Hierarchically Structured Carbon Nanofiber-Enabled Skin-Like Strain Sensors with Full-Range Human Motion Monitoring and Autonomous Self-Healing Capability

Abstract

Flexible strain sensors that mimic the properties of human skin have recently attracted tremendous attention. However, integrating multiple functions of skin into one strain sensor, e.g., stretchability, full-range motion response, and self-healing capability, is still an enormous challenge. Herein, a skin-like strain sensor was presented by the construction of hierarchically structured carbon nanofibers (CNFs), followed by encapsulation of elastic self-healing polyurethane (PU). The hierarchical sensing structure was composed of diversified CNFs with orientations from highly aligned to randomly oriented, and their different fracture mechanisms enabled the resultant strain sensor to successfully integrate key sensing properties including high sensitivity (gauge factor of 90), wide sensing range (∼80% strain), and fast response (52 ms). These properties, combined with high stretchability (870%) and excellent stability (>2000 cycles), allowed the sensor to precisely detect full-range human motions from large joint motions to subtle physiological signals. Moreover, the strain sensor had spontaneous self-healing capability at room temperature with high healing efficiencies of 97.7%, while the healing process could substantially be accelerated by the natural sunlight (24 h → 0.5 h). The healed sensor possessed comparable stretchability, sensing performance, and accurate monitoring ability of subtle body signals with the original sensor. The biomimetic self-healing functionality along with skin-like sensing properties makes it attractive for next-generation wearable electronics.

Multi-Layer Polyurethane-Fiber-Prepared Entangled Strain Sensor with Tunable Sensitivity and Working Range for Human Motion Detection

“…Furthermore, this type of tensile strain sensor based on knot structures no longer requires long-distance attachment and can even be achieved by conducting treatment at the knot structure. This is expected to innovate the structure and mechanism of tensile strain sensors [ 39 , 40 ].…”

Highly Stretchable, Highly Sensitive, and Antibacterial Electrospun Nanofiber Strain Sensors with Low Detection Limit and Stable CNT/MXene/CNT Sandwich Conductive Layers for Human Motion Detection

“…With the rapid rise in wearable electronic devices, flexible sensors are growing by leaps and bounds and are showing substantial applications in various fields, such as human motion monitoring, − artificial intelligence robotics, − and human–computer interaction. − Crack-structured strain sensors with conductive materials coated on a flexible substrate have become a widely used strategy ,, with advantages such as easy fabrication and short response time. However, it is still a challenge to combine high sensitivity and high tensile range due to the resistance change of crack-based sensors based on the breakage and reversion of the conductive network. , High sensitivity requires the sensor to undergo violent fracture or recovery of the conductive network at a weak stretch, which makes it impossible to maintain the conductive network at large strains .…”