Dynamic Color-Switching of Hydrogel Micropillar Array under Ethanol Vapor for Optical Encryption.

Responsive structural colors from artificially engineered micro/nanostructures are critical to the development of anti-counterfeiting, optical encryption, and intelligent display. Herein, the responsive structural color of hydrogel micropillar array is demonstrated under the external stimulus of ethanol vapor. Micropillar arrays with full color are fabricated via femtosecond laser direct writing by controlling the height and diameter of the micropillars according to the FDTD simulation. Color-switching of the micropillar arrays is achieved in <1 s due to the formation of liquid film among micropillars. More importantly, the structural color blueshift of the micropillar arrays is sensitive to the micropillar diameter, instead of the micropillar height. The micropillar array with a diameter of 772 nm takes 400 ms to complete blueshift under ethanol vapor, while that with a diameter of 522 nm blueshifts at 2400 ms. Microscale patterns are realized by employing the size-dependent color-switching of designed micropillar arrays under ethanol vapor. Moreover, Morse code and directional blueshift of structural colors are realized in the micropillar arrays. The advantages of controllable color-switching of the hydrogel micropillar array would be prospective in the areas of optical encryption, dynamic display, and anti-counterfeiting.

Tunable Thermochromic Graphene Metamaterials with Iridescent Color.

Thermochromic materials have been widely applied in energy-efficient buildings, aerospace, textiles, and sensors. Conventional thermochromic materials rely on material phase or structure changes upon thermal stimuli, which only enable a few colors, greatly limiting their applicability. Here, we propose and demonstrate the concept of dynamically tunable thermochromic graphene metamaterials (TGMs), which can achieve continuous color tunability (380-800 nm) with fast (<100 ms) response times. The TGMs are composed of an ultrathin graphene oxide (GO) film on a flexible metal substrate. We demonstrated that external thermal energy can dynamically adjust the water contents in the GO film to manipulate the color of TGMs. An impressive thermochromic sensitivity of 1.11 nm/°C covering a large percentage of the color space has been achieved. Prototype applications for a cup and smartphone have been demonstrated. The reversible TGMs promise great potential for practical applications of temperature sensing in optoelectronic devices, environmental monitoring, and dynamic color modulation.

Scalable Hydrogel-Based Nanocavities for Switchable Meta-Holography with Dynamic Color Printing.

Devices used for meta-optics display are currently undergoing a revolutionary transition from static to dynamic. Despite various tuning strategy demonstrations such as mechanical, electrical, optical, and thermal tunings, a longstanding challenge for their practical application has been the achievement of a conveniently accessible real-life tuning scheme for realizing versatile functionality dynamics outside the laboratory. In this study, we demonstrate a practical tuning strategy to realize a dynamic color printing with a switchable meta-holography exhibition based on hydrogel-based nanocavities. On the basis of the inflation sensitivity of a hydrogel to humidity alteration, its transmissive color was notably tuned from 450 to 750 nm. More intriguingly, by controlling the sample dry/immersed states in real time, we successfully enabled dual-channel switchable meta-holography. With the advantages of facile architecture, daily stimulus with large-area modulation, and high chromaticity, our proposed hydrogel-based nanocavities provide a promising path toward tunable display/encryption, optical sensors, and next-generation display technology.

Rapid Color-Switching of MnO2 Hollow-Nanosphere Films in Dynamic Water Vapor for Reversible Optical Encryption.

Drop-casting manganese oxide (MnO2 ) hollow nanospheres synthesized via a simple surface-initiated redox route produces thin films exhibiting angle-independent structural colors. The colors can rapidly change in response to high-humidity dynamic water vapor (relative humidity > 90%) with excellent reversibility. When the film is triggered by dynamic water vapor with a relative humidity of ≈100%, the color changes with an optimal wavelength redshift of ≈60 nm at ≈600 ms while there is no shift under static water vapor. The unique selective response originates from the nanoscale porosity formed in the shells by randomly stacked MnO2 nanosheets, which enhances the capillary condensation of dynamic water vapor and promotes the change of their effective refractive index for rapid color switching. The repeated color-switching tests over 100 times confirm the durability and reversibility of the MnO2 film. The potential of these films for applications in anti-counterfeiting and information encryption is further demonstrated by reversible encoding and decoding initiated exclusively by exposure to human breath.

Dynamic Color Displays Using Stepwise Cavity Resonators.

High-resolution multicolor printing based on pixelated optical nanostructures is of great importance for promoting advances in color display science. So far, most of the work in this field has been focused on achieving static colors, limiting many potential applications. This inevitably calls for the development of dynamic color displays with advanced and innovative functionalities. In this Letter, we demonstrate a novel dynamic color printing scheme using magnesium-based pixelated Fabry-Pérot cavities by gray scale nanolithography. With controlled hydrogenation and dehydrogenation, magnesium undergoes unique metal and dielectric transitions, enabling distinct blank and color states from the pixelated Fabry-Pérot resonators. Following such a scheme, we first demonstrate dynamic Ishihara plates, in which the encrypted images can only be read out using hydrogen as information decoding key. We also demonstrate a new type of dynamic color generation, which enables fascinating transformations between black/white printing and color printing with fine tonal tuning. Our work will find wide-ranging applications in full-color printing and displays, colorimetric sensing, information encryption and anticounterfeiting.

Two-Dimensional Active Tuning of an Aluminum Plasmonic Array for Full-Spectrum Response.

Color pixels composed of plasmonic nanostructures provide a highly promising approach for new display technologies, capable of vivid, robust coloration and incorporating the use of low-cost plasmonic materials, such as aluminum. Here we report a plasmonic device that can be tuned continuously across the entire visible spectrum, based on integrating a square array of aluminum nanostructures into an elastomeric substrate. By stretching the substrate in either of its two dimensions, the period and therefore the scattering color can be modified to the blue or the red of the at-rest structure, spanning the entire visible spectrum. The unique two-dimensional design of this structure enables active mechanical color tuning, under gentle elastic modulation with no more than 35% strain. We also demonstrate active image switching with this structure. This design strategy has the potential to open the door for next-generation flexible photonic devices for a wide variety of visible-light applications.

Structures, Organization, and Function of Reflectin Proteins in Dynamically Tunable Reflective Cells.

The reversible assembly of reflectin proteins drives dynamic iridescence in cephalopods. Squid dynamically tune the intensity and colors of iridescence generated by constructive interference from intracellular Bragg reflectors in specialized skin cells called iridocytes. Analysis of the tissue specificity of reflectin subtypes reveals that tunability is correlated with the presence of one specific reflectin sequence. Differential phosphorylation and dephosphorylation of the reflectins in response to activation by acetylcholine, as well as differences in their tissue-specific and subcellular spatial distributions, further support the suggestion of different roles for the different reflectin subtypes.

pH-Responsive, Wide Color Gamut Dynamic Color Display Enabled by PDMAEMA Brush-Based Fabry-Perot Resonant Cavity.

Dynamic color-changing materials have attracted broad interest due to their widespread applications in visual sensing, dynamic color display, anticounterfeiting, and image encryption/decryption. In this work, we demonstrate a novel pH-responsive dynamic color-changing material based on a metal-insulator-metal (MIM) Fabry-Perot (FP) cavity with a pH-responsive poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) brush layer as the responsive insulating layer. The pH-responsive PDMAEMA brush undergoes protonation at a low pH value (pH < 6), which induces different swelling degrees in response to pH and thus refractive index and thickness change of the insulator layer of the MIM FP cavity. This leads to significant optical property changes in transmission and a distinguishable color change spanning the whole visible region by adjusting the pH value of the external environment. Due to the reversible conformational change of the PDMAEMA and the formation of covalent bonds between the PDMAEMA molecular chain and the Ag substrate, the MIM FP cavity exhibits stable performance and good reproducibility. This pH-responsive MIM FP cavity establishes a new way to modulate transmission color in the full visible region and exhibits a broad prospect of applications in dynamic color display, real-time environment monitoring, and information encryption and decryption.

Dynamic Color Display with Viewing-Angle Tolerance Based on the Responsive Asymmetric Fabry-Perot Cavity.

At present, it remains challenging and desirable to prepare dynamic color-changing materials with wide viewing angles for practical applications. Herein, we proposed a responsive asymmetric metal-insulator-metal (MIM) Fabry-Perot resonance cavity to achieve dynamic color display with high viewing-angle tolerance. The responsive asymmetric MIM cavity is constructed with thermal-responsive poly(N-isopropyl acrylamide) (PNIPAm) brush as the mid-insulator layer sandwiched by two different metallic layers (Sn and Ag). The as-prepared MIM cavity shows both improved viewing-angle tolerance owing to the asymmetric architecture of the cavity and a wide tunable color gamut because of the thermal responsiveness of the mid PNIPAm layer. Remarkably, the as-prepared asymmetric MIM resonance cavity also possesses a relatively fast response rate and good repeatability. Together, with all these advantages, the proposed responsive asymmetric MIM cavity may open a new pathway to prepare high-performance color display material for future practical optical applications.

Tunable Color-Variable Solar Absorber Based on Phase Change Material Sb2Se3.

In this paper, a dynamic color-variable solar absorber is designed based on the phase change material Sb2Se3. High absorption is maintained under both amorphous Sb2Se3 (aSb2Se3) and crystalline Sb2Se3 (cSb2Se3). Before and after the phase transition leading to the peak change, the structure shows a clear color contrast. Due to peak displacement, the color change is also evident for different crystalline fractions during the phase transition. Different incident angles irradiate the structure, which can also cause the structure to show rich color variations. The structure is insensitive to the polarization angle because of the high symmetry. At the same time, different geometric parameters enable different color displays, so the structure can have good application prospects.

Graphene Metapixels for Dynamically Switchable Structural Color.

Structural coloration providing vibrant and tailored colors enables broad applications. Existing strategies of structural coloration either use resonances or diffraction induced by arrayed nanostructures with element sizes at a wavelength scale or are based on interference from vacuum-deposited large-area thin films. It is extremely challenging to achieve full color pixels with diffraction-limited resolution without sophisticated multiple-step nanostructure fabrication or externally applied field control. Realization of dynamically switchable full color displays with diffraction-limited resolution is even harder. This work demonstrates a structural color strategy with developed anisotropic graphene metapixels. The anisotropic optical property is given by the intrinsic birefringence of the layered structure of graphene metamaterials, and each metapixel is spatially encoded by direct laser printing with diffraction-limited resolution (250 nm). The colors can be dynamically and instantly switched by controlling the scattering of the light source to excite different modes based on the strong anisotropic optical properties of the graphene metapixels. The low-cost large-scale fabrication method allows experimental demonstration of a large-area (4 in.) flexible full color optical switchable display. Such a simple, effective and flexible method promises broad practical applications in color display and color image sensing related fields.

Healthcare Professional Perceptions of Blood Glucose Meter Features That Support Achievement of Self-Management Goals Recommended by Clinical Practice Guidelines.

BACKGROUND: Blood glucose meters remain an effective tool for blood glucose monitoring (BGM) but not all meters provide the same level of insight beyond the numerical glucose result. OBJECTIVE: To investigate healthcare professional (HCP) perceptions of four meters and how these meters support the achievement of self-management goals recommended by diabetes clinical practice guidelines. METHODS: Three hundred and fifty-three HCPs from five countries reviewed the features and benefits of four meters using interactive webpages and then responded to statements about the utility of each meter and ranked each meter in terms of clinical value. RESULTS: Meter D ranked significantly higher in terms of clinical utility for all 13 guideline questions (70%-84%, P < .05) compared to other meters. Endocrinologists (69%-85%), primary care physicians (PCP; 63%-80%), and diabetes nurses (DN; 80%-89%) consistently ranked meter D highest for all guideline questions. DNs ranked selected questions significantly higher compared to PCPs (8 of 13) or endocrinologists (3 of 13; P < .05). Meter D achieved strong endorsement from HCPs in France and Germany, followed by the United States and Canada, with comparatively lower responses from Italian HCPs (P < 0.05). With respect to self-management, 80% of HCPs selected meter D as their first choice for patients with type 1 diabetes to help patients improve diabetes management or understand their numbers to help them stay in range. CONCLUSIONS: HCPs had strong preference for a meter providing additional insights, messages, and guidance direct to the patient to support achievement of self-management goals recommended by diabetes clinical practice guidelines.

Patients With Diabetes Using a New Glucose Meter With Blood Sugar Mentor and Dynamic Color Range Indicator Features Show Improved Interpretation and Willingness to Act on Blood Glucose Results (ASCEND Study).

BACKGROUND: We examined whether dynamic color range indicator (DCRI) and blood sugar mentor (BSM) features in a new blood glucose meter could improve interpretation of results and encourage patient action. METHODS: One hundred and thirty three people with type 2 (T2D) (n = 73) or type 1 diabetes (T1D) (n = 60) evaluated information first without and then with DCRI or BSM guidance using interactive exercises. RESULTS: Subjects improved their ability to categorize results into low, in range, or high glycemic ranges by 29% (T2D) and 22% (T1D) (each P < .001). There was significantly greater willingness to act on high and low results shown with DCRI or BSM screens. Subjects also expressed a high degree of satisfaction with these features. CONCLUSIONS: Use of DCRI and BSM in this meter may help patients improve their diabetes management decisions.

Dynamic Tunable Color Display Based on Metal-Insulator-Metal Resonator with Polymer Brush Insulator Layer as Signal Transducer.

Dynamic color-changing nanomaterials have been widely investigated for applications in fields like optical sensors, wearable activity monitors, smart electronic devices, and anticounterfeiting materials due to the excellent ability to change their optical properties with external variation. Here, a simple metal-insulator-metal (MIM) trilayer Fabry-Perot resonance cavity with a poly(N-isopropylacrylamide) (PNIPAm) brush layer as a responsive element is reported as a thermal-induced colorimetric response platform. The dynamic changes of conformation and physical properties of PNIPAm brush layer in response to external signals give rise to a significant color change of the MIM Fabry-Perot resonance cavity. This MIM Fabry-Perot resonance cavity shows the advantages of dynamic color change, rapid response, good repeatability, and simple construction. Additionally, the as-prepared MIM cavity shows great potential in various applications such as color printing, multicolor indicator, and information anticounterfeiting.

Calibrated measurement of acuity, color and stereopsis on a Nintendo® 3DS™ game console.

Significance: A Nintendo® 3DS™ game can reliably test monocular near acuity, stereopsis and color without the need for occlusion patches or goggles. Purpose: We developed dynamic, forced-multiple choice games to measure monocular near acuity, color vision and stereopsis on the autostereoscopic barrier screen of the Nintendo 3DS gaming system. Methods: In an institutional review board-approved study, pediatric and adult patients and normal subjects performed routine patched near visual acuity, Ishahara's color test and Stereo Fly tests. Then each subject performed a two-phase orientation and testing game, "PDI Check", on a Nintendo 3DS. Results: Forty-five patients aged 5-60 years completed the routine and Nintendo near tests, resulting in positive, consistent, discriminatory correlation functions. From ROC curves, referral criteria were determined to separate poor from fair-to-normal monocular acuity with 98% sensitivity and 100% specificity, stereoacuity with 80% sensitivity and 97% specificity, and color with 83% sensitivity and 100% specificity. Conclusion: The Nintendo 3DS game PDI Check can provide consistent near vision testing via a dynamic, randomized method that does not require goggles for stereo, and does not require patching to assure monocular testing.

Lead Halide Perovskite Nanostructures for Dynamic Color Display.

Nanoprint-based color display using either extrinsic structural colors or intrinsic emission colors is a rapidly emerging research field for high-density information storage. Nevertheless, advanced applications, e. g., dynamic full-color display and secure information encryption, call for demanding requirements on in situ color change, nonvacuum operation, prompt response, and favorable reusability. By transplanting the concept of electrical/chemical doping in the semiconductor industry, we demonstrate an in situ reversible color nanoprinting paradigm via photon doping, triggered by the interplay of structural colors and photon emission of lead halide perovskite gratings. It solves the aforementioned challenges at one go. By controlling the pumping light, the synergy between interlaced mechanisms enables color tuning over a large range with a transition time on the nanosecond scale in a nonvacuum environment. Our design presents a promising realization of in situ dynamic color nanoprinting and will empower the advances in structural color and classified nanoprinting.

Scanning Plasmonic Color Display.

Control over plasmonic colors on the nanoscale is of great interest for high-resolution display, imaging, and information encryption applications. However, so far, very limited schemes have been attempted for dynamic plasmonic color generation. In this paper, we demonstrate a scanning plasmonic color generation scheme, in which subwavelength plasmonic pixels can be laterally switched on/off through directional hydrogenation/dehydrogenation of a magnesium screen. We show several dynamic plasmonic color displays with different scanning functions by varying the number and geometries of the palladium gates, where hydrogen enters the scanning screens. In particular, we employ the scanning effects to create a dynamic plasmonic quick response code. The information cannot be decrypted by varying the polarization states of light or by accessing the physical features. Rather, it can only be read out using hydrogen as a decoding key. Our work advances the established design concepts for plasmonic color printing and provides insights into the development of optical information storage and anticounterfeiting features.