Heal Sole: A Smart Insole Platform for Physiological Monitoring and Active Ankle Rehabilitation

Abstract

Wearable health monitoring systems have gained significant attention due to their potential for continuous, noninvasive physiological data collection. Smart insoles offer a unique platform for capturing lower-body biomechanical and physiological signals without interfering with daily activities. This paper presents Heal Sole, a prototype smart insole system integrating heart rate, temperature, and blood oxygen saturation $\left(\mathbf{S p O}_{\mathbf{2}}\right)$ sensors with motor-assisted ankle rehabilitation and a web-based monitoring interface. The system employs an ESP32 microcontroller with low-cost commercial sensors (MAX30105, MLX90614), communicating via MQTT over TLS to a FastAPI backend with PostgreSQL storage and real-time WebSocket visualization. A dual-motor mechanism enables controlled dorsiflexion and plantarflexion exercises with automatic direction reversal at range-of-motion limits. Validation with five participants across 15 rehabilitation sessions generated 6,880 sensor readings transmitted without data loss, demonstrating reliable end-to-end system architecture. Sessions with valid sensor contact showed expected physiological responses, including a mean heart rate increase of 4.7 bpm following exercise.