“This is the first demonstration of stacking multiple nanometres-thin membranes like LEGO blocks, which has been impossible because all functional electronic materials exist in a thick wafer form,” Kim notes.
In one experiment, the team stacked together films of two different complex oxides: cobalt ferrite, known to expand in the presence of a magnetic field, and PMN-PT, a material that generates voltage when stretched. When the researchers exposed the multilayer film to a magnetic field, the two layers worked together to both expand and produce a small electric current. In the case of cobalt ferrite and PMN-PT, each material has a different crystalline pattern.
“The big picture of this work is, you can combine totally different materials in one place together,” Kim explains. “Now you can imagine a thin, flexible device made from layers that include a sensor, computing system, a battery, a solar cell, so you could have a flexible, self-powering, internet-of-things stacked chip.”
The team is exploring various combinations of semiconducting films and is working on developing prototype devices, such as something Kim is calling an “electronic tattoo” — a flexible, transparent chip that can attach and conform to a person’s body to sense and wirelessly relay vital signs such as temperature and pulse.
The research was the outcome of close collaboration between the researchers at MIT and at the University of Wisconsin at Madison, which was supported by the Defense Advanced Research Projects Agency.
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