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Building a Wireless Micromachine

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A wireless micromachine. The miniature sandwich of gold and aluminum nitride is 100 micrometers across—a little wider than the width of a human hair. (Image Credit: Boston University)

A team of researchers, led by Boston University College of Engineering (ENG) PhD candidate Farrukh Mateen (ENG’18) and Raj Mohanty, a professor of physics at BU’s College of Arts & Sciences (CAS), are closing in on a solution. They have built a tiny micromechanical device and turned it on and off with one nanowatt of power—that’s a billionth of a watt—from three feet away. The device is a miniature sandwich of gold and aluminum nitride that vibrates, or resonates, at microwave frequencies. The tiny resonator is only 100 micrometers across—a little wider than the width of a human hair. “Wireless power is not new,” says Mateen. “Nikola Tesla demonstrated it at the 1893 World’s Fair; but we believe this is the first time it’s been used with a micromechanical resonator.” In a second round of experiments, the device achieved an impressive 15 percent efficiency using a higher radio frequency. The most promising application for this type of device lies in the emerging field of optogenetics: shining light on genetically modified brain cells to make them behave in a certain way. The field offers great potential for neuroscience research, as well as possible treatments for neurological disorders like Parkinson’s disease. But to plant a device in the body, especially the brain, is challenging. It needs to be tiny and efficient, low-power and low-radiation. Power must travel to the device quickly, through bone and brain tissue. “You don’t want to have to change batteries every day,” says Mohanty, corresponding author on both papers, “and you don’t want to fry your brain.”