Encapsulating and Inkjet-Printing Electronics on Flexible Substrates for Harsh Environment

We have developed a proof of concept for a flexible sensor in harsh environmental conditions by using the inkjet printing technique. Printing a conductive pattern on a flexible substrate poses several challenges like surface energy mismatch, nonuniform ink deposition, and crack formation leading to poor conductivity. Further, there is a need for a flexible, oil and chemical-resistant encapsulant material to protect the sensor from harsh environments. We proposed a process to overcome these challenges and validated this process by measuring the actual and theoretical resistance values of the printed patterns on the flexible substrates that were found to be comparable. The printed patterns were encapsulated with fluoroelastomer, well-known for excellent oil and chemical resistance. We investigated the effect of a harsh environment on conductivity by submerging it in hydraulic oil at temperatures 80°C–180°C. Results revealed a negligible change in resistance. Thus, we devised a single process that can be used for printing conductive patterns on various flexible substrates like Polyethylene terephthalate, Polydimethylsiloxane, and Silicone rubber. Furthermore, the effectiveness of fluoroelastomer as an encapsulant for the harsh environment was investigated.