Abstract:in temperature-responsive hydrogels. [4,7] Although requiring careful consideration of heat transfer, such photothermal shape changes can provide rapid kinetics (at least for hydrogels with small dimensions, where mass transport is fast), nearly complete reversibility, and large volume changes.Directing the motion of micro-and nanoscale objects at an air/water interface is important from numerous perspectives, ranging from improving fundamental understanding of biological systems [8] to designing synthetic mic… Show more
“…Finally, inclusion of a large square in the center of the sheet drives rolling about an axis perpendicular to the director and wrinkling along the edges of the sheet (Figure 2C). These deformations are similar to those observed in nematic sheets with polydomain inclusions [ 56 ] and isotropic gels with local photothermal inclusions [ 44 ] and again result from a balance of stretching and bending energies as the films attempt to accommodate the discontinuous target metric.…”
Section: Figuresupporting
confidence: 67%
“…Recently, we introduced a method to spatially pattern gold nanoparticles (AuNPs) in LCE fibers [ 43 ] and hydrogel sheets [ 44 ] with high spatial resolution using UV‐induced photoreduction of gold salt. [ 45,46 ] Following patterning, exposure to visible light induces localized photothermal deformation that drives shape‐morphing.…”
studies have focused on programming desired 3D structures of soft materials such as shape-memory polymers [2,3] and gels [4][5][6][7] by introducing spatial variations in thermal expansion/contraction, swelling, or molecular order. [8] A particularly useful class of materials to achieve dynamic 2D to 3D shape transformations are liquid crystal elastomers (LCEs), where the coupling between the orientational ordering of polymerized mesogens and the conformation of a polymer backbone can be leveraged for large, anisotropic deformations that are dictated by the director field. [9,10] Using oriented surface alignment layers [11] or microchannels, [12] director orientation can be patterned with a resolution approaching 10 µm. [13] A subsequent reduction of nematic ordering, usually driven by heating, leads to local contraction along the director and expansion along the transverse directions, driving out-of-plane buckling into 3D shapes that are "blueprinted" by the pattern of director orientation. However, while geometric methods allow for the deduction of the necessary inplane director orientation field to generate a desired profile of Gaussian curvature, [14][15][16][17] there are a number of practical drawbacks to this approach. First, prescription of complex director fields requires significant processing, making high-throughput fabrication, and evaluation of designs challenging. Additionally, the surface alignment methods needed to specify director orientation with high spatial resolution are only amenable to certain chemistries due to the need for high mesogen content, and thus cannot be widely generalized to all LCE systems. For example, while classical LCE systems based on siloxanes, [18,19] as well as recently developed systems that rely on simple and efficient "click" chemistries, [20] offer attractive thermal and mechanical properties for shape-morphing systems, they typically only allow for alignment of the director field with coarse spatial resolution such as through application of shear stress [21][22][23] or magnetic fields. [24] To circumvent the need for a spatially varying director orientation, where the direction of deformation varies but the magnitude is constant, a potential alternative method to drive shape changes is to instead locally prescribe the magnitude of deformation within an otherwise homogeneous director field. While spatial variations in the extent of deformation have been widely employed for shape Liquid crystal elastomers (LCEs) are an attractive platform for dynamic shape-morphing due to their ability to rapidly undergo large deformations. While recent work has focused on patterning the director orientation field to achieve desired target shapes, this strategy cannot be generalized to material systems where high-resolution surface alignment is impractical. Instead of programming the local orientation of anisotropic deformation, an alternative strategy for prescribed shape-morphing by programming the magnitude of stretch ratio in a thin LCE sheet with constant director orientation is...
“…Finally, inclusion of a large square in the center of the sheet drives rolling about an axis perpendicular to the director and wrinkling along the edges of the sheet (Figure 2C). These deformations are similar to those observed in nematic sheets with polydomain inclusions [ 56 ] and isotropic gels with local photothermal inclusions [ 44 ] and again result from a balance of stretching and bending energies as the films attempt to accommodate the discontinuous target metric.…”
Section: Figuresupporting
confidence: 67%
“…Recently, we introduced a method to spatially pattern gold nanoparticles (AuNPs) in LCE fibers [ 43 ] and hydrogel sheets [ 44 ] with high spatial resolution using UV‐induced photoreduction of gold salt. [ 45,46 ] Following patterning, exposure to visible light induces localized photothermal deformation that drives shape‐morphing.…”
studies have focused on programming desired 3D structures of soft materials such as shape-memory polymers [2,3] and gels [4][5][6][7] by introducing spatial variations in thermal expansion/contraction, swelling, or molecular order. [8] A particularly useful class of materials to achieve dynamic 2D to 3D shape transformations are liquid crystal elastomers (LCEs), where the coupling between the orientational ordering of polymerized mesogens and the conformation of a polymer backbone can be leveraged for large, anisotropic deformations that are dictated by the director field. [9,10] Using oriented surface alignment layers [11] or microchannels, [12] director orientation can be patterned with a resolution approaching 10 µm. [13] A subsequent reduction of nematic ordering, usually driven by heating, leads to local contraction along the director and expansion along the transverse directions, driving out-of-plane buckling into 3D shapes that are "blueprinted" by the pattern of director orientation. However, while geometric methods allow for the deduction of the necessary inplane director orientation field to generate a desired profile of Gaussian curvature, [14][15][16][17] there are a number of practical drawbacks to this approach. First, prescription of complex director fields requires significant processing, making high-throughput fabrication, and evaluation of designs challenging. Additionally, the surface alignment methods needed to specify director orientation with high spatial resolution are only amenable to certain chemistries due to the need for high mesogen content, and thus cannot be widely generalized to all LCE systems. For example, while classical LCE systems based on siloxanes, [18,19] as well as recently developed systems that rely on simple and efficient "click" chemistries, [20] offer attractive thermal and mechanical properties for shape-morphing systems, they typically only allow for alignment of the director field with coarse spatial resolution such as through application of shear stress [21][22][23] or magnetic fields. [24] To circumvent the need for a spatially varying director orientation, where the direction of deformation varies but the magnitude is constant, a potential alternative method to drive shape changes is to instead locally prescribe the magnitude of deformation within an otherwise homogeneous director field. While spatial variations in the extent of deformation have been widely employed for shape Liquid crystal elastomers (LCEs) are an attractive platform for dynamic shape-morphing due to their ability to rapidly undergo large deformations. While recent work has focused on patterning the director orientation field to achieve desired target shapes, this strategy cannot be generalized to material systems where high-resolution surface alignment is impractical. Instead of programming the local orientation of anisotropic deformation, an alternative strategy for prescribed shape-morphing by programming the magnitude of stretch ratio in a thin LCE sheet with constant director orientation is...
“…Although a single spinbot is unable to carry the object, the spinning force of the soft robots surrounding the cargo generates collective motion under the simplified external stimulus of planar magnetic rotation. This collective transportation motion is driven by capillary interactions 44 between the cargo and the spinbots at the air–water interface, retaining rotational movement around the cargo.Fig. 4Multifunctionality of 3D helical spinbots.…”
Magnetic soft robots facilitate the battery-free remote control of soft robots. However, parallel control of multiple magnetic robots is challenging due to interference between robots and difficult maneuvers. Here we present the orbital maneuvering of manifold magnetic soft robots. Magneto-induced motion (magnetomotility) that includes the hierarchy of rotation and resultant revolution allows for the independent control of the robot’s velocity and orbital radius. The soft robot achieves a speed of 60 body length (BL) s−1, which is approximately 50, 000 times faster with 1/7 the weight of the current lightest legged soft robot. The hierarchical magnetomotility is suitable for versatile locomotion such as stairs and uphill climbing, underwater and above water swimming. Owing to their swimming functionality, a swarm of such soft robots is capable of transportation of cargo. On-demand orbital maneuvering of magnetic soft robots provides a new methodology for concurrent actuation of multiple robots exhibiting collective behaviors.
“…Relatedly, Emrick and Hayward used light as a means to generate a graded response in Au‐nanoparticle patterned hydrogel disks. The variation in absorption across the material thickness generates motion and self‐assembly in a group of hydrogel disks under white light exposure 466. The photothermal gradient emanating radially out from the centrally patterned nanoparticle region results in a large degree of deswelling close to the nanoparticle interface, and a low degree of deswelling at the edges of the hydrogel disk.…”
of responsive materials as machines is in robotics. The vision, leadership, and research of Bar-Cohen is seminal in both invigorating and focusing current-day research activities to develop responsive materials [2] and implement [3] them as lightweight, dexterous, and gentle (e.g., soft) robotic elements. In this spirit, this review exhaustively details the materials, the nature of their stimuli-response, and discusses considerations for their implementation in robotic systems and subsystems.Robotics is a well-established but growing field of research. Sustained progress in both performance and functionality continue to be realized in commercial robotic systems largely based on conventional materials and their integration with mechanisms. A recent example is the Atlas robot from Boston Dynamics [4] (Figure 1a). The incorporation of stimuli-responsive materials in robotics has largely focused on component-level demonstrations to extend the performance of a subsystem (such as a hand or gripper).Stimuli-responsive materials, spanning nearly all classes of materials and size scales, are currently subject to widespread examination in corporate, government, and academic research laboratories (Figure 1b-d). [5][6][7] In some cases, these materials have already found widespread commercial implementation in end use and are comparatively mature. The materials and fundamentals of their responses are summarized in Figure 2. Shape memory alloys (SMAs) and ceramic piezoelectric materials are distinctive in that they are hard, stimuli-responsive materials. Deformation of these materials can produce large energy densities due to their inherent stiffness. Electroactive polymers (EAPs) remain a topic of considerable interest, particularly dielectric elastomer actuators (DEAs). Engineered systems are rapidly emerging and enabling performance gains in robotics, largely based on pneumatic or fluidic (such as HASEL [8] actuators) transport processes that localize deformation to generate force or produce motion. Soft materials, such as shape memory polymers (SMPs), hydrogels, and liquid crystalline polymer networks (LCNs) and elastomers (LCEs) may offer distinctive functional performance to robotic systems in allowing local control of deformation without the need for complex interfacing with mechanisms. As will be evident, each of these materials has inherent advantages and performance tradeoffs that must be considered in functional implementations. However, responsive material systems have a common obstacle to widespread use: the performance and Machines are systems that harness input power to extend or advance function. Fundamentally, machines are based on the integration of materials with mechanisms to accomplish tasks-such as generating motion or lifting an object. An emerging research paradigm is the design, synthesis, and integration of responsive materials within or as machines. Herein, a particular focus is the integration of responsive materials to enable robotic (machine) functions such as gripping, lifting, or motility (walk...
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