Humidity-Responsive Bilayer Actuators Based on a Liquid-Crystalline Polymer Network

Dai, Mian; Picot, OT Olivier; Verjans, Jmn Julien; Haan, de Lt Laurens; Schenning, Aphj Albert; Peijs, Ton; Bastiaansen, Cwm Cees

doi:10.1021/am400681z

Cited by 129 publications

(103 citation statements)

References 29 publications

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require external stimuli such as high electric fields, or high temperatures and pressures. [7,8] A variety of materials, such as graphene oxide, [9][10][11][12] polymers, [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] liquid crystals, [14,29,30] paper, [31,32] and biologically based materials [6][7][8][33][34][35][36] can serve as hygroscopic actuators. [7,8] A variety of materials, such as graphene oxide, [9][10][11][12] polymers, [13][14][15][16][17][18][19][20][21]

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mentioning

confidence: 99%

Spore‐Based Water‐Resistant Water‐Responsive Actuators with High Power Density

Çakmak

Tinay

Chen

et al. 2019

Adv Materials Technologies

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require external stimuli such as high electric fields, or high temperatures and pressures. [1,2] These materials can be driven by perturbations to the ambient humidity or with natural fluctuations. [7,8] A variety of materials, such as graphene oxide, [9][10][11][12] polymers, [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] liquid crystals, [14,29,30] paper, [31,32] and biologically based materials [6][7][8][33][34][35][36] can serve as hygroscopic actuators. These actuators exhibit curling and folding, [10,14,19] walking, [17,21,24,37] gripping, [18] and power generation functions. [7,8,38] Despite the potential of humidityresponsive materials, relatively low work densities and slow responses limit the scope of applications. Studies of hygroscopic properties of Bacillus spores have shown that these dormant microorganisms exhibit actuation capabilities, with energy densities up to about 20 MJ m −3 , which raise the possibility of using spores as building blocks of macroscopic actuators. [8] However, assembly of spores into larger materials while retaining their actuation performance presents challenges. In particular, because spores do not adhere strongly to each other, approaches that strengthen spore-spore interactions are needed. Therefore, initial demonstrations of spore-based actuators used mixtures of spores with water soluble adhesives. These mixtures were then deposited onto plastic films to create various actuators and energy harvesting devices. [7] However, the resulting materials exhibited low work density and specific work in comparison to individual spores. Importantly, while water soluble adhesives simplify the fabrication process, they are prone to degradation when placed in direct contact with water, making it difficult to use in waterdriven applications. Therefore, different approaches are needed to enhance the work density and robustness of spore-based materials.Here, we report spore-based actuators that use waterresistant UV-curable adhesives and achieve work densities up to 0.44 MJ m −3 , which is an order of magnitude higher than the synthetic humidity-responsive polymers. [22][23][24][25] The water resistance of the spore-based actuators allowed direct waterdriven actuation, which reduced the response times by nearly 100-fold. We also leveraged the UV curability of these adhesives to facilitate rapid fabrication of complex dynamic and/or adaptive structures using photolithography.Bacillus subtilis spores exhibit hygroscopic actuation capabilities (Figure 1c) and have shown high energy densities Active materials and surfaces that are less intrusive and more compatible with humans and their environment are critical for robotic applications. Humidity-and water-responsive materials are emerging as versatile alternatives to commonly used actuators in robotic systems, due to ease of actuation with humidity gradients and pervasiveness of water in the environment. However, these materials exhibit relatively low work densities and slow responses, and they are degraded when placed in ...

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mentioning

confidence: 99%

Spore‐Based Water‐Resistant Water‐Responsive Actuators with High Power Density

Çakmak

Tinay

Chen

et al. 2019

Adv Materials Technologies

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“…LCNs can be actuated by various stimuli such as light, [15] heat, [16] solvent, [17] and humidity. [18] Being a clean, remote, and precisely controllable stimulus, light is a particularly attractive energy source. [19] The light-triggered deformation of an LCN actuator is governed by the alignment distribution of the constituent liquid-crystal molecules within the polymer network, and developing methods for precise control over the director distribution in order to obtain desired photoactuation mode is an important topic of research.…”

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confidence: 99%

Programming Photoresponse in Liquid Crystal Polymer Actuators with Laser Projector

Wani

Zeng

Wasylczyk

et al. 2017

Advanced Optical Materials

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have emerged as promising materials for fabricating soft actuators. [12][13][14] LCNs combine the anisotropy of the constituent liquid-crystal (LC) molecules and the elasticity of polymer networks, and are capable of stimuli-responsive shape change at the macroscopic scale. LCNs can be actuated by various stimuli such as light, [15] heat, [16] solvent, [17] and humidity. [18] Being a clean, remote, and precisely controllable stimulus, light is a particularly attractive energy source. [19] The light-triggered deformation of an LCN actuator is governed by the alignment distribution of the constituent liquid-crystal molecules within the polymer network, and developing methods for precise control over the director distribution in order to obtain desired photoactuation mode is an important topic of research. [14,[20][21][22] Photoalignment has proven to be a successful technique in patterning complex alignments into liquid-crystalline materials [23][24][25] and in devising on-demand actuations into LCNs. [21] The technique is based on illuminating a thin photoresponsive layer, a "command surface," [26] with linearly polarized light. Upon illumination, the photoalignment layer becomes anisotropic, thereby changing the boundary conditions experienced by the liquid-crystal molecules in the vicinity, and forcing them to align either perpendicular [27] or parallel [28] to the light polarization. Photopatterning of director orientation can be achieved by spatially modulating the light polarization, [27] or exposure through mask(s). [28,29] White and co-workers have used a laser setup to raster scan a focussed laser beam with controlled polarization across the sample, and thus achieved local control in the director distribution. [30][31][32] Also spatial light modulators and digital micromirror devices have been used for high-throughput patterning. [17,[33][34][35] These demonstrations require either prepatterned masks or relatively complex optical set-ups for programming the desired director distribution.Herein, we use a laser projector with a microelectromechanical system (MEMS)-based scanning mirror assembly (PICO, Sony) to program the liquid-crystal alignment within a monolithic LCN film. Photopatterning is achieved by projecting an arbitrary computer-generated image onto the photoalignment layer, using predefined light polarization. The projector is capable of addressing a minimum feature size of 50 µm over an area of 25 × 14 mm 2 . A series of complex photoactuators, such as defect buckling, coiling strip with gradient in pitch, four-arm gripper, and bidirectional bending in an octopod, are demonstrated by engineering different director orientations via photopatterning. The photoactuators are fabricated by polymerizing LC monomer mixtures inside LC cells that have been A versatile, laser-projector-based method is demonstrated for programming alignment patterns into monolithic films of liquid crystal polymer networks. Complex images can be photopatterned into the polymer films with sub-100 µm resolution, using relative...

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“…They are usually limited to simple expansion and contraction. Yet, more complex motions, such as bending and twisting, can be realized through composite design expanding the range of potential applications . For example, a bilayer humidity sensor was developed by Dai et al by depositing a shape‐changing liquid crystalline material on a pre‐extended elastic substrate .…”

Section: Shape‐changing Materialsmentioning

confidence: 99%

Reversible shape‐shifting in polymeric materials

Zhou

Sheiko

2016

J Polym Sci B Polym Phys

121

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In recent years, significant progress has been made in polymeric materials, which alter shape upon external stimuli, suggesting potential applications in robotics, biomedical engineering, and optical devices. These stimuli-responsive materials may be categorized into two classes: (i) shapechanging materials in which a specific type of shape-shifting is encoded in the original material structure and (ii) shapememory materials, which do not possess any predetermined shape-shifting as prepared, yet allow programming of complex shape transformations on demand. While shape alterations in shape-changing materials are intrinsically reversible, shape memory is usually a one-way transformation from a metastable (programmed) to an equilibrium (original) state. Recently, different principles for both one-way reversible and two-way reversible shape memory have been developed. These offer a powerful combination of reversibility and programmability, which significantly expands the range of potential applications. The goal of this review is to highlight recent developments in reversible shape-shifting by introducing novel mechanisms, materials, and applications.

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Humidity-Responsive Bilayer Actuators Based on a Liquid-Crystalline Polymer Network

Cited by 129 publications

References 29 publications

Spore‐Based Water‐Resistant Water‐Responsive Actuators with High Power Density

Spore‐Based Water‐Resistant Water‐Responsive Actuators with High Power Density

Programming Photoresponse in Liquid Crystal Polymer Actuators with Laser Projector

Reversible shape‐shifting in polymeric materials

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