Thin-film color reflectors inspired by Morpho butterflies are fabricated. Using a combination of directional deposition, silica microspheres with a wide size distribution, and a PDMS (polydimethylsiloxane) encasing, a large, flexible reflector is created that actually provides better angle-independent color characteristics than Morpho butterflies and which can even be bent and folded freely without losing its Morpho-mimetic photonic properties.
Microencapsulation and controlled release have long been studied because of the high demand for practical delivery systems in the pharmaceutics and cosmetics fields. Multiphase emulsion drops have provided efficient templates for microcapsules, and various feasible methods have been developed for controlled release.[1] However, the emulsion-based approach has limitations for the in situ control of membrane permeability. Micro-origami has emerged as one of the most promising alternative approaches for producing tunable microcapsules with the potential to be applied, for example as drug carriers, [2] actuators, [3] microcontainers, [4] and microrobots.[5] Inspired by living organisms in nature such as the ice plant [6] and Venus flytrap, [7] two different micro-origami approaches have been employed to make various microstructures.[8] One approach uses solid patches connected by active hinge materials. Typical examples use various metalmetal, [9] metal-polymer, [10] and polymer-polymer [4] combinations. The patch and hinge system has enabled the capture, release, and gripping [11] of target materials, showing the feasibility of micro-origami structures. However, the microcapsule is limited to polyhedral shapes in this approach, and complete sealing of the gaps between patches requires exquisite control of the folding angles. Moreover, the delicate and complex fabrication processes make practical applications difficult. The second approach uses a bilayer structure composed of two different materials. For example, a metalpolymer bilayer can show bending/unbending when the polymeric active layer suffers significant volume change, but the metal layer remains unchanged. [12,13] Polymer materials have been employed in both layers to make biocompatible microcapsules. [14,15] However, complete sealing of the gaps in the bilayer contact regions remains an important, yet unmet, need. In addition, a simple and effective method for the fabrication of practical microcapsules has not yet been developed, and remains highly desirable. This is the main thrust of the present study.Herein, we report the use of biocompatible bilayer structures for the fabrication of tunable microcapsules based on micro-origami. Monodisperse bilayer microstructures were prepared using a facile photolithographic procedure, without employing photomask alignment. In addition, highly flexible hydrogels were selected as both active and passive layers, facilitating tight contact between patches. The bilayer structure therefore enabled in situ encapsulation, through a reversible transformation to microcapsules with a closed compartment. The resultant microcapsules showed negligible leakage of encapsulants and triggered release of the encapsulants could be achieved simply by inducing the unfolding of the hydrogel bilayer.The essential strategy of our approach relies on the anisotropic volume change of a hydrogel bilayer. As shown in Scheme 1 a, the active hydrogel layer shows significant volume expansion under external stimuli by swelling, whereas the passive h...
An electrically tunable photonic crystal is developed utilizing crystalline colloidal arrays of high refractive index particles. Through modulation of the refractive index of the particle, and the applied electric field, both the bandwidth and position of the photonic bandgap could be tuned. Full color modulation with high optical quality is achieved, which paves a way to develop a novel reflective display.
Superhydrophobic nanofiber films were created from electrospun nanofibers with undulated surfaces at multiple scales in micrometers and nanometers. The electrospun nanofibers were produced out of aqueous solutions which contained water-soluble polymers and different colloids: monodisperse silica or polystyrene microspheres for larger particles and monodisperse silica nanoparticles for smaller particles. Various types of fibrous films were produced depending on the properties of the dispersing medium, the effects of additives, and the compositions of the bidisperse colloids. When polystyrene microspheres were used as sacrificial templates, macropores were left behind in the nanofibers during the removal of polystyrene microspheres by calcination. The nonwoven films of electrospun nanofibers, which were decorated with silica microspheres or macropores, could be continuously produced with considerable ease under a relatively wide range of operating conditions. The surface properties of the films were characterized by contact angle measurement and an X-ray photoelectron spectrometer. Through the surface modification of the electrospun nanofibers with fluorinated silane coupling agents, superhydrophobic surfaces with low sliding angles were successfully prepared.
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