# Sub-millimeter precision wireless neuromodulation using a microwave split ring resonator

> **NIH NIH R21** · BOSTON UNIVERSITY (CHARLES RIVER CAMPUS) · 2022 · $247,500

## Abstract

Project Summary
 Minimally invasive neural modulation at sub-millimeter spatial resolution remains a critical yet unmet
biomedical need. Researchers have explored a broad spectrum of electromagnetic wave and developed
wireless neuromodulation methods. Due to its long wavelength, transcranial magnetic stimulation does not
provide sufficient spatial resolution to target a functional unit such as a single ocular dominance column in the
visual cortex or a diseased peripheral nerve. On the other hand, photons, with their short wavelength, offer
micrometer-scale spatial precision but can barely penetrate couple hundred micrometers into the tissue, not to
mention the human skull. Microwave (MW), with frequencies between 300 MHz and 300 GHz, fills the gap
between optical wave and magnetic wave, yet, has rarely been explored for neuromodulation. We propose a
minimally invasive neuromodulation device by taking advantage of a microwave split ring resonator (SRR)
design. The SRR has a perimeter of approximately one half of MW wavelength, thus acting as a resonant
antenna. It couples the microwave wirelessly and concentrates the microwave at the gap, producing a
localized electrical field of ~100 μm in space. Our scientific premise is based on the nonthermal neural
inhibitory effect of microwave and the resonance effect of the SRR. The SRR produces concentrated
microwave and allows for neuromodulation beyond the microwave diffraction limit, reaching ~100 μm spatial
precision. In the proposed work, we will design and fabricate an implantable SRR with titanium for its superior
biocompatibility. We will then validate the SRR’s potential in neural inhibition using primary neurons in vitro and
a mouse epilepsy model in vivo. By accomplishing the proposed studies, we will have developed a
biocompatible and implantable neuromodulation device. The centimeter-scale penetration depth provided by
microwave and the sub-millimeter spatial precision provided by SRR promises broad biomedical applications.
For central nervous system, our technology allows minimally invasive transcranial modulation of neural
activities inside brain and for clinical treatment of epilepsy. A multi-disciplinary team with complementary
expertise is assembled to implement the proposed activities.

## Key facts

- **NIH application ID:** 10516429
- **Project number:** 1R21EY034275-01
- **Recipient organization:** BOSTON UNIVERSITY (CHARLES RIVER CAMPUS)
- **Principal Investigator:** Ji-Xin Cheng
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $247,500
- **Award type:** 1
- **Project period:** 2022-08-01 → 2025-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10516429

## Citation

> US National Institutes of Health, RePORTER application 10516429, Sub-millimeter precision wireless neuromodulation using a microwave split ring resonator (1R21EY034275-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10516429. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*