A low-cost soft, flexible, and wearable sensor that can be used for diagnosis of pulse rate variability in humans has been developed at IIT Bombay. Being a high sensitivity flexible pressure/strain sensor, it can also be used for small- and large-scale motion monitoring, with potential applications in robotics, prosthetics, as well as minimal invasive surgery and identification of tumour/cancerous cells.

Researcher Dipti Gupta has fabricated these tactile (pressure and strain) sensors using low-cost polyurethane foam and nanomaterial-based inks that can coat several substrates. Reduced graphene oxide (rGO) was used as the sensing material. The fabrication of sensors based on reduced graphene oxide (rGO) as the sensing material was challenging due to the intrinsic hydrophobic (water-repellent) behaviour of graphene oxide inks as well as the agglomeration of graphene oxide flakes after reduction. A reducing agent called hydrazine and a dual-component additive comprising compounds benzisothiazolinone and methylisothiazolinone in appropriate proportion were used to synthesize rGO ink with a hydrophilic (water-loving) nature. Utilizing this hydrophilic rGO ink mixed with multiwalled carbon nanotubes (MWNTs), “a very simple, low-cost approach was found for the fabrication of a pressure sensor based on polyurethane (PU) foam coated with the rGO ink,” says a press release from the Department of Science and Technology.

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