Emergent nonlinear dynamics in 2D nanomaterials for flexible electronics and sensor applications

Strong many-body interactions, quantum confinement, interfacial coupling, and defect or strain induced symmetry breaking give two-dimensional (2D) nanomaterials highly nonlinear electronic, optical, thermal and mechanical nonlinear responses. As opposed to bulk materials, these nonlinear dynamics allow highly sensitive and adaptive responses to external electrical, optical, thermal and mechanical stimuli, positioning 2D systems as an promising platform to develop next generation flexible electronics and sensor technologies. It critically reviews the fundamental mechanisms of nonlinear charge transport, harmonic generation, exciton–phonon interactions, anharmonic thermal transport, nonlinear plasmonics and strain/defect-mediated nonlinearities of graphene, transition metal dichalcogenides, black phosphorus, h-BN, MXenes and van der Waals heterostructures. Special focus is given to the direct link between the nonlinear response of materials and the improved device functionality such as ultrafast optical switching, high gain optical detection, bistable memory operation, threshold switching mode, neuromorphic operation, strain amplified sensing, broadband chemical and biological detection. The review also addresses the benefits of nonlinear dynamics for the sensitivity, signal amplification, energy efficiency, and operational adaptability of flexible transistors, wearable sensors, optoelectronic systems and bio-integrated electronics. Computational methods like density functional theory, nonequilibrium transport models, and machine learning-based nonlinear response prediction are also assessed to gain insights into and manipulate emergent nonlinear phenomena. The major challenges of large area integration, operational stability, reproducibility, and scalable fabrication of devices are critically examined along with future possibilities of considering nonlinear architectures in wearable, implantable and neuromorphic advanced technologies. Overall, this review identifies nonlinear dynamics in 2D nanomaterials as a general design framework that provides a foundation for the design of adaptive, multifunctional and high performance flexible electronic and smart sensors.