Elongated liquid metal based self-healing polyurethane composites for tunable thermal conductivity and electromagnetic interference shielding

Abstract

Materials with desirable properties, including good deformability, high thermal conductivity, and superior electromagnetic interference (EMI) shielding, are in high demand in the modern electronics sector. Here we report, stretching-induced filler alignment method for elongate and align the liquid metal (LM) in the self-healing polyurethane (SPU) matrix along the draw direction, resulting in simultaneous enhancement in in-plane thermal conductivity (λ∥) and the EMI shielding effectiveness (SE) of the composites. LM/SPU composites with 80 wt% filler loading show λ∥ as high as 12.8 W·m-1·K-1 and EMI SE of 72 dB, respectively, at the draw ratio of 3. Excellent deformability of the LM facilitates its alignment in the composites, which improves electron and phonon transmission and allows for multiple reflections and absorption of electromagnetic waves, which greatly enhances λ∥ and EMI shielding. Moreover, LM/SPU composites show excellent healing properties. Thus, this work proposes incorporating multifunctional features into a composite system for flexible electronics.