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Untethered magnetic actuation is an attractive technique for controlling a batch of micrometer‐sized soft robots. Recent advancements have enabled each robot to follow its path independently using a single magnetic device. However, applications of magnetic soft microrobots are mostly biased toward the biomedical field. In this study, thermoplastic polyurethane–Fe3O4 nanocomposite soft spinning microrobots, that is, spinbots that actuate on a tabletop magnetic stirrer, were utilized as innovative precision manufacturing tools for spatially selective precision polishing and cleaning. The pivot motion of the revolving spinbots, which involves repetitive sweeping during rotation cycles, is explored. This sweeping action physically removes nanometer‐sized surface contaminants from the workpiece, achieving a cleaning efficiency of 99.6%. Multiple spinbots, up to 42 in total, simultaneously operated along their own orbital pathways on three vertically stacked wafers, thereby demonstrating an unprecedented cleaning method. In addition, the spinbots precisely removed materials from the workpiece using a three‐body abrasion mechanism. Furthermore, the spinbots contributed to precise material removal, resulting in remarkable surface polishing (Ra ≈ 1.8 nm). This novel polishing system, which uses the collective behavior of multiple spinbots on a tabletop magnetic stirrer, is 1000‐fold lighter than current state‐of‐the‐art equipment aimed at achieving similar levels of fine finishing. [ABSTRACT FROM AUTHOR]

On‐demand photo‐steerable amphibious rolling motions are generated by the structural engineering of monolithic soft locomotors. Photo‐morphogenesis of azobenzene‐functionalized liquid crystal polymer networks (azo‐LCNs) is designed from spiral ribbon to helicoid helices, employing a 270° super‐twisted nematic molecular geometry with aspect ratio variations of azo‐LCN strips. Unlike the intermittent and biased rolling of spiral ribbon azo‐LCNs with center‐of‐mass shifting, the axial torsional torque of helicoid azo‐LCNs enables continuous and straight rolling at high rotation rates (≈720 rpm). Furthermore, center‐tapered helicoid structures with wide edges are introduced for effectively accelerating photo‐motilities while maintaining directional controllability. Irrespective of surface conditions, the photo‐induced rotational torque of center‐tapered helicoid azo‐LCNs can be transferred to interacting surfaces, as manifested by steep slope climbing and paddle‐like swimming multimodal motilities. Finally, the authors demonstrate continuous curvilinear guidance of soft locomotors, bypassing obstacles and reaching desired destinations through real‐time on‐demand photo‐steering. [ABSTRACT FROM AUTHOR]

Lignin is a promising feedstock for renewable fuels and chemicals due to its aromatic skeleton and natural abundance. Lignin can be converted to diverse aromatic monomers as well as dicarboxylic acids depending on the applied conversion technologies. Despite its great potential, its native and processing-induced heterogeneity and complexity limit the conversion efficiency and product selectivity. In this study, magnesium ferrite (MgFe2O4) nanoparticle–peracetic acid (PAA) has been investigated as an efficient catalyst–oxidant incorporation for catalytic oxidative depolymerization of lignin under mild conditions. Typically, the increase in processing severity can enhance the lignin conversion while it results in the further decomposition of aromatic compounds to dicarboxylic acids. However, in this study, the incorporation of MgFe2O4 nanoparticles and PAA not only enhanced the total product yield but also improved the selectivity of aromatic monomers. The oxidative depolymerization system using the catalyst–oxidant combination resulted in 46 wt % of total oil product with a 61% selectivity of aromatic monomers under mild temperature (90 °C). In addition, this combination catalyst showed relatively good cycling stability based on the total product yield after recycling five times via magnetic separation. Overall, MgFe2O4 nanoparticles play an important role as a co-catalyst with a PAA oxidant in the oxidative conversion of lignin with an enhanced conversion efficiency and recyclability, and it will facilitate the valorization of lignin in future bio-based fuels and chemicals. [ABSTRACT FROM AUTHOR]

With intrinsic optical and dynamic properties of polysulfide chains, inverse vulcanized copolymers have demonstrated immense potential for infrared (IR) optical applications. However, preparing highly IR‐transparent sulfur‐rich copolymers without sacrificing their thermomechanical properties remains challenging. To overcome the trade‐off relationship between IR optical and thermomechanical properties, an in situ microphase separation strategy for the inverse vulcanization of elemental sulfur utilizing self‐crosslinkable 1,3,5‐trivinylbenzene (TVB) is presented. Even with 80 wt% sulfur content, the microphase‐separated TVB‐rich domain self‐reinforces the copolymer with a noteworthy modulus of ≈2.0 GPa and a high glass transition temperature (Tg) of 92.6 °C, while still exhibiting outstanding IR optical properties. This work is expected to provide insights into the fundamental structure–property relationships of sulfur‐rich copolymers and pave the way for various practical applications. [ABSTRACT FROM AUTHOR]

Eutectic gallium indium liquid metal (LM) is a promising conductive liquid for various electronic applications. In particular, the directional transport of LM droplets has potential applications in soft electronics to control electrical conductivity. Existing methods transport LM droplets by applying an electric field to generate an interfacial tension difference within the LM droplet due to nonuniform ionic distribution of the electrical double layer. However, these methods require confined channels and tethered systems to apply the electric field. In this study, channel‐free wireless transport of LM droplets is demonstrated via on‐demand magnetomechanical actuation of asymmetric microwall arrays comprising vertically aligned ferromagnetic iron particles embedded in polydimethylsiloxane. Asymmetric microwall of two different widths is designed to generate an asymmetric bending stiffness at a given magnetic field. The asymmetric microwall bends gradually in response to a linear external magnetic field perpendicular to the alignment axis of the iron particles. Therefore, nonuniform magnetomechanical bending induces a local height gradient along the microwall, causing gravitational‐force‐driven roll‐off motion of the LM droplet. Transport direction of LM droplet is modulated by varying the geometric parameters. Finally, the opposite‐directional transport of two LM droplets is demonstrated under a linear magnetic field by pre‐programming the asymmetric bending direction of each microwall array. [ABSTRACT FROM AUTHOR]

Miniaturized untethered soft robots are recently exploited to imitate multi‐modal curvilinear locomotion of living creatures that perceive change of surrounding environments. Herein, the use of Caenorhabditis elegans (C. elegans) is proposed as a microscale model capable of curvilinear locomotion with mechanosensing, controlled by magnetically reconfigured 3D microtopography. Static entropic microbarriers prevent C. elegans from randomly swimming with the omega turns and provide linear translational locomotion with velocity of ≈0.14 BL s−1. This velocity varies from ≈0.09 (for circumventing movement) to ≈0.46 (for climbing) BL s−1, depending on magnetic bending and twisting actuation coupled with assembly of microbarriers. Furthermore, different types of neuronal mutants prevent C. elegans from implementing certain locomotion modes, indicating the potential for investigating the correlation between neurons and mechanosensing functions. This strategy promotes a platform for the contactless manipulation of miniaturized biobots and initiates interdisciplinary research for investigating sensory neurons and human diseases. [ABSTRACT FROM AUTHOR]

In aqueous media, liquid crystalline droplets typically form spherical shapes in order to minimize surface energy. Recently, non-spherical geometry has been reported using molecular self-assembly of surfactant-stabilized liquid crystalline oligomers, resulting in branched and randomly oriented filamentous networks. In this study, we report a polymerization of liquid crystalline polymeric fibers within a micro-mold. When liquid crystal oligomers are polymerized in freely suspended aqueous media, curvilinear and randomly networked filaments are obtained. When reactive liquid crystalline monomers are oligomerized in a micro-channel, however, highly aligned linear fibers are polymerized. Within a top-down microfabricated mold, a bottom-up molecular assembly was successfully achieved in a controlled manner by micro-confinement, suggesting a unique opportunity for the programming architecture of materials via a hybrid approach. [ABSTRACT FROM AUTHOR]

Miniaturization of polymeric robots leads to difficulties in actuation inside viscous media due to the increased surface drag on the diminutive robot bodies. Herein, agile underwater swimming of polymeric microrobots is presented with the investigation of correlation between the magnetic propulsion and viscous drag on the robot. The polymeric microrobots swim with pivoting and tumbling motions during underwater rotation by in‐plane rotation of two permanent magnets underneath the plane, which results in orbital revolution‐type locomotion with a maximum swimming velocity of 56 body lengths per second (BL s−1). The rotational ability and orbital velocity of the polymeric microrobots are determined by correlated variables, i.e., liquid viscosity and frequency of magnet rotation, as elucidated by experimental results and theoretical analysis. Based on the understanding of underwater orbital maneuvers, the polymeric microrobots achieve agile swimmability at a viscosity similar to that of normal whole blood and self‐correcting maneuverability in diverse vascular‐like environments, including a stenosed tube with a coarse granular hill and a rough‐walled artificial blood vessel. Agile underwater swimming can improve versatile aquatic performances of miniaturized robots in blood vessels with arteriosclerosis or blood clots. [ABSTRACT FROM AUTHOR]

Azobenzene‐functionalized liquid crystalline polymer networks (azo‐LCNs) are promising candidates for light‐fueled contactless manipulation of miniaturized soft robots through embedding photoactive molecular switches into alignment‐programmable LCNs. In particular, the 3D helical geometry of azo‐LCNs is reported to achieve rapid photomotility by introducing rolling resistance. However, the maximum height of the obstacle that soft robot can overcome is limited by the helix diameter and the stress–strain responsivity. Herein, the helical diameter per unit length and photogenerated stress through molecular engineering of photoactive molecular switches are maximized. The carbon number of aliphatic spacers in the photoactive molecular switches is varied from two to eight to systematically investigate the structure–property–performance relations by studying the molecular geometry, physical properties of polymers, and photomotility of polymers. Furthermore, a finite‐element analysis simulation is presented to understand the rolling locomotion of helical torsional soft robots. Through molecular engineering, the helix diameter per unit length of 0.2 mg soft robots is maximized, demonstrating high Young's modulus (≈2 GPa) and photogenerated stress (>1 MPa), as well as large velocity per body length, compared with the previously reported soft robots. Finally, the molecularly engineered soft robots successfully climb stairs, which is a key task in robotic systems. [ABSTRACT FROM AUTHOR]

In recent years, the "Kirigami" have been exploited to engineer stretchable electronics that exhibit enhanced deformability without sacrificing their mechanical and electrical properties. However, kirigami‐inspired engineering is often limited to passive mechanical stretching for 3D shape morphing. To counter this problem, in this study, azobenzene‐functionalized liquid crystalline polymer networks (azo‐LCNs) are monolithically integrated with patterned reduced graphene oxide (rGO), called azo‐LCN/rGO, to achieve on‐demand shape reconfiguration in response to external stimuli (UV, NIR, solar rays, and portable light); in addition, the azo‐LCN/rGO exhibit highly enhanced mechanical and electrical properties. The cross‐sectional area and thickness of rGO patterns are controlled using a masking technique and evaporative self‐assembly. By the spatial patterning of rGO, insulating azo‐LCNs are converted into electrically conducting structures (381.9 S cm−1). The elastic modulus of <2 µm thick azo‐LCN can be tailored in the range of 1.3–6.4 GPa by integration with rGO layers of thickness less than 2 µm. Upon UV irradiation, azo‐LCN/rGO exhibit both for/backward in‐plane bending as well as out‐of‐plane chiral twisting, thus overcoming the typical trade‐off relationship between elastic modulus and deformability. Finally, an on‐demand contactless shape reconfiguration in azo‐LCN/rGO by UV irradiation in conjunction with passive mechanical strain is demonstrated. [ABSTRACT FROM AUTHOR]

The collective assembly of finite building blocks can induce complicated scaled‐up architecture for structural diversity and multifunctionality. In this study, the concept of 2D to 3D shape morphing via frontal photopolymerization is employed for the rapid and repetitive fabrication of geometrically tailorable building blocks. The photoabsorber generates an internal stress gradient which induces a mismatch of volumetric shrinkage within a photocured monolithic 3D structure. The final 3D curvilinear architecture is investigated through systematic analysis by controlling the spatiotemporal conditions of 3D shape morphing. The spatiotemporal effect consists of pre/postcuring methods and geometry of the 2D patterns inspired by fractal elements including even/odd condition, spirality, and self‐similarity. Finally, the concept of collective assembly is introduced to construct multiple objective architectures. Each morphed structure contributes to the assembly of hierarchical 3D structures as a building block. Inspired by famous architectures, the collective hierarchical 3D structures are demonstrated by replicating the form of certain landmarks. In addition, scaled‐up assembled 3D structure can withstand 150 times of its own weight and can be applied for the frame of electronic devices. The collective assembly of programmable building blocks has the potential for various versatile applications in rapid prototypes of optical metamaterials, antennas, and curved electronic devices. [ABSTRACT FROM AUTHOR]

Solid‐state electrolytes can alleviate the safety issues of electrochemical energy systems related to chemical and thermal instabilities of liquid electrolytes. While a liquid provides seamless ionic transport with almost perfect wettability between electrodes, a solid‐state electrolyte needs to demonstrate at least comparable electrochemical performance to liquid electrolytes as well as mechanical robustness and flexibility. Here, the facile preparation of montmorillonite (MMT)/dimethyl sulfoxide (DMSO) nanocomposites is reported, which show high ionic conductivities, mechanical strengths, and thermal stabilities by forming nacre‐mimetic "brick‐and‐mortar" structures. The molecularly confined structures of DMSO are confirmed by X‐ray diffraction peaks with d‐spacings of interplanar spacing that are slightly larger than MMTs. The MMT/DMSO composites have mechanical strengths and toughnesses of 55.3 ± 4.8 MPa and 210.2 ± 32.6 kJ m−2, respectively. The ionic conductivity is ≈2 × 10−4 S cm−1 at room temperature, and their thermal stability is in the range of −100 to 120 °C. The optical translucency, on‐demand eco‐degradability, and solution processability together make the MMT/DMSO composites unique materials with a wide range of solid‐state electrochemical applications including batteries. [ABSTRACT FROM AUTHOR]