Artificial muscles based on liquid crystal elastomers

Li, Min-Hui; Keller, Patrick

doi:10.1098/rsta.2006.1853

Cited by 250 publications

(191 citation statements)

References 45 publications

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“…Liquid crystalline (LC) elastomers show a contraction on heating from the nematic to isotropic phase and so can be pictured as actuators [152,153]. Similar behavior can also be seen in liquid crystalline gels [154], which opens the possibility for combining electrical switchability, the shape change associated with liquid crystalline elastomers with the volume change associated with gels [155,156].…”

Section: Lc Elastomersmentioning

confidence: 76%

Polymer Gel Actuators: Fundamentals

Calvert

2009

Biomedical Applications of Electroactive Polymer Actuators

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One view of materials development is to search for what materials correspond to empty spaces on a hypothetical multi-dimensional map of the properties of available materials. Following a biomimetic philosophy, for instance, it can be seen that tough ceramics and moldable short fiber composites with high moduli are possible but absent from the list of available synthetic materials. Likewise artificial muscle is missing, where the properties are defined as a developed stress of over 300 kPa, a linear contraction of 25 % and a response time of below one second. Currently dielectric elastomers come closest but have disadvantages [1,2].The actin-myosin muscle system provides the performance target for electroactive polymer actuators [3,4]. The process is driven chemically by the energy change from hydrolysis of the polyphosphate bond as ATP (adenosine triphosphate) binds to myosin and is converted to ADP (adenosine diphosphate) and phosphate. A simple chemical analogy suggests that muscle-like gels should be feasible but it is now clear that the task is much harder than it seems.Early work on gel actuation by Katchalsky-Katzir demonstrated that engines could be built using the chemical energy in diluting a lithium bromide solution to drive contraction and expansion of a collagen belt [5]. In essence, the collagen expands to take up the salt solution or contract to exclude the water. This change is both a molecular conformation change and a volume change. Other chemically driven gels, for instance polyacrylic acid fibers [6] which respond to a pH change, also rely on a solubility change giving rise to a volume change.

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Section: Lc Elastomersmentioning

confidence: 76%

Polymer Gel Actuators: Fundamentals

Calvert

2009

Biomedical Applications of Electroactive Polymer Actuators

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“…The different physical properties of LCE have been studied by various researchers [35][36][37][38][39][40][41][42][43][44][45], but the current applications of the material show that the research work that has so far been done on it is very insufficient. In the present study, an attempt was made to investigate the optical, thermal, and mechanical properties of monodomain NLCE so as to understand the physical behavior of this material and to develop new applications of it.…”

Section: Introductionmentioning

confidence: 99%

Study of the optical, thermal, and mechanical properties of nematic liquid crystal elastomers

Mani

Hadkar

Jessy

et al. 2016

Journal of Information Display

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In the present study, the optical, thermal, and mechanical properties of liquid crystal elastomers (LCEs) were investigated using various techniques. The presence of functional groups in LCE was studied using Fourier transform infrared spectroscopy. The phase transition temperatures were confirmed via polarizing optical microscopy and Fabry-Perot scattering studies. The differential thermal analysis was used for investigating the thermal behavior. A dynamic mechanical analysis was used to study the mechanical properties of LCE. The significant mechanical changes with a considerable reversible effect were observed for this soft material. The changes in the mechanical shape with the temperature are attributed to the change in the phase of the LCE material. ARTICLE HISTORY

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“…Comparisons between liquid crystals and biological muscles have a long history, beginning with the original proposal and theoretical analysis by De Gennes in 1975 and continuing to the present day [43][44][45][46]. This well-understood state of matter exhibits a shift in stiffness [47], volume and optical properties as a result of changes in the internal order of rod-like sub-unit mesogens.…”

Section: Skeletal Muscle-active Contractionmentioning

confidence: 99%

“…Various methods of alignment are used to obtain single-crystal monodomains, which ensure these elements act together. Shearing surface force [44], electrical [180] and magnetic fields [61] are all well-known methods for aligning mesogens before initiating polymerisation to preserve this orientation. Photoalignment can create spatially varying responses in two dimensions, demonstrated both continuously [181,182] and using a discrete voxel approach [60].…”

Section: Reproducing Positioning and Orientationmentioning

confidence: 99%

Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms

2016

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Shape-changing materials open an entirely new solution space for a wide range of disciplines: from architecture that responds to the environment and medical devices that unpack inside the body, to passive sensors and novel robotic actuators. While synthetic shape-changing materials are still in their infancy, studies of biological morphing materials have revealed key paradigms and features which underlie efficient natural shape-change. Here, we review some of these insights and how they have been, or may be, translated to artificial solutions. We focus on soft matter due to its prevalence in nature, compatibility with users and potential for novel design. Initially, we review examples of natural shape-changing materials-skeletal muscle, tendons and plant tissues-and compare with synthetic examples with similar methods of operation. Stimuli to motion are outlined in general principle, with examples of their use and potential in manufactured systems. Anisotropy is identified as a crucial element in directing shape-change to fulfil designed tasks, and some manufacturing routes to its achievement are highlighted. We conclude with potential directions for future work, including the simultaneous development of materials and manufacturing techniques and the hierarchical combination of effects at multiple length scales.

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Artificial muscles based on liquid crystal elastomers

Cited by 250 publications

References 45 publications

Polymer Gel Actuators: Fundamentals

Polymer Gel Actuators: Fundamentals

Study of the optical, thermal, and mechanical properties of nematic liquid crystal elastomers

Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms

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