Double-Helical Carbon Nanotube-Wrapped Elastomeric Mandrel for Electrical Shortage-Free, One-Body Multifunctional Fiber Systems

Soft and elastic fiber-based electronic devices exhibiting high electromechanical stability are highly desirable for sustainable and continuous utilization in various applications. However, effectively assembling the cathode and anode in a single body without unwanted interconnections and realizing an intimate contact interface between the electrode and substrate remain challenging. Here, an electrical shortage-free one-body fiber system with double-helix buckle electrodes created by torsion- and strain-mismatch between carbon nanotube (CNT) ribbons and a rubber substrate is reported. The as-used CNT ribbons serve as the strain-insensitive electrode, while the rubber mandrel-core fiber acts as the key matrix in the following three aspects: as an elastic substrate that ensures reversible structural changes during mechanical deformations; as a dielectric layer for capacitive strain sensing; and as an electrothermal expansion element for tensile contraction. Moreover, because of the mismatch-induced torque-balance structure, the helically wrapped CNT buckle electrodes can effectively absorb the applied stresses without noticeable delamination and electrical conductance loss. Consequently, the double-helix buckle fiber system can reliably provide multiple functions, viz. detection of various deformations (e.g., stretching, twisting, and pressing), electrochemical energy storage with excellent strain tolerance, and reversible electrothermal tensile actuation.