Ultrasensitive Multi-Functional Flexible Sensors Based on Organic Field-Effect Transistors with Polymer-Dispersed Liquid Crystal Sensing Layers

Ultrasensitive flexible sensors with multi-sensing functions are required for various applications in flexible electronics era. Here we demonstrate flexible polymer-dispersed liquid crystal (PDLC)integrated- organic field-effect transistors (OFETs) (PDLC-i-OFETs), which sensitively respond to various stimulations including weak gas (air) flow, direct physical touch, light, and heat. The flexible PDLC-iOFETs were fabricated by spin-coating the poly(methyl methacrylate) (PMMA)-dispersed 4,4'-pentylcyanobiphenyl (5CB) layers on the poly(3-hexylthiophene) (P3HT) channel layers of OFETs with 200 m-thick poly(ethylene naphthalate) (PEN) substrates. The flexible PDLC-i-OFET devices could sense very weak nitrogen gas flow (0.3 sccm), which cannot be felt by human skins, and stably responded to direct physical touches (0.6 similar to 4.8 g load). In addition, the present devices showed very sensitive photoresponses to a visible light and exhibited excellent heat-sensing characteristics at a temperature of 25 similar to 70 degrees C. In particular, the present flexible PDLC-i-OFET devices could sense two different stimulations at the same time, indicative of promising multi-sensing capabilities.