Reducing moisture ingress in flexible sensors with laser patterned polyimide

Polymeric materials that can more effectively act as barriers to environmental factors such as moisture are of significant interest to the sensor fabrication industry. Moisture ingress may corrode metallic traces or cause the decohesion of bonded interfaces of flexible sensors. Often, imparting a higher degree of moisture resistance necessitates encapsulating the sensors or applying specialty coatings. In this study, a laser patterning process is used to modify standard polyimide coverfilms used in flexible sensor manufacturing. The study achieved patterned polyimide surfaces in the partial wetting Cassie-Baxter regime which displayed reduced moisture diffusivity compared to the original polyimide surface by an order of magnitude. These surfaces displayed periodic structures with deep channels, a high developed interfacial area ratio, and a low contact angle. A laser-patterned sensor that makes use of this coverfilm-enhancing technique is demonstrated. Avoiding the need to apply additional moisture resistant films and instead laser patterning existing coverfilms could provide significant benefits to the flexible sensor industry, simplifying the fabrication of more robust sensors that are less prone to environmental degradation. (c) 2023 Society of Manufacturing Engineers (SME). Published by Elsevier Ltd. All rights reserved.