The sensor can detect strains and pressure exerted by human motions. Credit: Titash Mondal
Researchers have made a new recyclable sensor that can discern strains and pressure exerted by human motions such as blinking, twitching, frowning, breathing, pulse or the bending of knees and elbows1.
The sensor could potentially be used for human-machine interactions and personal healthcare, researchers at the Indian Institute of Technology Kharagpur in West Bengal say.
Existing sensors generate non-degradable electronic wastes that pollute the environment. To design a reusable one, the scientists loaded a thermoplastic polyurethane matrix with varying weights of graphene. They found that the sensor made using 7% graphene was the most sensitive.
The team, led by Titash Mondal and Kinsuk Naskar, found that the sensor changed its resistance in response to strains and pressure generated by human motions. Strains increased the sensor's resistance from zero to higher positive values whereas pressure decreased its resistance to negative values.
The sensor showed a very fast response and recovery time of 165 milliseconds. A free load of 5 kg and a stretching of its length by 4 to 6 cm did not deform it. Even after 250 loading and unloading cycles, it showed negligible loss in sensing efficiency.
Bending a finger at different angles generated strains that caused the sensor to generate distinguishable signals. This property can be utilised in virtual reality worlds and games. Placing the sensor over the radial artery in the wrist helped count a person’s heart beats. This suggests that minute pressure generated by arterial blood flow altered the resistance of the sensor, the researchers say.
