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Soft material robots are uniquely suited to address engineering challenges in extreme environments in new ways that traditional rigid robot embodiments cannot. Soft robot material flexibility, resistance to brittle fracture, low thermal conductivity, biostability, and self-healing capabilities present new solutions advantageous to specific environmental conditions. In this review, we examine the requirements for building and operating soft robots in various extreme environments, including within the human body, underwater, outer space, search and rescue sites, and confined spaces. We analyze the implementations of soft robotic devices, including actuators and sensors, which meet these requirements. Besides the structure of these devices, we explore ways to expand the use of soft robots in extreme environments with design optimization, control systems, and their future applications in educational and commercial products. We further discuss the current limitations of soft robots recognizing challenges to compliance, strength, and control. With this in mind, we present arguments for the future of robotics in which hybrid (rigid and soft) structures meet complex environmental needs. 

Abstract Liquid crystalline elastomers (LCEs) are anisotropic soft materials capable of large dimensional changes when subjected to a stimulus. The magnitude and directionality of the stimuli‐induced thermomechanical response is associated with the alignment of the LCE. Recent reports detail the preparation of LCEs by additive manufacturing (AM) techniques, predominately using direct ink write printing. Another AM technique, digital light process (DLP) 3D printing, has generated significant interest as it affords LCE free‐forms with high fidelity and resolution. However, one challenge of printing LCEs using vat polymerization methods such as DLP is enforcing alignment. Here, we document the preparation of aligned, main‐chain LCEs via DLP 3D printing using a 100 mT magnetic field. Systematic examination isolates the contribution of magnetic field strength, alignment time, and build layer thickness on the degree of orientation in 3D printed LCEs. Informed by this fundamental understanding, DLP is used to print complex LCE free‐forms with through‐thickness variation in both spatial orientations. The hierarchical variation in spatial orientation within LCE free‐forms is used to produce objects that exhibit mechanical instabilities upon heating. DLP printing of aligned LCEs opens new opportunities to fabricate stimuli‐responsive materials in form factors optimized for functional use in soft robotics and energy absorption. 

Abstract Optical polarizers encompass a class of anisotropic materials that pass-through discrete orientations of light and are found in wide-ranging technologies, from windows and glasses to cameras, digital displays and photonic devices. The wire-grids, ordered surfaces, and aligned nanomaterials used to make polarized films cannot be easily reconfigured once aligned, limiting their use to stationary cross-polarizers in, for example, liquid crystal displays. Here we describe a supramolecular material set and patterning approach where the polarization angle in stand-alone films can be precisely defined at the single pixel level and reconfigured following initial alignment. This capability enables new routes for non-binary information storage, retrieval, and intrinsic encryption, and it suggests future technologies such as photonic chips that can be reconfigured using non-contact patterning. 

Abstract Aerosol jet printing is a popular digital additive manufacturing method for flexible and hybrid electronics, but it lacks sophisticated real‐time process control schemes that would enable more widespread adoption in manufacturing environments. Here, an optical measurement system is introduced to track the aerosol density upstream of the printhead. The measured optical extinction, combined with the aerosol flow rate, is directly related to deposition rate and accurately predicts functional materials properties such as the electrical resistance of printed graphene films. This real‐time system offers a compelling solution for process drift and batch‐to‐batch variability, rendering it a valuable tool for both real‐time control of aerosol jet printing and fundamental studies of the underlying process science.