Researchers have created millimeter-sized metal tools that contort on command, clamping shut or popping open in response to specific chemical cues. The smart devices, described online September 17 in the Journal of the American Chemical Society, may one day be used to biopsy a liver, prop open an artery or deliver drugs to a target site.
Even tiny tools need some power source — a battery pack or electrical wires — but that adds unwanted bulk, says study leader David Gracias of Johns Hopkins University in Baltimore. Yet nature is filled with minimachines: muscles contract, leaves turn to the sun, a Venus fly trap snaps shut. “In nature, and in us, these respond to chemistry,” Gracias says.
It took some doing to make devices that could respond to chemicals in the right time and place, yet were still friendly inside the body. Gracias and his team began with thin silicon wafers and coated them with layers of chromium, nickel and gold. Using a high-tech version of a stencil, the researchers patterned the metal layers into parts that looked like a flower or open palm of the hand. They added hinges so the open hand could clamp shut.