Neural dust mote

A millimetre- or sub-millimetre-scale, wireless, battery-free implant that senses local electrophysiology (EMG, nerve, or in principle cortical signals) and communicates by ultrasonic backscatter. A canonical mote couples a piezoelectric crystal — which both harvests incident ultrasound for power and modulates the reflected echo — to a simple front-end (often a single transistor) that varies the crystal's electrical load with the recorded biopotential.

The design's appeal is that it removes wires, radios, and batteries, and exploits ultrasound's favourable penetration and small wavelength at millimetre scales in tissue. Demonstrations to date have measured peripheral nerve and muscle activity in rodents; scaling to dense cortical recording, to many independently-addressed motes, and to chronic human use are open engineering challenges.