ESP32 Nerve Conduction Tester

ISEF Category: Biomedical Engineering

Subcategory: Biomedical Devices  ·  Difficulty: Advanced  ·  Setup: School Lab  ·  Time: 1 to 2 Months

The Hook

Nerve conduction velocity is the gold standard for diagnosing carpal tunnel syndrome, but clinics charge hundreds of dollars per test. An ESP32 with a safety-isolated current driver and two surface electrodes can deliver a brief stimulus under 5 milliamps and time the response. Comparing your numbers to published normative ranges turns the project into a low-cost screening tool.

What Is It?

Nerve conduction velocity (NCV) measures how fast an electrical signal travels along a peripheral nerve. Lower velocity often indicates compression, as in carpal tunnel syndrome.

A constant-current driver delivers a brief, controlled stimulus under medical safety limits. Two recording electrodes downstream pick up the arrival time of the action potential. The distance between stimulus and recording sites divided by the delay gives velocity.

Published ulnar and median NCV ranges define normal versus possibly impaired. The device is a screening prototype, not a diagnostic instrument, and requires full informed consent and safety review.

Why This Is a Good Topic

Affordable neurodiagnostics matters in low-resource settings and the engineering is well-scoped. You will learn analog isolation, safety design, and biosignal timing.

Research Questions

• How does electrode spacing change measured velocity?
• What is the effect of stimulus amplitude on response latency?
• Does the device fall within published median nerve velocity ranges in healthy adults?
• To what extent does skin temperature shift readings?
• Which electrode preparation gives the cleanest response?
• How does fatigue or repeated stimulation change latency?
• What is the effect of subject body mass on apparent velocity?

Basic Materials

• ESP32 development board.
• Isolation transformer and opto-isolated current driver.
• Constant-current stimulator design (open hardware reference).
• Surface electrodes and conductive gel.
• Calibrated current probe.
• Informed-consent and safety documentation.

Advanced Materials

• Medical-grade isolated stimulator.
• Differential amplifier with active common-mode rejection.
• Clinical mentor and EMG lab.
• Calibrated reference NCV equipment.

Software & Tools

• Arduino IDE or PlatformIO: Programs the ESP32.
• Python (NumPy and SciPy): Analyzes latency traces.
• Open-source ECG/EMG visualizer: Displays signals in real time.
• Matplotlib: Reports velocity distributions vs. normative ranges.

Experiment Steps

1. Document maximum current and pulse width with a written safety review.
2. Calibrate the stimulator output with a current probe.
3. Lock electrode positions using a marker template.
4. Plan a baseline rest period and randomized stimulus order.
5. Capture latency traces and compute velocity.
6. Compare measured velocities to published normative ranges.

Common Pitfalls

• Skipping the safety isolation review.
• Reusing electrodes after they dry out.
• Letting skin temperature drift between trials.
• Treating amplitude as velocity or vice versa.
• Reporting one subject as a study.

What Makes This Competitive

Document safety review and current limits in writing. A competitive entry calibrates the stimulator output with a current probe, runs randomized-order trials within subjects, and reports agreement with published normative ranges across multiple healthy participants.

Project Variations

• Add an EMG channel for compound muscle action potential timing.
• Compare ulnar vs. median in the same subject.
• Add a cold-pressor stress and re-measure velocity.

Learn More

• PubMed: Search median nerve conduction screening review.
• NIH PubMed Central: Open-access peripheral neuropathy papers.
• FDA medical device safety guidance: Public regulatory documents.
• American Association of Neuromuscular and Electrodiagnostic Medicine: Open educational pages.
• MIT OpenCourseWare: Course 6.555 Biomedical Signal and Image Processing.