Synthesis and Characterization of a Transparent PMMA Based Triboelectric Nanogenerator for Wearable Electronic Applications
Authors: Sambyal Ashish Singh , Anand Deepak , Vaid Rakesh , Saikia Dulen , Chaure Nandu , Khosla Ajit 
Published: July 2022

With the increase in energy consumption with unprecedented rate, there is an urgent need for the development of independent, efficient and maintenance free power sources. With the growing emergence of flexible, wearable electronic devices in the current market, the requirement for portable and highly flexible power sources has also increased many folds. The electronic devices such as stretchable circuits [1], e-papers [2], bendable displays [3], e-skins [4], wearable electronic devices [5], etc. are receiving wide attention due to their applications in robotics, medical science, human machine interface, fitness trackers, smart watches and many more. The waste mechanical energy in the environment such as vibration, wind and human body motions can be converted into electricity by triboelectric energy harvesting technologies [6]. Energy is one of the essential requirements of the society and it is necessary to search newly and highly efficient technologies that harvest many forms of energy from the environment which is generally wasted. For the last two decades, the scientists and researchers have been focused on the synthesis and characterization of novel source of energy harvesting and self-powered devices useful for numerous energy applications without external inputs.

In this paper, a novel triboelectric nanogenerator (TENG) based on Polymethyl methacrylate (PMMA) as transparent and flexible polymer materials with gold nanoparticles (AuNPs) has been synthesized and characterized. The SEM image clearly reveals the spherical shape of the synthesized AuNPs. The XRD pattern of the prepared material shows accurate diffraction peaks at 2theta values indicate the presence of mixed phases of fluorine tin oxide (SnO2), AuNPs, and metallic copper (Cu) which are in excellent agreement with the previously mentioned 2theta values in the literature. Further, the EDS analysis confirms the presence of Sn, Au, O, and Cu within the synthesized TENG. Finally, the proposed synthesize PMMA-based TENG produces maximum AC output voltage and current signal up to 5V and 10 μA, respectively with very high transmittance of 100 %. The electric energy in terms of AC voltage produced by synthesized PMMA-based TENG is further converted into DC voltage which is used to light up light - emitting diodes in future.

The synthesized TENG consists of two parts such as lower part and upper part. The spacer (sponge or spring) is placed between the upper part as well as the lower part. The synthesized lower part of TENG consists of three layers such as (a) fluorine tin oxide (FTO), (b) copper (Cu), and (c) gold nanoparticles (AuNPs) whereas the upper part of the synthesized TENG consists of two layers such as (a) aluminum (Al) and (b) polymethyl methacrylate (PMMA) transparent and flexible polymer. By taking FTO substrate, we first deposit the copper layer with micrometer range of thickness on the top of FTO with the help of Magnetron Sputtering technique at 5.8 X 10-2 m bar base working pressure, 60 sccm gas-flow, 200 W power, 200˚C temperature for 5 minutes. Next, the freshly prepared AuNPs are prepared by using the following steps: (A) Seed solution preparation; (B) Growth solution preparation; and (C) Washing the gold nanoparticles:- By centrifugation process, only the gold nanoparticles remains and the other byproducts in the form of liquid is removed.

The spherical shape of the synthesized AuNPs has been observed within the SEM image. The XRD pattern of the prepared sample indicates the diffraction peaks of SnO2, AuNPs, and metallic Cu at different 2theta values. The EDS analysis further confirms the presence of Sn, Au, O, and Cu materials within the synthesized lower part of TENG while the UV-Visible spectroscopy analysis clearly shows 100 % light transmission and ~0 % light absorption of transparent and flexible PMMA polymer material used for synthesis of TENG.

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Figure 1