Holocellulose Nanofibril-Assisted Intercalation and Stabilization of Ti3C2Tx MXene Inks for Multifunctional Sensing and EMI Shielding Applications

2D transition-metal carbide/nitride (MXene)-based conductive inks have received tremendous attention due to their high electrical conductivity and other fascinating properties. However, the unstability of MXene-based inks, low fabrication yield of MXene flakes, and poor mechanical properties of printed products strongly limit the proper and large-scale printing of MXene patterns. Here, functioning as a dispersant, an intercalation agent, and reinforcement, sulfated holocellulose nanofibrils (HCNFs) with a unique "core-shell" structure are conducive to the fabrication, storage, and subsequent printing of MXene inks. The MXene/HCNF (MH) ink with high yield (97.2%), good stability, and good homogeneity exhibits excellent printing performance (high resolution and good coverage). It could print various products with adjustable thicknesses and electrical conductivity properties on different substrates. The products printed by the MH ink can be applied as multifunctional sensing materials responding to multiple external stimuli, such as stress/strain, blowing, humidity, and temperature. Furthermore, the resulting products also display a high electromagnetic interference (EMI) shielding effectiveness (SE) of 54.3 dB at a shallow thickness of 100 μm and an excellent specific EMI SE of SSE/t of 7159 dB cm2 g-1.