Self-powered wireless sensor device

Abstract

A self-powered wireless sensing device uses a friction antenna. The friction antenna includes a metal electrode layer and two layers of films for friction electrification. The metal electrode layer is placed between the two layers of films to form a sandwich structure. The metal electrode layer includes a separated first metal structure and a second metal structure. The first metal structure and the second metal structure have mirror-symmetrically arranged tips and form a minimum gap at the tips. When the friction antenna is stimulated by external mechanical movement, negative charges generated by friction electrification accumulate on the film. Based on electrostatic induction, an electric field is formed between the first metal structure and the second metal structure. The electric field intensity reaches a maximum at the tip gap. Once the electric field intensity reaches the breakdown threshold voltage, a discharge caused by the breakdown is generated at the gap. Electromagnetic wave emission is generated simultaneously with the breakdown discharge, thereby converting the mechanical movement into an electromagnetic wave signal with high sensitivity and distributed at a very high frequency.

Description

Technical Field

[0001] The invention relates to wireless sensing, and in particular to a self-powered wireless sensing device. Background Art

[0002] With the development of modern society, smart cities based on the Internet of Things (IoT) technology are expected to become a new lifestyle in the near future. IoT is characterized by intelligence, convenience and high security, so it is widely used in healthcare, transportation, building automation and industry. Sensors are called the eyes and ears of IoT. They can usually convert physical signals to be sensed into electrical signals and are one of the most important components of IoT. At present, widely distributed sensors still need batteries or wire-based power supply, and a large number of sensors also need transmission lines to transmit sensor signals, which undoubtedly brings great challenges to the application of IoT. On the one hand, powering sensors with a large number of batteries with limited service life brings difficulties in post-maintenance and environmental protection. On the other hand, wire-based power supply will bring many obstacles to the application of sensor systems, such as difficulty in realizing remote sensing required for implantable and wearable electronic devices. Even though wireless power transmission has been demonstrated to be used for powering sensor nodes, this method is still limited by limited transmission distance and still faces the problem of needing batteries and power transmission lines to power the energy transmission part. Therefore, it is extremely important to develop self-powered wireless solutions for sensor nodes. For example, there is a great need for developing an implantable sensor that can realize self-powered wireless sensing for in vivo systems to avoid the problems of surgical battery replacement and wire power supply. At the same time, this solution is also very beneficial for structural monitoring, human-computer interaction, health care, human sensor networks, etc.

[0003] In order to achieve this goal, a lot of research has been conducted in the field. Among them, the mainstream method is to drive traditional wireless sensor modules by collecting energy from the environment to realize self-powered wireless sensor systems, such as by using friction nanogenerators (TENGs), piezoelectric and thermoelectric energy harvesting devices. However, with the increase in energy consumption of commercial wireless sensor modules, higher requirements are placed on the output performance of energy harvesting devices, especially when the ambient energy is not sufficient. In addition, for most energy harvesting devices, due to different impedances and output characteristics, energy management circuits are often required, which brings additional energy requirements and makes the entire system bulky, which undoubtedly limits the application scope of the sensor module. Some of the latest studies do not use high-energy commercial wireless sensor modules, but use Maxwell displacement current or coil directional transmission to achieve wireless sensing. However, these current wireless sensing solutions have problems such as short effective transmission distance, large device size and constrained propagation direction. Therefore, there is an urgent need for a new self-powered wireless sensing solution with minimal intermediate steps and minimal energy loss, that is, once the signal is collected, it is transmitted wirelessly. Summary of the invention

[0004] The purpose of the present invention is to provide a self-powered wireless sensor device to solve the problems of high energy consumption, short effective transmission distance, large device size and restricted propagation direction of traditional wireless sensor modules.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A self-powered wireless sensor device includes a tribo-antenna (TA), the tribo-antenna includes a metal electrode layer and two layers of film for triboelectric charging, the metal electrode layer is placed between the two layers of film to form a sandwich structure, the metal electrode layer includes a separated first metal structure and a second metal structure, the first metal structure and the second metal structure have mirror-symmetrically arranged tips and form a minimum gap at the tips. Based on the working principles of triboelectric charging, electrostatic induction and breakdown discharge, the tribo-antenna can convert mechanical motion into an electromagnetic wave signal with high sensitivity and distributed at a very high frequency. Wherein, when the tribo-antenna is stimulated by external mechanical motion, the negative charge generated by triboelectric charging accumulates on the film, and based on electrostatic induction, an electric field is formed between the first metal structure and the second metal structure, and the electric field intensity reaches the maximum at the tip gap. Once the electric field intensity reaches the breakdown threshold voltage, the discharge caused by the breakdown is generated at the gap, and the electromagnetic wave emission is generated at the same time as the breakdown discharge. This process converts the mechanical motion into an electromagnetic wave signal with high sensitivity and distributed at a very high frequency. The tribo-antenna based on the film of the present invention has the characteristics of lightness, flexibility and high sensitivity. In a typical example, the friction antenna has a size of 3 cm×3 cm, a weight of 116 mg, a thickness of 100 μm, and soft properties.

[0007] Further:

[0008] The film is a fluorinated ethylene propylene (FEP) film, a polyethylene terephthalate (PET) film, a polydimethylsiloxane (PDMS) film or other electronegative material films.

[0009] The minimum gap is between 5 and 500 microns.

[0010] It also includes an electromagnetic wave receiving device, which includes a receiving coil or an antenna. The electromagnetic waves generated by the friction antenna are received by the receiving coil or the antenna without any direction constraints.

[0011] The structure and environment of the friction antenna are adapted to control the amplitude and spectrum of the generated electromagnetic waves for multi-source sensing.

[0012] Applications of multi-source sensing include implantable and wearable electronic devices, healthcare, structural monitoring, and human-machine interfaces.

[0013] The self-powered wireless sensor device may include a plurality of friction antennas, and output signals of the plurality of friction antennas may be distinguished by amplitude and spectrum of electromagnetic waves.

[0014] The multiple friction antennas are configured as keys of a self-powered wireless flexible keyboard, and the minimum gaps between the multiple friction antennas are different, so that each key can be distinguished by generating electromagnetic wave signals with different signal amplitudes and / or spectra.

[0015] The friction antenna is used as electronic skin to detect human motion signals and generate electromagnetic waves.

[0016] It also includes an electromagnetic wave receiving device, which includes a receiving coil and an LED-based lighting system. When the friction antenna does not detect a motion signal, no electromagnetic wave is emitted, and the LED is off; when the friction antenna detects a motion signal, an electromagnetic wave is generated and received by the receiving coil, lighting up the LED-based lighting system.

[0017] The beneficial effects of the present invention are:

[0018] 1. A novel self-powered wireless "instant transmission and sensing" solution is proposed: the friction antenna. Based on the working principles of friction electrification, electrostatic induction and breakdown discharge, the friction antenna can convert the input mechanical motion into a highly sensitive electromagnetic wave signal in the VHF band.

[0019] 2. The friction antenna has the characteristics of small size (e.g. 3cm×3cm), light weight (e.g. 116mg), thin thickness (e.g. 100μm), softness, deformability, high sensitivity, easy manufacturing, environmental protection, and low cost. It can be widely used in implantable and wearable electronic products, healthcare applications, structural monitoring, and human-computer interaction interfaces.

[0020] 3. The electromagnetic wave signal of the friction antenna is very significant, and the signal triggered by slight movement can be detected by a receiving coil or antenna at a distance of 10m without direction constraints. Based on this feature, a self-powered wireless motion sensing electronic skin is designed, which can light up the demonstration lighting system through human body movement.

[0021] 4. By adjusting the structure and environment of the friction antenna, the amplitude and spectrum of the electromagnetic wave can be controlled, which can be used for multi-source sensing. Based on this feature, a self-powered wireless flexible keyboard is designed. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1( a ) is a block diagram of a self-powered wireless sensor device according to an embodiment of the present invention.

[0023] Figure 1(b) shows the structural diagram and photograph of the friction antenna, and the gap structure is shown in the microscope image.

[0024] Figure 1(c) is a process flow chart of friction antenna manufacturing.

[0025] Figure 1(d) is a diagram of the working process of the friction antenna, which includes the working process of the friction antenna, a top view of the device, and a simulation diagram of the electric field distribution in the y direction of the friction antenna breakdown state based on COMSOL.

[0026] Figure 1(e) and Figure 1(f) are examples of typical friction antenna breakdown signals in the time domain and frequency domain, respectively.

[0027] Figure 1(g) and Figure 1(h) are examples of the changes in the amplitude and spectrum of the breakdown signal after the friction antenna changes the gap width and environmental factors.

[0028] Figure 2(a) is a block diagram of the test system.

[0029] Figure 2(b) shows the structure of the independent sliding TENG (FS-TENG) and the voltage-transferred charge output characteristic curve when loaded with a 10pF capacitor.

[0030] Figure 2(c) is a structural diagram of the breakdown arrester.

[0031] FIG2( d ) shows the received breakdown signal corresponding to different voltages on the breakdown arrester in the frequency domain.

[0032] FIG2(e) shows the relationship between the peak-to-peak value of the received breakdown signal voltage and the different voltages on the breakdown arrester.

[0033] FIG2( f ) shows the received breakdown signal corresponding to different gap distances between electrodes of the breakdown arrester in the frequency domain.

[0034] FIG2( g ) shows the relationship between the peak-to-peak value of the received breakdown signal voltage and the different gap distances between the electrodes on the breakdown arrester.

[0035] Figure 2(h) and Figure 2(i) show the relationship between the breakdown signal received in the frequency domain and the different movement directions of TENG in the time domain, respectively.

[0036] Figure 2(j) shows the received breakdown signal corresponding to different connecting wire distances between the breakdown arrester and TENG in the frequency domain.

[0037] FIG2( k ) shows the received breakdown signals corresponding to different spatial conductor distribution states in the frequency domain.

[0038] FIG2( l ) shows the received breakdown signal corresponding to different distances between the breakdown discharger and the receiver in the frequency domain.

[0039] FIG2(m) shows the relationship between the peak-to-peak value of the received breakdown signal voltage and the distance between the breakdown discharger and the receiver.

[0040] Figure 3(a) shows the complete process of breakdown discharge.

[0041] Figure 3(b) is the equivalent circuit model of the friction antenna and receiving system.

[0042] Figure 3(c) shows the synchronous measurement result of the received breakdown discharge signal and the current passing through the friction antenna.

[0043] Figure 3(d) is a block diagram illustrating the working principle of the friction antenna.

[0044] Figure 4(a) demonstrates the lightness, thinness, and flexibility of the friction antenna from multiple angles.

[0045] Figure 4(b) demonstrates that the breakdown signal can be detected at a distance of more than 10 meters.

[0046] Figure 4(c) is a schematic diagram of the electronic skin and flexible keyboard based on the friction antenna.

[0047] Figure 4(d) is a block diagram of the electronic skin and flexible keyboard system based on friction antenna.

[0048] Figure 4(e) is a demonstration system of a self-powered wireless human motion sensing electronic skin based on a friction antenna.

[0049] FIG4( f ) shows the relationship between the peak-to-peak voltage of the received breakdown signal and the rotation angle of the receiving coil.

[0050] Figure 4(g) is a photo of the flexible keyboard transmission and reception system, where the signal ‘1’ is transmitted and successfully received. DETAILED DESCRIPTION

[0051] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope and application of the present invention.

[0052] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for fixing as well as for coupling or communication.

[0053] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0054] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0055] Referring to Figures 1(a) and 1(b), in one embodiment, a self-powered wireless sensing device includes a friction antenna, wherein the friction antenna includes a metal electrode layer and two thin films for friction electrification, wherein the metal electrode layer is placed between the two thin films to form a sandwich structure, wherein the metal electrode layer includes a separated first metal structure and a second metal structure, wherein the first metal structure and the second metal structure have mirror-symmetrically arranged tips and form a minimum gap at the tips, wherein when the friction antenna is stimulated by external mechanical movement, negative charges generated by friction electrification accumulate on the film, and based on electrostatic induction, an electric field is formed between the first metal structure and the second metal structure, wherein the electric field intensity reaches a maximum at the tip gap, and once the electric field intensity reaches a breakdown threshold voltage, a discharge caused by breakdown is generated at the gap, and electromagnetic wave emission is generated simultaneously with the breakdown discharge, thereby converting the mechanical movement into an electromagnetic wave signal with high sensitivity and distributed at a very high frequency.

[0056] In some embodiments, the film may be a fluorinated ethylene propylene (FEP) film, a polyethylene terephthalate (PET) film, a polydimethylsiloxane (PDMS) film, or other negatively charged material films.

[0057] In some embodiments, the minimum gap is between 5 and 500 microns.

[0058] In some embodiments, as shown in FIG. 1( a ), the self-powered wireless sensing device further includes an electromagnetic wave receiving device, which includes a receiving coil or an antenna, and the electromagnetic waves generated by the friction antenna are received by the receiving coil or antenna without any direction constraints.

[0059] In some embodiments, the structure and environment of the friction antenna are adapted to control the amplitude and spectrum of the generated electromagnetic waves for multi-source sensing.

[0060] In some embodiments, applications of the multi-source sensing include implantable and wearable electronic devices, healthcare, structural monitoring, and human-computer interfaces.

[0061] In some embodiments, the self-powered wireless sensing device includes a plurality of friction antennas, and output signals of the plurality of friction antennas can be distinguished by amplitude and spectrum of electromagnetic waves.

[0062] In some embodiments, the multiple friction antennas are configured as keys of a self-powered wireless flexible keyboard, the minimum gaps of the multiple friction antennas are different, and each key is distinguished by generating electromagnetic wave signals with different signal amplitudes and / or spectra.

[0063] In some embodiments, the friction antenna is used as electronic skin to detect human motion signals and generate electromagnetic waves.

[0064] In some embodiments, as shown in Figures 4(c)-(e), in addition to the friction antenna used as electronic skin, the self-powered wireless sensing device also includes an electromagnetic wave receiving device, which includes a receiving coil and an LED-based lighting system. When the friction antenna does not detect a motion signal, no electromagnetic wave is emitted, and the LED is off; when the friction antenna detects a motion signal, an electromagnetic wave is generated and received by the receiving coil, thereby lighting up the LED-based lighting system.

[0065] The friction antenna of the embodiment of the present invention realizes a self-powered wireless sensing solution of "sense and transmit immediately". Based on the working principles of friction electrification, electrostatic induction and breakdown discharge, the friction antenna can convert mechanical motion into electromagnetic wave signals with high sensitivity and distributed at very high frequencies. The friction antenna based on the film has the characteristics of lightness, flexibility and high sensitivity. In a typical example, the friction antenna has a size of 3cm×3cm, a weight of 116mg, a thickness of 100μm, and softness. When a slight motion signal is input, the electromagnetic waves generated by the friction antenna can be received by the receiving coil 10 meters away without directional constraints. In particular, when the structure of the friction antenna and the environment in which it is located are changed, the amplitude and spectrum of the electromagnetic waves generated can be controlled, and this feature can be used for multi-source sensing. Therefore, the embodiment of the present invention provides an innovative solution for a self-powered wireless sensing platform. The friction antenna has great potential. It can be widely used in implantable and wearable electronic devices, health care applications, structural monitoring and human-computer interaction interfaces.

[0066] In the embodiment of the present invention, a friction antenna is used as a self-powered wireless "sense and transmit" solution, as shown in Figure 1(a). The friction antenna based on the film can convert mechanical motion into electromagnetic waves caused by breakdown distributed at very high frequencies, with the characteristics of high amplitude and long effective transmission distance. High sensitivity has proved its excellent wireless sensing performance.

[0067] In some embodiments, by controlling the structure and environmental factors of the friction antenna, the output signals of different friction antennas can be distinguished by the amplitude and spectrum of the electromagnetic wave.

[0068] As shown in the structural schematic diagram of the friction antenna in Figure 1(b), the metal electrode layer is placed in two layers of triboelectric film like a sandwich structure. Ethylene propylene fluoride (FEP) film is selected here. The thickness of the FEP film and the metal electrode layer are 50 microns and 0.3 microns respectively. Two metal electrode structures with mirror-symmetrical tip shapes are manufactured by electron beam evaporation process. The details of the manufacturing process are shown in Figure 1(c). The minimum spacing between the two metal structures is controlled to be 5-500 microns, which can be observed by a microscope. When the friction antenna receives external excitation, the negative charge generated by the triboelectric principle accumulates in the FEP layer. Based on electrostatic induction, an electric field will be formed between the electrodes, and the electric field strength reaches the maximum at the tip gap of the metal structure. Once the electric field strength reaches the breakdown threshold voltage, the discharge caused by the breakdown will occur at the gap, as shown in Figure 1(d).

[0069] Along with the breakdown discharge, the electromagnetic radiation can be detected by a receiving system connected to an oscilloscope and a coil, as shown in Figure 1(e) and (f). The distance between the friction antenna and the coil is 0.6 meters. When there is no excitation, the voltage in the coil will remain at 0V. Once excited, the coil will capture a high-frequency signal generated by the friction antenna, as shown in Figure 1(e). Through the fast Fourier transform analysis method, the time domain waveform can be converted into a frequency domain waveform, which is distributed in the very high frequency, as shown in Figure 1(f). At the same time, the LC oscillation signal of the receiving system is concentrated around 10MHz.

[0070] In addition, by adjusting the environment and structural parameters of the friction antenna, the amplitude and spectrum of the output signal can be controlled. Under the same mechanical motion, a larger gap can produce a stronger breakdown signal with a larger amplitude, as shown in Figure 1(g). By adding a metal film to the friction antenna, or placing it in an environment with spatially distributed conductors, the spectrum of the breakdown signal will change, as shown in Figure 1(h), where the LC oscillation signal is filtered out by a band-stop filter to highlight the breakdown signal. In this way, we can control the output signal of the friction antenna to distinguish different input sources that generate the signal.

[0071] A systematic study for evaluating the output performance of electromagnetic waves caused by breakdown and the relationship between influencing factors is shown in Figure 2(a). In order to ensure that the voltage generated by the TENG part remains consistent, the friction antenna is split into two independent parts for quantitative testing, including a separate sliding TENG (FS-TENG) and a breakdown discharge device consisting of two electrode structures, which are fixed on an optical platform. The FS-TENG consists of two copper electrodes and a FEP film layer, as shown in Figure 2(b). A nitrile rubber (NBR) film is used as the moving part on the FEP film layer for triboelectric charging. Based on the principle of electrostatic induction, a voltage output and an electric field will be generated on the metal electrode. A linear motor with a controlled motion range of 120 mm is used to drive the FS-TENG. The breakdown discharge device is made by a printed circuit board (PCB) process to ensure that the gap distance varies between 100 μm and 1 mm, as shown in Figure 2(c). The two electrodes of the FS-TENG are connected to the two poles of the breakdown discharge device. When the FS-TENG is triggered, the two poles of the breakdown discharge device will generate an electric field to enable breakdown discharge. The receiving part can be equivalent to an LC system with a natural frequency around 10MHz. Based on this experiment, the main influencing factors (summarized in Table 1) on the characteristics of the output electromagnetic wave are summarized in Figure 2 (dm).

[0072] Table 1 | Main influencing factors of breakdown signal

[0073]

[0074] Here, we mainly study the first six influencing factors in Table 1 and keep the other parameters unchanged. The initial state is set at D = 60cm, U = 2000V, d = 100μm, T = 23-24℃, H = 60-65%, l = 2×30cm, and negative movement direction (from right to left). By controlling U, the amplitude of the breakdown signal increases with the increase of U, and has no effect on the spectrum distribution, as shown in Figure 2(d) and (e). The amplitude of the breakdown signal also increases significantly with the increase of d, and has no effect on the spectrum distribution, as shown in Figure 2(f) and (g). The movement direction of FS-TENG was found to affect the initial phase and signal amplitude of the breakdown signal. When the FS-TENG is in the positive movement direction (from left to right), the initial phase is In the negative direction of motion (from right to left), the initial phase is As shown in Figure 2(h) and (i). Surprisingly, we found that l has an effect on both the amplitude and spectrum of the breakdown signal, as shown in Figure 2(j). We believe that the change in l causes the capacitance and inductance values ​​in the transmitting system to change. A similar phenomenon also occurs when the spatial conductor distribution is changed, as shown in Figure 2(k). The received signal amplitude decreases as D increases, but the spectrum does not change, as shown in Figure 2(l) and (m). In addition, environmental factors can also have a significant impact on the received breakdown signal, which are listed in Table 1.

[0075] Based on these experiments, we propose a model to explain the mechanism of the triboelectric antenna. When triggered by TENG, a strong electric field is generated between the two electrodes of the breakdown discharge device, causing electrons to move from the cathode to the anode. During the movement, electrons collide with air molecules at high speed, resulting in the generation of new electrons, positive ions and negative ions, causing electron avalanches and further generating plasma. The plasma can be regarded as a collective oscillation of a cluster of charged particles, which produces a zero impedance region to act as a conductor for electrons. Therefore, a pulse current is generated in the emission system, and its amplitude and pulse rise time are related to the voltage, gap width and environmental factors (gas type, air pressure, etc.). Finally, as the electric field weakens, the weakened electron avalanche can no longer support the path, causing the circuit to return to the open circuit state. The whole process is shown in Figure 3(a). The triboelectric antenna can be simply summarized as a circuit model including the capacitance from the electrode, the inductance from the instantaneous conduction circuit and the resistance, as shown in Figure 3(b). At the same time, the spatial conductor distribution can be regarded as affecting the capacitance and inductance values ​​of the second-order system. Once the pulse current appears, it will generate an underdamped oscillating current signal in the transmitting system, and its oscillation frequency is determined by the various parameters of the friction antenna, as shown in Figure 3(c). This oscillation can generate a changing magnetic field and a changing battery in the surrounding area to generate an omnidirectional electromagnetic wave, which is finally generated and received by the receiving part, as shown in Figure 3(d). The electromagnetic wave and the current of the transmitting system are measured at the same time, and the oscillation period generated by the breakdown is 10 -9 -10 -6 seconds, which exactly matches the measured frequency of the electromagnetic waves.

[0076] The friction antenna of the present invention has the characteristics of being light, flexible, highly sensitive and low cost, as shown in FIG4(a), and can be widely used for signal sensing and transmission without the need to introduce any other power source. We demonstrated two examples of self-powered wireless sensing based on friction antennas that can sense and transmit immediately. First, we designed the friction antenna to be used as an electronic skin to detect motion signals and transmit them in real time in the form of electromagnetic waves, which has the advantages of high signal strength and long transmission distance. In FIG4(b), we showed that the signal can be captured by an oscilloscope more than 10 meters away. To further demonstrate its sensitivity, a self-powered wireless motion sensing electronic skin based on a friction antenna is designed to detect human motion, as shown in FIG4(c) and (d). The receiving part is composed of a receiving coil, a signal processing circuit, a battery and an LED-based lighting system, as shown in FIG4(e). When there is no motion signal, no electromagnetic wave is emitted, and the LED is off. Once motion occurs, electromagnetic waves will be generated and transmitted, lighting up the LED lamp, as shown in FIG4(e), which has high sensitivity. In addition, we also demonstrated that there is no directional restriction in the transmission of electromagnetic waves by the friction antenna, as shown in Figure 4(f).

[0077] To further demonstrate the multi-source sensing capability of the friction antenna, a self-powered wireless flexible keyboard was designed, as shown in Figure 4(c) and (d). The structure of the flexible keyboard system is shown in Figure 4(g), which consists of a keyboard based on a friction antenna, a receiving system and a signal processing system. The receiving system consists of a receiving coil and an oscilloscope to capture the signal. For simplicity, we fabricated a four-key keyboard with four friction antennas with different gap distances as keys based on PET film. We can distinguish each key by different signal amplitudes. Through the local area network (LAN), we transmit the signal captured by the oscilloscope to the computer, and use MATLAB to process the captured signal to represent '1', '2', '3' and '4' respectively, as shown in Figure 4(g). Thus, the friction antenna fully realizes the function of a self-powered wireless keyboard. According to our research, the spectrum can also be used to distinguish different key signals, which needs future research. Therefore, friction antennas have low energy loss, long transmission distance, high sensitivity and multi-source sensing capabilities, and are of great value in the field of wireless sensing and transmission, such as harsh environment monitoring, health monitoring, implantable devices and human-computer interfaces.

[0078] The friction antenna of the present invention provides a "sense and transmit" type self-driven wireless sensing solution. Based on the working principles of friction electrification, electrostatic induction and breakdown discharge, the friction antenna can convert mechanical energy into electromagnetic wave signals. It converts mechanical motion into electromagnetic waves caused by breakdown distributed at very high frequencies, and has the characteristics of high amplitude and long effective transmission distance. The friction antenna is thin, flexible and highly sensitive, which enables it to achieve long-distance self-driven wireless breakdown signal transmission. High sensitivity has proven its excellent wireless sensing performance. The breakdown signal of the friction antenna has an effective transmission distance of more than 10m, and can receive an amplitude of 60mV at 10m. Our systematic study of the friction antenna shows that its output is affected by many factors, among which the amplitude and spectrum of the signal are affected by the gap spacing and environmental factors respectively, which enables it to achieve multi-source sensing. Therefore, by controlling the structure and environmental factors of the friction antenna, the output signals of different friction antennas can be distinguished by the amplitude and spectrum of the electromagnetic wave, and this feature is demonstrated by a self-powered wireless flexible keyboard. A self-driven wireless flexible keyboard is manufactured to send signals of different keys. The friction antenna of the present invention has important significance in the field of wireless sensing and self-driven signal transmission, and can be widely used in wearable and implantable electronic devices, biomedicine, human-machine interface and building monitoring, etc.

[0079] The background section of the present invention may contain background information about the problem or environment of the present invention, but does not necessarily describe the prior art. Therefore, the content included in the background section is not an admission by the applicant that the prior art is available.

[0080] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of the reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the absence of mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A self-powered wireless sensor device, characterized in that: The invention comprises a friction antenna, wherein the friction antenna comprises a metal electrode layer and two films for friction electrification, wherein the metal electrode layer is placed between the two films to form a sandwich structure, wherein the metal electrode layer comprises a first metal structure and a second metal structure which are separated, wherein the first metal structure and the second metal structure have tips which are arranged in mirror symmetry and form a minimum gap at the tips, wherein when the friction antenna is stimulated by external mechanical movement, negative charges generated by friction electrification accumulate on the film, and an electric field is formed between the first metal structure and the second metal structure based on electrostatic induction, wherein the electric field intensity reaches a maximum at the tip gap, and once the electric field intensity reaches a breakdown threshold voltage, a discharge caused by breakdown is generated at the gap, and electromagnetic wave emission is generated simultaneously with the breakdown discharge, thereby converting the mechanical movement into an electromagnetic wave signal with high sensitivity and distributed at a very high frequency, thereby realizing self-powered wireless sensing; It also includes an electromagnetic wave receiving device, which includes a receiving coil or an antenna. The electromagnetic waves generated by the friction antenna are received by the receiving coil or the antenna without any direction constraints.

2. The self-powered wireless sensor device according to claim 1, characterized in that: The film is a fluorinated ethylene propylene (FEP) film, a polyethylene terephthalate (PET) film, a polydimethylsiloxane (PDMS) film or other electronegative material films.

3. The self-powered wireless sensor device according to claim 1, characterized in that: The minimum gap is between 5 and 500 microns.

4. The self-powered wireless sensor device according to any one of claims 1 to 3, characterized in that: The structure and environment of the friction antenna are adapted to control the amplitude and spectrum of the generated electromagnetic waves for multi-source sensing.

5. The self-powered wireless sensor device according to claim 4, characterized in that: Applications of multi-source sensing include implantable and wearable electronic devices, healthcare, structural monitoring, and human-machine interfaces.

6. The self-powered wireless sensor device according to claim 4, characterized in that: The invention comprises a plurality of friction antennas, and the output signals of the plurality of friction antennas can be distinguished by the amplitude and the spectrum of the electromagnetic wave.

7. The self-powered wireless sensor device according to claim 6, characterized in that: The multiple friction antennas are configured as keys of a self-powered wireless flexible keyboard, and the minimum gaps between the multiple friction antennas are different, so that each key can be distinguished by generating electromagnetic wave signals with different signal amplitudes and / or spectra.

8. The self-powered wireless sensor device according to any one of claims 1 to 3, characterized in that: The friction antenna is used as electronic skin to detect human motion signals and generate electromagnetic waves.

9. The self-powered wireless sensor device according to claim 8, characterized in that: It also includes an electromagnetic wave receiving device, which includes a receiving coil and an LED-based lighting system. When the friction antenna does not detect a motion signal, no electromagnetic wave is emitted, and the LED is off; when the friction antenna detects a motion signal, an electromagnetic wave is generated and received by the receiving coil, lighting up the LED-based lighting system.

Images