No abstract

bare interconnects with regular yarns or attaching devices to the surface of fabrics, encapsulating both electrodes and devices within the cladding of a single fiber confers mechanical and moisture protection while allowing increased electrode and device density. However achieving device functionality at the single fiber level requires high electrical conductivity (>10 6 S m −1 ) without compromising elasticity. It is important to emphasize that elasticity is necessary for the fiber to withstand the fabric construction process in weaving [10] and knitting, [11] and also for daily use. [12] Studies have explored polymer nanocomposites, conductive polymers [13][14][15] and liquid metals, [16,17] to couple conductivity and elasticity at the fiber level. Despite these recent advances, the challenge of creating a fiber that is highly elastic and highly conductive remains largely unmet.We note that the structure of a fabric, in particular in knits, is routinely used to impart elasticity on the fabric level. [12,18] Similarly, structurebased elasticity has been leveraged extensively in stretchable electronics, [19,20] where thin metal traces in shapes of serpentines, [21][22][23][24] wrinkles, [25][26][27] and helices [24,28,29] have been attached to, or embedded in an elastomeric matrix. Upon stretching, the metal deforms through bending, allowing for tens of percent of reversible strain without impairing the conductivity.Electronic fabrics necessitate both electrical conductivity and, like any textile, elastic recovery. Achieving both requirements on the scale of a single fiber remains an unmet need. Here, two approaches for achieving conductive fibers (10 7 S m −1 ) reaching 50% elongation while maintaining minimal change in resistance (<0.5%) in embedded metallic electrodes are introduced. The first approach involves inducing a buckling instability in a metal microwire within a cavity of a thermally drawn elastomer fiber. The second approach relies on twisting an elastomer fiber to yield helical metal electrodes embedded in a stretchable yarn. The scalability of both approaches is illustrated in apparatuses for continuous buckling and twisting that yield tens of meters of elastic conducting fibers. Through experimental and analytical methods, it is elucidated how geometric parameters, such as buckling pre-strain and helical angle, as well as materials choice, control not only the fiber's elasticity but also its Young's modulus. Links between mechanical and electrical properties are exposed. The resulting fibers are used to construct elastic fabrics that contain diodes, by weaving and knitting, thus demonstrating the scalable fabrication of conformable and stretchable antennas that support optical data transmission.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202201081.

Broad adoption of magnetic soft robotics is hampered by the sophisticated field paradigms for their manipulation and the complexities in controlling multiple devices. Furthermore, high‐throughput fabrication of such devices across spatial scales remains challenging. Here, advances in fiber‐based actuators and magnetic elastomer composites are leveraged to create 3D magnetic soft robots controlled by unidirectional fields. Thermally drawn elastomeric fibers are instrumented with a magnetic composite synthesized to withstand strains exceeding 600%. A combination of strain and magnetization engineering in these fibers enables programming of 3D robots capable of crawling or walking in magnetic fields orthogonal to the plane of motion. Magnetic robots act as cargo carriers, and multiple robots can be controlled simultaneously and in opposing directions using a single stationary electromagnet. The scalable approach to fabrication and control of magnetic soft robots invites their future applications in constrained environments where complex fields cannot be readily deployed.