Liquid metal electromagnetic wave shielding and absorbing film for solving electromagnetic interference in flexible sensors

The presence of electromagnetic interference (EMI) leads to distortion of current and voltage waveforms, which reduces the accuracy and stability of sensor devices. The emergence of flexible electronic devices has broken the limits of physical space, as they can be bent and twisted at will. However, this characteristic exacerbates unwanted coupling of their internal sensing elements, which can interfere with each other. At present, the solution to EMI is based on electromagnetic shielding (EMS), but this method alone cannot solve internal EMI of flexible sensor devices. In this study, the gallium-based liquid metal (LM) circuits are printed on the Ecoflex@Fe film to realize a stretchable film with both EMS and wave-absorbing functions, which is expected to simultaneously address the effects of internal and external EMI. The results show that the shielding efficiency of the electromagnetic wave shielding and absorbing (EWSA) film is as high as 54.5 dB on one side, while the reflection loss on the other side is as low as -43.5 dB. In addition, the LM-based EWSA film maintains positive wave-absorbing and EMS properties during stretching in different directions and it can also effectively avoid EMI after 1000 times of stretching. Overall, the LM-based EWSA film, which enables broadband EMS and wave-absorption, provides a solution for the development of next-generation flexible electronic skin that eliminates both internal and external EMI.