A team of researchers from the Indian Institute of Science (IISc) and the Pandit Deendayal Energy University have come up with a potential fix for the problem of increasing waste from pressure sensors used in healthcare and other fields: alternative eco-friendly sensors which use paper, instead of petroleum-based polymers, as their basis.
"Our key contribution is the simplicity of the device," explains Navakanta Bhat, professor at the IISc's Center for Nano Science and Engineering (CeNSE) of his team's work. "It is like creating paper origami."
The proposed sensor is built from layers of plain and corrugated cellulose paper, coated with tin-monosulfide to act as a semiconductor. "Paper in itself is an insulator," Neha Sakhuja, first author, explains. "The major challenge was choosing an appropriate 3D device structure and material to give conductive properties to paper."
The resulting multi-layer sensor works by altering its conductivity based on the distance between the paper layers and the size of the air gaps between them — turning pressure into values, which can be read by a controlling system. In testing, prototype paper sensors provided the ability to detect a range of pressures from 0-120kPa with a one-millisecond response time — and proved its practicality in a successful project to build a paper-based foldable keypad as an input device.
The team believes that the paper sensors could be developed into flexible wearable devices for the healthcare sector, demonstrating their use to track muscle movements during chewing and arm or finger gestures using an Arduino Uno, where they would replace traditional pressure sensors built on a petroleum-based polymer — a plastic that is not biodegradable nor easily recyclable. The paper sensor, by contrast, is kinder to the environment once it has outlived its usefulness.
“The future applications of this device are limited only by our imagination," claims Bhat. "We would [also] like to work on increasing the stability and durability of these sensors and possibly collaborate with industries to manufacture them in large numbers."
The team's work has been published under closed-access terms in the journal ACS Sustainable Chemistry & Engineering.