Encapsulating and inkjet-printing flexible conductive patterns on a fluoroelastomer for harsh hydrocarbon fluid environments

Abstract

Flexible electronic devices are widely used in automobile, healthcare, space exploration, oil and gas, and marine industries, etc. Owing to the broad application areas, they are exposed to harsh environmental conditions that inhibit their stable performance. Thus, there is a need to develop flexible electronic devices that can sustain these conditions and achieve desirable performance. We developed flexible electronics for application in harsh environments involving hydrocarbon fluids at elevated temperatures. Fluoroelastomer FKM having excellent chemical resistance is used as a substrate and inkjet printing is used for its fabrication due to its ability to directly print on flexible substrates. A simple fabrication approach for flexible electronics is demonstrated via inkjet printing of silver patterns on an FKM substrate. The fabrication process involves surface pretreatment by corona treatment and multiple-layer printing with intermittent drying to overcome several challenges like surface energy mismatch, nonuniform ink deposition, and crack formation. The process was validated by comparing the actual and theoretical resistance values of the printed patterns. The printed flexible electronics are encapsulated by FKM to protect them from harsh environments. The effect of a harsh environment on the conductivity was evaluated by submerging it in hydraulic oil up to a temperature of 180 °C followed by a bending test. The results revealed a negligible change in resistance. Degradation of the silver and FKM is characterized using mass variation tests, microscopic images, and FTIR spectroscopy, which revealed negligible degradation of the flexible encapsulated patterns. The performance of FKM is compared to those of other substrates like polydimethylsiloxane (PDMS) and polyethylene terephthalate (PET) under harsh conditions; FKM was found to be an effective encapsulation material for our application. To our knowledge, no researchers have printed conductive silver patterns directly on a FKM substrate using inkjet printing and encapsulated them using FKM. This technique offers a simple solution for fabricating flexible electronics for harsh environments.