Straintronics and Twistronics in 2D Materials: Structural Control and Predictive Design.

Strain and twist offer geometric control over lattice reconstruction and electronic symmetry in two-dimensional (2D) materials. In contrast to chemical doping or compositional alloying, these deformations act on the material response by varying the deformation state and stacking registry. This review explores how the emerging fields of straintronics and twistronics are transforming from isolated demonstrations towards controllable design strategies for electronic, optoelectronic, magnetic, and quantum 2D material systems. Here, we organize a review of recent advances in controlled fabrication, spatially resolved characterization, multiscale modeling, and machine-learning-assisted analysis of twist- and strain-induced effects. The examples include carbon-based nanosheets, transition-metal dichalcogenides (TMDs), magnetic layers, and layered halide perovskites. Throughout this overview, we emphasize the link from imposed geometric input to local lattice reconstruction and, ultimately, to the measured material or device response. Finally, we identify the main barriers to translating strain- and twist-controlled 2D materials into electronic and optoelectronic devices.