Issue

Vol. 18 (2026)

Skin-Inspired Ultra-Linear Flexible Iontronic Pressure Sensors for Wearable Musculoskeletal Monitoring

https://doi.org/10.1007/s40820-025-01887-x
Pei Li
Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, People’s Republic of China
Shipan Lang
Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, People’s Republic of China
Lei Xie
Key Laboratory of Optoelectronic Technology & Systems (Education Ministry of China), Chongqing University, Chongqing 400044, People’s Republic of China
Yong Zhang
Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, People’s Republic of China
Xin Gou
Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, People’s Republic of China
Chao Zhang
Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, People’s Republic of China
Chenhui Dong
Department of Orthopedics, the Fourth medical center of Chinese PLA General Hospital, Beijing 100039, People’s Republic of China
Chunbao Li
Department of Orthopedics, the Fourth medical center of Chinese PLA General Hospital, Beijing 100039, People’s Republic of China
Jun Yang
Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, People’s Republic of China

Corresponding Author: Jun Yang

jyang@cigit.ac.cn

Nano-Micro Letters, Vol. 18 (2026), Article Number: 55

Abstract

The growing prevalence of exercise-induced tibial stress fractures demands wearable sensors capable of monitoring dynamic musculoskeletal loads with medical-grade precision. While flexible pressure-sensing insoles show clinical potential, their development has been hindered by the intrinsic trade-off between high sensitivity and full-range linearity (R2 > 0.99 up to 1 MPa) in conventional designs. Inspired by the tactile sensing mechanism of human skin, where dermal stratification enables wide-range pressure adaptation and ion-channel-regulated signaling maintains linear electrical responses, we developed a dual-mechanism flexible iontronic pressure sensor (FIPS). This innovative design synergistically combines two bioinspired components: interdigitated fabric microstructures enabling pressure-proportional contact area expansion (∝ P1/3) and iontronic film facilitating self-adaptive ion concentration modulation (∝ P2/3), which together generate a linear capacitance-pressure response (C ∝ P). The FIPS achieves breakthrough performance: 242 kPa−1 sensitivity with 0.997 linearity across 0–1 MPa, yielding a record linear sensing factor (LSF = 242,000). The design is validated across various substrates and ionic materials, demonstrating its versatility. Finally, the FIPS-driven design enables a smart insole demonstrating 1.8% error in tibial load assessment during gait analysis, outperforming nonlinear counterparts (6.5% error) in early fracture-risk prediction. The biomimetic design framework establishes a universal approach for developing high-performance linear sensors, establishing generalized principles for medical-grade wearable devices.


Highlights:
1 Bioinspired dual-mechanism sensor combining fabric microstructures (∝ P1/3 contact area) and ionic film (∝ P2/3 ion modulation) achieves 242 kPa−1 sensitivity with 0.997 linearity (0–1 MPa), yielding record LSF of 242,000.
2 Medical-grade validation via smart insole demonstrates 1.8% GRF error (vs. 6.5% in nonlinear sensors), enabling precise early fracture-risk prediction and validating medical-grade wearables.

Keywords

Iontronic sensor Skin-inspired design Linear range Linear sensing factor Biomechanical monitoring
Li, Pei, Shipan Lang, Lei Xie, Yong Zhang, Xin Gou, Chao Zhang, Chenhui Dong, Chunbao Li, and Jun Yang. 2025. “Skin-Inspired Ultra-Linear Flexible Iontronic Pressure Sensors for Wearable Musculoskeletal Monitoring”. Nano-Micro Letters 18 (September):55. https://doi.org/10.1007/s40820-025-01887-x.
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