A Mechanical Coupling Strategy for Scaling Electrochemical Artificial Muscles to Newton-Level Output.

Electrochemical artificial muscles have reached impressive single-fiber performance, but scaling this to practical force levels remains an open problem. Naive parallel bundling fails to sum filament forces linearly because defects and performance heterogeneity among filaments trigger cascading failure rather than load sharing. Here we show that mechanically coupling filaments through a ply-twisting assembly converts a bundle of independent carbon nanotube (CNT) filaments into a fault-tolerant, load-sharing unit. While conventional parallel-arranged, coiled-fiber bundles fracture once a single filament breaks, mechanically-coupled bundles redistribute load among neighboring filaments. The mechanically-coupled bundle exhibits 69.2% higher maximum load and 52.8% greater contractile stroke than parallel-arranged coiled-fiber bundles with the same filament count. The 50-filament bundle delivers an isometric output force of 1.4 N, and after dual-electrode encapsulation for stable operation in air, an 80-filament bundle lifts a 1 kg load. We further demonstrate the practical relevance of this fascicle-level coupling principle by integrating encapsulated bundles into a bionic hand and a wearable massager, achieving reliable pressing and acupoint stimulation. The fascicle-level mechanical coupling offers a general structural strategy for scaling the force output of fiber-based electrochemical actuators.