CN116147669A - Preparation method of multi-mode skin-like sensor - Google Patents

Abstract

The invention discloses a preparation method of a multimode skin-like sensor, which is characterized by comprising the following steps of: adding a certain mass of tannic acid solid into 5ml of water for dissolution, adding a certain mass of citric acid solid for uniform stirring, and carrying out hydrothermal reaction for 30-60 min at 20-40 ℃ to obtain TA@CA precursor liquid; adding a certain mass of polyvinyl alcohol solid into 20ml of water for dissolution, and carrying out hydrothermal reaction for 60-120 min at the temperature of 90-100 ℃ to obtain a polyvinyl alcohol solution; cooling the polyvinyl alcohol solution to 40-60 ℃, then adding 5ml of the TA@CA precursor solution prepared in the step one, stirring and reacting for 30-60 min to prepare PVA/CA@TA solution; slowly dripping 5ml of silver nitrate solution into PVA/CA@TA solution, and stirring and reacting for 60-120 min to prepare PVA/CA@TA/Ag solution; PVA/CA@TA/Ag solution is placed in an evaporation dish and crosslinked at a set temperature and humidity to obtain a hydrogel film with multi-mode sensing performance, and a flexible multi-mode skin-like sensor with strain, temperature and humidity sensing functions is developed.

Description

Preparation method of a multimodal skin-like sensor

technical field

The invention relates to the field of multimodal skin-like sensors, in particular to a preparation method of the multimodal skin-like sensors.

Background technique

The skin, the largest organ of the human body, not only protects internal tissues and organs, but also plays a vital role in our perception of the external environment. Developing electronic skins (e-skins) that can mimic the properties and functions of natural skin, by incorporating These stimuli are converted into visualized electronic signals in real time to monitor various environmental stimuli, including pressure, humidity, temperature, touch and vibration, showing great promise in intelligent robots, interfaces, health monitoring and human-machine prospect. So far, most e-skins are flexible strain sensors and pressure sensors, which can only detect strain stimuli or pressure stimuli. However, human skin can sense not only mechanical deformation, but also other environmental stimuli, such as temperature and humidity. As one of the important functions of electronic skin, the temperature sensing function can provide early warning to avoid the risk of high temperature damage. On the other hand, humidity monitoring is also very important in our daily life, which is related to living environment, medical facilities and physical health.

To integrate these multiple sensing functions into one electrical device, the most common strategy is to assemble different functional sensors (such as strain sensors, temperature sensors, pressure sensors, and humidity sensors) into multisensory systems through layer-by-layer techniques. However, this multilayer structure not only increases the complexity of the electronic skin, but also weakens the strain-sensing performance of the device, such as the limitation of detecting large strains, longer response and recovery time. In addition, due to structural constraints, as most multi-sensory temperature sensors with multi-layer structures, it is also difficult to achieve higher temperature coefficient of resistance (TCR), therefore, it is easy to design and fabricate multi-modal with excellent sensing performance Electronic skin sensors are an urgent problem to be solved.

Contents of the invention

In order to overcome the above-mentioned defects in the prior art, the present invention provides a method for preparing a multimodal skin-like sensor, through simple in-situ reduction and solvent casting techniques, with polyvinyl alcohol (PVA) as the base, citric acid ( CA) and tannic acid (TA) as reducing agents, and reduced silver nanoparticles (AgNPs) as conductive components, developed a flexible, transparent, recyclable, and multimodal skin with strain, temperature, and humidity sensing functions sample sensor.

Technical solutions

A method for preparing a multimodal skin-like sensor, specifically comprising the following steps:

Step 1, add a certain quality of solid tannic acid into 5ml of water to dissolve, add a certain quality of citric acid solid and stir evenly, and conduct a hydrothermal reaction at 20-40°C for 30-60 minutes to obtain a TA@CA precursor solution;

Step 2, adding a certain quality of solid polyvinyl alcohol into 20ml of water to dissolve, and reacting hydrothermally at 90-100°C for 60-120 minutes to obtain a polyvinyl alcohol solution;

Step 3: Cool the polyvinyl alcohol solution prepared in step 2 to 40-60°C, then add 5ml of the TA@CA precursor solution prepared in step 1 and stir for 30-60 minutes to prepare a PVA/CA@TA solution;

Step 4: Slowly add 5ml of silver nitrate solution dropwise to the PVA/CA@TA solution prepared in Step 3, stir and react for 60-120min to obtain the PVA/CA@TA/Ag solution;

In step five, the PVA/CA@TA/Ag solution prepared in step four is placed in an evaporating dish, and cross-linked at a set temperature and humidity to obtain a hydrogel film with multimodal sensing properties.

Further, the certain mass of tannic acid in step 1: the mass is 0.1-1 g, and the certain mass of citric acid in step 1: the mass is 1-4 g.

Further, the certain mass of polyvinyl alcohol in step 2: the mass is 1-3g.

Further, the concentration of the silver nitrate solution in step three is 10-35%.

Further, in Step 4, the cross-linking is carried out at a set temperature and humidity: the temperature is 30-40° C., the humidity is 40%-70%, and the cross-linking time is 12-24 hours.

Beneficial effect

Compared with the prior art, the present invention has the following beneficial effects: excellent strain sensing performance, such as fast response speed, low electrical signal hysteresis, excellent sensitivity and excellent repeatability, enabling the PVA/CA@TA/AgNPs sensor to Monitor various human motions, including facial motion and body motion; since the conductivity of PVA/CA@TA/AgNPs sensor changes with temperature, it can be designed as a temperature sensor with excellent thermal sense and high detection accuracy; thanks to PVA With the hydrophilicity of CA, the PVA/CA/AgNPs sensor can be used for detection in humid environments, and can detect the moisture of the human body in real time;

Using polyvinyl alcohol (PVA) as the substrate, citric acid (CA) and tannic acid (TA) as the reducing agent, and reducing silver nanoparticles (AgNPs) as the conductive component, the developed A flexible, transparent, recyclable, and multimodal skin-like sensor capable of strain, temperature, and humidity sensing is developed.

Description of drawings

Fig. 1 is the SEM figure of a kind of multimodal skin sample sensor of the present invention;

Fig. 2 is the strain sensing performance figure of the present invention;

Fig. 3 is a temperature sensing performance diagram of the present invention;

Fig. 4 is a humidity sensing performance diagram of the present invention;

Fig. 5 is a corresponding schematic diagram of the resistance when the present invention is used to detect human motion.

Detailed ways

In order to better illustrate and set forth the content of the present invention, the following will be expanded and described in conjunction with the accompanying drawings and implementation examples:

As shown in Figures 1-5, the present invention discloses a method for preparing a multimodal skin-like sensor, which specifically includes the following steps:

Step 1, add a certain quality of solid tannic acid into 5ml of water to dissolve, add a certain quality of citric acid solid and stir evenly, and conduct a hydrothermal reaction at 20-40°C for 30-60 minutes to obtain a TA@CA precursor solution;

Step 2, adding a certain quality of solid polyvinyl alcohol into 20ml of water to dissolve, and reacting hydrothermally at 90-100°C for 60-120 minutes to obtain a polyvinyl alcohol solution;

Step 3: Cool the polyvinyl alcohol solution prepared in step 2 to 40-60°C, then add 5ml of the TA@CA precursor solution prepared in step 1 and stir for 30-60 minutes to prepare a PVA/CA@TA solution;

Step 4: Slowly add 5ml of silver nitrate solution dropwise to the PVA/CA@TA solution prepared in Step 3, stir and react for 60-120min to obtain the PVA/CA@TA/Ag solution;

In step five, the PVA/CA@TA/Ag solution prepared in step four is placed in an evaporating dish, and cross-linked at a set temperature and humidity to obtain a hydrogel film with multimodal sensing properties.

Further, the certain mass of tannic acid in step 1: the mass is 0.1-1 g, and the certain mass of citric acid in step 1: the mass is 1-4 g.

Further, the certain mass of polyvinyl alcohol in step 2: the mass is 1-3g.

Further, the concentration of the silver nitrate solution in step three is 10-35%.

Further, in Step 4, the cross-linking is carried out at a set temperature and humidity: the temperature is 30-40° C., the humidity is 40%-70%, and the cross-linking time is 12-24 hours.

Example 1

A method for preparing a multimodal skin-like sensor, specifically comprising the following steps:

Step 1: Dissolve 0.1g of tannic acid solid in 5ml of water, add 1g of citric acid solid and stir evenly, and conduct a hydrothermal reaction at 20°C for 30min to obtain the TA@CA precursor;

Step 2, adding 1 g of polyvinyl alcohol solid into 20 ml of water to dissolve, and hydrothermally reacting at 90° C. for 60 minutes to obtain a polyvinyl alcohol solution;

Step 3: Cool the polyvinyl alcohol solution prepared in step 2 to 40°C, then add 5ml of the TA@CA precursor solution prepared in step 1 and stir for 30 minutes to prepare a PVA/CA@TA solution;

Step 4: Slowly add 5ml of 10% silver nitrate solution dropwise to the PVA/CA@TA solution prepared in Step 3, stir and react for 60min to obtain a PVA/CA@TA/Ag solution;

Step 5: Pour the PVA/CA@TA/Ag solution prepared in Step 4 into an evaporating dish, and perform cross-linking at 30°C and a relative humidity of 40% for 12 hours to obtain a PVA/CA@TA/AgNPs film;

As shown in Figure 1, it can be seen from the figure that there are a large number of folds in the cross section of the hydrogel. The strong interaction between TA and the polymer usually leads to the formation of a condensation layer on the surface of the polymer. This structure can effectively release the interfacial stress , to expand the specific surface area to improve the mechanical properties and mechanical deformation ability of flexible and stretchable sensors;

Example 2

A method for preparing a multimodal skin-like sensor, specifically comprising the following steps:

Step 1: Dissolve 0.2g of tannic acid solid in 5ml of water, add 1.5g of citric acid solid and stir evenly, and conduct a hydrothermal reaction at 20°C for 30min to obtain the TA@CA precursor;

Step 2, adding 1.5 g of polyvinyl alcohol solid into water to dissolve, and reacting hydrothermally at 90° C. for 60 minutes to obtain a polyvinyl alcohol solution;

Step 3: Cool the polyvinyl alcohol solution prepared in step 2 to 50°C, then add 5ml of the TA@CA precursor solution prepared in step 1 and stir for 60 minutes to prepare a PVA/CA@TA solution;

Step 4: Slowly add 5ml of silver nitrate solution with a concentration of 15% to the PVA/CA@TA solution prepared in Step 3, and stir for 80 minutes to prepare the PVA/CA@TA/Ag solution;

Step 5: Pour the PVA/CA@TA/Ag solution prepared in Step 4 into an evaporating dish, and perform crosslinking at 35°C and a relative humidity of 40% for 16 hours to obtain a PVA/CA@TA/AgNPs film;

As shown in Figure 2 (upper left), the electrical conductivity of the composite film comes from the reduced AgNPs, forming a conductive pathway. Based on the considerable mechanical properties such as excellent stretchability and good resilience, the prepared PVA/CA@TA/ The AgNPs composite thin film is designed as a resistive strain sensor, as shown in Fig. 2 (upper left), the relative resistance change of the sensor increases with the strain, the AgNPs network is destroyed as the sensor is stretched, and the tunneling distance between AgNPs increase, which leads to an increase in resistance, and conversely, when the sensor is released to its initial state, the conductive pathways of the AgNPs are rebuilt, resulting in a decrease in resistance, that is, the strain stimulus can be converted into a detectable change in resistance, for further evaluation The sensitivity of the strain sensor, plotted and linearly fitted to the strain in Fig. 2 (upper left), it can be seen that the sensitivity number (GF) is 2.2, and the correlation coefficient (R2) is 0.998, showing excellent linearity of the sensing signal, the The sensor is able to detect different strains well and exhibits good sensing stability under three cycles of cyclic stretching of PVA/CA@TA/AgNPs at fixed strains of 0.5%, 4%, 100%, The sensor, which produces a repeatable and strain-dependent resistance response, corresponds to Fig. 2 (top right), Fig. 2 (bottom left), Fig. 2 (bottom right), respectively, indicating high sensing discriminability and good sensing stability;

Example 3

A method for preparing a multimodal skin-like sensor, specifically comprising the following steps:

Step 1: Dissolve 0.5g of tannic acid solid in 5ml of water, add 2g of citric acid solid and stir evenly, and conduct a hydrothermal reaction at 30°C for 30min to obtain the TA@CA precursor;

Step 2, adding 2 g of polyvinyl alcohol solid into water to dissolve, and reacting hydrothermally at 90° C. for 60 minutes to obtain a polyvinyl alcohol solution;

Step 3: Cool the polyvinyl alcohol solution prepared in step 2 to 50°C, then add 5ml of the TA@CA precursor solution prepared in step 1 and stir for 80 minutes to prepare a PVA/CA@TA solution;

Step 4: Slowly add 5ml of 20% silver nitrate solution dropwise to the PVA/CA@TA solution prepared in Step 3, stir and react for 100min to obtain a PVA/CA@TA/Ag solution;

Step 5, import the PVA/CA@TA/Ag solution prepared in Step 4 into an evaporating dish, and perform cross-linking at 40°C and a relative humidity of 50% for 18 hours to obtain a PVA/CA@TA/AgNPs film;

As shown in Figure 3, due to the thermal response of AgNPs to ambient temperature, the as-prepared PVA/CA/AgNPs sensor can be used as a temperature sensor to sense thermal stimuli, and Figure 3 (top) depicts the performance of the sensor in the range of 30 to 70 °C Examining the negative temperature coefficient effect and monotonic resistance-temperature dependence, Figure 3 (bottom) depicts that the resistance change rate value of the sensor gradually decreases from 30°C to 50°C with a gradient of 1°C, and then maintains with the instantaneous stabilization of the temperature At a certain value, it indicates that the sensor can accurately detect temperature changes in real time;

Example 4

A method for preparing a multimodal skin-like sensor, specifically comprising the following steps:

Step 1: Dissolve 0.7g of tannic acid solid in 5ml of water, add 2g of citric acid solid and stir evenly, and conduct a hydrothermal reaction at 20°C for 30min to obtain the TA@CA precursor;

Step 2, adding 2.5 g of solid polyvinyl alcohol into 20 ml of water to dissolve, and reacting hydrothermally at 90° C. for 60 minutes to obtain a polyvinyl alcohol solution;

Step 3: Cool the polyvinyl alcohol solution prepared in step 2 to 50°C, then add 5ml of the TA@CA precursor solution prepared in step 1 and stir for 60 minutes to prepare a PVA/CA@TA solution;

Step 4: Slowly add 5m silver nitrate solution with a concentration of 20% to the PVA/CA@TA solution prepared in step 3, and stir for 80 minutes to prepare the PVA/CA@TA/Ag solution;

Step 5: Pour the PVA/CA@TA/Ag solution prepared in Step 4 into an evaporating dish, and perform cross-linking at 50°C and a relative humidity of 70% for 16 hours to obtain a PVA/CA@TA/AgNPs film;

As shown in Figure 4, due to the hygroscopicity of CA and PVA, the moisture resistance of the PVA/CA/AgNPs composite film is also sensitive to humidity changes, making it a potential humidity sensor, and the mechanism of the PVA/CA/AgNPs humidity sensor can be explained Because CA and PVA are easy to absorb moisture and retain moisture due to their rich hydrophilic groups, the accuracy of the sensor is calibrated with a standard saturated salt solution in Figure 4 (top), showing accurate measurement of ambient humidity, Figure 4 (Bottom) shows that a moisture absorption/desorption cycle test in the 50-90% relative humidity range was examined to assess the reliability of the humidity sensor, and no significant hysteresis behavior was observed in the resistance response; this indicates that the sensor has good humidity sensing reproducibility ;

Example 5

A method for preparing a multimodal skin-like sensor, specifically comprising the following steps:

Step 1: Dissolve 1 g of tannic acid solid in 5 ml of water, add 4 g of citric acid solid and stir evenly, and conduct a hydrothermal reaction at 20°C for 30 minutes to obtain a TA@CA precursor solution;

Step 2, adding 3 g of polyvinyl alcohol solid into 20 ml of water to dissolve, and reacting hydrothermally at 90° C. for 60 minutes to obtain a polyvinyl alcohol solution;

Step 3: Cool the polyvinyl alcohol solution prepared in step 2 to 50°C, then add 5ml of the TA@CA precursor solution prepared in step 1 and stir for 60 minutes to prepare a PVA/CA@TA solution;

Step 4: Slowly add 5ml of silver nitrate solution with a concentration of 35% to the PVA/CA@TA solution prepared in Step 3, and stir for 80 minutes to prepare the PVA/CA@TA/Ag solution;

Step 5: Pour the PVA/CA@TA/Ag solution prepared in Step 4 into an evaporating dish, and perform cross-linking at 30°C and a relative humidity of 60% for 20 hours to obtain a PVA/CA@TA/AgNPs film;

When used for human motion detection, as shown in Figure 5, the PVA/CA@TA/AgNPs composite film has the advantages of electrical conductivity, flexibility, stretchability, temperature regulation performance, humidity sensing performance and long-term stability. The sensor is used to simulate the skin's response function to variable stimuli. The high sensitivity and low strain detection limit of the film make it possible to be used as a strain sensor to accurately identify real-time subtle or large-scale movements of the human body. Figure 5 (top) records the sensor in the When different stimuli are integrated into the corresponding resistance responses of fingers and cheeks, when the fingers are bent at a fixed angle, a resistance response with good repeatability and stability can be produced as shown in Figure 5 (top), and small facial emotions can also be detected. For example, the cheeks are protruding, as shown in Figure 5 (below).

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the technical solutions of the present invention have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that it still The technical solutions described in the foregoing embodiments can be modified, or some of the technical features can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (5)

1. A method for preparing a multimodal skin-like sensor, comprising the steps of: Step 1, add a certain quality of solid tannic acid into 5ml of water to dissolve, add a certain quality of citric acid solid and stir evenly, and conduct a hydrothermal reaction at 20-40°C for 30-60 minutes to obtain a TA@CA precursor solution; Step 2, adding a certain quality of solid polyvinyl alcohol into 20ml of water to dissolve, and reacting hydrothermally at 90-100°C for 60-120 minutes to obtain a polyvinyl alcohol solution; Step 3: Cool the polyvinyl alcohol solution prepared in step 2 to 40-60°C, then add 5ml of the TA@CA precursor solution prepared in step 1 and stir for 30-60 minutes to prepare a PVA/CA@TA solution; Step 4: Slowly add 5ml of silver nitrate solution dropwise to the PVA/CA@TA solution prepared in Step 3, stir and react for 60-120min to obtain the PVA/CA@TA/Ag solution; In step five, the PVA/CA@TA/Ag solution prepared in step four is placed in an evaporating dish, and cross-linked at a set temperature and humidity to obtain a hydrogel film with multimodal sensing properties. 2. The preparation method of a kind of multimodal skin-like sensor according to claim 1, characterized in that: the tannic acid of a certain quality in step 1: the quality is 0.1～1g, and the tannic acid in step 1 A certain quality of citric acid: the quality is 1-4g. 3 . The method for preparing a multimodal skin-like sensor according to claim 1 , characterized in that: the polyvinyl alcohol of a certain mass in step 2: the mass is 1-3 g. 4. The method for preparing a multimodal skin-like sensor according to claim 1, characterized in that: the concentration of the silver nitrate solution in step 3 is 10-35%. 5. The preparation method of a multi-modal skin-like sensor according to claim 1, characterized in that: in step 4, the cross-linking is carried out at a set temperature and humidity: the temperature is 30-40°C, the humidity 40% to 70%, and the crosslinking time is 12 to 24 hours.

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