleton structure for the directional growth of the functional nano-bacterial cellulose network, giving the system greater compression resilience. The addition of textiles also solves the problem of flexible sensor devices fitting soft interfaces such as human skin. Due to the integrated in-situ preparation of biological methods and non-toxic and harmless raw materials, the prepared bacterial cellulose / textile-based flexible pressure sensor is non-toxic, biodegradable, and environmentally friendly.

[0017] The flexible pressure sensor based on bacterial cellulose and textiles provided by the present invention has a hierarchical sensing network, wherein the hierarchical sensing network is a conductive network structure of bacterial cellulose and nano-conductive fillers formed by the functional bacterial cellulose carrying conductive nano-fillers attached and grown on the fibers of the textiles, and the network is directional growth around the vertical warp and upper and lower surface fibers of the textile skeleton to form a three-dimensional structure. The conductive nano-network formed by bacterial cellulose / nano-conductive fillers can achieve high sensitivity under small-scale compressive strain, and the directional growth of the conductive network on the spacer fabric can increase the pressure sensing range of the device, so as to achieve high sensitivity under large stress. The formation of the hierarchical sensing structure achieves a significant improvement in sensitivity and compression working range.

[0018] The present invention provides a method for preparing a flexible pressure sensor based on bacterial cellulose and textiles. By using the biological preparation technology of in-situ fermentation, compressible textiles and conductive nanofillers are added to the culture system of fiber-producing bacteria, and the flexible pressure sensor of bacterial cellulose and textiles is obtained after 5-7 days of biological fermentation. The culture process and the added materials have no significant impact on humans and the environment, avoiding the impact of the addition of non-degradable flexible polymer materials on the environment, and the textiles can have strong compliance with soft interfaces such as human skin, meeting the needs of smart wear. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flow chart of the preparation method of the present invention;

[0020] Figure 2 This is a physical display diagram of the flexible pressure sensor based on bacterial cellulose and textiles prepared in Example 1;

[0021] Figure 3This is a microscopic morphology of the conductive bacterial cellulose prepared in Example 1 directional growth around the textile;

[0022] Figure 4a This is a comparison chart of the sensing performance of the flexible pressure sensor based on bacterial cellulose and textiles prepared in Example 1 and the two-dimensional bacterial cellulose sensing film prepared in Comparative Example 1;

[0023] Figure 4b This is a sensing performance diagram of the two-dimensional bacterial cellulose sensing film prepared in Comparative Example 1;

[0024] Figure 5 A comparison chart of sensing performance of flexible sensor devices prepared with different conductive fillers in Examples 1, 2, and 3;

[0025] Figure 6a This is a graph of the flexible sensor prepared in Example 1 monitoring the pulse of human physiological signals;

[0026] Figure 6b This is a graph of abdominal respiration monitoring of human physiological signals by the flexible sensor prepared in Example 1;

[0027] Figure 6c This is a gesture monitoring diagram of the flexible sensor prepared in Example 1. DETAILED DESCRIPTION

[0028] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0029] The present invention provides a method for preparing a flexible pressure sensor based on bacterial cellulose and textiles, comprising the following steps:

[0030] S1. Preparation of culture medium: The culture medium is HS culture medium, including glucose, yeast extract, peptone, citric acid, disodium hydrogen phosphate dodecahydrate, and deionized water. The culture medium is sterilized in a high-temperature and high-pressure sterilizer for use.

[0031] S2. Transplantation of materials: The fiber-producing bacteria selected in the present invention are Acetobacter xylinus (also known as Gluconacetobacter xylinus) obtained from the Institute of Microbiology, Chinese Academy of Sciences. The fiber-producing bacteria, nano-conductive fillers and textiles are added to the culture system and cultured at 30° C. for 5-7 days.

[0032] S3. Post-processing of the flexible pressure sensor. The textile-based hydrogel obtained by in-situ fermentation is boiled with a sodium hydroxide aqueous solution, then washed with deionized water until neutral, and finally freeze-dried to obtain the flexible pressure sensor.

[0033] Example 1

[0034] In this embodiment, a flexible sensor is prepared using conductive nano-polypyrrole (PPy), bacterial cellulose (BC), and three-dimensional spacer fabric as raw materials.

[0035] The structural feature of the device is that the bacterial cellulose network carries PPy nanoparticles and is oriented and attached to the upper and lower surfaces of the spacer fabric and the vertical warp fibers. The spacer fabric has a black appearance at the macroscopic level, and the bacterial cellulose nanonetwork carrying black nanoparticles is observed at the microscopic level. The specific preparation steps of the present invention are as follows:

[0036] S1. Preparation of culture medium: Add 2 g of glucose, 0.5 g of yeast extract, 0.5 g of peptone, 0.15 g of citric acid, 0.68 g of disodium hydrogen phosphate dodecahydrate, and 100 mL of deionized water to the culture medium, and then sterilize at 120°C under high temperature and high pressure for use.

[0037] S2. In situ culture: 2 mL of Acetobacter xylinum bacterial solution, 0.4 wt% polypyrrole (PPy), and 25×25 mm spacer fabric were added to the culture system, and dynamically cultured for 5 hours, and then statically cultured at 30° C. for 5-7 days.

[0038] S3. Post-processing of the flexible pressure sensor. Prepare 100 mL of 1 g / 100 mL sodium hydroxide aqueous solution, boil the obtained bacterial cellulose / PPy / spacer fabric hydrogel in the sodium hydroxide solution for sterilization, shake it in deionized water for 3 days, change the water every 4 hours to remove bacteria and debris, and finally freeze-dry to obtain the flexible pressure sensor.

[0039] Example 2

[0040] A flexible pressure sensor based on bacterial cellulose and textiles is different from Example 1 in that Example 2 uses 0.4 wt% of conductive carbon nanotubes (CNT) as conductive nanofiller to prepare the flexible sensor. Other aspects are similar to Example 1 and will not be described in detail.

[0041] Example 3

[0042] A flexible pressure sensor based on bacterial cellulose and textiles is different from Example 1 and Example 2 in that Example 3 uses 0.4wt% of graphene oxide (GO) as a conductive nanofiller to prepare a flexible sensor. Other aspects are substantially the same as Example 1 and will not be described in detail.

[0043] Comparative Example 1

[0044] A novel method for preparing a bacterial cellulose-based flexible pressure sensor, compared with Example 1, the difference is that no textile is added to the culture medium as a network for the directional growth of conductive bacterial cellulose, so the bacterial cellulose-based flexible pressure sensor is a two-dimensional bacterial cellulose film with a black appearance. As shown in FIG4 , the BC / PPy two-dimensional conductive film has a small compression range, so the working range is limited to 5 kPa, which is much lower than the working range of BC / PPy / spacer fabric (300 kPa).

[0045] Figure 1 This is the preparation flow chart of Example 1; the present invention provides a flexible pressure sensor based on bacterial cellulose and textiles, including conductive bacterial cellulose and a three-dimensional spacer fabric that enhances its working range. The three-dimensional spacer fabric is mainly composed of polyester fibers and has excellent shape retention and a three-dimensional fiber skeleton. Using the one-pot biopreparation technology of the in situ fermentation method, the compressible textile is cut into 15×15mm~25×25mm and conductive nanofillers (0.1wt%~0.4wt%) are added to the culture system of fiber-producing bacteria, and the functional bacterial cellulose carries the conductive nanofillers to attach and grow on the fibers of the textiles to form a hierarchical sensing structure.

[0046] Figure 2 This is a physical display of the bacterial cellulose-based flexible sensor device prepared in Example 1. Figure 2 It can be seen that the flexible pressure sensor based on bacterial cellulose and textiles provided by the present invention has good compressibility and bendability.

[0047] Figure 3 This is a microscopic morphology of the conductive bacterial cellulose prepared in Example 1 directional growth around a textile, from which it can be seen the conductive network structure of the bacterial cellulose and the nano-conductive filler, the vertical warp of the network around the textile skeleton, and the three-dimensional structure of the fiber growth on the upper and lower surfaces.

[0048] Figure 4a This is a comparison chart of the sensing performance of the bacterial cellulose-based flexible sensor device prepared in Example 1 and the two-dimensional bacterial cellulose sensing film prepared in Comparative Example 1. Figure 4b This is a sensing performance diagram of the two-dimensional bacterial cellulose sensing film prepared in Comparative Example 1;

[0049] from Figure 4a and 4b It can be seen that the compression range of the BC / PPy two-dimensional conductive film prepared in Comparative Example 1 is small, and therefore the working range is limited to 5 kPa, which is much lower than the working range (300 kPa) of the BC / PPy / spacer fabric flexible pressure sensor prepared in Example 1.

[0050] Figure 5The following is a comparison chart of the sensing performance of flexible sensor devices prepared with different nano-conductive fillers in Examples 1, 2, and 3. Figure 5 It can be seen that the pressure sensor prepared in Example 2 has lower relative current change value and sensitivity than that in Example 1. The pressure sensor prepared in Example 3 has lower relative current change value and sensitivity and a smaller working range than that in Example 1 and Example 2. This may be due to the different properties and conductive mechanisms of the nano-conductive fillers.

[0051] Figure 6a This is a graph of the flexible sensor prepared in Example 1 monitoring human physiological signal pulse. Figure 6b This is a graph of abdominal breathing monitoring of human physiological signals by the flexible sensor prepared in Example 1. Figure 6c This is a gesture monitoring diagram of the flexible sensor prepared in Example 1.

[0052] from Figure 6a-6c It can be seen that the flexible sensor prepared in Example 1 has stable and distinguishable electrical signal changes in human joint movements with a larger compression strain range (such as gestures, etc.) and physiological activities with a fine compression strain range (such as pulse, breathing, etc.).

[0053] For matters not mentioned above, the prior art applies.

[0054] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art to which the present invention belongs may make various modifications or supplements to the specific embodiments described or replace them in a similar manner, but they will not deviate from the direction of the present invention or exceed the scope defined by the attached claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A flexible pressure sensor based on bacterial cellulose and textiles, characterized in that: The flexible pressure sensor is a bacterial cellulose network carrying conductive nanofillers and directional attached to the upper and lower surfaces and vertical warp fibers of the compressible textile; The compressible textile is a three-dimensional spacer fabric; It is prepared by the following method, and the specific steps are as follows: The fiber-producing bacteria, conductive nanofillers and compressible textiles are added to a culture medium of the fiber-producing bacteria, and cultured at a certain temperature for a period of time to obtain a textile-based hydrogel; the textile-based hydrogel is sterilized, washed and freeze-dried to obtain the flexible pressure sensor.

2. The flexible pressure sensor according to claim 1, characterized in that: The conductive nanofiller includes one or more of polypyrrole, gold nanoparticles, silver nanoparticles, silver nanowires, vanadium dioxide, graphene oxide, Mxene, and carbon nanotubes.

3. The flexible pressure sensor according to claim 1, characterized in that: The compressible textile is a polyester fiber textile, the raw material of which includes polyester fiber; and / or the raw material of which also includes polyurethane fiber.

4. The flexible pressure sensor according to claim 1, characterized in that: The culture medium is HS culture medium, which includes glucose, yeast extract, peptone, citric acid, disodium hydrogen phosphate dodecahydrate, and deionized water.

5. The flexible pressure sensor according to claim 1, characterized in that: The fiber-producing bacteria is Acetobacter xylinum of the genus Acetobacter.

6. The flexible pressure sensor according to claim 1, characterized in that: The mass of the conductive nanofiller is 0.1 wt% to 0.4 wt% of the mass of the culture medium.

7. The flexible pressure sensor according to claim 1, characterized in that: The textile-based hydrogel was obtained by culturing at 30°C for 5-7 days.

8. The flexible pressure sensor according to claim 1, characterized in that: The culture medium is sterilized in a high-temperature and high-pressure sterilizer for use; and\or, the textile-based hydrogel is sterilized by boiling a sodium hydroxide aqueous solution and then washed with deionized water until neutral; and\or, the size of the compressible textile is 15×15mm to 25×25mm.

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