Flexible bracelet for energy storage in wearables technology

Author(s)

Carla Giselle Martins Real

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Elétrica e de Computação
• Defense date: 2019-04-10

Examining board members

Hudson Giovani Zanin; Alfredo Carlos Peterlevitz; Ambrósio Florêncio de Almeida Neto

• Advisor: Hudson Giovani Zanin; Helder Jose Ceragioli

Abstract

Energy storage devices are a key part in various industries such as portable electronics, wearables, electric vehicles, and solar and wind power systems. With the growing development of these markets, the enhancemen tof these devices has become necessary to meet the new demands. Therefore, It is desirable that these devices be low cost, lightweight, small, environmentally friendly and exhibit rapid charge transfer and long lifetime. In this scenario, Electric Double Layer Capacitors (EDLCs) or pseudocapacitors, which are part of the family of electrochemical capacitors (ECs), are interesting alternatives to meet these needs compared to conventional batteries. In this project, we developed a bracelet prototype that acts as an EC device in wearable technologies. To consolidate this device, we tested several composite material electrodes. The composite is a combination of carbon materials (ie, carbon nanotube (CNT), activated carbon (AC), carbon fibers (ACNFs) and carbon black (CB)) and polymers (ie polyvinyl alcohol (PVA), polycyclonitrile (PAN) and polyvinylidene fluoride (PVDF)). As proof of concept, we sealed the material in coin cells device and explored the electrochemical properties of an aqueous solution of lithium sulfate ($Li_2SO_4)$ as electrolyte as well as the electrochemical properties of an aqueous solution of lithium sulphate $(Li_2SO_4)$ as electrolyte, taking into account safety issues derived from flammable and toxic organic electrolytes. The energy storage device takes the form of a leaf composed of a thin film that allowed it to be flexible in all directions meeting the requirements of a variety of emerging applications such as wearables. In addition to the device, we developed some features for the bracelet such as time/date dialing, timing and monitoring heart rate. As the energy source of the bracelet, we use a series-parallel association of the developed supercapacitor. Thus, we consolidated a technology that used a bank of supercapacitors in a wristband format that provides ~8V e ~0,03A (AU)

• FAPESP's process: 17/03371-0 - Elastic bracelet for energy storage and supply on wearable technology
• Grantee: Carla Giselle Martins Real
• Support Opportunities: Scholarships in Brazil - Master