Researchers from Columbia University and Delft University of Technology have created ultra-compact "implantable motes" that can report on localized temperature within the human body and which are powered entirely from ultrasonic signals — all on a single, tiny chip.
"We wanted to see how far we could push the limits on how small a functioning chip we could make," Professor Ken Shepard explains of the study he led." This is a new idea of 'chip as system' — this is a chip that alone, with nothing else, is a complete functioning electronic system. This should be revolutionary for developing wireless, miniaturized implantable medical devices that can sense different things, be used in clinical applications, and eventually approved for human use."
The chip designed by Shepard's team measures under 0.1mm³ (around 0.004in³) and draws under 1nW of power, which it gathers from an external off-the-shelf ultrasound imager. Upon receipt of the ultrasound signal, the mote reports back the temperature of its surroundings.
"The small displaced volume of these motes allows them to be implanted or injected using minimally invasive techniques with improved biocompatibility," the team explains. "We demonstrate their sensing functionality in vivo for an ultrasound neurostimulation procedure in mice. Our motes have the potential to be adapted to the distributed and localized sensing of other clinically relevant physiological parameters."
Shepard's team isn't the only one investigating ultra-tiny implants powered by ultrasonic signals, though: Last month a team of engineers from the University of California, Berkeley showed off an oxygen sensor which, while considerably larger than the device created by Shepard's team, could also be easily implanted and which is both powered by and communicates via ultrasonic signals.
The team's work has been published under open-access terms in the journal Science Advances.