Skin-inspired ultra-linear flexible iontronic pressure sensors for wearable musculoskeletal monitoring

As wearable health monitoring advances, the demand for flexible pressure sensors that combine high sensitivity, full-range linearity, and medical-grade accuracy continues to grow. Now, researchers from the Chongqing Institute of Green and Intelligent Technology, led by Prof. Chao Zhang and Prof. Jun Yang, have developed a bioinspired dual-mechanism iontronic pressure sensor (FIPS) that mimics human skin structure—achieving record-breaking linearity and sensitivity for real-time musculoskeletal load monitoring.

Why This Sensor Matters

• Ultra-Linear Response: Maintains R² > 0.997 across 0–1 MPa, overcoming the typical trade-off between sensitivity and linearity in flexible sensors.
• Medical-Grade Accuracy: Achieves 1.8% error in ground reaction force (GRF) estimation—far superior to nonlinear sensors (6.5% error).
• Scalable & Stable: Demonstrates excellent reproducibility, long-term stability, and scalability for smart insole integration.

Innovative Design and Features

• Dual-Mechanism Sensing: Combines contact area expansion (∝P¹ᐟ³) and ion concentration modulation (∝P²ᐟ³) to produce a linear capacitance-pressure response (C ∝ P).
• Skin-Inspired Structure: Uses woven iontronic fabric embedded in a polyurethane matrix, mimicking the dermal collagen-elastic fiber network for wide-range mechanical adaptability.
• High LSF: Achieves a linear sensing factor (LSF) of 242,000—the highest reported to date for flexible pressure sensors.

Applications and Performance

• Smart Insole Integration: Enables real-time tibial load monitoring during walking and running on various terrains (concrete, track, lawn).
• Gait Analysis: Accurately classifies walking speeds with ~100% accuracy and predicts tibial stress with high precision.
• Durability: Withstands >10,000 loading cycles and maintains stable performance under bending, humidity, and temperature variation.

Conclusion and Outlook

This work introduces a universal design paradigm for high-performance linear flexible sensors, bridging the gap between biological inspiration and engineering precision. The FIPS platform opens new avenues for wearable biomechanics, sports medicine, and rehabilitation robotics, offering a transformative tool for early fracture-risk prediction and personalized musculoskeletal health monitoring.

Stay tuned for more innovations from Prof. Chao Zhang and Prof. Jun Yang’s team at the Chongqing Institute of Green and Intelligent Technology!