Inspired by octopus ‘suckers’, scientists have developed flexible wearable sensors that stick to the skin, paving the way for novel health trackers that could monitor a variety of human activities.
For a wearable sensor to be truly effective, it must be flexible and adhere fully to both wet and dry skin but still remain comfortable for the user, according to the researchers from Sungkyunkwan University (SKKU) in South Korea.
The material that the sensing compounds rest upon is crucial. Woven yarn is a popular substrate, but it sometimes does not fully contact the skin, especially if that skin is hairy. Typical yarns and threads are also vulnerable to wet environments.
Adhesives can lose their grip underwater, and in dry environments they can be so sticky that they can be painful when peeled off.
To overcome these challenges, researchers worked to develop a low-cost, graphene-based sensor with a yarn-like substrate that uses octopus-like suckers to adhere to skin.
They coated an elastic polyurethane and polyester fabric with graphene oxide and soaked in L-ascorbic acid to aid in conductivity while still retaining its strength and stretch.
From there, they added a coating of a graphene and poly(dimethylsiloxane) (PDMS) film to form a conductive path from the fabric to the skin. Finally, they etched tiny, octopus-like patterns on the film.
The sensor could detect a wide range of pressures and motions in both wet and dry environments.
The device also could monitor an array of human activities, including electrocardiogram signals, pulse and speech patterns, demonstrating its potential use in medical applications, researchers said.