Embedded firmware · Low Power Electronics · Implantable · Wearable ·Biomedical Devices.
I engineer wireless biomedical systems - from custom hardware to embedded firmware and real-world validation.
PhD candidate in Electrical and Computer Engineering at NC State, in the Vazquez-Guardado Lab (ASSIST Center). My work spans battery-free NFC implants for optogenetics, Bluetooth potentiostats for electrochemical sensing, and wearable ECG/EMG front-ends.
Patterned wireless transcranial optogenetics ↗ · Nature Neuroscience, 2025
News
- 2026Presenting the Brain Sync platform as a poster at BMES 2026.
- Dec 2025Wireless transcranial optogenetics paper out in Nature Neuroscience, featured by Northwestern News.
- 2025Received the Burroughs Wellcome Fund GDEP Award.
- 2025Gut–brain optogenetics paper published in AJP-GI.
- 2024Enteric nervous system optogenetics paper published in Biosensors & Bioelectronics.
In the press
Northwestern News · Dec 2025
NC State ECE · 2025
Selected work
Sense, decide and act on a living system — without wires, and often without batteries.
Wireless, battery-free optogenetic devices
NFC-powered implants and patches that deliver light to the brain and gut of freely moving animals, built with Northwestern University. This device family is behind three of my co-authored papers.
Patterned transcranial optogenetics
Programmable μ-LED brain patch
A soft, wireless, battery-free patch whose μ-LED array delivers patterned light through the skull — work with Northwestern University published in Nature Neuroscience (2025). In the demo, the array plays Tetris to show pixel-level control.
My part: the custom NFC control electronics and ATtiny84 firmware that drive the array at variable intensities.
Closed-loop interbrain synchrony
Battery-free NFC optogenetics, phase-locked across two brains
A wireless implant platform that synchronizes light stimulation across two freely moving mice, switched in closed loop by real-time pose tracking. Built with Northwestern University.
- 47 of 57 devices phase-locked within 2.5 mHz at ≤0.1% jitter
- SLEAP + Bonsai pose stream → Python controller → tonic / burst modes
- MATLAB tuning GUI that calibrated all 57 implants
Electrochemical sensing
Low-power wireless electronics for reading chemistry in real time.
Electrochemical sensing
Wireless multi-technique potentiostat
A custom nRF52840 Bluetooth potentiostat designed to run the four common electrochemical techniques: cyclic voltammetry, square-wave voltammetry, differential pulse voltammetry and (fast) chronoamperometry. Three are implemented and validated so far.
- Zephyr RTOS firmware; excitation waveforms from a 16-bit DAC8831
- SWV, DPV and fast chronoamperometry validated on ferricyanide (3–15 mM)
- Benchmarked against a commercial potentiostat
SWV, DPV and FCA on the board: applied cell potential (top) and ferricyanide response (bottom).
Wearable biopotential sensing
Analog front-ends and Bluetooth electronics for ECG and EMG on the body.
Recorded with the hydrogel electrodes: EMG bursts from repeated fist clenches (top) and ECG (bottom).
Low Power ECG/EMG Modules with On-Board Electrodes
ExG modules built for Dr. Ni’s lab from Duke University: an INA333 amplifier at 1000× gain, driven-right-leg noise reduction, custom hydrogel–copper electrodes and nRF54 BLE. In the clip, a fist clench shows up as a live EMG trace.
Wearable biopotentials
Earlier projects
Earlier work, from my undergraduate senior design.
Senior design, 2022 · Provisional patent draft
SmartSwaddle infant vital-sign monitor
A sensor pod in a fabric swaddle that streams heart rate, SpO₂, temperature, breathing, lung sounds and sleep position over Bluetooth, with alarms on a MATLAB monitor. Built by a five-person team for SIDS prevention.
Capabilities
Firmware & embedded
C, Zephyr RTOS, BLE, NFC, SPI/I²C, DMA and ISR design on nRF52840 / nRF54, MSP430, CC2640, ATtiny84, NXP KL25Z
Electronics & optics
Biopotential AFEs, potentiostats, DAC/ADC interfacing, filter design, μ-ILED and photodiode optoelectronics, PCB design, SPICE
Signals & data
MATLAB, Python, ECG/EMG, PPG/SpO₂, SWV/DPV analysis, calibration statistics, real-time pose tracking (SLEAP, Bonsai)
Mechanical & tools
SolidWorks, Fusion 360 enclosures for wearables and implants, Code Composer Studio, MDK-ARM
Publications
- Nature Neuroscience · 2025Patterned wireless transcranial optogenetics generates artificial perception ↗Wu, M., …, Riahi, M., et al.
- AJP-GI · 2025Optogenetic activation of the gut–brain axis using a fully implantable wireless battery-free device ↗Hibberd, T. J., …, Riahi, M., et al.
- Biosensors & Bioelectronics · 2024Remote optogenetic control of the enteric nervous system via a wireless, battery-free device ↗Efimov, A. I., …, Riahi, M., et al.
Awards
- Burroughs Wellcome Fund GDEP Award2025–27
- Provost’s Doctoral Fellowship2022–23
- NCSU Undergraduate Research Award2022
- B.Sc. Biomedical Engineering, Summa Cum Laude2022
- Silver Medal, 31st National Mathematics Olympiad2014
Contact
Vazquez-Guardado Lab, ASSIST Center, NC State University. For collaborations or questions about the work.
© 2026 Mohammad Riahi
Raleigh, NC