A skin-like biomedical technology that uses a mesh of conducting nanowires and a layer of elastic polymer might be a step toward development of electronic bandages that monitor biosignals for medical applications and provide therapeutic stimulation through the skin.

Developed by a team from Purdue University, the University of Illinois, and Oklahoma State University, the device's conducting nanowires are approximately 50 nanometers in diameter, 150 microns long, and are embedded inside a thin layer of elastomer, or elastic polymer, 1.5 microns thick.

The material mimics the human skin's elastic properties and sensory capabilities.

The bandage's high adhesive properties reduce the potential for inadvertent delamination. Image credit: Purdue University/Min Ku KimThe bandage's high adhesive properties reduce the potential for inadvertent delamination. Image credit: Purdue University/Min Ku Kim"It can intimately adhere to the skin and simultaneously provide medically useful biofeedback such as electrophysiological signals," says Chi Hwan Lee, assistant professor of biomedical engineering and mechanical engineering at Purdue.

Earlier approaches to developing such a technology have used thin films made of ductile metals such as gold, silver, and copper. However, these films are susceptible to fractures by over-stretching and cracking.

Use of nanowire mesh film makes the device more resistive to stretching and breaking. The film also has a high surface area compared to conventional thin films, with more than 1,000 times greater surface roughness, according to its developers. Once attached to the skin, its adhesion is stronger, reducing the potential for inadvertent delamination.

"The nanowires mesh film was initially formed on a conventional silicon wafer with existing micro- and nano-fabrication technologies," Lee says. "Our unique technique, called crack-driven transfer printing, allows us to controllably peel off the device layer from the silicon wafer and then apply onto the skin."

To demonstrate its utility in medical diagnostics, the device was used to record electrophysiological signals from the heart and muscles. Recording such signals from the skin can provide wearers and clinicians with quantitative measures of heart and muscle activity.

Future research will be dedicated to developing a transdermal drug-delivery bandage that can transport medications through the skin in an electronically controlled fashion. Such a system might include built-in sensors to detect the level of injury and autonomously deliver the appropriate dose of drugs.

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