Strain-Invariant,Highly Water Stable All-Organic Soft Conductors Based on Ultralight Multi-Layered Foam-Like Framework Structures

Soft and flexible conductors are essential for the development of soft robots, wearable electronics, electronic tissue, and implants. However, conventional soft conductors are inherently characterized by a large change in conductance upon mechanical deformation or under alternating environmental conditions, e.g., humidity, drastically limiting their application potential. This work demonstrates a novel concept for the development of strain-invariant, highly elastic and highly water stable all-organic soft conductors, overcoming the limitations of previous strain-invariant soft conductors. For the first time, thin film deposition technologies are combined in a three-dimensional fashion, resulting in micro- and nano-engineered, multi-layered (<50 nm), ultra-lightweight (< 15 mg cm⁻³) foam-like framework structures based on Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and Polytetrafluoroethylene (PTFE), characterized by a highly strain-invariant conductivity (≈184 S/m) between 80% compressive and 25% tensile strain. Both the initial electrical and mechanical properties are retained during long-term cycling, even after 2000 cycles at 50% compression. Furthermore, the PTFE thin film renders the framework structure highly hydrophobic, resulting in stable electrical properties, even when immersed in water for a month. Such innovative multi-scaled and multi-layered functional materials are of interest for a broad range of applications in soft electronics, energy storage and conversion, sensing, water and air purification, as well as biomedicine.