Energy Harvester And Self-powered Sensor Based On Triboelectric Nanogenerator

With the rapid development of the Internet of things technology,the widely distributed sensor network required by the Internet of things has been integrated into every comer of the world,providing sufficient technical support for physiological health monitoring and medical care monitoring.The power required to drive these sensors is small,yet the number of sensors is enormous,requiring a mobile,sustainable and environmentally friendly energy supply.At present,the energy supply of sensors is dominated by batteries.However,the management and recycling of batteries is an extremely difficult task.The hazardous chemicals left behind after the batteries are scrapped have posed a significant threat to the environment.In view of the energy supply problem of the sensor,the energy harvester and sensor based on the principle of triboelectric nanogenerator have become a research hotspot in related fields.Although the mobility and application scenarios of self-powered sensors based on the triboelectric nanogenerator principle are constantly developing,and higher requirements for the sensitivity of self-driven sensors are put forward in related fields such as human body sign monitoring.However,the improving the sensitivity of self-powered sensors is still a difficult problem.Based on the above background,this paper explored and fabricated the self-powered sensor with the highest sensitivity based on the principle of triboelectric nanogenerator,and carried out theoretical analysis on how to improve the sensitivity.In this paper,an ultra-thin,transparent and flexible self-powered curvature sensor with a thickness of only 5.5 ?m was fabricated through a microfabrication process using graphene as the electrode and an ultra-thin substrate material deposited by vapor deposition.The details are as follows:(1)The selection of common industrial materials polydimethylsiloxane(PDMS)and expandable microspheres mixture as the material of triboelectric nanogenerator friction layer,using the characteristics of heat expansion,expandable microspheres by heating,formed a large number of microstructure in the surface of friction layer,the friction power under the different pressure with different output,and according to the principle of the pressure sensor as a driver.Self-powered pressure sensors with mass ratios of 0.1%,0.2%,0.5%and 1%were prepared for the friction layer.Changes in the surface microstructure of the friction layer were photographed by scanning electron microscope.According to the density of the expandable microsphere on the surface of the friction layer,the change of the contact area of the friction layer of the triboelectric nanogenerator under different pressures was calculated by mathematical method,and the relationship between the mass ratio of the expandable microsphere and PDMS and the sensitivity of the self-powered pressure sensor was analyzed.The curves of the output voltage of the triboelectric nanogenerator with a mass ratio of 0.1%,0.2%,0.5%and 1%of the friction microsphere-PDMS in the friction layer were tested respectively when the external pressure varied from 5 to 1000 Pa,and the curves were compared with the theoretical output.It was found from the experimental results that the sensitivity of the pressure sensor reached the maximum 150 mV/Pa when the microsphere-PDMS mass ratio was 1%.In addition,the output test,stability test,response speed and repeatability test were carried out for devices with a mass ratio of 1%of the friction Ilayer's expanded microsphere-PDMS.(2)To select good biological compatibility of poly dimethyl benzene(parylene)thin films as substrate material,the method of chemical vapor deposition growth of graphene on copper foil to parylene film substrate by wet method as electrode,made microstructure lithography process as the top and bottom friction layer pads,thus making ultra-thin transparent flexible friction power,the thickness of about 5.5 p.m,under 550 nm wavelength light transmittance was 80%.The ultra-thin transparent flexible triboelectric nanogenerator with a size of 2×2 cm2 was fixed on the vertical plane,and the linear displacement table was used for vertical impact at frequencies of 0.5,1,1.5,2 and 2.5 Hz,respectively.The output voltage of the test device was stable at 3 V and the response time was about 20 ms.van der Waals force was applied to attach the 2×2 cm2 device to the surface of a 8×8 cm2 polyethylene terephthalate(PET)film with a thickness of 50 ?m.The PET film was stuck between the linear displacement table and a fixed vertical baffle,and the curvature of the PET film was adjusted by changing the translation position,so as to change the curvature of the device.The output of open circuit voltage and short circuit current of the triboelectric nanogenerator was tested under the bending with the curvature of 40,60,80,100 and 120 m-1.(3)The ultra-sensitive pressure sensor was attached to the chest of the human body to test the response of the device in shallow breathing and deep breathing respectively.The sensor was attached to the wrist of the human body for pulse monitoring,and the impact of pulse in one pulse cycle on the output of the device was analyzed.An ultra-thin,flexible and transparent self-powered sensor is attached to a human finger to monitor the curvature of the finger.