Chemically Responsive Elastomers Exhibiting Unity-Order Refractive Index Modulation

Crowding for Confinement: Reversible Isomerization of First-Generation Donor-Acceptor Stenhouse Adduct Derivatives in Water Modulated by Thermoresponsive Dendritic Macromolecules

Mimicking nature, the reversible isomerization of hydrophobic dyes in aqueous solutions is appealing for bio-applications. Here, we report on the reversible isomerization of first-generation solvatochromic donor-acceptor Stenhouse adducts (DASAs) in water within dendritic matrices, realized either through the dendronization of DASAs or the incorporation of DASA pendants into dendronized copolymers. These dendritic macromolecules contain three-fold dendritic oligoethylene glycols (OEGs), which afford the macromolecules water-solubility and unprecedented thermoresponsive behavior. The thermoresponsive behavior of both dendronized DASAs and dendronized copolymers is dominated by the peripherals of dendritic OEGs. However, the hydrophilicity of the acceptor from DASA moieties also play a role in mediating their thermal phase transitions, and more importantly, tailor the hydrophobic interactions between dendritic OEGs and DASA moieties. Intriguingly, dendritic topologies contribute confinement to encapsulate the DASA moieties through crowding effects, and cooperative interactions from the crowded dendritic OEGs modulate the DASA moieties with different isomerization in aqueous media. The thermally induced collapse of dendritic OEGs, accompanied by the aggregation of dendritic macromolecules, leads to the formation of hydrophobic domains, which exert enhanced crowding effects to efficiently encapsulate the DASA moieties. Compared to the low molar mass of dendronized DASAs, thermally collapsed dendronized copolymers can efficiently retard the hydration of DASA pendants through cooperation between neighboring dendritic OEGs and afford the DASA pendants with better confined microenvironments to mediate their isomerization recovery by up to 90% from a cyclic charged (hydrophilic) state into a noncharged (hydrophobic) linear state in water. This dendritic confinement exhibits excellent fatigue resistance after several cycles of alternating photo-irradiation and thermal annealing at elevated temperatures.

Facile Access to High Solid Content Monodispersed Microspheres via Dual-Component Surfactants Regulation toward High-Performance Colloidal Photonic Crystals

Monodispersed microspheres play a major role in optical science and engineering, providing ideal building blocks for structural color materials. However, the method toward high solid content (HSC) monodispersed microspheres has remained a key hurdle. Herein, a facile access to harvest monodispersed microspheres based on the emulsion polymerization mechanism is demonstrated, where anionic and nonionic surfactants are employed to achieve the electrostatic and steric dual-stabilization balance in a synergistic manner. Monodispersed poly(styrene-butyl acrylate-methacrylic acid) colloidal latex with 55 wt% HSC is achieved, which shows an enhanced self-assembly efficiency of 280% compared with the low solid content (10 wt%) latex. In addition, Ag-coated colloidal photonic crystal (Ag@CPC) coating with near-zero refractive index is achieved, presenting the characteristics of metamaterials. And an 11-fold photoluminescence emission enhancement of CdSe@ZnS quantum dots is realized by the Ag@CPC metamaterial coating. Taking advantage of high assembly efficiency, easily large-scale film-forming of the 55 wt% HSC microspheres latex, robust Ag@CPC metamaterial coatings could be easily produced for passive cooling. The coating demonstrates excellent thermal insulation performance with theoretical cooling power of 30.4 W m-2, providing practical significance for scalable CPC architecture coatings in passive cooling.

Refractive index adjustable intraocular lens design to achieve diopter control for improving the treatment of ametropia after cataract surgery

Intraocular lens (IOL) implantation is currently the most effective clinical treatment for cataracts. Nevertheless, due to the growth of the eye axis in patients with congenital cataracts during the process of growth and development, the progressive incapacity of an IOL with a fixed focus does not meet the demands of practical usage, leading to the occurrence of ametropia. This work describes an innovative class of an IOL bulk material that offers good biosafety and light-controlled refractive index adjustment. Acrylate materials were synthesized for the preparation of IOLs by free radical polymerization of ethylene glycol phenyl ether methacrylate (EGPEMA), hydrophilic monomer 2-(2-ethoxyethoxy) ethyl acrylate (EA), and functional monomer hydroxymethyl coumarin methacrylate (CMA). Under 365/254 nm ultraviolet (UV) irradiation, the coumarin group could adjust the polymer material's refractive index through reversible photoinduced dimerization/depolymerization. Meanwhile, the potential for the IOL use is enabled by its satisfactory biosafety. Such a light-induced diopter adjustable IOL will be more appropriate for implantation during cataract surgery since it will not require the correction needed for ametropia and will offer more accurate and humane treatment. STATEMENT OF SIGNIFICANCE.

Wearable and interactive multicolored photochromic fiber display

Endowing flexible and adaptable fiber devices with light-emitting capabilities has the potential to revolutionize the current design philosophy of intelligent, wearable interactive devices. However, significant challenges remain in developing fiber devices when it comes to achieving uniform and customizable light effects while utilizing lightweight hardware. Here, we introduce a mass-produced, wearable, and interactive photochromic fiber that provides uniform multicolored light control. We designed independent waveguides inside the fiber to maintain total internal reflection of light as it traverses the fiber. The impact of excessive light leakage on the overall illuminance can be reduced by utilizing the saturable absorption effect of fluorescent materials to ensure light emission uniformity along the transmission direction. In addition, we coupled various fluorescent composite materials inside the fiber to achieve artificially controllable spectral radiation of multiple color systems in a single fiber. We prepared fibers on mass-produced kilometer-long using the thermal drawing method. The fibers can be directly integrated into daily wearable devices or clothing in various patterns and combined with other signal input components to control and display patterns as needed. This work provides a new perspective and inspiration to the existing field of fiber display interaction, paving the way for future human-machine integration.

Tailored diffractions of asymmetric columns and symmetric rows in two-dimensional multi-element phase gratings

Two-dimensional multi-element phase gratings can be engineered to show an even symmetry along one direction while an odd symmetry along the other direction in terms of offset refractive indices in each unit cell. The interplay of such even and odd symmetries has been explored to tailor diffraction columns and rows on demand by making offset refractive indices to satisfy specific requirements and hence attain different types of destructive interference. The resultant tailoring effects include the directional column elimination, the grouped column elimination, and the directional column selection as well as the natural row absence, the grouped row elimination, and the central row selection.

Photosensitive Nanodiscs Composed of Human Photoreceptors for Refractive Index Modulation at Selective Wavelengths

A photoreceptor on the retina acts as an optical waveguide to transfer an individual photonic signal to the cell inside, which is determined by the refractive index of internal materials. Under the photoactivation of photoreceptors making conformational and chemical variation in a visual cell, the optical signal modulation is demonstrated using an artificial photoreceptor-based waveguide with a controlling beam refraction. Two types of nanodiscs are made of human photoreceptor proteins, short-wavelength-sensitive opsin and rhodopsin, with spectral sensitivity. The refractive index and nonlinear features of those two photosensitive nanodiscs are investigated as fundamental properties. The photonanodiscs are photoactivated in such a way that allow refractive index tuning over 0.18 according to the biological function of the respective proteins with color-dependent response.

Aggregation-Induced Emission Luminogens with Photoresponsive Behaviors for Biomedical Applications

Fluorescent biomedical materials can visualize subcellular structures and therapy processes in vivo. The aggregation-induced emission (AIE) phenomenon helps suppress the quenching effect in the aggregated state suffered by conventional fluorescent materials, thereby contributing to design strategies for fluorescent biomedical materials. Photoresponsive biomedical materials have attracted attention because of the inherent advantages of light; i.e., remote control, high spatial and temporal resolution, and environmentally friendly characteristics, and their combination with AIE facilitates development of fluorescent molecules with efficient photochemical reactions upon light irradiation. In this review, organic compounds with AIE features for biomedical applications and design strategies for photoresponsive AIE luminogens (AIEgens) are first summarized briefly. Applications are then reviewed, with the employment of photoresponsive and AIE-active molecules for photoactivation imaging, super-resolution imaging, light-induced drug delivery, photodynamic therapy with photochromic behavior, and bacterial targeting and killing being discussed at length. Finally, the future outlook for AIEgens is considered with the aim of stimulating innovative work for further development of this field.

Tunable metamaterial filter for optical communication in the terahertz frequency range

We present a design of a tunable terahertz (THz) filter (TTF) used in an indoor communication system. The unit cell of TTF is composed of ring-shaped and cross-shaped nanostructures. By utilizing the micro-electro-mechanical system (MEMS) technique to modify the height between the ring-shaped and cross-shaped nanostructures in the incident transverse electric (TE) mode, the resonant frequencies can be tuned from 0.530 THz to 0.760 THz, which covers an atmospheric window from 0.625 THz to 0.725 THz for indoor wireless optical communication applications. This design of TTF provides an effective approach to select and filter specific signals. It makes the data processing more flexible at the transmission end of the communication system. Furthermore, such a TTF design can be realized the commercialization of communication system components due to its integrated circuit (IC) process compatibility, miniaturization and high flexibility.

2D hybrid networks of gold nanoparticles: mechanoresponsive optical humidity sensors

Plasmonic coupling is a fascinating phenomenon occurring between neighboring metal nanostructures. We report a straightforward approach to study such process macroscopically by fabricating 2D networks of gold nanoparticles, interconnected with responsive hygroscopic organic linkers. By controlling the humidity we tune the interparticle distance to reversibly trigger plasmonic coupling collectively over several millimeters.