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Realtime insole monitoring
For MEC278, we built a pressure sensing insole for CAM boots that gives real time rehab feedback using thin film sensors and an ESP32 setup.
Background
Standard CAM boots are usually treated as one size fits all, even though injuries like turf toe, Jones fractures, and diabetic ulcers need different loading behavior. That makes rehab hard to evaluate because two patients with the same diagnosis can load the foot very differently. We built this system to pair injury specific insoles with quantitative pressure tracking so clinicians and patients can actually see force distribution during recovery.
Technical architecture
The build uses three thin film pressure sensors on a rigid bottom sole at the heel and two forefoot zones to capture the main load regions. On top of that sits a modular flexible TPU insole with variable infill, using a lower density gyroid pattern around the injury area to offload pressure. An ESP32 reads the sensors and sends data over ESP-NOW to a wearable OLED display and a GUI dashboard. Users can enter body weight and pressure thresholds for alerts. The rigid sole also houses electronics with JST connectors for easier debugging and sensor swaps.
Results & iteration
The injury specific sole used black TPU with gyroid infill at the injury site for localized compliance. In testing, toe box pressure dropped from 13.1% to 5.8% during two leg standing and from 28.8% to 11.5% during one leg standing compared to a rigid control sole. The stiffness zoning made targeted offloading possible without losing overall stability.
Early prototypes compared three TPU materials and multiple infill patterns including hexagons, thin lines, and hollow regions. Black TPU with gyroid gave the best compressive behavior. We originally tried 50 kg load cells, but calibration with point loads was inconsistent, so we switched to thin film pressure sensors. The team evaluated layouts from three to seven sensors to balance integration effort and useful diagnostics.
A custom GUI includes user weight and pressure thresholds based on clinician interviews, since unclear gait force patterns often stall recovery. The final architecture uses modular swappable injury specific inserts, a side mounted electronics box with reset access, and wireless monitoring on both wrist and desktop.