Trapping Structural Coloration by a Bioinspired Gyroid Microstructure in Solid State

In theory, gyroid photonic crystals in butterfly wings exhibit advanced optical properties as a result of their highly interconnected microstructures. Because of the difficulties in synthesizing artificial gyroid materials having periodicity corresponding to visible wavelengths, human-made visible gyroid photonic crystals are still unachievable by self-assembly. In this study, we develop a physical approachtrapping of structural coloration (TOSC)through which the visible structural coloration of an expanded gyroid lattice in a solvated state can be preserved in the solid state, thereby allowing the fabrication of visible-wavelength gyroid photonic crystals. Through control over the diffusivity and diffusive distance for solvent evaporation, the single-molecular-weight gyroid block copolymer photonic crystal can exhibit desired structural coloration in the solid state without the need to introduce any additives, namely, evapochromism. Also, greatly enhanced reflectivity is observed arising from the formation of porous gyroid nanochannels, similar to those in butterfly wings. As a result, TOSC facilitates the fabrication of the human-made solid gyroid photonic crystal featuring tunable and switchable structural coloration without the synthesis to alter the molecular weight. It appears to be applicable in the fields of optical communication, energy, light-emission, sensors, and displays

Trapping Structural Coloration by a Bioinspired Gyroid Microstructure in Solid State

In theory, gyroid photonic crystals in butterfly wings exhibit advanced optical properties as a result of their highly interconnected microstructures. Because of the difficulties in synthesizing artificial gyroid materials having periodicity corresponding to visible wavelengths, human-made visible gyroid photonic crystals are still unachievable by self-assembly. In this study, we develop a physical approachtrapping of structural coloration (TOSC)through which the visible structural coloration of an expanded gyroid lattice in a solvated state can be preserved in the solid state, thereby allowing the fabrication of visible-wavelength gyroid photonic crystals. Through control over the diffusivity and diffusive distance for solvent evaporation, the single-molecular-weight gyroid block copolymer photonic crystal can exhibit desired structural coloration in the solid state without the need to introduce any additives, namely, evapochromism. Also, greatly enhanced reflectivity is observed arising from the formation of porous gyroid nanochannels, similar to those in butterfly wings. As a result, TOSC facilitates the fabrication of the human-made solid gyroid photonic crystal featuring tunable and switchable structural coloration without the synthesis to alter the molecular weight. It appears to be applicable in the fields of optical communication, energy, light-emission, sensors, and displays

Trapping Structural Coloration by a Bioinspired Gyroid Microstructure in Solid State

In theory, gyroid photonic crystals in butterfly wings exhibit advanced optical properties as a result of their highly interconnected microstructures. Because of the difficulties in synthesizing artificial gyroid materials having periodicity corresponding to visible wavelengths, human-made visible gyroid photonic crystals are still unachievable by self-assembly. In this study, we develop a physical approachtrapping of structural coloration (TOSC)through which the visible structural coloration of an expanded gyroid lattice in a solvated state can be preserved in the solid state, thereby allowing the fabrication of visible-wavelength gyroid photonic crystals. Through control over the diffusivity and diffusive distance for solvent evaporation, the single-molecular-weight gyroid block copolymer photonic crystal can exhibit desired structural coloration in the solid state without the need to introduce any additives, namely, evapochromism. Also, greatly enhanced reflectivity is observed arising from the formation of porous gyroid nanochannels, similar to those in butterfly wings. As a result, TOSC facilitates the fabrication of the human-made solid gyroid photonic crystal featuring tunable and switchable structural coloration without the synthesis to alter the molecular weight. It appears to be applicable in the fields of optical communication, energy, light-emission, sensors, and displays

Isoelectric Focusing in a Silica Nanofluidic Channel: Effects of Electromigration and Electroosmosis

Isoelectric focusing of proteins in a silica nanofluidic channel filled with citric acid and disodium phosphate buffers is investigated via numerical simulation. Ions in the channel migrate in response to (i) the electric field acting on their charge and (ii) the bulk electroosmotic flow (which is directed toward the cathode). Proteins are focused near the low pH (anode) end when the electromigration effect is more significant and closer to the high pH (cathode) end when the electroosmotic effect dominates. We simulate the focusing behavior of Dylight labeled streptavidin (Dyl-Strep) proteins in the channel, using a relationship between the protein’s charge and pH measured in a previous experiment. Protein focusing results compare well to previous experimental measurements. The effect of some key parameters, such as applied voltage, isoelectric point (pI), bulk pH, and bulk conductivity, on the protein trapping behavior in a nanofluidic channel is examined

Stationary Chemical Gradients for Concentration Gradient-Based Separation and Focusing in Nanofluidic Channels

Previous work has demonstrated the simultaneous concentration and separation of proteins via a stable ion concentration gradient established within a nanochannel (Inglis Angew. Chem., Int. Ed. 2001, 50, 7546−7550). To gain a better understanding of how this novel technique works, we here examine experimentally and numerically how the underlying electric potential controlled ion concentration gradients can be formed and controlled. Four nanochannel geometries are considered. Measured fluorescence profiles, a direct indicator of ion concentrations within the Tris–fluorescein buffer solution, closely match depth-averaged fluorescence profiles calculated from the simulations. The simulations include multiple reacting species within the fluid bulk and surface wall charge regulation whereby the deprotonation of silica-bound silanol groups is governed by the local pH. The three-dimensional system is simulated in two dimensions by averaging the governing equations across the (varying) nanochannel width, allowing accurate numerical results to be generated for the computationally challenging high aspect ratio nanochannel geometries. An electrokinetic circuit analysis is incorporated to directly relate the potential drop across the (simulated) nanochannel to that applied across the experimental chip device (which includes serially connected microchannels). The merit of the thick double layer, potential-controlled concentration gradient as a particle focusing and separation tool is discussed, linking this work to the previously presented protein trapping experiments. We explain why stable traps are formed when the flow is in the opposite direction to the concentration gradient, allowing particle separation near the low concentration end of the nanochannel. We predict that tapered, rather than straight nanochannels are better at separating particles of different electrophoretic mobilities

High-Efficiency Broadband Meta-Hologram with Polarization-Controlled Dual Images

Holograms, the optical devices to reconstruct predesigned images, show many applications in our daily life. However, applications of hologram are still limited by the constituent materials and therefore their working range is trapped at a particular electromagnetic region. In recent years, the metasurfaces, an array of subwavelength antenna with varying sizes, show the abilities to manipulate the phase of incident electromagnetic wave from visible to microwave frequencies. Here, we present a reflective-type and high-efficiency meta-hologram fabricated by metasurface for visible wavelength. Using gold cross nanoantennas as building blocks to construct our meta-hologram devices with thickness ∼ λ/4, the reconstructed images of meta-hologram show polarization-controlled dual images with high contrast, functioning for both coherent and incoherent light sources within a broad spectral range and under a wide range of incidence angles. The flexibility demonstrated here for our meta-hologram paves the road to a wide range of applications related to holographic images at arbitrary electromagnetic wave region

High-Efficiency Broadband Meta-Hologram with Polarization-Controlled Dual Images

Holograms, the optical devices to reconstruct predesigned images, show many applications in our daily life. However, applications of hologram are still limited by the constituent materials and therefore their working range is trapped at a particular electromagnetic region. In recent years, the metasurfaces, an array of subwavelength antenna with varying sizes, show the abilities to manipulate the phase of incident electromagnetic wave from visible to microwave frequencies. Here, we present a reflective-type and high-efficiency meta-hologram fabricated by metasurface for visible wavelength. Using gold cross nanoantennas as building blocks to construct our meta-hologram devices with thickness ∼ λ/4, the reconstructed images of meta-hologram show polarization-controlled dual images with high contrast, functioning for both coherent and incoherent light sources within a broad spectral range and under a wide range of incidence angles. The flexibility demonstrated here for our meta-hologram paves the road to a wide range of applications related to holographic images at arbitrary electromagnetic wave region