Additive manufacturing of polymeric matrices with capacitive and haptic properties

• Autor(a) principal: Lima, Martinho Tavares Carrega de
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/40220
• topic: Flexible electronics; Capacitive sensor; Additive manufacturing (AM); Inkjet printing; Piezoelectric haptics; Automobile industry; P(VDF-TrFE)

In this work, an innovative approach into the development of a flexible sensor matrix with capacitive and haptic properties by using additive manufacturing (AM) technologies is conducted. The flexible tactile capacitive sensor is fabricated using a thin polyethylene terephthalate (PET) sheet for its substrate, silver nanoparticle ink for the strip electrodes of the matrix, and a poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) piezoelectric copolymer in an 80/20 ratio for the dielectric and piezoelectric layer. The capacitive sensor resolution is provided by nine independent capacitors formed by a 3x3 electrode grid of the device. The study conducted in this dissertation focuses on the electric and piezoelectric properties of the fabricated device, as well as its microstructure. However, an in-depth analysis of the relevant properties of the materials composing the device matrix is also conducted, justifying the use of two AM techniques: Ink-based Material Jetting and Robocasting. The conducted studies also confirm the existence of the desired crystalline β-phase of PVDF within the active layer, as it possesses a high dipole moment and is therefore prone to piezoelectric behavior, with a Curie temperature of 131°C. Therefore, a bulk longitudinal piezoelectric coefficient, d₃₃, of approximately 18 pC/N is measured by the Berlincourt method and an effective d*₃₃ of 33.1 pm/V is determined locally using piezoresponse force microscopy (PFM) measurements on the active polymer layer. The piezoelectric behavior allows for the generation of a haptic response when 302 V AC voltage is applied to the active layer. The sensor device with layer adhesion displayed by scanning electron microscopy (SEM) is presented as a matrix of capacitors capable of doubling its original capacitance of approximately 40 pF under external impact.