Cork as a novel material for Printed Electronics

• Autor(a) principal: Azevedo, João Mendonça de
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/145439
• topic: Cork; cork electronics; printed electronics; cellulose nanofibers; planarizing layer; ultraviolet sensors; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia dos Materiais

Cork is one of the oldest materials used by Man, with exceptional characteristics that allow its introduction in the field of electronics as a material that is not only innovative but also sustainable. Composite cork agglomerates from cork industrial waste have all the intrinsic properties of natural cork, making it a great starting point for introducing cork into electronics. Motivated by the growing need in the use of new natural and self-sustainable materials, it was developed with the use of another ecological and innovative material, cellulose nanofibers, a simple, low energy and low-cost method of surface planarization, which improves significantly the surface characteristics of cork for later use as an electronic substrate. Several surface studies were carried out on the cork agglomerate at various stages of the planarization process to optimize each step of the overall process. Due to the hydrophobicity of cork surface, oxygen low-pressure plasma treatment was performed as an essential initial step for surface activation, followed by an extensive surface analysis through SEM, ATR-FTIR spectrum, contact angle measurements, and surface energy calculation to understand the induced changes. Subsequently, several types of thin cellulose nanofibers layers were applied over the activated cork agglomerate surface, significantly reducing the surface roughness hitherto presented, with improved adhesion. As a result, planarized cork agglomerate substrates display lower surface roughness, being optimized to be used in a wide range of electronic devices. Proving its applicability in electronic devices, the produced planarized substrates were successfully used alongside carboxymethyl cellulose and zinc oxide in the development of screen- printed ultraviolet sensors, presenting high production replicability, higher photocurrents than the equivalent substrate without any type of treatment, and stable performances over continuous use cycles.