← Back to Design & Engineering
Realtime insole monitoring
Pressure sensing insole for CAM walking boots (MEC278): thin film sensors, ESP32 telemetry, and injury specific TPU geometry for rehab feedback.
Background
Standard CAM walking boots mostly use one size fits all thinking for diverse injuries (turf toe, Jones fractures, diabetic ulcers, and more). That creates ambiguity in treatment effectiveness: different patients load the foot differently even when the diagnosis matches. Our system pairs injury specific insoles with quantitative pressure tracking so clinicians and patients get real-time feedback on force distribution during rehabilitation.
Technical architecture
The build integrates three thin film pressure sensors on a rigid bottom sole, placed at the heel and two forefoot locations to capture primary load-bearing zones. A modular flexible TPU insole with variable infill sits on top, using a low-density gyroid pattern over the injured region to offload pressure. An ESP32 reads sensor data and sends it over ESP-NOW to both a wearable OLED “smartwatch” that shows live pressure percentages and a GUI dashboard where the user enters weight and allowable pressure thresholds for alerts. The rigid sole houses the electronics with JST connectors for fast debugging and sensor swaps.
Results & iteration
The injury specific sole uses black TPU with gyroid infill at the injury site for localized compliance. In testing, that reduced toe-box pressure from 13.1% to 5.8% during two-leg standing and from 28.8% to 11.5% during one-leg standing versus a rigid control sole. Discrete stiffness regions enable targeted offloading without sacrificing overall thickness or stability, aiming to reduce reliance on crutches while keeping rehab effective.
Early prototypes compared three TPU materials and several infill patterns (hexagons, thin lines, hollow regions); black TPU with gyroid patterns gave the best compressive behavior. Initial 50 kg load cells were replaced with thin film pressure sensors after calibration struggles with point loads. The team evaluated three to seven sensor layouts, balancing integration effort with diagnostic value.
A custom GUI incorporates user weight and pressure thresholds informed by clinician interviews, many recoveries stall when force patterns during gait stay unclear. The final architecture uses modular, swappable injury specific sole inserts, a side-mounted electronics box with reset, and wireless monitoring on both wrist and desktop.