High-Throughput Electrospinning System| Skin-Inspired,Permeable,Structure-Gradient Fiber Mats for Pressure Sensing inRehabilitation Assistance

Hong Kong Polytechnic University Assistant Professor Qi-Yao Huang: Wearable, Breathable Pressure-Sensing Fabric – Bioinspired Gradient Structure via Electrospinning Enables High Sensitivity and Wide-Range Pressure Sensing

Rehabilitation training is crucial for patients to restore function, alleviate pain, and improve health. However, traditional devices rely on professionals, incurring high costs and inconvenience. Flexible, self-powered textile-based pressure sensors offer lightweight, soft, and breathable solutions, significantly enhancing wearing comfort. Nevertheless, existing triboelectric pressure-sensing fabrics still face challenges such as limited sensing range and insufficient sensitivity under high pressure, restricting their application in rehabilitation monitoring. Therefore, developing triboelectric pressure-sensing fabrics with both high sensitivity and a broad sensing range is a current research priority.

To address this, Assistant Professor Qi-Yao Huang’s team at Hong Kong Polytechnic University proposed a breathable, gradient-structured fiber mat (Structure-Gradient Fiber Mat, SGFM) inspired by human skin for triboelectric pressure-sensing fabrics. Fabricated using template-assisted layer-by-layer electrospinning, the SGFM successfully mimics the mechanical gradient properties of skin. This unique design enables the SGFM-based triboelectric pressure-sensing fabric to exhibit exceptional performance, achieving high sensitivities of 0.068 kPa⁻¹ (0–53 kPa) and 0.013 kPa⁻¹ (53–660 kPa). Furthermore, integrating this material into a wearable rehabilitation monitoring system allows real-time tracking of pulse signals, quadriceps activity, and plantar pressure, providing reliable support for posture correction. This innovation demonstrates significant potential in improving rehabilitation efficiency and offers a new solution for smart rehabilitation devices. The study, titled "Skin-inspired, Permeable, Structure-gradient Fiber Mats for Pressure Sensing in Rehabilitation Assistance," was published in Advanced Fiber Materials.

The gradient structure of SGFM was achieved via template-assisted layer-by-layer electrospinning by adjusting the material ratios in the spinning solution. During electrospinning, a metal mesh collector served as a template, forming skin-like raised structures on the SGFM surface (Fig. 1a–b). The fiber mat’s structure gradually transitions from dense at the top to loose at the bottom (Fig. 1c(I–IV)). Due to its porous structure, SGFM exhibits excellent breathability (74 mm/s) and moisture permeability (528 g/m²/day), comparable to cotton fabric and far superior to silicone rubber (Fig. 1d), highlighting its wearing comfort.

Figure 1: Morphology and breathability characterization.

The gradual variation in carbon nanotube (CNT) concentration during layer-by-layer electrospinning induces progressive structural changes in the fiber mat. This material and structural design endows SGFM with gradients in material composition, dielectric properties, and mechanical behavior along its thickness, enhancing sensitivity and pressure-sensing range. X-ray diffraction (XRD) confirmed the gradient variation in material composition (Fig. 2a–b). SGFM maintains a high dielectric constant while exhibiting low dielectric loss (0.0235 at 1 kHz), with a relative permittivity ~2.6× higher (3.07) than homogeneous SEBS fiber mats (HFM) prepared without a metal mesh collector (Fig. 2c).

Critically, CNT content adjustment alters fiber diameter and porosity, giving SEBS-BTO-CNT fiber mats varying Young’s moduli and distinct compression behaviors under pressure. Compared to HFM, SGFM shows higher compressive stress (980 kPa) at high strain (94%) (Fig. 2d). Cyclic compression tests confirmed SGFM’s stability across strains (Fig. 2e), with minimal hysteresis and full stress recovery after 1,000 cycles (Fig. 2f).

Figure 2: Dielectric and mechanical properties.

As pressure increases from 5 kPa to 660 kPa, the SGFM-based triboelectric fabric’s open-circuit voltage rises from 1.1 V to 11.1 V (Fig. 3a), demonstrating strong responsiveness across a wide range. Owing to its high permittivity, low loss, and gradient structure, the SGFM-based sensor outperforms HFM and HFM-BTO in sensitivity (Fig. 3b–c). It also exhibits fast response/recovery times (25 ms/15 ms, Fig. 3d), frequency insensitivity (1–4 Hz, Fig. 3e), and stable output over 30,000 cycles (Fig. 3f).

The fabric retains high washability and abrasion resistance. After 20 washes, it remains intact with only slight sensitivity loss (Fig. 3g, 3i). Even after 10,000 abrasion cycles, though the encapsulation layer wears, SGFM and conductive fabric stay intact, preserving performance (Fig. 3h, 3j).

Figure 3: Pressure-sensing performance.

As a proof of concept, the SGFM-based fabric was applied to monitor Bulgarian split squats—a key post-ACL-surgery exercise. The system integrates pulse monitoring (wrist), quadriceps tracking (thigh), and plantar pressure sensing (9-sensor insole) (Fig. 4). Machine learning achieves 100% accuracy in error detection, aiding posture correction.

Figure 4: SGFM-based triboelectric fabric for rehabilitation monitoring.

Paper link: https://link.springer.com/article/10.1007/s42765-025-00531-y