Micro-scale optical components play a crucial role in imaging and display technology, biosensing, beam shaping, optical switching, wavefront-analysis, and device miniaturization. Herein, we demonstrate liquid compound micro-lenses with dynamically tunable focal lengths. We employ bi-phase emulsion droplets fabricated from immiscible hydrocarbon and fluorocarbon liquids to form responsive micro-lenses that can be reconfigured to focus or scatter light, form real or virtual images, and display variable focal lengths. Experimental demonstrations of dynamic refractive control are complemented by theoretical analysis and wave-optical modelling. Additionally, we provide evidence of the micro-lenses' functionality for two potential applications—integral micro-scale imaging devices and light field display technology—thereby demonstrating both the fundamental characteristics and the promising opportunities for fluid-based dynamic refractive micro-scale compound lenses.

Three‐dimensional ordered porous materials known as inverse opal films (IOFs) were synthesized using nanocrystals with precisely defined morphologies. Comprehensive theoretical and experimental studies of the volume fraction ratio and electrostatic interactions between nanocrystals and polystyrene templating particles enabled the formation of highly ordered crack‐free photonic structures. The synthetic strategy was first demonstrated using titanium dioxide (TiO2) nanocrystals of different shapes and then generalized to assemble nanocrystals of other functional materials, such as indium tin oxide and zinc‐doped ferrite. Tunable photocatalytic activity of the TiO2 IOFs, modulated through the choice of the shape of TiO2 nanocrystals in conjunction with selecting desired macroscopic features of the IOF, was further explored. In particular, enhanced activity is observed for crack‐free, highly ordered IOFs whose photonic properties can improve light absorption via the slow light effect. This study opens new opportunities in designing multi‐length‐scale porous nanoarchitectures having enhanced performance in a variety of applications.

Easy-to-use sensors for ethanol solutions have broad applications ranging from monitoring alcohol quality to combating underage drinking. Although there are a number of electronic and colorimetric sensors available for determining alcohol concentration, there is currently no device that can concurrently provide a prompt, well-defined, quickly recoverable readout and remain readily affordable. Here, we developed a field-ready, colorimetric indicator that provides fast, clear identification of ethanol/water mixtures between 0 to 40% based on the discoloration of a wetted photonic crystal. We cooperatively exploit the iridescence and the geometrical gating in silica inverse opal films (IOF), together with a finetuned surface chemistry gradient, to distinguish ethanol concentrations by their wettability patterns in different segments of the IOF. The resultant all-in-one colorimetric sensor delivers a striking and instantaneous optical response at ethanol concentration as low as 5%. We further improve the ease of use by seamlessly integrating this colorimetric platform with drinking glassware (a glass stirrer and a vial). This research provides an optimal means for colorimetric ethanol detection and is a step towards the immersible sensing of diverse molecules (e.g. biomarkers) in aqueous solutions without expensive laboratory tests.

homogenized milks (Dufour and Riaublanc, 1997). MIR with an ATR cell was successfully applied to the determination of polyethylene glycol during in-vitro digestion of bread (Belleville et al., 1995) and to the study of conformational changes of ␤-lactoglobulin under pH and ethanol effects (Dufour et al., 1994).We formed films using the wet spinning process that is used in the food sector to make textured products. The spinning process has the advantage of being operated in a continuous mode and is applicable on an industrial scale. Using this technique, Dumont (1997, 1998) evaluated the effects of plasticizers such as polyols and urea on mechanical properties of films and their chemical composition. They also studied the effects of washing and tanning. The addition of plasticizers enhanced mechanical characteristics. Washing eliminated the plasticizers and made films brittle. More resistant films were obtained by tanning the proteins with formaldehyde, well known as a cross-linking agent.The spinning process was historically applied to the production of textile fibers and several studies have been reported on the molecular structure of such fibers. It was long been known that X-ray diffraction and mechanical measurements are in agreement with a uniform alignment of the protein chains in the direction of the fiber axis. The orientation is induced by a stretching of the fibers at the spinneret exit. The orientation developed along the spinning path is mainly the result of competition between the orienting effect of the velocity field and the disorienting effect of Brownian motions (Ziabicki,1967). The structure of silk fibers has been investigated using Raman spectroscopy (Magoshi et al., 1985). At extension rates of 100-450 mm/min, the fibroin molecules are oriented in the direction of extension and present a random coil conformation. By increasing the extension rates over 500 mm/min, the secondary structure of the protein mostly becomes organized in ␤ sheet form. The oriented model observed in the case of textile fibers has been thereafter considered for edible fibers made of plant proteins (Hartman, 1978;Culioli et al., 1996). No evidence has confirmed the hypothesis concerning a structural arrangement of the molecules in edible fibers.Our objective was to clarify whether the spinning process induces an organization of the proteins in films. Changes in the secondary and tertiary structures of proteins during film processing, as well as the network orientation of films, were investigated by spectroscopic and rheological methods.

Conspectus Inverse opals (IOs) are highly interconnected three-dimensional macroporous structures with applications in a variety of disciplines from optics to catalysis. For instance, when the pore size is on the scale of the wavelength of visible light, IOs exhibit structural color due to diffraction and interference of light rather than due to absorption by pigments, making these structures valuable as nonfading paints and colorants. When IO pores are in an ordered arrangement, the IO is a 3D photonic crystal, a structure with a plethora of interesting optical properties that can be used in a multitude of applications, from sensors to lasers. IOs also have interesting fluidic properties that arise from the re-entrant geometry of the pores, making them excellent candidates for colorimetric sensors based on fluid surface tension. Metal oxide IOs, in particular, can also be photo- and thermally catalytically active due to the catalytic activity of the background matrix material or of functional nanoparticles embedded within the structure. Evaporation-induced self-assembly of sacrificial particles has been developed as a scalable method for forming IOs. The pore size and shape, surface chemistry, matrix material, and the macroscopic shape of the IO, as well as the inclusion of functional components, can be designed through the choice of deposition conditions such as temperature and humidity, types and concentrations of components in the self-assembly mixture, and the postassembly processing. These parameters allow researchers to tune the optical, mechanical, and thermal transport properties of IOs for optimum functionality. In this Account , we focus on experimental and theoretical studies to understand the self-assembly process and properties of metal oxide IOs without (bare) and with (hybrid) plasmonic or catalytic metal nanoparticles incorporated. Several synthetic approaches are first presented, together with a discussion of the various forces involved in the assembly process. The visualization of the deposition front with time-lapse microscopy is then discussed together with analytical theory and numerical simulations to determine the conditions needed for the deposition of a continuous IO film. Subsequently, we present high-resolution scanning electron microscopy (SEM) of assembled colloids over large areas, which provides a detailed view of the evolution of the assembly process, showing that the organization of the colloids is initially dictated by the meniscus of the evaporating suspension on the substrate, but that gradually all grains rotate to occupy the thermodynamically most favorable orientation. High-resolution 3D transmission electron microscopy (TEM) is then presented together with analysis of the wetting of the templating colloids by the matrix precursor to provide a detailed picture of the embedding of metallic nanoparticles at the pore–matrix interface. Finally, the resulting properties and applications in optics, wetting, and cata...

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A non‐invasive, at‐home test for neonatal jaundice can facilitate early jaundice detection in infants, improving clinical outcomes for neonates with severe jaundice and helping to prevent the development of kernicterus, a type of brain damage whose symptoms include hearing loss, impairment of cognitive capacity, and death. Here a photonic sensor that utilizes color changes induced by analyte infiltration into a chemically functionalized inverse opal structure is developed. The sensor is calibrated to detect differences in urinary surface tension due to increased bile salt concentration in urine, which is symptomatic of abnormal liver function and linked to jaundice. The correlation between neonatal urinary surface tension and excess serum bilirubin, the physiologic cause of neonatal jaundice, is explored. It is shown that these non‐invasive sensors can improve the preliminary diagnosis of neonatal jaundice, reducing the number of invasive blood tests and hospital visits necessary for healthy infants while ensuring that jaundiced infants are treated in a timely manner. The use of inverse opal sensors to measure bulk property changes in bodily fluids can be extended to the detection of several other conditions, making this technology a versatile platform for convenient point‐of‐care diagnosis.

International audienceWe show here that coherent dual-polarization multi-band OFDM (DP-MB-OFDM) is a good candidate for long-haul WDM transmission and sub-wavelength optical switching. We demonstrate that optical add-drop of OFDM sub-bands as narrow as 8 GHz inside a 100 Gbps DP-MB-OFDM signal constituted of four sub-bands spaced by 12 GHz is feasible in the middle of a 10x100-km DCF-free G.652 fibre line