Development of functional fibers for wearable applications

• Autor(a) principal: Lima, Nuno Rodrigo Cândido
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/57612
• topic: Wearable electronics; energy storage; supercapacitor; electrospinning; functional fibers; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia dos Materiais

Wearable energy storage systems have been intensely investigated to cope with the increase in energy demand for wearable electronics. With bulky and rigid energy storage devices being non-practical for wearable technology, one-dimensional fibers show great promise in this area due to good flexibility and adaptation to deformation. The goal of this thesis was to create a cheap supercapacitor (SC) capable of using simulated body fluids (SBF) as the electrolyte in view of potential applications in the field of wearable electronics, e.g. in biomedical monitoring applications. In this thesis, different materials were tested as electrodes for a one-dimensional (fiber-shaped) flexible supercapacitor (SC) whilst using cellulose acetate (CA) electrospun fibers as the separator; these included: aluminum (Al) wire and copper (Cu) evaporated on the top of CA fibers; Al wire with Cu wire; Al wire with carbon ink deposited on CA fibers; exfoliated graphite wire or carbon fibers bundle (CF) with Al wire; and a CF symmetrical SC. The later revealing a greater electrochemical cycling stability. Hence, in an attempted to further optimize the CF symmetrical SC architecture, the surface of CFs was further functionalized with a ZnO:PVDF composite and polypyrrole (Ppy). CFs functionalized with Ppy showed a specific capacitance three-fold higher than that of carbon fibers symmetrical SC, an energy density of 159.65 mWh kg-1 and a power density of 11.49 W kg-1. Furthermore, replacing the SBF with a 0.1 M of KOH it was possible to achieve higher specific capacitances (3.60 F/g vs. 0.23 F/g at 100 mV/s).