A highly stretchable, transparent, and conductive polymer

TLDR

Stretchable electronics have largely relied on strain engineering and nanocomposites, while intrinsically stretchable molecular materials are scarce but promise simpler fabrication, robust devices, and better contact. The study presents a highly stretchable PEDOT:PSS polymer enhanced by additives that modify morphology and increase conductivity. The polymer is engineered by adding multifunctional enhancers that alter morphology and serve as dopants to boost conductivity. The resulting films achieve >3100 S/cm at 0 % strain and >4100 S/cm at 100 % strain, retain 3600 S/cm after 1000 cycles to 100 % strain, stay above 100 S/cm at 600 % strain with 800 % fracture strain, and enable transistor interconnects five times denser than conventional wavy designs.

Abstract

Previous breakthroughs in stretchable electronics stem from strain engineering and nanocomposite approaches. Routes toward intrinsically stretchable molecular materials remain scarce but, if successful, will enable simpler fabrication processes, such as direct printing and coating, mechanically robust devices, and more intimate contact with objects. We report a highly stretchable conducting polymer, realized with a range of enhancers that serve a dual function: (i) they change morphology and (ii) they act as conductivity-enhancing dopants in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The polymer films exhibit conductivities comparable to the best reported values for PEDOT:PSS, with over 3100 S/cm under 0% strain and over 4100 S/cm under 100% strain-among the highest for reported stretchable conductors. It is highly durable under cyclic loading, with the conductivity maintained at 3600 S/cm even after 1000 cycles to 100% strain. The conductivity remained above 100 S/cm under 600% strain, with a fracture strain of 800%, which is superior to even the best silver nanowire- or carbon nanotube-based stretchable conductor films. The combination of excellent electrical and mechanical properties allowed it to serve as interconnects for field-effect transistor arrays with a device density that is five times higher than typical lithographically patterned wavy interconnects.