Closed-Loop TENS Stroke Wrist Rehab

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Closed-Loop TENS Stroke Wrist Rehab

ISEF Category: Biomedical Engineering

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

The Hook

After a stroke, many patients can't lift their wrist. Hours of repeated practice rebuild the nerve pathways. A closed-loop electrical stimulator that pushes wrist extensors only when the muscle is rested could double the dose of effective therapy. You can build a research-grade prototype with a TENS unit, Arduino, and an EMG sensor.

What Is It?

TENS units deliver mild electrical pulses to muscles and nerves. Modifying one with a microcontroller lets you change pulse amplitude in real time based on a feedback signal.

Median-frequency or RMS amplitude of EMG drops as a muscle fatigues. By reading those fatigue indices on the wrist extensors, the system can pause or reduce stimulation when fatigue is detected and resume when the muscle recovers.

The project simulates post-stroke conditions with healthy volunteers doing repeated wrist extensions to fatigue, never delivering high amplitudes and always staying under medical safety limits.

Why This Is a Good Topic

Stroke rehab devices are a growing market and a legitimate engineering area. Hardware is cheap. You will learn biosignal processing, real-time control, and medical-safety engineering.

Research Questions

  • How does fatigue index change with stimulation duration?
  • What is the effect of closed-loop vs. fixed amplitude on time-to-fatigue?
  • Does adaptive stimulation maintain a target wrist angle longer?
  • To what extent does electrode placement shift outcomes?
  • Which fatigue index responds fastest to recovery?
  • How does pulse frequency affect comfort?
  • What is the effect of skin preparation on EMG quality?

Basic Materials

  • TENS unit (over-the-counter, modified safely).
  • Arduino or ESP32.
  • MyoWare EMG sensor.
  • Surface electrodes and gel.
  • Goniometer or IMU on the wrist.
  • Informed-consent form with safety review.

Advanced Materials

  • Medical-grade neuromuscular stimulator.
  • Calibrated current source.
  • Clinical mentor.
  • Multi-channel EMG amplifier.

Software & Tools

  • Arduino IDE or PlatformIO: Programs the controller.
  • Python (NumPy and SciPy): Computes fatigue indices offline.
  • OpenBCI or BrainBay clones: Visualizes biosignals.
  • Matplotlib: Plots wrist-angle traces.

Experiment Steps

  1. Document safety limits (current, pulse width) before any human contact.
  2. Calibrate the stimulator and confirm current with a current probe.
  3. Lock electrode placement using a marker template.
  4. Decide closed-loop vs. fixed-amplitude protocol and randomize order.
  5. Run within-subject trials with rest periods and adverse-event logging.
  6. Compare angle-time-on-target metrics and fatigue trajectories.

Common Pitfalls

  • Skipping a safety review and current measurement.
  • Reusing electrodes after they dry out.
  • Defaulting to high amplitude because the subject 'tolerates it'.
  • Treating one subject as a study.
  • Confusing motion artifact with EMG fatigue.

What Makes This Competitive

Safety review and current limits in writing are mandatory. A competitive entry then runs a small within-subject crossover comparing closed-loop vs. fixed-amplitude stimulation, reports improvements in time-to-target wrist angle, and benchmarks against published wrist-rehab outcomes.

Project Variations

  • Switch to elbow flexors and study supination control.
  • Add a vision-based hand-tracking target instead of wrist angle.
  • Replace EMG with mechanomyography.

Learn More

  • PubMed: Search closed-loop FES stroke rehab reviews.
  • NIH PubMed Central: Open-access neurorehabilitation papers.
  • FDA TENS guidance documents: Public safety standards.
  • MyoWare documentation: Free wiring guides.
  • MIT OpenCourseWare: Course 6.555 Biomedical Signal and Image Processing.
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