Anisotropic magnetic liquid metal film for wearable wireless electromagnetic sensing and smart electromagnetic interference shielding

Smart and wearable electromagnetic (EM) functional materials that can reasonably use EM energy and prevent EM pollution are of great significance to the future information society, but their design and preparation are still challenging. Here, a multifunctional EM response film is prepared based on a magnetic liquid metal droplet-filled elastomer with magnetic field-induced anisotropic structure, which can reversibly construct conductive network and tune heterogeneous interface during cyclic stretching. This film can withstand up to 600% tensile strain and shows stretching-enhanced electrical conductivity. Its EM interference shielding effectiveness (SE) significantly increases with stretching, and the relative SE change (Delta SE/SE0) shows a linear response to the tensile strain. The specific shielding effectiveness (an ultrahigh value of 404 dB mm-1 at 400% strain) and strain sensitivity of the film outperform other stretchable EM functional materials. More interestingly, this film exhibits rapid switching between EM wave transmission and shielding through continuous stretching, which enables an off/on switchable EM interference shielding function. Furthermore, it can be used in a wearable EM sensor to wirelessly monitor human movements by recording changes of EM wave intensity.