Portable heater from pencil on paper
doi:10.1038/nindia.2019.99 Published online 1 August 2019
Given a sheet of paper and a pencil, one may not think of a probable use for them beyond scribbling, but scientists in the Department of Electronics at Savitribai Phule Pune University have put them to an unconventional use. They have designed and fabricated a low-cost portable heater that might be useful in school, college and research laboratory experiments as well as in medical applications1.
Devices built on paper substrates such as sensors and strain gauges already exist, and the advent of graphene and 3D graphene has broadened applications of carbon-based devices in domains as diverse as catalysis and energy applications. The "pencil-on-paper" heater is a step in this direction (see diagram).
The scientists applied several strokes from a high graphite content pencil to produce a thick coating of graphite on the paper. They placed copper wire to make electrical contacts over the coated surface. This functioned as the heating element. The simple heater was operated using a battery, making it easily portable. The temperature of the heater was changed by varying the input power from the battery.
"Even though the fabrication process is rudimentary, temperatures of up to 100 degrees Celsius can be easily achieved without the paper catching fire," the authors say. Such high temperatures can be safely maintained for about 40 minutes.
"The use of the device has been successfully demonstrated as a heating source in research and therapeutic domains," the report says.
1. Morarka, A. & Joshi, A. C. Pencil trace on cellulose compounds: a heat source. Curr. Sci. 117 (2019) Article