Seminars

Tactile electronic skin (e-skin) that replicates both the mechanical compliance and sensory functions of natural skin is essential for next-generation physical hu-man–robot interaction (pHRI). Capacitive pressure sensors (CPS) are a core sensing modality in e-skin systems due to their low power consumption, compatibility with soft materials, and ability to detect static and dynamic pressures. Despite extensive development, most CPS designs suffer from a fundamental sensitivity–pressure trade-off, where sensitivity decreases with increasing pressure. In addition, CPS responses are often coupled with in-plane deformation modes such as stretch and shear, complicating signal interpretation in soft and wearable applications.
To overcome these limitations, hybrid response pressure sensors (HRPS) and stretch-insensitive hybrid response pressure sensors (SHRPS) were previously developed by integrating electrically conductive porous nanocomposites (PNCs) with ultrathin dielectric layers. These sensors exhibit coupled piezoresistive and piezo capacitive responses, enabling enhanced sensitivity over a wide pressure range and effective decoupling of pressure from stretch and shear. However, the electromechanical mechanisms underlying these advantages remained unclear, and a unified framework to guide sensor design and operation has been lacking.
This dissertation develops a unified electromechanical framework to explain and predict CPS sensitivity across material systems, sensor architectures, and loading conditions. The sensitivity–pressure trade-off is shown to be governed by key parameters across three interconnected stages: (i) fabrication-stage material and structural parameters, including Young’s modulus, dielectric loss, and dielectric layer thickness;(ii) post-fabrication tuning via excitation frequency; and (iii) deformation mechanisms that decouple out-of-plane compression from in-plane stretch and shear.
First, the frequency-dependent behavior of HRPS is systematically studied, demonstrating that excitation frequency acts as an effective post-fabrication tuning parameter through two governing dimensionless quantities. Second, the deformation mechanisms responsible for the stretch-insensitive behavior of SHRPS are elucidated, showing that the electrical response is dominated by pressure-induced out-of-plane deformation. Third, a generalized double-branch equivalent circuit model is developed to unify CPS with engineered dielectrics, HRPS, and CPS with engineered electrodes, yielding a closed-form sensitivity expression that links electromechanical response to material properties, structural parameters, and interfacial conditions.