Electronic skin and preparation method thereof

Abstract

The present invention provides an electronic skin and a method for preparing the same. The electronic skin comprises, from bottom to top, a base layer, an electrode layer, a first friction layer, a second friction layer, a thermoelectric film layer, and an encapsulation layer. The electrode layer, the first friction layer, the second friction layer, and the thermoelectric film layer together constitute a pressure sensing element. The thermoelectric film layer serves as the other electrode of the pressure sensing element. The pressure sensing element is configured to generate an electric potential difference between the electrode layer and the thermoelectric film layer through the triboelectric effect of the first and second friction layers when the electronic skin is subjected to external pressure. The thermoelectric film layer is divided into two parts. The thermoelectric film layer is configured to generate a temperature difference between the two parts when the electronic skin comes into contact with an external object, thereby generating a voltage difference between the two parts, thereby detecting the external temperature. An embodiment of the present invention provides an electronic skin that can perform signal detection without external power supply, and effectively separates pressure signals and temperature signals.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic skin, and in particular to electronic skin and a preparation method thereof. Background Art

[0002] With the rapid development of intelligent robots, flexible electronic skin with diverse sensory functions has become a crucial gateway for future intelligent robots to interact with their environment. By attaching artificial electronic skin to specific areas of the body, robots or individuals with disabilities can achieve the same sensory capabilities as human skin. To further resemble the functional characteristics of human skin, flexible electronic skin integrates multiple sensing functions, including pressure, temperature, and strain, in addition to tactile perception. Pressure and temperature are the two most common stimuli. However, currently, achieving multifunctional sensing on a single electronic skin often suffers from drawbacks such as complex manufacturing processes, severe signal interference, and the need for a continuous external power supply, which greatly limits its practical application.

[0003] The triboelectric effect, piezoelectric effect, and thermoelectric effect can convert physical signals such as external stimuli (such as pressure and temperature) into electrical signal outputs in real time without the need for any external energy supply, providing a solution for zero-power electronic skin. However, existing multifunctional electronic skins rely heavily on back-end algorithms to achieve decoupling of complex sensor signals and redundant signal processing, which greatly increases the energy consumption of the entire artificial skin system. The current flexible power units are not sufficient to fully meet the requirements of electronic skin for flexibility, ultra-thinness, biocompatibility, and energy sustainability. Therefore, the effective separation of different sensor signals of multifunctional electronic skin and the corresponding energy sustainability are the prerequisites for the further development of multifunctional electronic skin wearable devices in the future. Summary of the Invention

[0004] One object of the present invention is to achieve effective separation of pressure signals and temperature signals in electronic skin, and at the same time provide an electronic skin that can perform signal detection without external power supply.

[0005] A further object of the present invention is to improve the sensitivity of pressure signal detection.

[0006] In particular, the present invention provides an electronic skin comprising, from bottom to top, a substrate layer, an electrode layer, a first friction layer, a second friction layer, a thermoelectric film layer, and an encapsulation layer;

[0007] The electrode layer, the first friction layer, the second friction layer, and the thermoelectric film layer together constitute a pressure sensing element. The thermoelectric film layer serves as another electrode of the pressure sensing element. The pressure sensing element is configured to generate a potential difference between the electrode layer and the thermoelectric film layer through the triboelectric effect of the first friction layer and the second friction layer when the electronic skin is subjected to external pressure, thereby detecting the external pressure.

[0008] The thermoelectric film layer is divided into two parts. The thermoelectric film layer is configured so that when the electronic skin contacts an external object, there is a temperature difference between the two parts, thereby causing a voltage difference between the two parts, thereby detecting the external temperature.

[0009] Optionally, the pressure sensing element is configured to change the contact area between the first friction layer and the second friction layer when the electronic skin is subjected to external pressure, thereby generating a potential difference between the electrode layer and the thermoelectric film layer.

[0010] Optionally, a surface of the first friction layer facing the second friction layer has a plurality of protrusions;

[0011] Each of the protrusions is configured to have a tip portion, the tip portion facing the second friction layer;

[0012] The electronic skin is configured such that when not subject to external pressure, the tip of the first friction layer contacts the second friction layer; when subject to external pressure, the protrusion of the first friction layer deforms, thereby increasing the contact area between the first friction layer and the second friction layer, thereby generating an electric potential difference between the electrode layer and the thermoelectric film layer.

[0013] Optionally, one part of the thermoelectric thin film layer is a metal film, and the other part is a thermoelectric material film.

[0014] Optionally, the thermoelectric material film is made of a mixed material of a conductive polymer and a carbon nanomaterial.

[0015] Optionally, the conductive polymer is poly (3,4-ethylenedioxythiophene) (PEDOT:PSS), aniline (PANI), polypyrrole (PPy) and poly (3-hexylpolythiophene) (P3HT);

[0016] The carbon nanomaterial is carbon nanotube or graphene.

[0017] Optionally, the base layer and the second friction layer are both made of polyethylene terephthalate (PET), polystyrene or polyimide;

[0018] The material of the electrode layer is indium tin oxide or a metal material for magnetron sputtering;

[0019] The first friction layer and the packaging layer are both made of polydimethylsiloxane or silicone rubber.

[0020] Optionally, the electronic skin further includes an electrostatic shielding layer, and the electrostatic shielding layer is located on the upper surface of the encapsulation layer.

[0021] Optionally, the electrostatic shielding layer is made of metal.

[0022] In particular, the present invention also provides a method for preparing the electronic skin as described above, comprising the following steps:

[0023] An electrode layer, a first friction layer, a second friction layer, a thermoelectric thin film layer and a packaging layer are sequentially formed on the substrate layer from bottom to top;

[0024] The electrode layer, the first friction layer, the second friction layer, and the thermoelectric film layer together constitute a pressure sensing element. The thermoelectric film layer serves as another electrode of the pressure sensing element. The pressure sensing element is configured to generate a potential difference between the electrode layer and the thermoelectric film layer through the triboelectric effect of the first friction layer and the second friction layer when the electronic skin is subjected to external pressure, thereby detecting the external pressure.

[0025] The thermoelectric film layer is divided into two parts. The thermoelectric film layer is configured so that when the electronic skin contacts an external object, there is a temperature difference between the two parts, thereby causing a voltage difference between the two parts, thereby detecting the external temperature.

[0026] According to the solution of an embodiment of the present invention, a flexible, self-powered, temperature-pressure integrated electronic skin based on coupled triboelectric and thermoelectric effects is provided, that is, the electronic skin can detect temperature and pressure without external power supply, and the temperature detection signal and the pressure detection signal are completely independent and can be effectively separated. The electronic skin is composed of a flexible pressure sensing element based on a triboelectric nanogenerator and a flexible thermoelectric film layer. At the same time, due to the integrated structural design, pressure sensing and temperature sensing achieve independent separation of physical layer signals, avoiding the complex decoupling process after mixing different sensing signals. In summary, one of the important inventive points of this embodiment is that the separation and detection of temperature signals and pressure signals are achieved without the need for external power supply, which is an effect achieved by the above-mentioned integrated structural design.

[0027] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Hereinafter, some specific embodiments of the present invention will be described in detail in an illustrative and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0029] Figure 1 shows a schematic structural diagram of an electronic skin according to an embodiment of the present invention;

[0030] Figure 2 shows another schematic exploded view of an electronic skin according to one embodiment of the present invention;

[0031] Figure 3 shows a working principle diagram of a thermoelectric thin film layer according to one embodiment of the present invention;

[0032] Figure 4 shows a mechanism diagram of a pressure sensing element according to one embodiment of the present invention;

[0033] Figure 5 shows the electrical response curves of the electronic skin to different vertically applied pressures according to one embodiment of the present invention;

[0034] Figure 6 shows a pressure sensitivity curve of an electronic skin according to an embodiment of the present invention;

[0035] Figure 7 shows a graph of response and recovery time of an electronic skin subjected to external pressure according to one embodiment of the present invention;

[0036] Figure 8 shows a graph of the electrical response of the electronic skin to different temperature gradients according to one embodiment of the present invention;

[0037] Figure 9 shows a sensitivity curve of temperature sensing of an electronic skin according to one embodiment of the present invention;

[0038] Figure 10 shows a temperature response and recovery time graph of an electronic skin according to one embodiment of the present invention;

[0039] Figure 11 A sensitivity curve of the electronic skin tested under a temperature difference of 10K according to one embodiment of the present invention is shown;

[0040] Figure 12 A sensitivity curve of the electronic skin tested under a temperature difference of 20K according to an embodiment of the present invention is shown;

[0041] Figure 13 A sensitivity curve of the electronic skin tested under a temperature difference of 30K according to one embodiment of the present invention is shown;

[0042] Figure 14 shows a thermoelectric voltage output curve of an electronic skin under different temperature difference conditions at a pressure of 0-100 kPa according to one embodiment of the present invention;

[0043] Figure 15 shows a graph of sensing performance of an electronic skin at high temperature according to one embodiment of the present invention;

[0044] Figure 16 shows a graph showing the response performance of the electronic skin to low temperature according to one embodiment of the present invention;

[0045] Figure 17 A graph showing the response curves of the electronic skin under the action of water droplets of different numbers according to one embodiment of the present invention is shown;

[0046] Figure 18 Shows photos of the finger bent at 30°, 45°, and 90° after the electronic skin is attached to the finger joint, as well as the corresponding output performance curves;

[0047] Figure 19 shows output performance curves of the electronic skin according to one embodiment of the present invention in an original state and after 1500 and 3000 cycles under a pressure of 25 kPa;

[0048] Figure 20 shows an electrical output curve of an electronic skin without an electrostatic shielding layer according to an embodiment of the present invention;

[0049] Figure 21 FIG. 4 shows an electrical output curve of an electronic skin provided with an electrostatic shielding layer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the features in the following embodiments and embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0051] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show the structures related to the present application and are not drawn according to the number, shape and size of the structures in actual implementation. In actual implementation, the type, quantity and proportion of each structure may be changed at will, and its structural layout may also be more complicated.

[0052] Additionally, in the following description, specific details are provided to provide a thorough understanding of the examples. However, one skilled in the art will appreciate that the aspects described can be practiced without these specific details.

[0053] Figure 1 FIG. 4 shows a schematic structural diagram of an electronic skin according to an embodiment of the present invention. Figure 2 FIG. 1 shows another schematic exploded view of an electronic skin according to an embodiment of the present invention. Figure 1 and Figure 2 As shown, the electronic skin comprises, from bottom to top, a base layer 1, an electrode layer 2, a first friction layer 3, a second friction layer 4, a thermoelectric film layer 5, and an encapsulation layer 6. The electrode layer 2, first friction layer 3, second friction layer 4, and thermoelectric film layer 5 together constitute a pressure sensing element. The thermoelectric film layer 5 serves as the other electrode of the pressure sensing element. When the electronic skin is subjected to external pressure, the pressure sensing element is configured to generate a potential difference between the electrode layer 2 and the thermoelectric film layer 5 through the triboelectric effect of the first and second friction layers 3 and 4, thereby detecting the external pressure. The thermoelectric film layer 5 is divided into two sections. When the electronic skin comes into contact with an external object, a temperature difference between the two sections is generated, resulting in a voltage difference between the two sections, thereby detecting the external temperature. In this embodiment, the materials of each layer of the electronic skin are selected to be flexible, making the electronic skin flexible.

[0054] According to the solution of an embodiment of the present invention, a flexible, self-powered, temperature-pressure integrated electronic skin based on coupled triboelectric and thermoelectric effects is provided, that is, the electronic skin can detect temperature and pressure without external power supply, and the temperature detection signal and the pressure detection signal are completely independent and can be effectively separated. The electronic skin is composed of a flexible pressure sensing element based on a triboelectric nanogenerator and a flexible thermoelectric film layer. At the same time, due to the integrated structural design, pressure sensing and temperature sensing achieve independent separation of physical layer signals, avoiding the complex decoupling process after mixing different sensing signals. In summary, one of the important inventive points of this embodiment is that the separation and detection of temperature signals and pressure signals are achieved without the need for external power supply, which is an effect achieved by the above-mentioned integrated structural design.

[0055] The pressure sensing element is configured to change the contact area between the first friction layer and the second friction layer when the electronic skin is subjected to external pressure, thereby generating an electric potential difference between the electrode layer and the thermoelectric film layer. The structure in which the contact area of ​​the first friction layer and the second friction layer changes when subjected to force can have various forms. The embodiment of the present invention provides a structure with extremely high sensitivity, such as Figure 1 and Figure 2As shown, the surface of the first friction layer facing the second friction layer has multiple protrusions, each of which has a pointed end, with the tip facing the second friction layer. The electronic skin is configured such that when not under external pressure, the tips of the first friction layer contact the second friction layer. When subjected to external pressure, the protrusions of the first friction layer deform, increasing the contact area between the first and second friction layers, thereby generating a potential difference between the electrode layer and the thermoelectric film layer. The sharpness of the tips and the density of the protrusions on the first friction layer can be configured according to actual needs. In one embodiment, the material of the first friction layer may be, for example, polydimethylsiloxane, silicone rubber, or neoprene. The material of the second friction layer may be, for example, polyethylene terephthalate (PET), polystyrene, or Kapton. When selecting the material for the second friction layer, a flexible material should be selected that can serve as both the friction layer and the substrate of the thermoelectric film layer.

[0056] One part of the thermoelectric film layer is a metal film, and the other part is a thermoelectric material film. The material of the thermoelectric material film is a mixture of conductive polymers and carbon nanomaterials. When selecting the material of the thermoelectric film layer, it is necessary to make it possible to serve as an electrode of the pressure sensing element and also to be used as a sensing element to detect temperature without affecting the sensing performance. The material selection of each layer in the electronic skin needs to cooperate with each other to achieve the same purpose. In a preferred embodiment, the internal resistance of the selected pressure sensing element is huge, even reaching the GΩ level, the resistance of the thermocouple film is only at the MΩ level, and the resistance of the electrode layer is much smaller than the internal resistance of the entire device. At the same time, the resistance value of the thermoelectric film layer varies little within the same order of magnitude, so that the thermoelectric film layer can be used as an electrode of the pressure sensing element and also to be used as a sensing element to detect temperature without affecting the sensing performance.

[0057] The thermoelectric conversion efficiency of the thermoelectric thin film layer is determined by the thermoelectric quality factor (ZT), which is expressed as follows:

[0058] ZT=S 2 σT / K

[0059] Where S is the Seebeck coefficient, σ is the electrical conductivity, T is the Kelvin temperature, and K is the thermal conductivity. To select suitable materials, the inventors conducted extensive experiments and identified several possible options, such as a hybrid of a conductive polymer and a carbon nanomaterial. The conductive polymer for the thermoelectric thin film layer can be poly (3,4-ethylenedioxythiophene) (PEDOT:PSS), aniline (PANI), polypyrrole (PPy), and poly (3-hexylpolythiophene) (P3HT), while the carbon nanomaterial can be, for example, multi-walled or single-walled carbon nanotubes or graphene.

[0060] The electrode layer may be made of, for example, indium tin oxide or a metal material for magnetron sputtering, such as gold, aluminum, silver, or copper. The base layer may be made of, for example, polyethylene terephthalate (PET), polystyrene, or Kapton. The encapsulation layer may be made of, for example, a polymer film such as polydimethylsiloxane or silicone rubber.

[0061] In one embodiment, the electronic skin further includes an electrostatic shielding layer 7, which is located on the upper surface of the encapsulation layer 6. The electrostatic shielding layer 7 is made of a metal material, such as copper, gold, aluminum, silver, or other metals with good conductivity.

[0062] Specifically, the present invention also provides a method for preparing the electronic skin of the aforementioned embodiment, comprising the following steps: forming, from bottom to top, an electrode layer 2, a first friction layer 3, a second friction layer 4, a thermoelectric film layer 5, and an encapsulation layer 6 on a base layer 1. The features of this preparation method correspond exactly to those of the aforementioned electronic skin and are not further described here. In one embodiment, the electronic skin further includes an electrostatic shielding layer 7 formed on the upper surface of the encapsulation layer 6. This electrostatic shielding layer 7 is grounded.

[0063] In one embodiment, the preparation method of the first friction layer includes the following steps: cutting the acrylic sheet into a preset size, such as 2*4 cm; setting the power of the laser cutting machine used to construct the microstructure mold to 10-15W, and spraying the release agent on the surface of the porous mold; spin-coating the pre-prepared PDMS (curing agent and base 1:10) or Ecoflex, silicone and other elastomer solutions on the mold surface (for example, the rotation speed is 400-600r), and placing it in a drying oven for drying; taking it out and soaking it in alcohol for a certain period of time, and after peeling it off, a first friction layer with a microstructure (protrusion) is obtained.

[0064] In one embodiment, a method for preparing a thermoelectric thin film layer includes the following steps:

[0065] 1) mixing the carbon nanomaterial with a surfactant (such as sodium dodecylbenzenesulfonate) and dispersing them in deionized water, and ultrasonically dispersing the agglomerated carbon nanomaterial;

[0066] 2) Mixing a conductive polymer (such as PEDOT:PSS) with a dispersed carbon nanomaterial solution, adding a polar solvent (such as DMSO dimethyl sulfoxide), and magnetically stirring for a certain period of time to form a mixture solution;

[0067] 3) Use a laser cutting machine to cut the second friction layer into a preset size, such as 2*4 cm, and divide it into two equal parts, left and right. Use a mask on the right part and perform magnetron sputtering (power 50-100W, pressure 1-2Pa, time 20-40mins) to coat the left half with a metal film, such as a copper film;

[0068] 4) Remove the mask and apply the mixed solution obtained in step 2) on the right side;

[0069] 5) placing the film in an oven for annealing to obtain a thermoelectric thin film layer.

[0070] Figure 2 In the process, a wire is drawn between the thermoelectric film layer and the electrode layer and connected to a voltmeter. At the same time, two wires are drawn from both ends of the electrostatic film layer and connected to an external voltmeter. Figure 2 This demonstrates the basic principle of separating temperature and pressure sensing signals. The thermoelectric film layer generates a horizontal potential difference due to temperature changes, while the triboelectric pressure sensor generates a voltage signal due to vertical force. By monitoring the voltage output in different directions, real-time changes in pressure and temperature can be detected.

[0071] This method of directly distinguishing temperature and pressure sensing signals avoids the complex decoupling process required by traditional multifunctional sensors. Because the temperature and pressure sensing signals are physically independent, the machine can directly collect and utilize the sensing signals, eliminating the need for complex algorithm development. Furthermore, since the thermoelectric voltage is in the millivolt range, the amplification circuit can be directly used for signal acquisition in back-end circuits.

[0072] Figure 3 The diagram shows the working principle of a thermoelectric thin film layer according to one embodiment of the present invention. In this embodiment, one portion of the thermoelectric thin film layer is made of a mixture of PEDOT-PSS and carbon nanotubes, and the other portion is made of copper. According to the Seebeck effect:

[0073] V thermo =S×ΔT

[0074] Where S and ΔT are the Seebeck coefficient and temperature gradient, respectively. When exposed to an external heat source, the thermoelectric film layer efficiently converts thermal energy into electricity. The temperature difference between the device and the object generates a Seebeck voltage through the thermoelectric effect, allowing the electronic skin to sense the surface temperature of an object, such as skin, at a constant reference temperature.

[0075] Figure 4 FIG. 1 shows a mechanism diagram of a pressure sensing element according to an embodiment of the present invention. Figure 4As shown, in the initial state, the first triboelectric layer, with surface microstructures (protrusions), acts as a positive triboelectric layer in contact with the negative triboelectric layer (second triboelectric layer). Due to the triboelectric effect, the first and second triboelectric layers possess positive and negative charges, respectively. Furthermore, electrostatic induction generates negative and positive charges in the upper and lower electrodes (thermoelectric film layer and electrode layer), respectively. This charge transfer process only occurs during assembly. When pressure is applied to the device, it undergoes slight deformation, primarily manifesting in the surface microstructures. As the surface structure compresses, the contact area of ​​the triboelectric material increases significantly, thereby enhancing the triboelectric effect and generating more charge. As the induced charge generated by electrostatic induction further increases, a potential difference develops between the upper and lower plates of the device. The open-circuit voltage (V) is linearly correlated with the applied pressure, allowing pressure changes to be monitored using the open-circuit voltage, which is related to the contact area of ​​the triboelectric material. When the protrusions in the first triboelectric layer are conical microstructures, the contact area change rate is generally higher in the low-pressure region. The increase in external pressure forces the second triboelectric layer to press against the base of the conical microstructure. Since the change rate of the contact area is very small, the open circuit voltage of the device tends to saturate. Therefore, the sensitivity of the high voltage area is generally significantly lower than that of the low voltage area. When the applied external force is withdrawn, the contact materials separate from each other, and the friction charge will generate an induced potential difference between the upper and lower surfaces. The open circuit voltage generated by the separation is V oc It is worth mentioning that under the influence of external charge, the thermoelectric thin film layer and the packaging layer can easily form a single-electrode mode of the nanogenerator, which seriously interferes with the monitoring of the temperature signal.

[0076] To monitor the temperature sensing performance of the electronic skin, a homemade semiconductor heating device was constructed. To test the performance of the pressure sensing element, a stepper motor was used to apply a periodic force to the device. A force gauge attached to the stepper motor could measure the applied pressure in real time.

[0077] Figure 5 FIG shows the electrical response curve of the electronic skin to different vertically applied pressures according to an embodiment of the present invention. Figure 5 It can be seen that when the minimum pressure is 1Pa, the electronic skin still receives a voltage response. When a force of 93kPa is applied, the real-time output voltage can reach around 35V. When the applied force is larger, the voltage output device saturates.

[0078] Figure 6 FIG shows a pressure sensitivity curve of an electronic skin according to an embodiment of the present invention. Figure 6It can be seen that the sensitivity curve of the electronic skin is mainly divided into two parts. In the low-pressure range of 1Pa-2kPa, the pressure sensing sensitivity can reach 1.394V / kPa. In the high-pressure range of 2kPa-100kPa, the pressure sensing sensitivity can reach 0.379V / kPa. The high sensitivity and wide pressure detection range are mainly due to the microstructure of the triboelectric layer surface. Due to the low Young's modulus, the conical microstructure easily undergoes large deformation under small pressure. When the test pressure is applied to the electronic skin surface, the gap between the triboelectric layers decreases, and the voltage output of the electronic skin increases as the contact area between the first and second triboelectric layers increases.

[0079] Figure 7 FIG1 shows a graph of the response and recovery time of the electronic skin when subjected to external pressure according to an embodiment of the present invention. Figure 7 It can be seen that the response and recovery time of the pressure sensing element are very fast, with a response time of 57.6ms and a recovery time of 60.3ms.

[0080] Figure 8 FIG1 shows a graph of the electrical response of the electronic skin to different temperature gradients according to an embodiment of the present invention. Figure 8 The thermoelectric film effectively converts thermal energy from an external object into electrical energy. When the temperature gradient reaches 60K, the thermoelectric film's output reaches its maximum value of approximately 15mV. The saturation of the thermoelectric voltage is due to the thermoelectric film's hot carrier concentration reaching its maximum at higher temperatures. In particular, when the test temperature is maintained at a fixed level, the corresponding thermoelectric output exhibits a horizontal trapezoidal pattern, demonstrating that the flexible thermoelectric film can measure both dynamic and static temperatures. Figure 9 FIG1 shows a sensitivity curve of temperature sensing of an electronic skin according to an embodiment of the present invention. Figure 9 It can be seen that in the temperature range of 270K-360K, the sensor has good linearity and the sensitivity can reach 220μV / K. Figure 10 FIG1 shows a temperature response and recovery time curve of the electronic skin according to an embodiment of the present invention. Figure 10 It can be seen that the electronic skin's response time to temperature is 1.8 seconds and its recovery time is 4.2 seconds.

[0081] In multifunctional electronic skin, it is crucial to respond to different stimuli simultaneously. However, these stimuli often interfere with each other, and resolving this interference is a key issue driving the development of flexible electronic skin. This embodiment of the present invention measures the pressure sensing performance of a temperature-pressure integrated electronic skin under different temperature stimuli. Figure 11 The figure shows the sensitivity curve of the electronic skin tested under 10K temperature difference according to one embodiment of the present invention. Figure 11It can be seen that when the electronic skin has a temperature difference of 10K, the sensitivity of the pressure sensing element is 1.397V / kPa and 0.37V / kPa respectively. Figure 12 The figure shows the sensitivity curve of the electronic skin tested under 20K temperature difference according to one embodiment of the present invention. Figure 12 It can be seen that when the temperature difference of the device increases to 20K, the sensitivity of the pressure sensing element is 1.364V / kPa and 0.384V / kPa respectively. Figure 13 The figure shows the sensitivity curve of the electronic skin tested under 30K temperature difference according to one embodiment of the present invention. Figure 13 As can be seen, when the temperature difference increases to 30K, the sensitivity of the pressure sensing element is 1.386V / kPa and 0.376V / kPa, respectively. It can be seen that under different temperature stimulation conditions, the pressure sensing part of the electronic skin still maintains good stability, indicating that temperature changes do not interfere with the normal operation of the pressure sensing element.

[0082] In addition to measuring the pressure sensing stability under different temperature stimuli, the stability of temperature sensing under different pressures was also verified. Figure 14 The figure shows the thermoelectric voltage output curve of the electronic skin according to one embodiment of the present invention under different temperature difference conditions at a pressure of 0-100 kPa. Figure 14 It can be seen that the thermoelectric voltage output of the electronic skin remains unchanged, indicating that applying pressure to the electronic skin does not interfere with the normal operation of the temperature sensor.

[0083] Figure 15 FIG1 shows a graph of the sensing performance of the electronic skin at high temperature according to an embodiment of the present invention. Figure 15 It can be seen that the electronic skin has good consistency in sensing performance at the same temperature. Figure 16 FIG1 shows a graph showing the response performance of the electronic skin to low temperature according to an embodiment of the present invention. Figure 16 It can be seen that as the temperature difference changes from positive to negative, the thermoelectric voltage value also changes to negative, and still has good consistency. Figure 9 It can be seen that the electronic skin responds to room temperature (T=300K) by about 2mV and to high temperature (T=360K) by about 15mV.

[0084] The device not only has high pressure sensing sensitivity, but is also capable of detecting small pressures. Figure 17 FIG1 shows a response curve of the electronic skin according to an embodiment of the present invention under the action of water droplets of different numbers. Figure 17 It can be seen that when droplets are added to the surface of the electronic skin, the pressure sensing element will generate a tribovoltage output of about 0.1 V. As more droplets are added to the device surface, the output of the pressure sensing element gradually increases. Figure 18The following pictures show the electronic skin attached to the finger joints and the fingers bent at 30°, 45°, and 90°, as well as the corresponding output performance curves. Figure 18 It can be seen that as the bending angle increases, the output of the device also increases.

[0085] In addition to sensitivity, response time, recovery time and consistency, stability is one of the most important indicators of sensor performance. Figure 19 The output performance curves of the electronic skin according to one embodiment of the present invention are shown in the original state under a pressure of 25 kPa and after 1500 and 3000 cycles. Figure 19 It can be seen that the output of the electronic skin remains stable after 3000 cycles.

[0086] In addition, in order to verify the effect of the electrostatic shielding layer on the electrical output performance of the electronic skin, the inventors conducted a comparative test. Figure 20 It can be seen that the device without electrostatic shielding layer has an electrical output of up to 600mV when touched by a finger. Figure 21 It can be seen that the influence of this external interfering charge is effectively eliminated.

[0087] Therefore, the solution of the embodiment of the present invention combines the triboelectric and thermoelectric effects, which can simultaneously sense temperature and pressure stimuli and convert them into two independent voltage signals. When temperature and pressure are applied at the same time, high temperature sensing sensitivity (220μV / K) and excellent pressure sensing sensitivity can be achieved. In addition, the horizontal thermoelectric film is sensitive to temperature, while the self-powered pressure sensing element is very sensitive to pressure in the vertical direction. The innovative design of the device structure can realize the separation of temperature and pressure sensing signals without the need to develop additional algorithms or perform complex decoupling calculations. More importantly, all these sensing functions can be achieved without an external power supply and maintain good stability.

[0088] At this point, it should be recognized by those skilled in the art that although a number of exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that conform to the general principles of the present invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims

1. An electronic skin, characterized in that: From bottom to top, it includes a base layer, an electrode layer, a first friction layer, a second friction layer, a thermoelectric film layer and a packaging layer; The electrode layer, the first friction layer, the second friction layer, and the thermoelectric film layer together constitute a pressure sensing element. The thermoelectric film layer serves as another electrode of the pressure sensing element. The pressure sensing element is configured to generate a potential difference between the electrode layer and the thermoelectric film layer through the triboelectric effect of the first friction layer and the second friction layer when the electronic skin is subjected to external pressure, thereby detecting the external pressure. The thermoelectric film layer is divided into two parts. The thermoelectric film layer is configured so that when the electronic skin comes into contact with an external object, a temperature difference is generated between the two parts, thereby causing a voltage difference between the two parts, thereby detecting the external temperature. One part of the thermoelectric thin film layer is a metal film, and the other part is a thermoelectric material film.

2. The electronic skin according to claim 1, characterized in that The pressure sensing element is configured to change the contact area between the first friction layer and the second friction layer when the electronic skin is subjected to external pressure, thereby generating a potential difference between the electrode layer and the thermoelectric film layer.

3. The electronic skin according to claim 2, characterized in that The surface of the first friction layer facing the second friction layer has a plurality of protrusions; Each of the protrusions is configured to have a tip portion, the tip portion facing the second friction layer; The electronic skin is configured such that when not subject to external pressure, the tip of the first friction layer contacts the second friction layer; when subject to external pressure, the protrusion of the first friction layer deforms, thereby increasing the contact area between the first friction layer and the second friction layer, thereby generating an electric potential difference between the electrode layer and the thermoelectric film layer.

4. The electronic skin according to any one of claims 1 to 3, characterized in that: The thermoelectric material film is made of a mixture of conductive polymer and carbon nanomaterial.

5. The electronic skin according to claim 4, characterized in that The conductive polymer is poly (3,4-ethylenedioxythiophene), aniline, polypyrrole and poly (3-hexylpolythiophene); The carbon nanomaterial is carbon nanotube or graphene.

6. The electronic skin according to any one of claims 1-3 and 5, characterized in that: The materials of the base layer and the second friction layer are both polyethylene terephthalate, polystyrene or polyimide; The material of the electrode layer is indium tin oxide or a metal material for magnetron sputtering; The first friction layer and the packaging layer are both made of polydimethylsiloxane or silicone rubber.

7. The electronic skin according to any one of claims 1-3 and 5, characterized in that: It also includes an electrostatic shielding layer, which is located on the upper surface of the packaging layer.

8. The electronic skin according to claim 7, characterized in that The electrostatic shielding layer is made of metal.

9. A method for preparing an electronic skin according to any one of claims 1 to 8, characterized in that: The steps include: An electrode layer, a first friction layer, a second friction layer, a thermoelectric thin film layer and a packaging layer are sequentially formed on the substrate layer from bottom to top; The electrode layer, the first friction layer, the second friction layer, and the thermoelectric film layer together constitute a pressure sensing element. The thermoelectric film layer serves as another electrode of the pressure sensing element. The pressure sensing element is configured to generate a potential difference between the electrode layer and the thermoelectric film layer through the triboelectric effect of the first friction layer and the second friction layer when the electronic skin is subjected to external pressure, thereby detecting the external pressure. The thermoelectric film layer is divided into two parts. The thermoelectric film layer is configured so that when the electronic skin contacts an external object, there is a temperature difference between the two parts, thereby causing a voltage difference between the two parts, thereby detecting the external temperature.

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