High-strain-sensitive dynamically adjustable electromagnetic interference shielding elastomer with pre-linked nickel chains

Smart electromagnetic interference (EMI) shielding materials with dynamic adjustable shielding performances are attractive, which however still suffer from complicated preparation, large thickness, inconvenient trigger mode, and relatively narrow adjustment range. Here, the off/on switchable EMI shielding elastomers are developed via precisely dispersing the spiked Ni microparticles (diameter: 2–3 µm) into polydimethylsiloxane matrix. By the gentle stir under low speed (300 r min⁻¹) for a short time (3 min), the Ni particles could form irregular clusters as short chains, which approach being linked together but still maintain tiny gaps (<3 µm) among them, showing a unique pre-linked-chains arrangement. The original elastomers show good impedance matching and low dielectric loss, allowing most EM waves to pass through. The stretching force presses the short pre-linked Ni chains to form massive microscale conductive paths inside (enlarge ∼6 orders of the original conductivity at 20% strain), which significantly enhance the capability of conduction loss and therefore trigger strong EMI shielding ability. The elastomer exhibits continuously and reversibly variable EMI shielding performances (∼35 dB for a 0.3 mm single film, ∼55 dB for the sandwich design) during mechanical stretching and releasing by 0–20% strain. In addition, the applicability of the smart EMI shielding elastomer is demonstrated by a wireless strain sensing system, which shows the possibility for the wearable smart EMI shielding to monitor human body motion precisely.