Image: A polymer nanowire sensor attached to a Coca-Cola can (Photo courtesy of Stanford University).

Flexible electronics that can bend to accommodate almost any shape and form are the basis for ultrasensitive biosensors that can be attached to organs like the heart and brain, flexible computer displays, and wearable electronics.

Developed by researchers at Stanford University (CA, USA), the nanowire electronics are embedded in a polymer layer 15 times thinner than plastic wrap to insulate and support the electronics mechanically. The technology is based on a simple, versatile, and wafer-scale water-assisted transfer printing (WTP) method. The sensors can then be attached to virtually any surface, and can be released from it repeatedly without any damage; among the materials tested were paper, textiles, plastics, glass, aluminum foil, and latex gloves, polydimethylsiloxane (PDMS), aluminum foil, and ultrathin polymer substrates.

The WTP method relies on the phenomenon of water penetrating into the interface between Nickel (Ni) and Silicon Dioxide (SiO2). The transfer yield is nearly 100%, and the transferred devices, including NW resistors, diodes, and field effect transistors, maintain their original geometries and electronic properties with high fidelity. Some of the major applications of the process are in biological research; nanowire devices could be attached directly to heart or brain tissues to measure the electrical signals from those tissues. The study describing the WTP process and potential applications was published early online on June 22, 2011, in Nano Letters.

“What really makes the devices so flexible, what allows the devices to bend with the flexible substrate, is the short length of the nanowires used to fabricate the circuitry,” said lead author Professor Xiaolin Zheng, PhD, of the department of mechanical engineering. “The length of these nanowires is only a couple thousandths of a millimeter long. Compared to the curvature of the objects we’re attaching them to, that is really short, so there is very little strain on the nanowires.”

“Researchers could measure heart arrhythmias or how a neuron fires. Those signals are electrical, but to measure them you need a very conformable, very thin coating that allows the signals to propagate across the substrate,” added Professor Zheng. “The transfer process could also be used in developing high-efficiency flexible solar cells and would likely have uses in robotics, as well. The possibilities are really unlimited.”

Guangzhou Jia Yu medical equipment Limited