Soft and Strong: Elastic Conductors with Bio-Inspired Self-Protection.

Skin is soft yet strong - a combination achieved by integrating compliant elastin with stiff but wavy collagen, producing non-linear mechanical properties. Inspired by this structure, stiff conductive wires are engineered into sinusoidal patterns and mechanically interlocked them with highly elastic fibers using a reimagined woven fabric approach. The result is a highly conducting and stretchable yarn that also has high tensile strength - a combination that is attractive for wearable applications where comfort and durability are valued. With a diameter of ≈1 mm-comparable to many commercial yarns-the fabric-based yarn exhibits low stiffness across a broad strain range (up to 270% under 2 N of force) while demonstrating a self-protective transition to high stiffness and strength (up to 30 MPa) as it nears failure. Additionally, this yarn offers excellent flexibility, high strain tolerance (exceeding 500%), inherent breathability, and superior weavability. By tuning the number of elastic fibers and electrode fibers, it can further tailor these stretchable conductive yarns into strain-insensitive connecting yarns (low impedance at MHz frequencies, GF = 0.0003) and mechanical sensing yarns with dual strain and proximity sensing capabilities. The integration of these functional yarns enables system-level smart textile applications, such as wristband controllers.