Clinically approved neural stimulators are limited by battery requirements, as well as by their large size compared with the stimulation targets. Here, we describe a wireless, leadless and battery-free implantable neural stimulator that is 1.7 mm3 and that incorporates a piezoceramic transducer, an energy-storage capacitor and an integrated circuit. An ultrasonic link and a hand-held external transceiver provide the stimulator with power and bidirectional communication. The stimulation protocols were wirelessly encoded on the fly, reducing power consumption and on-chip memory, and enabling protocol complexity with a high temporal resolution and low-latency feedback. Uplink data indicating whether stimulation occurs are encoded by the stimulator through backscatter modulation and are demodulated at the external transceiver. When embedded in ex vivo porcine tissue, the integrated circuit efficiently harvested ultrasonic power, decoded downlink data for the stimulation parameters and generated current-controlled stimulation pulses. When cuff-mounted and acutely implanted onto the sciatic nerve of anaesthetized rats, the device conferred repeatable stimulation across a range of physiological responses. The miniaturized neural stimulator may facilitate closed-loop neurostimulation for therapeutic interventions.
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The computer code used for analysing data is provided at https://github.com/maharbizgroup/StimDust.
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This work was supported in part by the National Institutes of Health NIH grant no. R21EY027570; the Defense Advanced Research Projects Agency (DARPA) BTO grant/contract no. HR011-15-2-0006; the National Science Foundation NSF EAGER grant no. 1551239; the McKnight Foundation Technological Innovations in Neuroscience Award (to M.M.M. and J.M.C.); the Chan Zuckerberg Biohub (to R.M. and M.M.M.); and a NIH Training grant T32 GM008155 (to D.K.P.).
M.M.M., J.M.C., R.M.N. and J.E.K. are members of iota Biosciences, Inc. All of the other authors declare no competing interests.
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Piech, D.K., Johnson, B.C., Shen, K. et al. A wireless millimetre-scale implantable neural stimulator with ultrasonically powered bidirectional communication. Nat Biomed Eng 4, 207–222 (2020). https://doi.org/10.1038/s41551-020-0518-9