Kalliope Margaronis1
University of Cambridge1
Triboelectric generators rely on contact-generated surface charge transfer between materials with different electron affinities, converting mechanical energy into useful electricity. They could potentially be used as power sources for implantable medical devices, which currently mostly run on batteries. Implantable medical devices are an important area of modern medicine, with tens of millions of people living with an implanted medical device, such as cochlear implants and pacemakers. Replacing batteries in implanted medical devices with triboelectric energy harvesters could negate the need for battery replacement surgeries, and could also provide a more convenient, efficient and reliable way of powering such devices.<br/>Two of the main hurdles to consider before replacing batteries with triboelectric nanogenerators (TENGs) are power output and biocompatibility. In order to optimise the performance of a TENG, materials with high surface charge density must be used. Nanostructuring the surface of a material increases its surface area, allowing for greater charge density and therefore larger electrical output. With these considerations poly-L-lactic acid (PLLA) and polytetrafluoroethylene (PTFE) have been investigated as possible biocompatible materials to use in an implanted TENG. We have recently shown that tribopositive PLLA nanotubes grown by melt-press template wetting can be fabricated and optimised for higher triboelectric output through control of polymer crystallinity [1]. As a counter material for TENG applications, PTFE is a highly tribonegative material which, like PLLA, is already widely used as a biocompatible material in the biomedical industry. We therefore investigate the performance of TENGs based on combinations of nanostructured PLLA and PTFE. Importantly, as TENG devices can be actuated at different frequencies, the frequency response of these devices is also presented in this work, with a view to power implantable devices using ultrasound, which represents a low-loss form of energy transfer through human tissue.<br/><br/>[1] Kalliope Margaronis <i>et al</i> 2021 <i>J. Phys. </i><i>Mater.</i> <b>4</b> 034010