Auxetic mechanical metamaterials: efficient strain engineering for highly reliable free-form displays

With the growing integration of display technology into various aspects of daily life, research on free-form displays with minimal structural constraints has gained increased attention. However, the transition of free-form display technology from an early developmental stage to a growth phase presents several technical challenges, particularly Poisson’s effect in stretchable platforms that can lead to image distortion and spatial stress imbalances. This review presents a strain-engineering design strategy that leverages auxetic mechanical metamaterials (AMMs) with negative Poisson’s ratios and explores their potential applications in free-form displays. Effective approaches for controlling deformation in 2D and 3D configurations are examined by analyzing the geometric design and structural configuration of the re-entrant, chiral, and perforated sheet structures. Furthermore, integrating AMM-based architectures into free-form displays could enable precise regulation of in-plane and out-of-plane deformations, potentially mitigating mechano-optical issues, compensating for resolution, and expanding the design flexibility of 3D shape morphing. The findings prompt future directions for next-generation free-form displays and propose that AMM-based strain engineering could serve as a crucial design approach for enhancing device stability and reliability.