A carbon fiber elastomer film for mechanically anisotropic enhancement of stretchable electronics

Stretchable electronic devices with micro- to sub-millimeter thickness are increasingly used in soft robotics, wearable healthcare, and human-machine interfaces. However, the mechanical isotropy of commonly used elastomers leads to undesirable deformation in transverse directions, reducing actuation efficiency, sensing precision, and geometric stability. Here, we present a low-cost, easy-to-produce and readily applicable carbon fiber elastomer film (CFEF) that imparts pronounced mechanical anisotropy when laminated onto isotropic elastomers. The CFEF is fabricated by embedding unidirectionally aligned carbon fiber monofilaments within a polydimethylsiloxane (PDMS) matrix. The composite exhibits high stiffness along the carbon fiber axis, while remaining highly compliant in the direction perpendicular to the fibers. Fabrication requires only commercially available materials and standard processes, ensuring compatibility with existing devices. For a 200 μm thick PDMS film, it suppresses transverse strain by 95%. Applied to strip-type multilayer dielectric elastomer actuators, the CFEF increases actuation strain by 22%. In dielectric elastomer sensors, an anisotropy ratio of 80.6:1 is achieved. This approach offers an effective and manufacturing-friendly solution for tailoring directional mechanical properties in thin, soft electronic systems without compromising flexibility.