Devices

A battery-free, 3 mm sensor that is powered and read out by ultrasound. Demonstrated in 2016 on rat sciatic nerve and muscle at UC Berkeley.

Device — Peripheral nerve

Neural dust (ultrasonic backscatter mote)

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wireless · ultrasound · backscatter · battery-free · peripheral nerve · EMG · ENG · Berkeley · academic · preclinical

Neural dust (ultrasonic backscatter mote)

One-line verdict: The first demonstration that a battery-free sensor the size of a grain of sand can be powered and read out by ultrasound alone, shown in rat nerve and muscle and not yet in a brain implant.

Quick tags: Recording · Peripheral nerve · Species: Rat · Demonstrated: 2016

Overview

What it is: A mote with a piezoelectric crystal, one transistor and a pair of recording electrodes. An external ultrasound transducer sends pulses that power the crystal. A voltage spike at the nerve or muscle changes the circuit, which changes the echo that returns to the transducer. That change in the echo (backscatter) carries the signal.

Why it matters: It removes the battery, the lead and the radio from an implant. Ultrasound passes through tissue where radio-frequency links lose power, so the concept points at motes deep in the body and, in the authors’ longer-term view, in the brain.

Status: Academic demonstration. The sources cited here report rat experiments only, in peripheral nerve (ENG) and muscle (EMG), under anesthesia. No human implant is reported in them.

Spec Card Grid

Identity

  • Device name: Neural dust mote
  • Inventors / key authors: Dongjin Seo, Ryan M. Neely, Konlin Shen, Jan M. Rabaey, Jose M. Carmena, Michel M. Maharbiz (and co-authors)
  • Org: University of California, Berkeley
  • Published: Neuron, August 2016
  • Species: rat
  • Primary use: recording (stimulation is discussed as a future use)

Geometry & Architecture

  • Mote size (demonstrated): 3 mm long, 1 × 1 mm cross-section, attached to a nerve fiber
  • Mote size (reported follow-up): shrunk to a 1 mm cube, per Berkeley’s release
  • Power and data link: ultrasound, both directions, no battery
  • Interrogation: six 540 ns ultrasound pulses every 100 µs in the reported experiment

Tissue Interface

  • Targets: sciatic nerve and muscle in anesthetized rats
  • Penetrating?: not described as penetrating in the sources cited here

Evidence and limits

  • Evidence: rat recordings of nerve and muscle activity read out wirelessly; the signal is a change in echo amplitude, so readout quality depends on mote alignment with the transducer.
  • Not shown in the cited sources: chronic implantation, brain recording, human use.

Engineering Verdict

Strengths: no battery, no lead, no RF antenna; scales conceptually to many motes read by one transducer.

Limitations: depends on ultrasound reaching the mote, so bone and gas block the link; mote and transducer alignment sets signal quality; only acute rat data in the cited work.

What it feeds into: later wireless microimplant work such as Neurograins uses radio-frequency links instead of ultrasound.

References