Photolithographically Printed Flexible Silk/PEDOT:PSS Temperature Sensors

Abstract

Precise, real-time monitoring of temperature in flexible and bioconformable formats finds applications in healthcare and disease diagnostics. There is interest in the fabrication of biocompatible and biodegradable devices that can be safely resorbed inside the body or easily disposed of in the environment, reducing waste. Here, a fully organic, silk-protein-based temperature sensor is reported with attractive properties such as flexibility, transparency, conformability, durability, and biodegradability together with high sensitivity and accuracy. The sensor is composed of a flexible, photoactive silk fibroin substrate, on which interdigitated electrodes are photolithographically micropatterned using a photoactive silk sericin–PEDOT:PSS conductive ink. A temperature sensitive layer comprising photoactive silk sericin and rGO is integrated on the electrodes. Finally, the sensor is sheathed in a fibroin layer to eliminate interference from humidity. The sensor exhibits a high sensitivity of −0.99% °C−1 in the temperature range of 20–50 °C along with excellent stability in humidity from 10 to 90% RH. It possesses high cycling stability over multiple heating/cooling cycles. These layers are covalently integrated, improving mechanical stability and the retention of electrochemical behavior under deformation. The sensor is shown for the monitoring of surface temperature, including rapid measurement of skin temperature with accuracy. Finally, the temperature sensor is able to effectively degrade over a period of ∼10 days under proteolytic conditions. Such sensors have potential in personalized healthcare monitoring devices, improving efficient disease detection and diagnosis.