Curvature-Matching Mechanics in Skin-Based Bioelectronics to Minimize Interfacial Stresses

Abstract

A geometrical and mechanical design strategy is proposed for bioelectronics to improve wearability and comfort by reducing the magnitude of interfacial stresses and ensuring that the spatial stress distributions are below the somatosensory threshold for skin sensitivity. Conceptually, bioelectronic devices with soft polymeric encapsulations and internal rigid electronic components result in a mechanically hybrid composite structure, with intrinsically soft mechanics to facilitate integration with biological tissues through mechanical compliance. For accurate signal acquisition and sensing in curvilinear regions (e.g., limbs, chest, forehead), bioelectronic devices are pressed and bent to closely match the skin morphology, resulting in additional interfacial stresses. In the present work, we demonstrate how curvature-matching designs for the bioelectronic–skin interface can reduce the resulting normal and shear stresses generated from device adhesion and skin stretching during dynamic motions. Finite element modeling of the skin curvature, encapsulation, and internal electronic layouts was used to quantify the spatial distribution of the underlying stresses at the skin interface based on a mismatch curvature angle θ between the device and skin. The results show that curvature-matching designs for selected cases of θ = 30 deg and 60 deg can reduce the normal and shear stresses by up to 45% and 70%, respectively, even for a stretch of up to λ = 1.3. The proposed curvature-matching design strategy can inform the future design of user-specific bioelectronics to create anatomically compatible geometrical layouts that enhance mechanical compliance and enable physiological monitoring and integration in curved body structures.