Electrospun Hollow Nanofiber Surfaces as Dielectric Mediums for Highly Sensitive Flexible Capacitive Pressure Sensors in Low-Pressure Regimes

Flexible capacitive pressure sensors have gained significant attention in flexible electronics, offering extensive material and design options for various active sensing needs. Despite significant advances, achieving high sensitivity at very low pressures (<5 kPa) remains a challenge. Tailoring the dielectric layer is one of the most effective strategies to address this issue, with recent work showing that incorporating nanostructures can substantially improve sensor performance. Here, we employ coaxially electrospun hollow nanofibers characterized by a high surface-to-volume ratio, enhanced air gaps, and densely packed microstructure-nanostructure to fabricate a highly sensitive capacitive pressure sensor. Systematic characterization across varying pressure ranges revealed that the sensor achieved superior sensitivity in the low-pressure range (0.2–2 kPa), outperforming sensors fabricated using traditional electrospun nanofiber dielectric layers. In particular, the sensor exhibited a maximum sensitivity of 1.05 kPa⁻¹ at a pressure of 1 kPa. This performance gain is attributed to the hollow air core of the fibers, which improves dielectric properties by increasing surface area, roughness, deformability, and charge formation. However, the sensor’s sensitivity reduces at higher pressures, ultimately falling below that of conventional single-shell fiber-based sensors due to the reduced influence of the air gaps within the hollow fibers. These findings highlight the potential of hollow fiber architectures for low-pressure-sensing applications while also highlighting opportunities for further optimization.