Energetically Autonomous Thermochromic Smart Tags

• Autor(a) principal: Lochmatter, Luna Ilda Taborda Félix
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/147980
• topic: Thermochromic inks; Smart indicator; Thermal insulating films; Thermal monitoring; Gradual colour shift; Domínio/Área Científica::Engenharia e Tecnologia::Nanotecnologia

Set-top-boxes contribute significantly to energy consumption of the common household. These devices are usually ignored and unproperly placed in confined spaces. Poor positioning of set-top-boxes can obstruct heat dissipation, leading to their overheating and endangering correct functioning and long-term operation. Monitoring the thermal conditioning of the device is critical to ensure its standard performance. This project aims to produce a paper thermochromic smart tag capable of monitoring the STB's superficial temperature through a colour change activated by the released heat. This offers an aesthetic, dynamic, and energetically autonomous solution to inform the consumer of its thermal conditioning and alerting them to potentially compromising situations regarding the device's safety and long-term operation. The thermochromic smart tag is produced using low-cost, easily scalable printing/coating technologies together with natural-based materials, such as cellulose/paper and cork, for sustainability purposes. To ensure a gradual colour shift with the change of the set-top-boxes temperature, layers of thermal insulating mixtures are deposited on office paper, creating levels of activation of the TC material. Dispersions of thermal insulating materials are formulated using cellulose derivatives or polydimethylsiloxane as binder mixed with insulating particles, such as microcellulose, silica nanoparticles, and cork wastes. Printing/coating trials were performed with these dispersions, and the films were evaluated regarding their printing/coating quality, thermal gradient and stability over time. Interesting results were obtained with samples coated by doctor blade coating with dispersions of cork:polydimethylsiloxane (10:90 %(w/w)), which present a tailored thermal gradient between the film and the substrate with a dependency of film’s thickness, defined by the number of coating steps. Thicker thermal insulating films induce a higher thermal gradient, which translates into a slower colour transition of the TC material for a given transition temperature when integrated with the thermochromic smart tag. This way, activation only occurs for continuous heating, alerting for potentially harmful situations for the set-top-box.