Photonic Crystal Films Research Articles

Carbon Dot-Functionalized Colloidal Particles for Patterning and Controllable Layer-Structured Photonic Crystals Construction

The cracked morphology and iridescent properties of photonic crystal (PC) films have greatly limited their applications in the field of color pigments and optical instruments. Herein, we fabricated...

Temperature characteristics of Ge/ZnS one-dimension photonic crystal for infrared camouflage

In this paper, we investigate the temperature characteristics of Ge/ZnS one-dimension photonic crystal film for infrared camouflage, which is demonstrated low infrared emissivity at room temperature. The prepared film exhibits infrared camouflage capability with variable temperatures up to 400 °C. The infrared emissivity is 0.091 for 3–5 μm and 0.128 for 8–14 μm respectively at 400 °C. The thermal images also indicate the reduction of thermal radiation with the radiation temperature of 112.3 °C, while the real object temperature is 400 °C. This work demonstrates the infrared camouflage performance of Ge/ZnS one-dimension photonic crystal at variable temperatures. • We proposed an infrared camouflage structure for both 3–5 μm and 8–14 μm based on Ge/ZnS one-dimension photonic crystal. • The structure exhibits ideal dual-band infrared low emissivity characteristic up to 400 °C with temperature insensitivity. • The thermal radiation measurements indicate that the structure can meet the requirements of high-temperature infrared camouflage.

Bright Structural Color and High Hydrophobic Properties of Photonic Crystal Films on the Ceramic Glaze Layer via Vertical Deposition Self‐Assembly Method

AbstractIn this work, structural color films on ceramic substrate were prepared through vertical deposition self‐assembly. The morphology, optical property and hydrophobicity of the films were characterized by field‐emission scanning electron microscopy (FE‐SEM), optical photos and contact angle meter. The results show that the SiO2 colloidal crystals with ordered arrangement are successfully immersed into the ceramic glaze after sintered, and the structural color films prepared on the ceramic glaze layer show a periodically ordered structure. Compared with the structural color films on alumina substrate, further researches on the structural color films on ceramic substrate were carried out, and the hydrophobic property and stability of the structural color films on ceramic substrate are better, which is attributed to the combination of SiO2 photonic crystal and ceramic glaze. Moreover, the structural color films on the ceramic glaze layer show excellent hydrophobic performance when the sintering temperature was 600 °C.

Bioinspired bowl-array enabled angle-independent and fast responsive photonic colors for environmental sensing

Bioinspired adaptive coloring strategies advance the investigation of responsive photonic crystal (PC) colors for environmental visual sensing, but are being encumbered by inherent strong angle-dependent structural colors of their highly ordered photonic microstructures. Herein, imitating hexagonal pit array on the elytral surface of a male beetle- Chlorophila obscuripennis and utilizing optically isotropic features of the unique concave axisymmetric geometry, biomimetic micro-sized bowl-array enabled angle-independent and flexible one-dimensional PC colors are first demonstrated based on transfer printing technique which is certified as a facile, energy efficient and universal nanofabrication strategy. The photonic films assembled by functional copolymers and inorganic oxides are successfully transferred onto bowls on the surface of polydimethylsiloxane, exhibiting flexible and brilliant pixel array-like non-iridescent colors. Even after being twisted and stretched, water-washing and rubbing, the nanomaterial-based photonic films on the bowls still show glossy and stable angle-independent colors, presenting powerful strengths for practical visual sensing. In practical terms, functional copolymers based PC films on the bowls are developed as humidity and organic solvents colorimetric sensors free of angles with desirable sensitivity, remarkable durability and repeatability. And integrating photonic multilayered films with different response features, multi-mode pattern displays are realized. The remarkable sensing and display applications reflect the high values of the novel bowls enabled angle-independent photonic color building strategy.

Emerging microfluidic chips on medical application

<p indent=0mm>In recent years, with the rapid development of the social economy, new science and technology emerge endlessly. Microfluidic chips have become a research hotspot integrating biochemistry, medicine, electronics, materials and their interdisciplinary aspects because of their unique advantages such as low reagent consumption, low energy consumption, high reaction speed, high throughput, and liquid self-driving. Microfluidics is developed based on micro-electro-mechanical system (MEMS) technology, which is a kind of technology that accurately manipulates the micro-fluid in microtubules. With the continuous development of flexible materials (paper, photonic crystal film) and complex machining processes (femtosecond laser, two-photon 3D printing, <italic>etc</italic>.), microfluidic chips have moved towards a multifunctional innovation route with highly integrated technologies. Therefore, its development is changing rapidly. There are numerous review reports on microfluidic chips, but there is still a lack of reports on microfluidic chips’ latest applications, especially in the medical field. Therefore, we summarize the recent progress of medical microfluidics research comprehensively so that readers can fully understand the field. In this paper, the frontier methods of microfluidic chip preparation, detection techniques and related applications in the medical field are mainly reviewed. Besides, the main challenges and future development of microfluidic chips are summarized and prospected.

Gecko-inspired smart photonic crystal films with versatile color and brightness variation for smart windows

Many reptiles, such as Phelsuma geckos, skillfully employ both structural and pigmentary elements to generate versatile colors. Meanwhile, they can also modulate skin brightness through the dispersion and aggregation of pigment-containing cells. Inspired by this amazing biological process, the thermochromic pigments and viologen-based electrochromic materials were ingeniously integrated into colloidal photonic crystals to fabricate multi-responsive photonic crystal films for the first time. Through modulating the reflection and absorption of light, i.e., structural and pigmentary components, the as-prepared photonic crystal films could display RGB colors under different environmental temperatures and tune the color brightness in response to external electric field, mimicking the versatile color variation of geckos. The introduction of viologen resulted in a more vivid color thanks to its absorption of incoherent scattering light inside the colloidal particles aggregates. Furthermore, we employed a new strategy called shear-induced technique to assemble monodisperse microspheres into ordered nanostructure, which could produce large-sized photonic crystal films. As a demonstration, the multi-responsive photonic crystal films were used as a prototype of new generation smart windows, fusing both active (electrochromic) and passive (thermochromic) ways for light modulation, which could serve as interior mood regulator for the person in car.

Photonic Crystal Palette of Binary Block Copolymer Blends for Full Visible Structural Color Encryption

AbstractStructural color (SC) arising from a periodically ordered self‐assembled block copolymer (BCP) photonic crystal (PC) is useful for reflective‐mode sensing displays owing to its capability of stimuli‐responsive structure alteration. However, a set of PC inks, each providing a precisely addressable SC in the full visible range, has rarely been demonstrated. Here, a strategy for developing BCP PC inks with tunable structures is presented. This involves solution‐blending of two lamellar‐forming BCPs with different molecular weights. By controlling the mixing ratio of the two BCPs, a thin 1D BCP PC film is developed with alternating in‐plane lamellae whose periodicity varies linearly from ≈46 to ≈91 nm. Subsequent preferential swelling of one‐type lamellae with either solvent or non‐volatile ionic liquid causes the photonic band gap of the films to red‐shift, giving rise to full‐visible‐range SC correlated with the pristine nanostructures of the blended films in both liquid and solid states. The BCP PC palette of solution‐blended binary solutions is conveniently employed in various coating processes, allowing facile development of BCP SC on the targeted surface. Furthermore, full‐color SC paintings are realized with their transparent PC inks, facilitating low‐power pattern encryption.

Photonic Crystal Polymeric Thin-Film Dye-Lasers for Attachable Strain Sensors.

In this report, using two-dimensional photonic crystals (PhC) and a one-dimensional PhC nano-beam cavity, we realized the development of all-polymeric dye-lasers on a dye-doped, suspended poly-methylmethacrylate film with a wavelength-scale thickness. In addition to the characterization of basic lasing properties, we also evaluated its capacity to serve as an attachable strain sensor. Through experimentation, we confirmed the stable lasing performances of the dye-laser attaching on a rough surface. Moreover, we also theoretically studied the wavelength responses of the utilized PhC resonators to stretching strain and further improved them via the concept of strain shaping. The attachability and high strain sensing response of the presented thin film PhC dye-lasers demonstrate their potential as attachable strain sensors.

A set of multifunctional equipment for deposition of colloidal photonic crystal films and monolayers

It is impossible to obtain colloidal photonic crystal film of given properties without special equipment. In order to minimize the influence of external disturbing influences such devices should be automated. To obtain large-area or hetero structures it is rational to combine in one universal device equipment for the implementation of several depositional methods. In this paper the authors present two automated devices for both special and universal purposes. They can be used to obtain films and monolayers by vertical lifting of the substrate from the colloidal suspension, vertical deposition by pumping out the suspension, electrophoresis and Langmuir-Blodgett technique and its combinations.

Core/shell colloidal nanoparticles based multifunctional and robust photonic paper via drop-casting self-assembly for reversible mechanochromic and writing

Photonic crystals film that possesses periodic dielectric structure have shown great prospect in developing environmentally friendly paper alternatives due to the unique properties of dye free and non-photobleaching, but their practical application is limited by the weak interaction between colloidal particles. Although some progress has been obtained, it is still a challenge to develop photonic paper with the desired mechanical and optical properties. Herein, multifunctional hard core/soft shell nanoparticles with controlled size are fabricated by semi-continuous seed emulsion polymerization method. Compared with convention colloidal particles, these core/shell nanoparticles can facile self-assemble into large-scale dense ordered structure film via dried at room temperature due to the relatively low glass transition temperature (Tg) of the shell layers. The facile fabrication route enables the continuous high-through put production of the photonic papers. The as-formed papers not only possess the capacity to solvent (water/ethanol) rewritable and multicolor painting, but also can rapidly reversible mechanochromic. Moreover, due to the good compatibility of core/shell interface, these photonic films possess excellent mechanical properties, demonstrating that this multifunctional film makes the fabrication of novel robust rewritable papers possible and enables visual monitoring of deformation degree.

Tuning and fixing of uniform Bragg reflection color of gel-immobilized colloidal photonic crystal films

We demonstrate the facile tuning of uniform Bragg reflection color from red to blue by uniaxial compression of gel films containing single-crystalline loosely packed colloidal crystals. The tuned colors can be fixed by photopolymerization of a polymer precursor solution contained in the compressed gel films.

First- and second-order SPP-mode co-induced dual-polarized refractive-index sensor based on photonic crystal fiber and gold film

A dual-polarized photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR) was proposed for measuring the refractive indexes (RIs) of liquids. A gold film and a liquid analyte were successively wrapped around the outer surface of the PCF to stimulate the external SPR effect, which greatly reduced the manufacturing difficulties, compared to depositing the gold film and filling the inner air holes of the PCF with liquid analyte. The performance of the proposed PCF sensor was numerically investigated using the finite-element method. The results show that the proposed PCF sensor can realize dual-polarized detection in the RI range of 1.36–1.42. The x and y polarization (X-P and Y-P) core modes were coupled to the X-P second-order and Y-P first-order surface-plasmon polariton modes, respectively. As the the RI of the analyte increased, the wavelength sensitivity increased and, as a result, maximum values of 15 900 nm RIU−1 for X-P and 16 900 nm RIU−1 for Y-P were achieved. Correspondingly, we obtained a maximum amplitude sensitivity of 2026.05 RIU−1 for X-P and 2102.65 RIU−1 for Y-P. In addition, the fabrication tolerance of the proposed PCF was increased to ±0.4 μm, which made the proposed PCF a favorable candidate for the detection of liquids.

Polychrome photonic crystal stickers with thermochromic switchable colors for anti-counterfeiting and information encryption

Thermochromic photonic crystal (TCPC) has attracted wide interests for the easy change in vivid colors by external stimuli. In this article, a new type of polychromic photonic crystal film with switchable colors is fabricated by a self-designed bending-induced ordering equipment. After addition of micron-sized heat-sensitive pigment microcapsules into the photonic crystal (PC) system, the ordered and hierarchical structure of the uniform TCPC film can be formed, which is confirmed by USAXS and FESEM. The color-switchable performance after 1000-cycle testing proves its potentials for multi-level anti-fake applications. Meanwhile, the appearance of the TCPC film can quickly transform from opaque to transparent for encryption with mild heating. By using low glass transition temperature copolymer as matrix, the TCPC film can be designed as colorful tags and stickers with different shapes. The as-prepared polychrome TCPC stickers have great application potentials in anti-counterfeiting, information encryption, color display, decorations and so on. Significantly, this new preparation technique opens a powerful route to fabricate the large-sized stimuli-responsive PC films without change of the intrinsic crystal structure through adding different functional nanomaterials, which is beneficial for design of various advanced colorful smart PC devices.

Chiral Photonic Liquid Crystal Films Derived from Cellulose Nanocrystals.

As a nanoscale renewable resource derived from lignocellulosic materials, cellulose nanocrystals (CNCs) have the features of high purity, high crystallinity, high aspect ratio, high Young's modulus, and large specific surface area. The most interesting trait is that they can form the entire films with bright structural colors through the evaporation-induced self-assembly (EISA) process under certain conditions. Structural color originates from micro-nano structure of CNCs matrixes via the interaction of nanoparticles with light, rather than the absorption and reflection of light from the pigment. CNCs are the new generation of photonic liquid crystal materials of choice due to their simple and convenient preparation processes, environmentally friendly fabrication approaches, and intrinsic chiral nematic structure. Therefore, understanding the forming mechanism of CNCs in nanoarchitectonics is crucial to multiple fields of physics, chemistry, materials science, and engineering application. Herein, a timely summary of the chiral photonic liquid crystal films derived from CNCs is systematically presented. The relationship of CNC, structural color, chiral nematic structure, film performance, and applications of chiral photonic liquid crystal films is discussed. The review article also summarizes the most recent achievements in the field of CNCs-based photonic functional materials along with the faced challenges.

Large-strain and full-color change photonic crystal films used as mechanochromic strain sensors

Mechanochromic strain sensors based on photonic crystals, which can change structural color upon mechanical deformation, are promising for many applications including health monitoring and damage detection. Here, a large-strain and full-color change photonic crystal film as a mechanochromic strain sensor is reported. The mechanochromic photonic crystal (MPC) film with grating nanostructure is achieved by a fast and low-cost inverted nanoimprint lithography. The film enables bright and reversible color shift in the full visible range as it is stretched up to a large strain, which is proven in strain direction parallel and perpendicular to the grating. It is demonstrated that the MPC film can be used as a mechanochromic strain sensor able to visualize strain evolution and strain range of low carbon steel in tensile test, which brings a significant step toward visualizing strain monitoring.

Optical properties of colloidal crystals with structural colors on paper substrates using a rapid coating technology

Structural colors generated by colloidal crystals offer a promising method to create large-scale nanostructures due to their stability in comparison with dyes and pigments. However, the low durability and the low efficiency of colloidal crystals limit their practical applications. In this work, a rapid coating technology was applied in fabricating colloidal crystals on paper substrates with silicon dioxide microspheres in order to develop a fast and efficient method to produce structural colors. It was confirmed that the silicon dioxide colloidal microspheres could form a uniform photonic crystal film on papers in the end of the assembly process, and the formation mechanism of photonic crystal on papers were proposed. The optical properties of structural colors on papers were investigated and the position of photonic band gap was characterized. The results showed that the varied structural colors across the visible region confirmed by reflectance spectra could be adjusted by controlling the sizes of the microspheres and viewing angles, and this was consistent with the law of the Bragg diffraction. The CIE1976L*a*b* values of the structural colors were in agreement with their reflectance spectra. The rapid coating technology producing colloidal crystals is efficient with low cost and high adhesion, which can be used in the design and application of green printing and packaging industries.

Novel Retroreflective Structural Color Films Based on Total Internal Reflection Interference

Structural color materials have tremendous applications and been extensively investigated in the past decades. Most of them involve either nanoscale periodic photonic crystal structure or film interference mechanisms. Herein, we report a novel retroreflective structural color film (RSCF) based on a combined effect of interference and total internal reflection (TIR). The RSCF is consisted of a microscale polymer hemisphere array formed on the same polymer matrix. When exposed to white light illumination, the non-hemisphere-side of the film exhibits non-iridescent color under coaxial illumination and observation, and iridescent color under noncoaxial illumination and observation. In contrary, the hemisphere-side of the film does not show any colors regardless of coaxial or noncoaxial illumination and observation. Furthermore, an elastic polyurethane-based RSCF can exhibit dynamically and reversibly changing colors during uniaxial tensile/compressive deformation.

Features of the deposition of photonic crystal films of polystyrene and silica

The paper presents the results of research in the field of deposition technology for self-organizing colloidal films. Such structures can be used in the manufacture of controlled photonic crystal devices. Therefore, it is important to determine methods and modes of obtaining high-quality ordered periodic opal structures. We compare the methods of vertical deposition and electrophoresis and discuss the features of their application in the deposition of films formed from colloidal particles of polystyrene and silica. We have found that vertical film deposition when the substrate is pulled out of the colloidal suspension is the most technologically convenient and suitable for both materials. The electrophoresis method is more difficult to implement, but it allows you to control the deposition process in dynamics. n this article, we present the identified rational modes of obtaining photonic crystal films by both methods.

Thermo‐Adaptive Block Copolymers: Thermo‐Adaptive Block Copolymer Structural Color Electronics (Adv. Funct. Mater. 11/2021)

In article number 2008548, Seunggun Yu, Cheolmin Park, and co-workers demonstrate thermo-adaptive flexible electronic devices, based on thin self-assembled block copolymer photonic crystal films. The reversible structural color of the thermo-responsive photonic crystal film facilitates the development of a sensing display as well as diagnostic thermal patches, making it a step forward in emerging thermotronics suitable for a variety of human-interactive flexible photo-electronics.

Synthesis and properties of iridescent Ni–Co composite photonic crystal films by pulse anodization

A thin film material, composed of Ni–Co alloy and photonic crystal, is presented in this paper. It not only has good magnetic properties but also shows bright structural color. Alternating current (AC) electrodeposition is used to prepare this composite film in a porous anodic alumina photonic crystal template. It was found that with the increase of the Co content in the deposition solution, the coercivity of the Ni–Co alloy nanorods prepared at the same deposition time first decreases and then increases, the maximum coercivity value is about 1370 Oe. The XRD results show that the Co (002) diffraction peak disappears and a new Co (100) diffraction peak appears as the Co content increases. PPMS results show that the magnetic properties of the Ni–Co alloy nanorods were enhanced due to the decrease of the pore diameter of the photonic crystal template. This happened because the aspect ratio became larger, which is consistent with the uniform rotation mechanism. The results also indicate that the pore size of the photonic crystal template is proportional to the immersion time in the deposition solution. Therefore, the structural color of the composite film has a red shift with the growth of the pore widening time. With good magnetic behavior and the stable structural color, this Ni–Co composite photonic crystal film can be applied in the field of anti-counterfeiting.