Straining techniques for strain engineering of 2D materials towards flexible straintronic

Straintronics of two-dimensional (2D) materials offers enormous promise for both fundamental research and smart technologies. Strain engineering of 2D materials has recently witnessed an upsurge of interest, driven by the growing demands of building flexible semiconductor devices under miniaturization. 2D materials have received considerable attention to tune their fascinating electrical, optical, and vibrational properties for flexible electronics due to their high stretchability and flexibility. For this, a variety of controllable straining techniques have been developed by mimicking either natural phenomena or mechanical processes. In the literature, strained nano-/microstructures of 2D materials have been extensively reviewed for highlighting their potential in tunable electronics, however a systematic assessment of the straining techniques utilized to create such strained structures is still lacking. In this review, we provide detailed one-to-one assessments of the straining methods used to create diverse strained structures of 2D materials and their limitations, covering recent advancements and in-depth discussions. In addition, the importance and advantages of applying straining techniques to improve the performance of flexible straintronic devices have also been covered. These will open pathways for exploiting the straining techniques for their meticulous applications.