A Wireless Network of MicroimplantsFor Neural Recording and Microstimulation

Jihun Lee1, Ah-Hyoung Lee1, Vincent Leung2, Jiannan Huang3, Peter Asbeck3, Patrick P. Mercier3, Stephen Shellhammer4, Lawrence Larson1, Farah Laiwalla1, and Arto Nurmikko1

1Brown University, 2Baylor University, 3University of California San Diego, 4Qualcomm

IntroductionIntroduction

In-vivo Networking ExperimentsIn-vivo Networking Experiments

Block diagram for Neurograin NetworkBlock diagram for Neurograin Network

Future Work and ReferenceFuture Work and Reference

▪ We present a wireless multichannel system composed of wirelessly networked

submillimeter size electronic microchips (“Neurograins”) [1].

▪ An electromagnetic link at ~1 GHz enables bidirectional communication and

control of individual neurograin performing either a neural recording or

stimulating.

▪ The wireless network operates on a customized time division multiple access

(TDMA) protocol designed to scale up to 1000 neurograins [2].

BPSK: Binary Phase Shift Keying, ASK-PWM: Amplitude-shift Keying and Pulse Width Modulation

In-vivo Neurograin RecordingIn-vivo Neurograin Recording

▪ Post-processing was done to make with gold epicortical electrodes on

recording or attach intracortical tungsten electrodes for stimulation. [3]

▪ Multi-node recording Neurograin collected 40 Hz sinusoidal signals in saline

simultaneously.

▪ Array of stimulation Neurograin generated pattern stimulation in saline in a

response to downlink commands assigning one chip at a time to stimulate.

References

[1] Lee, Jihun, et al. "Wireless Ensembles of Sub-mm Microimplants Communicating as a Network near 1 GHz in a

Neural Application." bioRxiv (2020).

[2] Lee, Ah-Hyoung, et al. "A scalable and low stress post-CMOS processing technique for implantable microsensors."

Micromachines 11.10 (2020): 925.

[3] Leung, Vincent W., et al. "Distributed Microscale Brain Implants with Wireless Power Transfer and Mbps Bi-

directional Networked Communications." 2019 IEEE Custom Integrated Circuits Conference (CICC). IEEE, 2019.

* Research supported by a gift to Brown University

▪ Our goal is to develop intracortical Neurograin by

porting 65 nm-based Neurograin into 22 nm node.

▪ The next-generation Neurograin will perform stimulation

and recording under bidirectional communication.

Characterization of System-on-chipCharacterization of System-on-chip

Workshop on

Advanced

NeuroTechnologies

Intracortical Neurograin

Neurograins on U.S dime

(each chip 650 μm × 650 μm × 250 μm)Wireless communication

(10 Mbps Uplink, 1 Mbps Downlink)

▪ External wireless hub with software-defined radio transmits RF energy/downlink

command and received backscattered data

▪ Each neurograins preforms 1) RF energy harvesting, 2) wireless data

communication and 3) ECoG neural recording or biphasic current stimulation

▪ Neurograin system is demonstrated as a cortical implant in a small animal (rat)

model with anatomical limitations restricting the implant to 48 neurograins.

▪ 3 coil system establishes efficient wireless link with Neurograin ensemble.

▪ Under Ketamine, an ensemble of 48 recording neurograins captured

1) spontaneous low frequency oscillation.

2) post-stimulus evoked field responses dependent on anesthesia.

In-vivo Neurograin StimulationIn-vivo Neurograin Stimulation

▪ With ensemble of stimulating neurograins,

1) 100 Hz stimulation evoked pulse-width dependent local field responses.

2) 400 Hz current injection triggered neural burst activities.

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