A pure bio-based flexible sensing material and a preparation method and application thereof

Abstract

The application discloses a kind of pure bio-based flexible sensing materials and its preparation method and application.Preparation method includes the following steps: gel state Tempo oxidized nanocellulose is dispersed in aqueous solution, then dialdehyde modified cassava starch is added to it, and it is heated at 70-90 DEG C for 0.5-1h to make it gelatinize, the mass ratio of dialdehyde modified cassava starch and Tempo oxidized nanocellulose is 1:(0.1-0.5), to obtain A liquid.A liquid is compounded with gelatin aqueous solution, the obtained solution is poured into mould and refrigerated, and the gel is immersed in 0.02-0.1mol / L FeCl3 solution for 24-48h, to obtain the pure bio-based flexible sensing material.The pure bio-based flexible sensing material of the application has excellent mechanical strength and good conductivity, and can realize high sensitivity sensing performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of sensing technology, and particularly relates to a pure bio-based flexible sensing material and a preparation method and application thereof. BACKGROUND

[0002] Flexible hydrogel sensors are widely used in wearable devices, health monitoring, artificial electronic skin and other fields. However, there are still great challenges in the characteristics of flexible hydrogel sensors, such as fast response, significant sensing stability, incomplete recyclability, green environmental protection, low cost and the like. Chinese patent CN118580425A discloses a hydrophobic association hydrogel based on high amylose corn starch and a preparation method and application thereof. The high amylose corn starch is mixed with imidazole ionic liquid to prepare a hydrophobic association hydrogel, and the tensile stress thereof only reaches 70 KPa. In addition, the main part of the gel material is still a petroleum-based material. In addition, there are documents that disclose that dialdehyde starch is compounded with gelatin to prepare a gel, and when the compression strain is 80%, the compression stress is only 0.8 MPa. (Tianqi C, Yuxue S, Yue W, et al. Mechanical, microstructural, and rheological characterization of gelatin-dialdehyde starch hydrogels constructed by dual dynamic crosslinking [J]. LWT, 2022, 161).

[0003] In addition, since the petroleum-based flexible sensor is not degradable under natural conditions and cannot be recycled, a large amount of electronic waste generated after being discarded will seriously threaten the environment and ecology, which is not conducive to green and sustainable development. At the same time, many conductive hydrogels have poor mechanical properties and will inevitably be damaged and destroyed in the deformation of the application scene. Therefore, driven by the two problems of environment and application, it is urgent to develop a pure bio-based conductive hydrogel strain sensor with excellent mechanical properties, sensing stability, biodegradability and recyclability. SUMMARY

[0004] In view of the deficiencies in the prior art, the purpose of the present application is to provide a pure bio-based flexible sensing material and a preparation method and application thereof, which mainly solve the practical problems of existing sensors that are difficult to degrade after recycling, poor mechanical properties and high cost.

[0005] In order to achieve the above-mentioned purpose, the present application is realized by the following technical scheme:

[0006] In a first aspect, the present application provides a preparation method of a pure bio-based flexible sensing material, comprising the following steps:

[0007] (1) dispersing the gel-state Tempo-oxidized nanocellulose in an aqueous solution, and adding dialdehyde-modified cassava starch to the aqueous solution, heating to gelatinize, and ultrasonic dispersion to obtain A liquid;

[0008] (2) mixing and dispersing the A liquid with an aqueous gelatin solution;

[0009] (3) pouring the solution obtained in step (2) into a mold, and after cold storage, immersing the gel in a Fe 3+ salt solution, cooling and solidifying to obtain the product.

[0010] Preferably, in step (1), the heating temperature is 70-90℃, and the heating time is 30-60 min.

[0011] Preferably, in step (2), the weight / volume fraction of gelatin in water is 8-12wt%.

[0012] Preferably, in step (2), the mass ratio of the A liquid to the aqueous gelatin solution is (0.6-1.2):10.

[0013] Preferably, in step (3), the Fe 3+ salt solution is selected from one or more of FeCl3 solution, Fe2(SO4)3 solution, and FePO4 solution.

[0014] Preferably, in step (3), the Fe 3+ salt solution is FeCl3 solution, and the concentration is 0.02-0.1mol / L.

[0015] Further preferably, in step (3), the concentration of the FeCl3 solution is 0.06mol / L, the immersion time is 24h, and the immersion temperature is 4℃.

[0016] Preferably, in step (3), the immersion time is 24-48h, and the immersion temperature is 2-4℃.

[0017] Preferably, in step (3), the cold storage is at 2-4℃ for 24-48h, and the cooling and solidification temperature is 2-5℃.

[0018] In some embodiments, the water is deionized water.

[0019] In some embodiments, the nanocellulose is Tempo-oxidized nanocellulose.

[0020] Cassava starch is a good adhesive material and is easy to modify. The flexible sensor material is prepared by impregnating a solution of Tempo-oxidized nanocellulose, gelatin and dialdehyde-modified cassava starch in FeCl3 solution. The dialdehyde-modified cassava starch forms dynamic covalent bonds with the amino groups in the gelatin, improving the mechanical properties of the flexible sensor. FeCl3 forms coordination bonds with the hydroxyl groups in the Tempo-oxidized nanocellulose, further improving the mechanical properties of the flexible sensor. FeCl3 also imparts good sensing performance to the gel.

[0021] The flexible sensing material of the present application can improve the mechanical properties of the gel while achieving high sensitivity sensing performance.

[0022] The flexible sensing material can achieve the design of the gel network, enabling the sensing material to have fast response and high sensitivity.

[0023] The dialdehyde-modified cassava starch has biodegradability and is non-toxic. Its application in the field of flexible sensors provides a possibility for the high-value utilization of cassava starch and expands the application field of cassava starch.

[0024] The dialdehyde-modified cassava starch of the present application is prepared by oxidizing cassava starch with sodium periodate under acidic conditions. Specifically, cassava starch with a concentration of 6-12 wt% is mixed with sodium periodate at a mass ratio of 1:(0.2-1.5), and the oxidation reaction is carried out in the dark at a pH of 3.5-4, with a reaction temperature of 35-40℃ and a reaction time of 4-6h.

[0025] Preferably, the mass ratio of sodium periodate to cassava starch is (0.2-1.5):1, the concentration of cassava starch is 6-12 wt%, the pH of the solution is adjusted to 3.5, the reaction temperature is 35℃, the reaction time is 4h, and the reaction is carried out in the dark.

[0026] Further preferably, the mass ratio of sodium periodate to cassava starch is 1.5:1.

[0027] In a second aspect, the present application provides a pure bio-based flexible sensing material prepared by the above preparation method.

[0028] In a third aspect, the present application provides the use of the pure bio-based flexible sensing material in the preparation of flexible wearable sensors and / or health detection sensing materials.

[0029] The beneficial effects achieved by one or more embodiments of the present application are as follows:

[0030] (1) The dialdehyde-modified cassava starch prepared by the present application is used as a raw material to form a gel solution by compounding with Tempo-oxidized nanocellulose and gelatin, and the gel solution is impregnated in Fe3+ Fe is constructed in salt solution 3+ Fe in salt solution 3+ OH in Tempo-oxidized nanocellulose - form coordination structure, which can fix Fe 3+ in the gel network, and improve the mechanical strength of the gel, so that the flexible gel material has a more extensive application scenario in sensing.

[0031] (2) The preparation process of the dialdehyde modified cassava starch provided by the present application is simple, the reaction conditions are mild, and is suitable for large-scale application.

[0032] (3) The pure bio-based flexible sensing material prepared by the method has excellent mechanical strength and good conductivity, and can realize high-sensitivity sensing performance. When the gel is immersed in a 0.06 mol / L FeCl3 solution, the tensile stress of the gel is 201.4 KPa, the tensile strain is 151.1%, the compressive stress is 5376.43 KPa, and the compressive strain is 93.51%. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 Tensile property diagram of the flexible sensing gel material of Comparative Example 2, Example 5, 6, 7, 8, and 9 immersed in a 0.02-0.1 mol / L FeCl3 solution.

[0034] Figure 2 Compression property diagram of the flexible sensing gel material of Comparative Example 2, Example 5, 6, 7, 8, and 9 immersed in a 0.02-0.1 mol / L FeCl3 solution.

[0035] Figure 3 Tensile property diagram of the gel material of Comparative Example 1.

[0036] Figure 4 Compression property diagram of the gel material of Comparative Example 1. DETAILED DESCRIPTION

[0037] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0038] The present application does not have special restrictions on the type and source of the gelatin raw material used. The following takes pig bone gelatin as an example; the pure gelatin gel is a light yellow gel, the tensile stress is 12 KPa, the tensile strain is 58%, the compressive stress is 164.47 KPa, and the compressive strain is 78.5%.

[0039] Comparative Example 1

[0040] (1) Take 1 g of absolute dry cassava starch, without oxidation treatment;

[0041] (2) Take 5.76 g of gelatinous Tempo-oxidized nanocellulose, emulsify and disperse at a concentration of 0.5% for 5 min at 15,000 rpm;

[0042] (3) Compound the cassava starch of step (1) with the Tempo-oxidized nanocellulose treated in step (2) at a ratio of 1:0.3, gelatinize at 80°C, 300 rpm for 30 min, and then ultrasonic for 5 min;

[0043] (4) Take 10 g of absolute dry gelatin, dissolve in 30 g of water, ultrasonic for 5 min at 45°C;

[0044] (5) Compound the liquid obtained in step (3) with the liquid obtained in step (4) so that the weight / volume fraction of gelatin in water is 10 wt%;

[0045] (6) Disperse the solution obtained in step (5) in a water bath at 65°C, 300 rpm;

[0046] (7) Pour the solution obtained in step (6) into a mold, and place it in a 4°C environment to cool and form for 24 h;

[0047] (8) Soak the gel obtained in step (7) in a 0.06 mol / L FeCl3 solution for 24 h to obtain a flexible sensing gel.

[0048] As shown in Figure 3 and Figure 4 : the obtained flexible sensing gel has a tensile stress of 17.7 KPa, a tensile strain of 36.5%, a compressive stress of 207.1 KPa, and a compressive strain of 67.1%.

[0049] Example 1

[0050] (1) Take 2.0 g of NaIO4 and dissolve it in 50 ml of distilled water. Then slowly add 5 g of cassava starch to the NaIO4 solution, and adjust the pH of the mixture to 3.5 by dropwise adding 1 mol / L hydrochloric acid. The oxidation reaction is carried out at 35°C in the dark for 4 h, the reaction product is washed with distilled water and centrifuged 4 times, and 1# dialdehyde-modified cassava starch is obtained by freeze-drying;

[0051] (2) Take 5.76 g of gelatinous Tempo-oxidized nanocellulose, emulsify and disperse at a concentration of 0.5% for 5 min at 15,000 rpm;

[0052] (3) The No. 1 dialdehyde-modified cassava starch obtained in step (1) was compounded with the Tempo-oxidized nanocellulose after step (2) at a ratio of 1:0.3. After being gelatinized at 80°C and 300 rpm for 30 min, it was ultrasonically treated for 5 min;

[0053] (4) 10 g of absolute dry gelatin was weighed and dissolved in 30 g of water, and ultrasonically treated for 5 min at 45°C;

[0054] (5) The liquid obtained in step (3) was compounded with the liquid obtained in step (4) so that the weight / volume fraction of gelatin in water was 10 wt%;

[0055] (6) The solution obtained in step (5) was dispersed in a water bath at 65°C and 300 rpm;

[0056] (7) The solution obtained in step (6) was poured into a mold and cooled and shaped in a 4°C environment for 24 h;

[0057] (8) The gel obtained in step (7) was immersed in a 0.06 mol / L FeCl3 solution for 24 h to obtain a flexible sensing gel.

[0058] Results: The flexible sensing gel obtained has a tensile stress of 23.6 KPa, a tensile strain of 74.9%, a compressive stress of 1043.87 KPa, a compressive strain of 90.26%, and an ionic conductivity of 0.57 x 10 -2 Sm -1 .

[0059] Example 2

[0060] (1) 4.0 g of NaIO4 was dissolved in 50 ml of distilled water. Then 5 g of cassava starch was slowly added to the NaIO4 solution, and the pH of the mixture was adjusted to 3.5 by dropwise addition of 1 mol / L hydrochloric acid. The oxidation reaction was carried out at 35°C in the dark for 4 h. The reaction product was washed with distilled water and centrifuged 4 times, and 2 was obtained by freeze-drying;

[0061] (2) 5.76 g of gelatin Tempo-oxidized nanocellulose was weighed and emulsified and dispersed at a concentration of 0.5% for 5 min at 15000 rpm;

[0062] (3) The No. 2 dialdehyde-modified cassava starch obtained in step (1) was compounded with the Tempo-oxidized nanocellulose after step (2) at a ratio of 1:0.3. After being gelatinized at 80°C and 300 rpm for 30 min, it was ultrasonically treated for 5 min;

[0063] (4) 10 g of absolute dry gelatin was weighed and dissolved in 30 g of water, and ultrasonically treated for 5 min at 45°C;

[0064] (5) The liquid obtained in step (3) is compounded with the liquid obtained in step (4) so that the weight volume fraction of gelatin in water is 10wt%;

[0065] (6) The solution obtained in step (5) is dispersed in a 65°C water bath at 300rpm;

[0066] (7) The solution obtained in step (6) is poured into a mold and cooled and shaped in a 4°C environment for 24h;

[0067] (8) The gel obtained in step (7) is immersed in a 0.06mol / L FeCl3 solution for 24h to obtain a flexible sensing gel.

[0068] Results: The flexible sensing gel obtained has a tensile stress of 57.9KPa, a tensile strain of 57.9%, a compressive stress of 1287.26KPa, a compressive strain of 90.47%, and an ionic conductivity of 0.55x10 -2 Sm -1 .

[0069] Example 3

[0070] (1) 5.0g of NaIO4 is dissolved in 50ml of distilled water. Then 5g of cassava starch is slowly added to the NaIO4 solution, and the pH value of the mixture is adjusted to 3.5 by dropwise addition of 1mol / L hydrochloric acid. The oxidation reaction is carried out at 35°C in the dark for 4h, and the reaction product is washed with distilled water and centrifuged 4 times, and 3# dialdehyde modified cassava starch is obtained by freeze drying;

[0071] (2) 5.76g of gelatin Tempo oxidized nanocellulose is weighed and dispersed at a concentration of 0.5% for 5min at 15000rpm;

[0072] (3) The 3# dialdehyde modified cassava starch obtained in step (1) is compounded with the Tempo oxidized nanocellulose treated in step (2) at a ratio of 1:0.3, and after gelatinization at 80°C, 300rpm for 30min, ultrasonic treatment is carried out for 5min;

[0073] (4) 10g of absolutely dry gelatin is weighed and dissolved in 30g of water at 45°C, and ultrasonic treatment is carried out for 5min;

[0074] (5) The liquid obtained in step (3) is compounded with the liquid obtained in step (4) so that the weight volume fraction of gelatin in water is 10wt%;

[0075] (6) The solution obtained in step (5) is dispersed in a 65°C water bath at 300rpm;

[0076] (7) The solution obtained in step (6) is poured into a mold and cooled and shaped in a 4°C environment for 24h;

[0077] (8) The gel obtained in step (7) is immersed in a 0.06 mol / L FeCl3solution for 24 h to obtain a flexible sensing gel.

[0078] Results: The flexible sensing gel obtained has a tensile stress of 73.1 KPa, a tensile strain of 55.2%, a compressive stress of 2587 KPa, a compressive strain of 93.64%, and an ionic conductivity of 0.59 x 10 -2 Sm -1 .

[0079] Example 4

[0080] (1) 6.0 g of NaIO4is weighed and dissolved in 50 ml of distilled water. Then 5 g of cassava starch is slowly added to the NaIO4solution, and the pH value of the mixture is adjusted to 3.5 by dropwise addition of 1 mol / L hydrochloric acid. The oxidation reaction is carried out at 35°C in the dark for 4 h, and the reaction product is washed with distilled water and centrifuged 4 times, and 4# dialdehyde modified cassava starch is obtained by freeze-drying;

[0081] (2) 5.76 g of gel-state Tempo-oxidized nanocellulose is weighed and dispersed at a concentration of 0.5% for 5 min at 15000 rpm;

[0082] (3) The 4# dialdehyde modified cassava starch obtained in step (1) is compounded with the Tempo-oxidized nanocellulose treated in step (2) at a ratio of 1:0.3, and after gelatinization at 80°C and 300 rpm for 30 min, ultrasonic treatment is performed for 5 min;

[0083] (4) 10 g of absolutely dry gelatin is weighed and dissolved in 30 g of water at 45°C, and ultrasonic treatment is performed for 5 min;

[0084] (5) The liquid obtained in step (3) is compounded with the liquid obtained in step (4) so that the weight / volume fraction of gelatin in water is 10 wt%;

[0085] (6) The solution obtained in step (5) is dispersed in a water bath at 65°C and 300 rpm;

[0086] (7) The solution obtained in step (6) is poured into a mold and cooled and shaped in a 4°C environment for 24 h;

[0087] (8) The gel obtained in step (7) is immersed in a 0.06 mol / L FeCl3solution for 24 h to obtain a flexible sensing gel.

[0088] Result: The obtained flexible sensing gel has a tensile stress of 140.8 KPa, a tensile strain of 74.9%, a compressive stress of 1148.76 KPa, and a compressive strain of 94.37%. -2 Sm -1 .

[0089] Comparative Example 2

[0090] (1) 7.5 g of NaIO4 was weighed and dissolved in 50 ml of distilled water. Then 5 g of cassava starch was slowly added to the NaIO4 solution, and the pH of the mixture was adjusted to 3.5 by dropwise addition of 1 mol / L hydrochloric acid. The oxidation reaction was carried out at 35°C in the dark for 4 h, and the reaction product was washed with distilled water and centrifuged 4 times, and 5# dialdehyde modified cassava starch was obtained by freeze-drying;

[0091] (2) 5.76 g of gel-state Tempo-oxidized nanocellulose was weighed and emulsified and dispersed at a concentration of 0.5% for 5 min at 15000 rpm;

[0092] (3) The 5# dialdehyde modified cassava starch obtained in step (1) was compounded with the Tempo-oxidized nanocellulose treated in step (2) at a ratio of 1:0.3, and after gelatinization at 80°C, 300 rpm for 30 min, ultrasonic treatment was performed for 5 min;

[0093] (4) 10 g of absolutely dry gelatin was weighed and dissolved in 30 g of water at 45°C, and ultrasonic treatment was performed for 5 min;

[0094] (5) The liquid obtained in step (3) was compounded with the liquid obtained in step (4) so that the weight / volume fraction of gelatin in water was 10 wt%;

[0095] (6) The solution obtained in step (5) was dispersed in a water bath at 65°C, 300 rpm;

[0096] (7) The solution obtained in step (6) was poured into a mold and cooled and shaped in a 4°C environment for 24 h to obtain a flexible sensing gel.

[0097] Result: The obtained flexible sensing gel has a tensile stress of 140.8 KPa, a tensile strain of 74.9%, a compressive stress of 1148.76 KPa, and a compressive strain of 94.37%.

[0098] Example 5

[0099] (1) Take 7.5 g NaIO4 and dissolve it in 50 ml distilled water. Then slowly add 5 g tapioca starch to the NaIO4 solution, and adjust the pH of the mixture to 3.5 by adding 1 mol / L hydrochloric acid dropwise. The oxidation reaction is carried out at 35°C in the dark for 4 h. The reaction product is washed with distilled water and centrifuged 4 times, and 5# dialdehyde-modified tapioca starch is obtained by freeze-drying;

[0100] (2) Take 5.76 g gel-state Tempo-oxidized nanocellulose, and emulsify and disperse it at a concentration of 0.5% for 5 min at 15,000 rpm;

[0101] (3) Compound 5# dialdehyde-modified tapioca starch obtained in step (1) with the Tempo-oxidized nanocellulose treated in step (2) at a ratio of 1:0.3, and after gelatinization at 80°C and 300 rpm for 30 min, ultrasonic for 5 min;

[0102] (4) Take 10 g absolutely dry gelatin, dissolve it in 30 g water, and ultrasonic for 5 min at 45°C;

[0103] (5) Compound the liquid obtained in step (3) with the liquid obtained in step (4) so that the weight / volume fraction of gelatin in water is 10 wt%;

[0104] (6) Disperse the solution obtained in step (5) in a water bath at 65°C and 300 rpm;

[0105] (7) Pour the solution obtained in step (6) into a mold, and cool and shape it in a 4°C environment for 24 h;

[0106] (8) Dip the gel obtained in step (7) in a 0.02 mol / L FeCl3 solution for 24 h to obtain a flexible sensing gel.

[0107] Results: The tensile stress of the obtained flexible sensing gel is 71.8 KPa, the tensile strain is 77.6%, the compressive stress is 937.30 KPa, and the compressive strain is 94.89%.

[0108] Example 6

[0109] (1) Take 7.5 g NaIO4 and dissolve it in 50 ml distilled water. Then slowly add 5 g tapioca starch to the NaIO4 solution, and adjust the pH of the mixture to 3.5 by adding 1 mol / L hydrochloric acid dropwise. The oxidation reaction is carried out at 35°C in the dark for 4 h. The reaction product is washed with distilled water and centrifuged 4 times, and 5# dialdehyde-modified tapioca starch is obtained by freeze-drying;

[0110] (2) Take 5.76 g gel-state Tempo-oxidized nanocellulose, and emulsify and disperse it at a concentration of 0.5% for 5 min at 15,000 rpm;

[0111] (3) The 5th dialdehyde-modified cassava starch obtained in step (1) was compounded with the Tempo-oxidized nanocellulose treated in step (2) at a ratio of 1:0.3. After being gelatinized at 80°C and 300 rpm for 30 min, it was ultrasonically treated for 5 min;

[0112] (4) 10 g of absolute dry gelatin was weighed and dissolved in 30 g of water, and ultrasonically treated for 5 min at 45°C;

[0113] (5) The liquid obtained in step (3) was compounded with the liquid obtained in step (4) so that the weight / volume fraction of gelatin in water was 10 wt%;

[0114] (6) The solution obtained in step (5) was dispersed in a water bath at 65°C and 300 rpm;

[0115] (7) The solution obtained in step (6) was poured into a mold and cooled and shaped in a 4°C environment for 24 h;

[0116] (8) The gel obtained in step (7) was immersed in a 0.04 mol / L FeCl3 solution for 24 h to obtain a flexible sensing gel.

[0117] Results: The tensile stress of the obtained flexible sensing gel was 108.9 KPa, the tensile strain was 77.2%, the compressive stress was 1990.27 KPa, the compressive strain was 89.63%, and the ionic conductivity was 0.17 x 10 -2 Sm -1 .

[0118] Example 7

[0119] (1) 7.5 g of NaIO4 was dissolved in 50 ml of distilled water. Then 5 g of cassava starch was slowly added to the NaIO4 solution, and the pH value of the mixture was adjusted to 3.5 by dropwise adding 1 mol / L hydrochloric acid. The oxidation reaction was carried out at 35°C in the dark for 4 h. The reaction product was washed with distilled water and centrifuged 4 times, and 5th dialdehyde-modified cassava starch was obtained by freeze-drying;

[0120] (2) 5.76 g of gelatin Tempo-oxidized nanocellulose was weighed and emulsified and dispersed at a concentration of 0.5% for 5 min at 15000 rpm;

[0121] (3) The 5th dialdehyde-modified cassava starch obtained in step (1) was compounded with the Tempo-oxidized nanocellulose treated in step (2) at a ratio of 1:0.3. After being gelatinized at 80°C and 300 rpm for 30 min, it was ultrasonically treated for 5 min;

[0122] (4) 10 g of absolute dry gelatin was weighed and dissolved in 30 g of water, and ultrasonically treated for 5 min at 45°C;

[0123] (5) The liquid obtained in step (3) is compounded with the liquid obtained in step (4) so that the weight volume fraction of gelatin in water is 10 wt%;

[0124] (6) The solution obtained in step (5) is dispersed in a 65°C water bath at 300 rpm;

[0125] (7) The solution obtained in step (6) is poured into a mold and cooled to form a gel in a 4°C environment for 24 h;

[0126] (8) The gel obtained in step (7) is immersed in a 0.06 mol / L FeCl3 solution for 24 h to obtain a flexible sensing gel.

[0127] Results: The flexible sensing gel obtained has a tensile stress of 201.4 KPa, a tensile strain of 151.1%, a compressive stress of 5376.43 KPa, a compressive strain of 93.51%, and an ionic conductivity of 0.57 x 10 -2 Sm -1 .

[0128] Example 8

[0129] (1) 7.5 g of NaIO4 is dissolved in 50 ml of distilled water. Then 5 g of cassava starch is slowly added to the NaIO4 solution, and the pH of the mixture is adjusted to 3.5 by dropwise addition of 1 mol / L hydrochloric acid. The oxidation reaction is carried out at 35°C in the dark for 4 h, and the reaction product is washed with distilled water and centrifuged 4 times, and 5# dialdehyde modified cassava starch is obtained by freeze-drying;

[0130] (2) 5.76 g of gelatin Tempo-oxidized nanocellulose is weighed and dispersed at a concentration of 0.5% for 5 min at 15000 rpm;

[0131] (3) The 5# dialdehyde modified cassava starch obtained in step (1) is compounded with the Tempo-oxidized nanocellulose treated in step (2) at a ratio of 1:0.3, and after gelatinization at 80°C and 300 rpm for 30 min, ultrasonic treatment is performed for 5 min;

[0132] (4) 10 g of absolutely dry gelatin is weighed and dissolved in 30 g of water at 45°C, and ultrasonic treatment is performed for 5 min;

[0133] (5) The liquid obtained in step (3) is compounded with the liquid obtained in step (4) so that the weight volume fraction of gelatin in water is 10 wt%;

[0134] (6) The solution obtained in step (5) is dispersed in a 65°C water bath at 300 rpm;

[0135] (7) Pour the solution obtained in step (6) into a mold and cool to form a gel in a 4°C environment for 24 h;

[0136] (8) The gel obtained in step (7) is immersed in a 0.08 mol / L FeCl3solution for 24 h to obtain a flexible sensing gel.

[0137] Results: The flexible sensing gel obtained has a tensile stress of 130.6 KPa, a tensile strain of 97.1%, a compressive stress of 5753.54 KPa, a compressive strain of 86.44%, and an ionic conductivity of 0.73 x 10 -2 Sm -1 .

[0138] Example 9

[0139] (1) 7.5 g of NaIO4was weighed and dissolved in 50 ml of distilled water. Then 5 g of cassava starch was slowly added to the NaIO4solution, and the pH of the mixture was adjusted to 3.5 by dropwise addition of 1 mol / L hydrochloric acid. The oxidation reaction was carried out at 35°C in the dark for 4 h, and the reaction product was washed with distilled water and centrifuged 4 times, and 5# dialdehyde modified cassava starch was obtained by freeze-drying;

[0140] (2) 5.76 g of gel-state Tempo-oxidized nanocellulose was weighed and dispersed at a concentration of 0.5% for 5 min at 15,000 rpm;

[0141] (3) The 5# dialdehyde modified cassava starch obtained in step (1) was compounded with the Tempo-oxidized nanocellulose treated in step (2) at a ratio of 1:0.3, and after gelatinization at 80°C and 300 rpm for 30 min, ultrasonic treatment was performed for 5 min;

[0142] (4) 10 g of absolutely dry gelatin was weighed and dissolved in 30 g of water at 45°C, and ultrasonic treatment was performed for 5 min;

[0143] (5) The liquid obtained in step (3) was compounded with the liquid obtained in step (4) so that the weight / volume fraction of gelatin in water was 10 wt%;

[0144] (6) The solution obtained in step (5) was dispersed in a 65°C water bath at 300 rpm;

[0145] (7) Pour the solution obtained in step (6) into a mold and cool to form a gel in a 4°C environment for 24 h;

[0146] (8) The gel obtained in step (7) is immersed in a 0.10 mol / L FeCl3solution for 24 h to obtain a flexible sensing gel.

[0147] Result: The obtained flexible sensing gel has tensile stress of 122.8 KPa, tensile strain of 86.5%, compressive stress of 3519.72 KPa, compressive strain of 95.16%, and ion conductivity of 0.96*10 -2 Sm -1 .

[0148] Result analysis:

[0149] Figure 1 The tensile property diagram of the flexible sensing gel material of Comparative Example 2, Examples 5, 6, 7, 8 and 9 immersed in 0.02-0.1 mol / L FeCl3 solution. Figure 2 The compressive property diagram of the flexible sensing gel material of Comparative Example 2, Examples 5, 6, 7, 8 and 9 immersed in 0.02-0.1 mol / L FeCl3 solution. It can be seen that, compared with Comparative Example 2, the tensile property and compressive property of the gel material obtained in Examples 5-9 are greatly improved, and with the increase of Fe 3+ concentration, although the performance of the obtained gel material is obviously enhanced, however, when the Fe 3+ concentration is too high, the coordination effect of -COOH is too strong, which leads to the expansion of the structure of the gel material, affects the compactness of the network structure in the gel, and finally leads to the decrease of the mechanical property of the material.

[0150] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for the preparation of a pure bio-based flexible sensing material, characterized by, Comprising the following steps: (1) dispersing the gel-state Tempo-oxidized nanocellulose in an aqueous solution, adding dialdehyde-modified cassava starch to the aqueous solution, heating to gelatinize, and ultrasonic dispersion to obtain A liquid; (2) compounding the A liquid with an aqueous gelatin solution and stirring to disperse; (3) The solution obtained in step (2) is poured into a mold, and after refrigeration, the gel is immersed in a Fe 3+ salt solution, and solidified by cooling, and thus obtained.

2. The method of producing a pure bio-based flexible sensing material according to claim 1, characterized in that, The dialdehyde-modified cassava starch in step (1) is prepared by oxidizing cassava starch with sodium periodate under acidic conditions; the specific preparation method is as follows: mixing cassava starch with sodium periodate, and performing oxidation reaction under dark conditions at pH 3.5-4, reaction temperature 35-40℃, and reaction time 4-6h.

3. The method of producing a pure bio-based flexible sensing material according to claim 2, characterized in that, The mass ratio of sodium periodate to cassava starch is (0.2-1.5):1, and the concentration of cassava starch is 6-12wt%.

4. The method of producing a pure bio-based flexible sensing material according to claim 1, characterized in that, In step (1), the heating temperature is 70-90℃, and the heating time is 30-60min.

5. The method of producing a pure bio-based flexible sensing material according to claim 1, characterized in that, In step (2), the weight / volume fraction of gelatin in water is 8-12wt%.

6. The method of producing a pure bio-based flexible sensing material according to claim 1, characterized in that, In step (2), the mass ratio of A liquid to aqueous gelatin solution is (0.6-1.2):

10.

7. The method of producing a pure bio-based flexible sensing material according to claim 1, characterized in that, In step (3), the Fe 3+ The salt solution is selected from one or more of FeCl3solution, Fe2(SO4)3solution, FePO4solution.

8. The method of producing a pure bio-based flexible sensing material according to claim 1, characterized in that, In step (3), the Fe 3+ The salt solution is FeCl3 solution with a concentration of 0.02-0.1 mol / L; in step (3), the time for immersion is 24-48 h and the temperature for immersion is 2-4℃.

9. A purely bio-based flexible sensing material, characterized in that, Prepared by the preparation method of any one of claims 1-8.

10. Use of the pure bio-based flexible sensing material of claim 9 in the preparation of flexible wearable sensors and / or health detection sensing materials.

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