UC San Diego

The cover image is based on the article Effects of Microstructural Properties on Auxeticity and Negative Thermal Expansion of a Class of 2D Lattice Systems by Yun‐Che Wang et al., https://doi.org/10.1002/pssb.70188. When reciprocally scanning the constituent’s coefficient of thermal expansion (CTE), the black and red curves show the effective CTE of the inset lattice solid with small connecting joints (green color), consisting of bi‐material (orange and yellow color), curved ligaments. At the antipeaks, the effective CTE approaches zero, and their locations shift from solid to dashed curves as the joint size increases. The left‐ and right‐hand sides of the antipeaks possess negative and positive effective CTE, respectively. The lattice solid simultaneously exhibits auxetic behavior. The size and elastic modulus of the connecting joints play an important role in the overall CTE and Poisson’s ratio of mechanical metamaterials. Therefore, additional parameters are available for designing materials exhibiting negative characteristics.