Skin-Mimicking Soft Strain Sensor with Elastic Resilience, Crack Tolerance, and Amphibious Self-Adhesion

Area of Science:

• Materials Science
• Biomimetics
• Robotics

Background:

• Human skin exhibits remarkable elastic resilience, fatigue resistance, and self-adhesion, properties difficult to replicate in artificial mechanoreceptive materials.
• Existing electronic skin technologies struggle to integrate these key properties for advanced healthcare monitoring and humanoid soft robots.

Purpose of the Study:

• To develop an elastically resilient, crack-tolerant, amphibiously adhesive, and strain-sensitive electronic skin (ERCAS-skin).
• To achieve a hierarchical and gradient design that mimics human skin's mechanical and adhesive properties.

Main Methods:

• Fabrication of ERCAS-skin using a skin-like binary structure: a carbon nanotube-coated thermoplastic polyurethane nanofibrous scaffold within a gradient cross-linking polydimethylsiloxane (PDMS) matrix.
• Characterization of mechanical properties, including Young's modulus (2.4 MPa), crack tolerance (1285 J m^-2), elastic resilience (95% recovery), and wet adhesion (0.76 N cm^-1).
• Evaluation of strain-sensing capabilities and application as a self-adhesive sensor for hand gesture recognition and a motion sensor for robotic fish.

Main Results:

• The hierarchical and gradient design enabled significant mechanical compliance and crack tolerance via matrix-to-scaffold stress transfer.
• Gradient cross-linking in the PDMS matrix achieved high elastic resilience and strong wet adhesion through hydrophobic chain mobility.
• The carbon nanotube polyurethane's crack generation mechanism provided high strain-sensing sensitivity and a broad detection range.

Conclusions:

• ERCAS-skin successfully integrates high elastic resilience, crack tolerance, amphibious adhesion, and sensitive strain-sensing capabilities.
• The developed electronic skin demonstrates potential for advanced applications in human gesture recognition (air and water) and fatigue-free robotic monitoring.