INTEGRATED MULTILAYER TRIBOELECTRIC NANOGENERATOR FROM BIO-BASED COMPOSITES FOR MECHANICAL ENERGY HARVESTING TECHNOLOGY

Abstract

In the past three years, medical electronic devices has been extensively developed for real-time diagnosis and health monitoring. Since their physical design requires flexibility, stretchability, and lightweight properties, finding an alternatively electrical power source to replace the use of battery has become one of the key issues to be addressed. Triboelectric nanogenerator (TENG), which can harvest the mechanical energy from rubbing to produce electricity, is focused in this work. Biomaterials such as silk fibroin (SF) and bacterial cellulose (BC) were selected as the main friction layers. However, most biomaterials still provide low electrical output. Therefore, the aim of this study was to enhance the electrical output of these biomaterial TENG through two strategies: (1) incorporating the dielectric magnesium aluminum layer double hydroxide nanosheet (MgAl LDH NS) to improve electrical output by improving dielectric constant, and (2) modifying the device structure to be multilayer TENG (M-TENG) by inserting charge-trapping layer between friction layer and electrodes. For the first strategy, higher dielectric constant of MgAl LDH successfully enhanced the maximum output power (Pmax) of SF/MgAl LDH and BC/MgAl LDH, by increasing charge density. The SF/MgAl LDH at 3% achieved the Pmax of about 165 µW (power density = 18.3 µW/cm2), while the BC/MgAl LDH at 1.5% generated 542 µW (power density of 60.2 µW/cm2). Once the optimal conditions were established, the second strategy was focused on the M-TENG design. SF/lignin composite film was inserted between SF/MgAl LDH film and its electrode. Similarly, the BC/lignin was used for the BC-based system. The results clearly showed that inserting charge-trapping layer of SF/lignin and BC/lignin further improve electrical output. The SF-based M-TENG produced a Pmax of 205 µW (22.8 µW/cm2), which is 1.2 times higher than that of SF/MgAl LDH. Likewise, inserting BC/lignin between BC/MgAl LDH and electrode generated a Pmax of 918 µW (102 µW/cm2). It is almost 26 times higher than BC/MgAl LDH 1.5%(v/v). The aromatic ring from lignin structure helped retain the charge, preventing its loss before orderly transfer to the load. Finally, the results of this work confirm the potential of using biomaterials for high efficiency power supply for small electronic devices as demonstrated by the ability to power more than a hundred LED.

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