A schematic of the nanomesh conductors (a). A picture of a nanomesh conductor attached to a fingertip (b). An SEM image of nanomesh conductor formed on a silicone skin replica by dissolving PVA nanofibers. (Credit: DGIST)

An “electronic skin” microsystem tracks heart rate, respiration, muscle movement and other health data, and wirelessly transmits it to a smart phone. The electronic skin offers several improvements over existing trackers, including greater flexibility, smaller size, and the ability to stick the self-adhesive patch — which is a very soft silicone about 4 cm (1.5 in.) in diameter — just about anywhere on the body.

The microsystem contains about 50 components connected by a network of 250 tiny wire coils embedded in protective silicone. The soft material enables it to conform to body, unlike other hard monitors. It wirelessly transmits data on movement and respiration, as well as electrical activity in the heart, muscles, eyes, and brain to a smart phone application.

Unlike flat sensors, the tiny wires coils in this device are three-dimensional, which maximizes flexibility. The coils can stretch and contract like a spring without breaking. The coils and sensor components are also configured in an unusual spider web pattern that ensures “uniform and extreme levels of stretchability and bendability in any direction.” It also enables tighter packing of components, minimizing size.

The key to creating this novel microsystem is stretching the elastic silicone base while the tiny wire arcs, made of gold, chromium and phosphate, are laid flat onto it. The arcs are firmly connected to the base only at one end of each arc. When the base is allowed to contract, the arcs pop up, forming three-dimensional coils.

The entire system is powered wirelessly rather than being charged by a battery. The researchers also considered key electrical and mechanical issues to optimize the system's physical layout, such as sensor placement or wire length, to minimize signal interference and noise.