Design and fabrication of flexible wearable triboelectric nanogenerators

An increasing demand for power sources accessible everywhere and at anytime led to the development of harvesting technologies to convert directly mechanical energy from the surrounding environment into electrical energy. A huge step forward in this field arrive in 2006 with the invention of nanogenerators (NG). These devices can convert mechanical energy into electrical one, generating power of the order of some milliwatts. This low level, with the development of modern devices, is enough to directly supply some simple devices or to store energy into capacitors. The most promising type of nanogenerators is based on triboelectric effect. Triboelectric NGs can transform any type of mechanical movement into electrical energy utilizing the mutual movement of two materials. The simplicity of their working mechanism made triboelectric nanogenerators (TENGs) good candidates to develop wearable devices able to produce energy by everyday actions. The countless fields in which these types of devices can be applied range from the civil to the military environment, bringing numerous advantages in terms of equipment's lightness and size. This work's goal is to design a flexible, bio-compatible and with low environmental impact TENG in view of wearable use. To do this, transparent and conductive hydrogels were used as electrodes. They are cellulose-based and exploit ions coming from a dissolved salt to conduct electricity. Different salt concentrations have been investigated in order to have the best output performance. Furthermore, various conditioning circuits have been tested to understand which is the best way to manage power and to store energy into capacitors.