Scientists often take inspiration from nature when developing new materials. For example, octopus and mollusks can be excellent specimens of adhesive technology because their technique beats human scientists. Now, a team of scientists from South Korea’s Daegu Gyeongbuk Institute of Science and Technology (DGIST) have developed a new waterproof, wearable biosensor that can stick to the skin in a unique way.
For a wearable sensor to be truly effective, it must adhere fully to the skin. This means being flexible, staying attached when the skin is wet or dry, and working well even if there’s a lot of hair growing. Thus, the choice of substrate, the material that the sensing compounds rest upon, is crucial. Woven yarn is a popular substrate, but it sometimes doesn’t 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, Changhyun Pang, Changsoon Choi and colleagues worked to develop a low-cost, graphene-based sensor with a yarn-like substrate that uses octopus-like suckers to adhere to skin, reports American Chemical Society.
An elastic polyurethane and polyester fabric was coated with graphene oxide and then soaked in L-ascorbic acid to aid in conductivity while still retaining its strength and stretch. Next, the scientists 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, the researchers say.
The team is eyeing the sensor’s use for not only personal health monitoring but also for potential new and innovative medical applications both externally and internally.
“Our approach has opened up a new possibility for wearable and skin-adherent electronic fabric sensors working even in wet environments for health-care monitoring and medical applications in vitro and in vivo,” the researchers wrote.