Bidirectional anisotropic electromagnetic shielding in MXene hydrogels with low filler loading enabled by pine-tree-like directional structure

MPC hydrogels with 4.0 wt% MXene show controllable EMI SE (33–65 dB) at 2-10 mm thickness. • Bidirectional freezing creates unique “pine-tip” morphology and anisotropic EMI shielding in MPC hydrogels. • CNF enhances physical cross-linking, providing hydrogels with excellent compression, UV shielding, and sensing stability. The rapid advancement of wearable and portable medical electronic devices demands flexible electromagnetic interference (EMI) shielding materials with excellent mechanical properties and high shielding effectiveness. Herein, we report an anisotropic MXene/polyvinyl alcohol (PVA)/cellulose nanofibers (CNF) (MPC) hydrogel fabricated via a simple physical cross-linking strategy combined with directional freezing technique. At an MXene loading of 4.0 wt%, the resulting MPC hydrogel achieves a tunable average EMI shielding effectiveness (SE) ranging from approximately 33 to 65 dB over a thickness of 2–10 mm. In addition, the hydrogel exhibits excellent UV shielding performance and reliable sensing stability. Interestingly, the macrostructural morphology of the MPC hydrogel resembles a “pine-tree-like” architecture, which imparts anisotropic EMI shielding properties, with the axial direction showing slightly higher shielding effectiveness than the radial direction. Furthermore, the bidirectionally freeze-cast MPC hydrogel demonstrates notably improved compressive strength, attributed to the formation of abundant physical cross-linking points between MXene and the polymer matrix, leading to a denser network structure. This study provides a new strategy for developing flexible sensors based on hydrogels featuring low filler loading and bidirectional electromagnetic shielding performance. Download: Download high-res image (176KB) Download: Download full-size image