High-efficiency flexible liquid metal/elastomer composite film with designability for strain-invariant electromagnetic shielding and Joule-heating applications

With the development of flexible electronics towards sophistication and miniaturization, the demand for stretching-stable ultra-thin electromagnetic interference (EMI) shielding films is increasing. Liquid metal (LM) with metallic conductivity and extreme fluidity is a satisfactory choice for preparing stretchable EMI shields. However, manufacturing high-efficiency flexible LM-based EMI shields with ultra-thin thickness and strain-stable shielding effectiveness (SE) through a facile strategy remains challenging. Herein, we proposed fabricating flexible and ultra-thin LM and polydimethylsiloxane (PDMS) composite films by facile scraping and mechanical sintering process. The resultant film with only ∼24 vol% LM and ∼150 μm thickness could show specific SE (SSE = SET/thickness) of ∼298 dB/mm and exhibit strain-invariant EMI-shielding behavior and higher SSE up to ∼400.9 dB/mm at 75 % strain, which almost ranks at the top of SSE values compared to formerly reported LM-based polymer composites. Moreover, the PDMS/LM film can be followed by structural design, and the potential of the designed film for directionally tunable EMI shielding is demonstrated by locally activating the conductive pathways and rotation. Furthermore, the stable conductive network provided relatively stable Joule-heating performance during stretching. This work develops a simpler strategy to construct a flexible conductive film for strain-invariant EMI shielding and Joule heating, and it also shows great potential for application in designable EMI shields.