Fabrication of a Low Cost Triboelectric Nanogenerator (TENG) for Wearable Devices

Abstract

During the last few years, considerable research has been conducted for the design and development of the self-powered devices to supply sustained power to various electronic devices by converting waste mechanical energy into useful electrical energy. Out of many energy sources available in nature, mechanical energy has attracted the researchers due to its availability in abundance. Various methods such as an electromagnetic [1], electrostatic [2] and piezoelectric [3] are being used for converting this waste mechanical energy into useful electrical energy. A novel, eco-friendly and highly reliable triboelectric nanogenerator (TENG) with low cost of fabrication has been considered for fabrication of proposed device [4]. Contact electrification process has been used at the interface of two different materials (metal and a polymer) to generate the electrical energy in the proposed TENG. In order to enhance the surface charge density of the contact electrification process, it is required that the surface area of contact should be increased by surface engineering using micro and nanostructures [5]. Many studies have shown the polymer surface engineering by various processes like template based moldings and plasma treatment [6], surface engineering on the metals like gold nanoparticles (AuNP’s) of different shapes and sizes on the other hand have shown various applications where gold have been used such as in sensors as it is highly robust against the oxygen present in the air and thus it may not get corroded or oxidized unlike other metals. With the deposition of gold nanoparticles on the surface of the metal, an improvement in the output parameters will be observed as compared with the metal without any surface engineering. Another advantage of using gold nanoparticles is that no special protection packaging is required in order to protect the TENG device because of the gold’s robustness against oxygen. The surface stability of gold nanoparticles makes them suitable in various TENG applications.In this paper, we present a very simple technique to fabricate a triboelectric nanogenerator consisting of aluminum and PDMS (Polydimethylsiloxane) layers to harvest mechanical energy present in our surroundings. The proposed TENG device is capable of generating electricity by the process of contact-separation based triboelectrification between the anodic layer of aluminum (metal) and a cathodic layer of PDMS (polymer). To improve the performance of fabricated TENG, spherical shaped gold nanoparticles were synthesized and sprayed on the metallic layer to increase its contact area by increasing the surface roughness. In order to characterize the samples, various characterization techniques has been used like FESEM (Field Emission Scanning Electron Microscopy) and EDS (Energy Dispersive X-ray Spectroscopy). With the application of static weights/ force by hand on the fabricated TENG device, an open circuit voltage of 169 mV, short circuit current of 120.4 µA and maximum output power of 6.006µW has been achieved for an applied load resistance of 68 kΩ. Further the voltage, current and power output performance of the fabricated device has been measured and studied for different load resistances. The fabricated TENG demonstrates its application in the self-powered systems and wearable devices. The deposition of gold nanoparticles (AuNP’s) on the surface of the aluminum metal results in increasing the surface charge density with an increase in the surface area of contact between the metal and the PDMS based polymer layer. The device is sandwiched and force is applied either by fingers or by the use of static weights. With the variations in the force applied, there is a variation in various parameters like open circuit voltage, short circuit current and power. From the results it has been observed that the AuNP’s based TENG generates good results in spite of the fact that the gold has inferior triboelectric coefficient as compared with other metals. The AuNP’s based TENG so fabricated shows high robustness even in very hot and humid environment. References Bin, et al. Electromagnetic Energy Harvesting from Vibrations of Multiple Frequencies. J. Micromechanics Microengineering 19, 035001 (2009).Suzuki, , Miki, D., Edamoto, M. &Honzumi, M.A MEMS Electrets Generator with Electrostatic Levitation for Vibration-Driven Energy-Harvesting Applications. J. Micromechanics Micro engineering 20, 104002 (2010).Seol, M. L. et al. 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