MXene-based flexible electronics: current advances and future perspectives
The rapid expansion of the Internet of Things and wearable technologies has driven demand for flexible, lightweight, multifunctional electronics, yet conventional rigid devices fail to meet conformability, comfort, and durability requirements for health monitoring, soft robotics, and human-machine interfaces. Two-dimensional materials such as graphene and transition metal dichalcogenides exhibit limitations in electrical conductivity, tunable surface properties, and scalable synthesis. MXenes, discovered in 2011, offer metallic conductivity, hydrophilicity, mechanical robustness, and chemical versatility via the general formula Mn+1XnTx (T = –O, –F, –OH). Synthesized from MAX phase precursors through selective etching of the A layer using hydrofluoric acid or alternative etchants, delamination yields single- or few-layer nanosheets processable into inks, films, fibers, and composites. Surface terminations profoundly influence properties: –O terminations induce a bandgap (~1 eV in Ti2CO2), enabling semiconductor-like behavior, while –F terminations preserve metallic conductivity. Recent synthesis advances include electrochemical, molten salt, and halogen-based etching, improving termination control and reducing environmental hazards, though large-scale, high-quality production with minimal defects and uniform termination coverage remains challenging. In flexible electronics, microstructured Ti3C2Tx films achieve pressure sensitivities up to 8.4 kPa−1 over 0.1–100 kPa, and negative temperature coefficients enable linear responses of 0.8%/°C within 25–45 °C. Nitrogen-doped Ti3C2Tx electrodes deliver specific capacitances of 495 F g−1, while Mg2+ intercalated MXenes provide 765 mA h g−1 in lithium-ion capacitors. Despite persistent challenges in stability, scalability, and integration, ongoing research in surface engineering, advanced manufacturing, and multifunctional designs promises to overcome these hurdles, with future efforts focusing on bioinspired systems, neural interfaces, and environmentally sustainable protocols.