Linearity is the core measurement capability of flexible sensing technology. Insufficient linearity not only increases the complexity of system calibration and data decoupling but also directly impacts the physical comparability of signals and measurement traceability.
The Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, proposed a novel mechanism for skin-inspired dual-mode ionic-electric sensing based on multi-scale structural regulation strategies, developing a controllable fabrication method system for high-linearity, wide-range ionic-electric flexible pressure sensors. Inspired by the layered fibrous network and ionic signal regulation mechanisms of human skin, the team introduced a dual-mechanism synergistic model of "fabric microstructure contact area evolution (∝P1/3) + ion concentration adaptive modulation (∝P2/3)." By coupling two distinct nonlinear effects—geometric contact and electrochemical modulation—the mechanism achieves an overall output relationship approaching ideal linearity (C∝P), fundamentally breaking through the limitations of traditional "structurally nonlinear responses." Based on this mechanism, the team fabricated a new type of ionic-electric flexible pressure sensor, achieving a linearity R2=0.997 and sensitivity of 242 kPa-1 across a broad operating range of 0–1 MPa, with a linear sensitivity factor (LSF) as high as 242,000. The sensor was integrated into an intelligent shoe sole platform, establishing a real-time mapping model of gait-tibia load. During walking and running tests, it achieved load assessment errors of only 1.8%, significantly outperforming traditional nonlinear sensing solutions.
Inspired by the gradient modulus structure of human skin—"epidermal rigidity—dermal viscoelasticity—subcutaneous compliance"—the team constructed a heterogeneous composite structure based on electrospinning, embedding a high-modulus nanofiber network into a low-modulus ionogel matrix. This architecture enables stepwise control of loads through multiple layers, achieving synergistic stress dispersion and confined ion migration regulation. The device demonstrates near-perfect linear high sensitivity across a broad pressure range of 1 MPa, with a linear sensitivity factor reaching 81,300, placing it at the forefront among ionic flexible sensors.
The team also proposed a novel approach for gradient modulus low-drift ionic flexible sensors: by introducing a glass fiber-reinforced layer and hierarchical crosslinking structure into the ionic gel system, a continuous modulus gradient distribution from top to bottom ("soft—medium—hard") is achieved, effectively relieving stress concentration at the sensing interface. This structure maintains stable electromechanical response relationships even under high-pressure loading, enabling the flexible sensor to demonstrate excellent signal consistency and environmental stability in multi-cycle testing.