Liquid crystalline elastomers (LCEs) exhibit a number of remarkable physical effects, including the unique, high-stroke reversible mechanical actuation when triggered by external stimuli. This article reviews some recent exciting developments in the field of LCEs materials with an emphasis on their utilization in actuator applications. Such applications include artificial muscles, industrial manufacturing, health and microelectromechanical systems (MEMS). With suitable synthetic and preparation pathways and well-controlled actuation stimuli, such as heat, light, electric and magnetic field, excellent physical properties of LCE materials can be realized. By comparing the actuating properties of different systems, general relationships between the structure and the property of LCEs are discussed. How these materials can be turned into usable devices using interdisciplinary techniques is also described.
Inspired by heliotropism in nature, artificial heliotropic devices that can follow the sun for increased light interception are realized. The mechanism of the artificial heliotropism is realized via direct actuation by the sunlight, eliminating the need for additional mechatronic components and resultant energy consumption. For this purpose, a novel reversible photo‐thermomechanical liquid crystalline elastomer (LCE) nanocomposite is developed that can be directly driven by natural sunlight and possesses strong actuation capability. Using the LCE nanocomposite actuators, the artificial heliotropic devices show full‐range heliotropism in both laboratory and in‐field tests. As a result, significant increase in the photocurrent output from the solar cells in the artificial heliotropic devices is observed.
Dye‐sensitized solar cells with an energy storage function are demonstrated by modifying its counter electrode with a poly (vinylidene fluoride)/ZnO nanowire array composite. This simplex device could still function as an ordinary solar cell with a steady photocurrent output even after being fully charged. An energy storage density of 2.14 C g−1 is achieved, while simultaneously a 3.70% photo‐to‐electric conversion efficiency is maintained.
A general method for the formation of a broad family of silicon nanotube arrays (Si NTAs) relevant to diverse fields--ranging from energy storage to therapeutic platforms--is described. Such nanotubes demonstrate a thickness-dependent dissolution behavior important to its potential use in drug delivery. Under selected conditions, novel porous silicon nanotubes can be prepared when the shell thickness is on the order of 12 nm or less, capable of being loaded with small molecules such as luminescent ruthenium dyes associated with dye-sensitized photovoltaic devices.
Microsupercapacitors (MSCs) are promising
energy storage devices to power miniaturized portable electronics
and microelectromechanical systems. With the increasing attention
on all-solid-state flexible supercapacitors, new strategies for high-performance
flexible MSCs are highly desired. Here, we demonstrate all-solid-state,
flexible micropseudocapacitors via direct laser patterning on crack-free,
flexible WO3/polyvinylidene fluoride (PVDF)/multiwalled
carbon nanotubes (MWCNTs) composites containing high levels of porous
hierarchically structured WO3 nanomaterials (up to 50 wt
%) and limited binder (PVDF, <25 wt %). The work leads to an areal
capacitance of 62.4 mF·cm–2 and a volumetric
capacitance of 10.4 F·cm–3, exceeding that
of graphene based flexible MSCs by a factor of 26 and 3, respectively.
As a noncarbon based flexible MSC, hierarchically nanostructured WO3 in the narrow finger electrode is essential to such enhancement
in energy density due to its pseudocapacitive property. The effects
of WO3/PVDF/MWCNTs composite composition and the dimensions
of interdigital structure on the performance of the flexible MSCs
are investigated.
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