Cheap, Flexible, and Thermal-Sensitive Paper Sensor through Writing with Ionic Liquids Containing Pencil Leads.

The flexible and portable paper-based sensors have a broad potential application in electronic detection and devices. In this work, a flexible thermoresponsive paper sensor was reported by writing on A4 paper with composite pencil leads which contain thermoresponsive pyrene-based ionic liquid [Pyrmim]+[Br]-. The [Pyrmim]+[Br]- was transferred onto the A4 paper surface with graphite by pencil writing for the facile preparation of thermal-sensitive paper chips. The as-prepared paper sensor was very sensitive to the NIR irradiation and warm objects. What is more, the pliable paper chip also had regular responses along with the varication of the folding angles, which could be employed for the angle goniometer of electronic robots.