Directing traffic with patterns: Biological entities, such as bacteria, may direct their motion in response to their environment, but this usually does not lead to large-scale patterns or collective behavior. Peng et al. found that the orientational ordering of a liquid crystal could direct the flow of self-propelling bacteria, which in turn influenced the patterning of the liquid crystal molecules. Patterns on a substrate caused surface anchoring of the liquid crystals that transmitted to the ordering of the bacteria, thus imparting control on what would otherwise be chaotic out-of-equilibrium behavior. Science , this issue p. 882

Maxwell stress–activated shape-morphing liquid crystal elastomer actuators are efficient, fast, and forceful.

Stimuli-responsive liquid crystal elastomers with molecular orientation coupled to rubber-like elasticity show a great potential as elements in soft robotics, sensing, and transport systems. The orientational order defines their mechanical response to external stimuli, such as thermally activated muscle-like contraction. Here we demonstrate a dynamic thermal control of the surface topography of an elastomer prepared as a coating with a pattern of in-plane molecular orientation. The inscribed pattern determines whether the coating develops elevations, depressions, or in-plane deformations when the temperature changes. The deterministic dependence of the out-of-plane dynamic profile on the in-plane orientation is explained by activation forces. These forces are caused by stretching-contraction of the polymer networks and by spatially varying molecular orientation. The activation force concept brings the responsive liquid crystal elastomers into the domain of active matter. The demonstrated relationship can be used to design coatings with functionalities that mimic biological tissues such as skin.

Soft materials that respond to wireless external stimuli are referred to as “smart” materials due to their promising potential in real‐world actuation and sensing applications in robotics, microfluidics, and bioengineering. Recent years have witnessed a burst of these stimuli‐responsive materials and their preliminary applications. However, their further advancement demands more versatility, configurability, and adaptability to deliver their promised benefits. Here, a dual‐stimuli‐responsive soft bimorph material with three configurations that enable complex programmable 3D shape‐morphing is presented. The material consists of liquid crystal elastomers (LCEs) and magnetic‐responsive elastomers (MREs) via facile fabrication that orthogonally integrates their respective stimuli‐responsiveness without detrimentally altering their properties. The material offers an unprecedented wide design space and abundant degree‐of‐freedoms (DoFs) due to the LCE's programmable director field, the MRE's programmable magnetization profile, and diverse geometric configurations. It responds to wireless stimuli of the controlled magnetic field and environmental temperature. Its dual‐responsiveness allows the independent control of different DoFs for complex shape‐morphing behaviors with anisotropic material properties. A diverse set of in situ reconfigurable shape‐morphing and an environment‐aware untethered miniature 12‐legged robot capable of locomotion and self‐gripping are demonstrated. Such material can provide solutions for the development of future soft robotic and other functional devices.