Photomechanics of Liquid‐Crystalline Elastomers and Other Polymers

Ikeda, Tomiki; Mamiya, Jun‐ichi; Yu, Yanlei

doi:10.1002/anie.200602372

Cited by 953 publications

(615 citation statements)

References 182 publications

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“…The extent of azobenzene isomerization (efficiency) is considerably lessened by embedding this photochromic moiety in a polymeric material-evident in the work of Morawetz, which contrasts the kinetics and photostationary state concentration of azobenzene photoisomerization in dilute solution, plasticized, and bulk forms (5). Photoisomerization in polymeric materials becomes less efficient and slower with increase in storage modulus (6). Accordingly, photomechanical power densities of monolithic polymeric actuators are limited unless circumvented as demonstrated in this study.…”

mentioning

confidence: 77%

Contactless, photoinitiated snap-through in azobenzene-functionalized polymers

Shankar

Smith

Tondiglia

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Photomechanical effects in polymeric materials and composites transduce light into mechanical work. The ability to control the intensity, polarization, placement, and duration of light irradiation is a distinctive and potentially useful tool to tailor the location, magnitude, and directionality of photogenerated mechanical work. Unfortunately, the work generated from photoresponsive materials is often slow and yields very small power densities, which diminish their potential use in applications. Here, we investigate photoinitiated snap-through in bistable arches formed from samples composed of azobenzene-functionalized polymers (both amorphous polyimides and liquid crystal polymer networks) and report ordersof-magnitude enhancement in actuation rates (approaching 10 2 mm/ s) and powers (as much as 1 kW/m 3 ). The contactless, ultra-fast actuation is observed at irradiation intensities <<100 mW/cm 2 . Due to the bistability and symmetry of the snap-through, reversible and bidirectional actuation is demonstrated. A model is developed to elucidate the underlying mechanics of the snap-through, specifically focusing on isolating the role of sample geometry, mechanical properties of the materials, and photomechanical strain. Using light to trigger contactless, ultrafast actuation in an otherwise passive structure is a potentially versatile tool to use in mechanical design at the micro-, meso-, and millimeter scales as actuators, as well as switches that can be triggered from large standoff distances, impulse generators for microvehicles, microfluidic valves and mixers in laboratory-on-chip devices, and adaptive optical elements.photochemistry | elastic instability T ransduction of light into work in photoresponsive polymeric materials does not require contact and can be remotely triggered potentially over long distances. The ease with which light can be manipulated spatio-temporally in intensity, phase, and polarization further distinguish this novel input stimulus in mechanically active systems. Prior demonstrations of photomechanical effects in polymeric materials have used both photothermal (1) and photochemical (2-4) mechanisms. Photochemical routes, in nearly all cases using the photoisomerization of azobenzene, are particularly interesting because they offer broader opportunities for modulating photomechanical responses with irradiation wavelength and polarization.The basis of light-to-work transduction (actuation) in azobenzenefunctionalized polymeric materials is the rate and efficiency of the isomerization/reorientation of the embedded azobenzene chromophores. The extent of azobenzene isomerization (efficiency) is considerably lessened by embedding this photochromic moiety in a polymeric material-evident in the work of Morawetz, which contrasts the kinetics and photostationary state concentration of azobenzene photoisomerization in dilute solution, plasticized, and bulk forms (5). Photoisomerization in polymeric materials becomes less efficient and slower with increase in storage modulus (6). Accordingly, pho...

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mentioning

confidence: 77%

Contactless, photoinitiated snap-through in azobenzene-functionalized polymers

Shankar

Smith

Tondiglia

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…[16] With the recently developed laser lithography and molecular alignment engineering [17,18] it is now possible to pattern these soft materials in arbitrary 3D forms with a predefined actuation performance. The light-induced deformation can vary with illumination conditions, allowing one monolithic LCE structure to perform different actions, where a conventional robot would need numerous discrete actuators, each of them individually controlled.…”

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confidence: 99%

Light‐Driven Soft Robot Mimics Caterpillar Locomotion in Natural Scale

Rogóż

Zeng

Chen

et al. 2016

Advanced Optical Materials

311

180

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“…Commonly commercial azo-dyes have maximum absorption for the photoisomerization at about 350 nm. 27,28 Hence, these dyes are not suited for DLW polymerization process as this wavelength overlaps with the two photon absorption peak of the photo-initiator. For this reason the absorption maximum of the azo-dye is tuned to around 530 nm by changing the substituent on the aromatic rings.…”

Section: Sample Fabricationmentioning

confidence: 99%

Optically controlled elastic microcavities

et al. 2015

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Whispering gallery mode (WGM) resonators made from dielectrics like glass or polymers have outstanding optical properties like huge cavity quality (Q) factors which can be achieved on scales compatible with on-chip integration. However, tunability of these resonances is typically difficult to achieve or not suitable for robust device applications. We report here on the fabrication of polymeric micro-goblet WGM resonators with an optically controlled and stable reversible tunability over a large spectral range. This tunability is achieved by integration of photo-responsive liquid crystalline elastomers (LCEs) into micro-goblet cavities. The optical response of the elastomer allows reshaping the goblet by employing low pump power, leading to a fully reversible tuning of the modes. The structure can be realistically implemented in on-chip devices, combining the ultra-high Q factors, typical of WGM resonators, with reliable, optical tunability. This result serves as an example of how light can control light, by invoking a physical reshaping of the structure. This way of optical tuning creates interesting possibilities for all-optical control in circuits, enabling interaction between signal and control beams and the realization of self-tuning cavities. Keywords: liquid crystal elastomers; polymeric cavities; tunable micro-resonators; whispering gallery modes INTRODUCTION Solid-state optical microcavities are versatile photonic devices which come in a large variety of appearances. 1 Of particular interest are whispering gallery mode (WGM) resonators which feature small modal volume and large quality (Q) factors. 2 They are highly attractive for fundamental physics studies like cavity quantum electrodynamics, 3 as well as for applications like single photon sources, 4 optical sensing 5 or communication technology. 6,7 A key feature of WGM microcavities is the occurrence of ultra-narrow optical resonances and the functionality of the cavity often relies on the shift of the resonance frequency. This is the case, e.g., for optical sensors where the modal shift indicates the presence of attached bio-molecules or a change in the composition of the surrounding medium. 5 Essential features of such resonators are thus a large free spectral range and a narrow linewidth of the resonances but for many applications additionally an active manipulation of the cavity resonances is required. Examples are the tuning of the cavity into resonance with a quantum emitter 8,9 or utilization of the cavity in optical filters and light modulators. 10 In the last decade, a new class of WGM resonators has emerged featuring ultra-high Q factors. These resonators have spherical, cylindrical, toroidal, disk or goblet shapes 1,9,11 and are made of silica, polymers or liquids. Besides their excellent sensing capabilities they can also be turned into micro-lasers when incorporating laser dyes 12 or quantum dots 13 or be coupled to form photonic molecules. 14 But an obstacle effectively hindering some applications of these cavities is the limited tunab...

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Photomechanics of Liquid‐Crystalline Elastomers and Other Polymers

Cited by 953 publications

References 182 publications

Contactless, photoinitiated snap-through in azobenzene-functionalized polymers

Contactless, photoinitiated snap-through in azobenzene-functionalized polymers

Light‐Driven Soft Robot Mimics Caterpillar Locomotion in Natural Scale

Optically controlled elastic microcavities

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