A Super‐Stretchable Liquid Metal Foamed Elastomer for Tunable Control of Electromagnetic Waves and Thermal Transport

It is remarkably desirable and challenging to design a stretchable conductive material with tunable electromagnetic‐interference (EMI) shielding and heat transfer for applications in flexible electronics. However, the existing materials sustained a severe attenuation of performances when largely stretched. Here, a super‐stretchable (800% strain) liquid metal foamed elastomer composite (LMF‐EC) is reported, achieving super‐high electrical (≈10(4) S cm(−1)) and thermal (17.6 W mK(−1)) conductivities under a large strain of 400%, which also exhibits unexpected stretching‐enhanced EMI shielding effectiveness of 85 dB due to the conductive network elongation and reorientation. By varying the liquid and solid states of LMF, the stretching can enable a multifunctional reversible switch that simultaneously regulates the thermal, electrical, and electromagnetic wave transport. Novel flexible temperature control and a thermoelectric system based on LMF‐EC is furthermore developed. This work is a significant step toward the development of smart electromagnetic and thermal regulator for stretchable electronics.