Seyed Morteza Seyedpour, Raghav Pathak, Mohammad Azhdari, Tim Ricken, Ghader Rezazadeh
Soft robotic systems demand tactile interfaces that combine mechanical compliance, high bandwidth, and drift-free operation, capabilities that remain elusive in conventional sensing skins. Bioinspired micropillar architectures offer a promising solution, yet their rational design is hindered by the absence of a predictive theoretical framework that captures the strong coupling between finite-strain hyperelasticity, piezoelectricity, and electrostriction. To address this gap, we present a fully coupled, nonlinear continuum model for soft piezoelectric micropillar composites, formulated within a rigorous thermodynamic framework using the Gent hyperelastic law, Piola–Kirchhoff stress measures, and consistent electromechanical coupling. The uniaxial model, justified by lateral constraint from the soft embedding matrix, reveals that DC electrical bias and mechanical static bias force jointly modulate effective stiffness and natural frequency, a tunability that emerges only through geometric and material nonlinearity. Dynamic simulations under representative tactile stimuli demonstrate amplitude-dependent resonance bending, hysteresis, and broadband response. Crucially, the composite’s acoustic impedance closely matches biological tissues, enabling hybrid tactile–ultrasonic sensing. By clarifying the fundamental role of nonlinearity in frequency-tunable perception, this work provides a foundation for next-generation tactile skins that adapt their sensitivity in real time for soft robotics, haptics, and biomedical interfaces. • Bio-inspired micropillar composites are suitable for tactile sensing and haptics. • A coupled Gent hyperelastic with piezoelectric constitutive law is presented. • DC bias and mechanical static bias force jointly tune stiffness and natural frequency. • Predicts broadband responses and tissue-like acoustic impedance. • Reduced Duffing model captures resonance bending, hysteresis, and bifurcations.