# Chip-scale fT/cm/Hz^(1/2) optical magnetic gradiometry for gradient magnetoencephalography imaging at room temperature

> **NIH NIH R21** · UNIVERSITY OF CALIFORNIA LOS ANGELES · 2020 · $165,496

## Abstract

Chip-scale fT/cm/Hz1/2 optical magnetic gradiometry for gradient magnetoencephalography imaging at
room temperature
 Magnetoencephalography (MEG) provides a direct and non-invasive modality to brain electrophysiological
activity, with fundamental measurement principles and signal dynamics highly distinct yet complementary to
electroencephalography. Current leading instrumentations such as a superconducting interference device
enables remarkable few fT sensitivities, significant for imaging of postsynaptic potentials and about 10(7) smaller
than Earth’s static magnetic field. Operating the superconducting sensor, however, requires liquid helium
cryogenics, large-sized insulating dewar tanks, and heavily-field-shielded expensive environments, resulting in
specialized imaging centers in the country and hardly portable for frontline diagnostics or wide-spread hospital
usage. Objective: here we propose to demonstrate a chip-scale room-temperature magnetic gradiometer with
similar sensitivities in unshielded ambient environments, enabled by our gradient approach and our recent
laser measurements at the thermodynamical limits. Our gradiometer is based on a laser-driven silicon
optomechanical resonant oscillator, combined with static Lorentz-force magnetic field sensing, for optical
readout at 1 fT/cm/Hz1/2 sensitivities and 5 fT/cm accuracies at room temperature.
 Our precise and accurate sensor intrinsically measures the magnetic gradient and has similar performance
metrics of the magnetic field energy resolution per unit bandwidth, compared to state-of-the-art
superconducting interference devices and optically-pumped spin-exchange-relaxation-free atomic
magnetometers. In this R21 exploratory grant, we will demonstrate the “first light” measurements on the
gradiometer, with the three Specific Aims: (1) demonstrating a dual-loop fT/cm/Hz1/2 magnetic gradiometer on-
chip and at room temperature; (2) demonstrating gradiometer co-localization with a total field magnetometer,
along with RF signal processing; and (3) validation of gradiometer in simulated sources and MEG testbeds.

## Key facts

- **NIH application ID:** 9965922
- **Project number:** 5R21EB026778-03
- **Recipient organization:** UNIVERSITY OF CALIFORNIA LOS ANGELES
- **Principal Investigator:** Chee Wei Wong
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $165,496
- **Award type:** 5
- **Project period:** 2018-09-05 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9965922

## Citation

> US National Institutes of Health, RePORTER application 9965922, Chip-scale fT/cm/Hz^(1/2) optical magnetic gradiometry for gradient magnetoencephalography imaging at room temperature (5R21EB026778-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9965922. Licensed CC0.

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