Untethered soft robotic matter with passive control of shape morphing and propulsion

There is growing interest in creating untethered soft robotic matter that can repeatedly shape-morph and self-propel in response to external stimuli. Toward this goal, we printed soft robotic matter composed of liquid crystal elastomer (LCE) bilayers with orthogonal director alignment and different nematic-to-isotropic transition temperatures (T_(NI)) to form active hinges that interconnect polymeric tiles. When heated above their respective actuation temperatures, the printed LCE hinges exhibit a large, reversible bending response. Their actuation response is programmed by varying their chemistry and printed architecture. Through an integrated design and additive manufacturing approach, we created passively controlled, untethered soft robotic matter that adopts task-specific configurations on demand, including a self-twisting origami polyhedron that exhibits three stable configurations and a “rollbot” that assembles into a pentagonal prism and self-rolls in programmed responses to thermal stimuli

Untethered soft robotic matter with passive control of shape morphing and propulsion

There is growing interest in creating untethered soft robotic matter that can repeatedly shape-morph and self-propel in response to external stimuli. Toward this goal, we printed soft robotic matter composed of liquid crystal elastomer (LCE) bilayers with orthogonal director alignment and different nematic-to-isotropic transition temperatures (T_(NI)) to form active hinges that interconnect polymeric tiles. When heated above their respective actuation temperatures, the printed LCE hinges exhibit a large, reversible bending response. Their actuation response is programmed by varying their chemistry and printed architecture. Through an integrated design and additive manufacturing approach, we created passively controlled, untethered soft robotic matter that adopts task-specific configurations on demand, including a self-twisting origami polyhedron that exhibits three stable configurations and a “rollbot” that assembles into a pentagonal prism and self-rolls in programmed responses to thermal stimuli

3D printing of liquid crystal elastomeric actuators with spatially programed nematic order

This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi:10.1002/adma.201706164.Liquid crystal elastomers (LCEs) are soft materials capable of large, reversible shape changes, which may find potential application as artificial muscles, soft robots, and dynamic functional architectures. Here, the design and additive manufacturing of LCE actuators (LCEAs) with spatially programed nematic order that exhibit large, reversible, and repeatable contraction with high specific work capacity are reported. First, a photopolymerizable, solvent-free, main-chain LCE ink is created via aza-Michael addition with the appropriate viscoelastic properties for 3D printing. Next, high operating temperature direct ink writing of LCE inks is used to align their mesogen domains along the direction of the print path. To demonstrate the power of this additive manufacturing approach, shape-morphing LCEA architectures are fabricated, which undergo reversible planar-to-3D and 3D-to-3D′ transformations on demand, that can lift significantly more weight than other LCEAs reported to date.The authors gratefully acknowledge support from the National Science Foundation through the Harvard MRSEC (Grant No. DMR-1420570) and the DMREF (Grant No. DMR-1533985). A.K. and R.L.T. acknowledge support from their National Science Foundation Graduate Research Fellowships. J.A.L. acknowledges support from the Vannevar Bush Faculty Fellowship Program sponsored by the Basic Research Office of the Assistant Secretary of Defense for Research and Engineering and funded by the Office of Naval Research Grant N00014-16-1-2823 as well as the generous donation from the GETTYLAB in support of our work. This work made use of the Shared Experimental Facilities supported in part by the MRSEC Program of the National Science Foundation under award number DMR-1419807. Finally, the authors thank L. K. Sanders and C. Settens for technical assistance and Brian Donovan and Tyler Guin (AFRL) for useful discussions. (DMR-1420570 - National Science Foundation through Harvard MRSEC; National Science Foundation; DMR-1533985 - DMREF; Vannevar Bush Faculty Fellowship Program - Basic Research Office of the Assistant Secretary of Defense for Research and Engineering; N00014-16-1-2823 - Office of Naval Research; DMR-1419807 - MRSEC Program of the National Science Foundation)Accepted manuscrip

3D Printing of Liquid Crystal Elastomeric Actuators with Spatially Programed Nematic Order

This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi:10.1002/adma.201706164.Liquid crystal elastomers (LCEs) are soft materials capable of large, reversible shape changes, which may find potential application as artificial muscles, soft robots, and dynamic functional architectures. Here, the design and additive manufacturing of LCE actuators (LCEAs) with spatially programed nematic order that exhibit large, reversible, and repeatable contraction with high specific work capacity are reported. First, a photopolymerizable, solvent-free, main-chain LCE ink is created via aza-Michael addition with the appropriate viscoelastic properties for 3D printing. Next, high operating temperature direct ink writing of LCE inks is used to align their mesogen domains along the direction of the print path. To demonstrate the power of this additive manufacturing approach, shape-morphing LCEA architectures are fabricated, which undergo reversible planar-to-3D and 3D-to-3D′ transformations on demand, that can lift significantly more weight than other LCEAs reported to date.The authors gratefully acknowledge support from the National Science Foundation through the Harvard MRSEC (Grant No. DMR-1420570) and the DMREF (Grant No. DMR-1533985). A.K. and R.L.T. acknowledge support from their National Science Foundation Graduate Research Fellowships. J.A.L. acknowledges support from the Vannevar Bush Faculty Fellowship Program sponsored by the Basic Research Office of the Assistant Secretary of Defense for Research and Engineering and funded by the Office of Naval Research Grant N00014-16-1-2823 as well as the generous donation from the GETTYLAB in support of our work. This work made use of the Shared Experimental Facilities supported in part by the MRSEC Program of the National Science Foundation under award number DMR-1419807. Finally, the authors thank L. K. Sanders and C. Settens for technical assistance and Brian Donovan and Tyler Guin (AFRL) for useful discussions. (DMR-1420570 - National Science Foundation through Harvard MRSEC; National Science Foundation; DMR-1533985 - DMREF; Vannevar Bush Faculty Fellowship Program - Basic Research Office of the Assistant Secretary of Defense for Research and Engineering; N00014-16-1-2823 - Office of Naval Research; DMR-1419807 - MRSEC Program of the National Science Foundation)Accepted manuscrip

A MICROMECHANICAL-BASED MODEL OF STIMULUS RESPONSIVE LIQUID CRYSTAL ELASTOMERS

Stimulus responsive elastomers are advanced engineered materials that perform desired functionalities when triggered by external stimuli. Liquid crystal elastomers (LCEs) are one important example that exhibit reversible actuation when cycled above and below their nematic-to-isotropic transition temperature. Here, we propose a micromechanical-based model that is centered on the evolution of the chain distribution tensor of the LCE network. Our model, framed within the statistical model of the chain network, enables a mesoscale description of their mechanical response under an external thermal stimulus. We compare the model to prior experimental observations of the bending response of 3D printed LCE elements with controlled director alignment

Shape-shifting structured lattices via multimaterial 4D printing

© 2019 National Academy of Sciences. All rights reserved. Shape-morphing structured materials have the ability to transform a range of applications. However, their design and fabrication remain challenging due to the difficulty of controlling the underlying metric tensor in space and time. Here, we exploit a combination of multiple materials, geometry, and 4-dimensional (4D) printing to create structured heterogeneous lattices that overcome this problem. Our printable inks are composed of elastomeric matrices with tunable cross-link density and anisotropic filler that enable precise control of their elastic modulus (E) and coefficient of thermal expansion (α). The inks are printed in the form of lattices with curved bilayer ribs whose geometry is individually programmed to achieve local control over the metric tensor. For independent control of extrinsic curvature, we created multiplexed bilayer ribs composed of 4 materials, which enables us to encode a wide range of 3-dimensional (3D) shape changes in response to temperature. As exemplars, we designed and printed planar lattices that morph into frequency-shifting antennae and a human face, demonstrating functionality and geometric complexity, respectively. Our inverse geometric design and multimaterial 4D printing method can be readily extended to other stimuli-responsive materials and different 2-dimensional (2D) and 3D cell designs to create scalable, reversible, shape-shifting structures with unprecedented complexity

Material Agency and 4D Printing

Material agency presents a radical shift in design thinking: matter is deemed as the active generator of design. This chapter investigates the potentialities of the synergy between adaptive materials and emergent additive manufacturing techniques. In this context, 4D printing is explored as the tool that enables the material-centered design and fabrication approach. By means of this technique, it is possible to generate stimuli-responsive material systems that can enact self-adaptation of architectural constructs, responding to environmental change with a shape-shifting behaviour. Moreover, a fast, innovative, 3D printing method, Rapid Liquid Printing, allows for this process to potentially scale up to an architectural scale, as it offers the opportunity of quickly printing at large-scales with a wide array of materials, from industrial grade rubbers to responsive silicones