For the first time, researchers have developed a microchip that is powered by the same energy-rich molecules that fuel living cells, researchers say. This advance could one day lead to devices that are implanted within cells and harvest biological energy to operate.
The molecule adenosine triphosphate (ATP) stores chemical energy and is used inside cells to ferry energy from where it is generated to where it is consumed. The new microchip relies on enzymes known as sodium-potassium ATPases. These molecules break down ATP to release energy the enzymes use to pump sodium and potassium ions across membranes, generating an electrical potential during the process.
“Ion pumps are electronics-like components in living systems,” says study senior author Ken Shepard, an electrical engineer at Columbia University in New York. Shepard and his colleagues detailed their findings in the 7 December edition of the journal Nature Communications.
The researchers embedded sodium-potassium ATPases taken from pig brains in artificial fatty membranes. There were more than 2 million of these molecules active per square millimeter of the membranes, about 5 percent of the density naturally occurring in mammalian nerve fibers.
In the presence of ATP, these ion pumps generated 78 millivolts. A “biocell” of two membranes provides enough of a voltage to operate a CMOS integrated circuit. The ion pumps have a chemical-to-electrical energy conversion efficiency of of 14.9 percent.
“These ion pumps generated an electrical field that we harnessed to power a solid-state system,” Shepard says.
Since ATP is only really found within cells and not in the bloodstream, Shepard cautions that this new system is not a way to power conventional implantable medical devices such as pacemakers.
“However, such a system might power an implant small enough to sit inside a cell,” Shepard says. “Solid-state materials are already used in nanoparticles for various therapeutic and imaging purposes in the body, but those are all just passive materials. Our idea is to make something that would have the ability to compute and act, to make decisions and then actuate in some way.”
Future research could also incorporate other membrane proteins into electronics, such as those responsible for taste and smell, Shepard says. "There could be many ways to couple solid-state systems with the biological machinery of cells," he says.
Charles Q. Choi is a science reporter who contributes regularly to IEEE Spectrum. He has written for Scientific American, The New York Times, Wired, and Science, among others.