Enabling and Localizing Omnidirectional Nonlinear Deformation in Liquid Crystalline Elastomers

Auguste, Anesia D.; Ward, Jeremy W.; Hardin, James O.; Kowalski, Benjamin A.; Guin, Tyler; Berrigan, John D.; White, Timothy J.

doi:10.1002/adma.201802438

Cited by 38 publications

(30 citation statements)

References 29 publications

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“…All three compositions exhibit strain hardening at elongations beyond 150 % strain. In prior examinations of mechanical deformation of LCEs, this behavior is observed following the reorientation of LC mesogens in the direction of the applied stress . Though the IG‐PD‐LCE composition shows the greatest degree of strain hardening, the Iso composition exhibits analogous behavior (reaching values comparable to that of the nematic‐genesis polydomain), potentially indicating that a nematic LC phase may be induced from an initially disordered state.…”

Section: Figuresupporting

confidence: 55%

Mechanotropic Elastomers

et al. 2019

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Liquid crystal elastomers (LCEs) are anisotropic polymeric materials. When subjected to an applied stress, liquid crystalline (LC) mesogens within the elastomeric polymer network (re)orient to the loading direction. The (re)orientation during deformation results in nonlinear stress‐strain dependence (referred to as soft elasticity). Here, we uniquely explore mechanotropic phase transitions in elastomers with appreciable mesogenic content and compare these responses to LCEs in the polydomain orientation. The isotropic (amorphous) elastomers undergo significant directional orientation upon loading, evident in strong birefringence and x‐ray diffraction. Functionally, the mechanotropic displacement of the elastomers to load is also nonlinear. However, unlike the analogous polydomain LCE compositions examined here, the isotropic elastomers rapidly recover after deformation. The mechanotropic orientation of the mesogens in these materials increase the toughness of these thiol‐ene photopolymers by nearly 1300 % relative to a chemically similar elastomer prepared from wholly isotropic precursors.

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Section: Figuresupporting

confidence: 55%

Mechanotropic Elastomers

et al. 2019

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“…The enforcement of alignment at the surfaces is translated across the bulk associated with intermolecular interactions of liquid crystals. Similar approaches can be employed to generate homeotropic orientation through the cell thickness 517. An increasingly popular approach to introduce surface‐enforced alignment of liquid crystals is photoalignment 513,518,519.…”

Section: Liquid Crystal Elastomers and Networkmentioning

confidence: 99%

Materials as Machines

2020

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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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“…The transformation between two states was fully repeatable over at least ten cycles (Figure S13 and Movie S1, Supporting Information), as expected from the neat sample (Figure S5, Supporting Information) and the other nematic LCEs. [ 17–25 ]…”

Section: Figurementioning

confidence: 99%

Dynamic Manipulation of Friction in Smart Textile Composites of Liquid‐Crystal Elastomers

Ohzono

Saed

Yue

et al. 2020

Adv Materials Inter

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Functional flexible polymer films and sheets [1] such as textiles, tapes, and laminating materials, are used in many applications. Their friction against other surfaces [2][3][4] is one of the most important factors in their practical use, since this affects the force transmission between objects, e.g., in gripping and sliding, and in tactile sensing. In many situations, the ability to switch their friction characteristics on demand [5][6][7][8][9] would

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Enabling and Localizing Omnidirectional Nonlinear Deformation in Liquid Crystalline Elastomers

Cited by 38 publications

References 29 publications

Mechanotropic Elastomers

Mechanotropic Elastomers

Materials as Machines

Dynamic Manipulation of Friction in Smart Textile Composites of Liquid‐Crystal Elastomers

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