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.
Reliable early-stage detection of foodborne pathogens is a global public health challenge that requires new and improved sensing strategies. Here, we demonstrate that dynamically reconfigurable fluorescent double emulsions can function as highly responsive optical sensors for the rapid detection of carbohydrates fructose, glucose, mannose, and mannan, which are involved in many biological and pathogenic phenomena. The proposed detection strategy relies on reversible reactions between boronic acid surfactants and carbohydrates at the hydrocarbon/water interface leading to a dynamic reconfiguration of the droplet morphology, which alters the angular distribution of the droplet’s fluorescent light emission. We exploit this unique chemical–morphological–optical coupling to detect Salmonella enterica , a type of bacteria with a well-known binding affinity for mannose. We further demonstrate an oriented immobilization of antibodies at the droplet interface to permit higher selectivity. Our demonstrations yield a new, inexpensive, robust, and generalizable sensing strategy that can help to facilitate the early detection of foodborne pathogens.
This report describes a straightforward and versatile approach to the fabrication of polymer films composed of microscale dome or well features that create structural color by interference from total internal reflection. The fabrication approach utilizes assembly of glass particles at monomer oil− water interfaces, providing control over the radius of curvature and contact angle of the resultant microstructures. The influence of the microscale concave interface geometry and refractive index contrast on the structural colors produced is systematically investigated, and the results are compared with those predicted by optical modeling. By dynamically changing such parameters, for example, by deforming the surfaces with mechanical force or using temperature to change refractive index, stimuli-responsive color-changing surfaces and structurally colored patterned images are demonstrated. This simple design and fabrication method to produce structurally colored surfaces may be of interest for both fundamental and applied research areas such as dynamic displays, anticounterfeiting technology, and colorimetric sensors.
Figure 4. Optical properties of direct-write colloidal crystals. Photographs of a) small-grain and b) large-grain colloidal crystal imaged under ring lighting around the objective lens. c) Schematic depicting the characterization of optical properties by illuminating the colloidal crystal with collimated light at an angle normal to the crystal and observing the projection of diffracted colors on a hemispherical screen. Photograph of colors projected from the d) smallgrain and g) large-grain colloidal crystal. Colors from the e) small-grain and h) large-grain samples linearly mapped onto azimuthal angle φ and polar angle θ. f) Plot of radiant intensity versus θ for each of the RGB channels, obtained by averaging over all values of φ. i) Plot of radiant intensity versus azimuthal angle φ derived from the blue channel of (h), ranging φ = 0°-60° averaged over the sixfold symmetry regions, at θ = 52°. The solid blue line is the radiant intensity and the shaded region represents standard deviation. The highest peak is from the largest grain, A; the second highest peak is from the second-largest grain, B; and the lowest radiant intensity, denoted by the solid black line, is an estimate of the amount of light from various other small grains, C. The dashed line represents the background illumination of the ping pong ball, measured in a noncolored region. j) Optical image of the illuminated region, with A, B, and C grain structures identified. k) SEM image analysis confirms that the largest grain A and the second-largest grain B are relatively orientated at 19.5°. www.advancedsciencenews.com
Dark-field microscopy is a standard imaging technique widely employed in biology that provides high image contrast for a broad range of unstained specimens 1. Unlike bright-field microscopy, it accentuates high spatial frequencies and can therefore be used to emphasize and resolve small features. However, the use of dark-field microscopy for reliable analysis of blood cells, bacteria, algae, and other marine organisms often requires specialized, bulky microscope systems, and expensive additional components, such as dark-field-compatible objectives or condensers 2,3. Here, we propose to simplify and downsize dark-field microscopy equipment by generating the high-angle illumination cone required for dark field microscopy directly within the sample substrate. We introduce a luminescent photonic substrate with a controlled angular emission profile and demonstrate its ability to generate high-contrast dark-field images of micrometre-sized living organisms using standard optical microscopy equipment. This new type of substrate forms the basis for miniaturized lab-on-chip dark-field imaging devices, compatible with simple and compact light microscopes.
We present a rigorous investigation of resonant coupling between microspheres based on multipole expansions. The microspheres have diameters in the range of several micrometers and can be used to realize various photonic molecule configurations. We reveal and quantify the interactions between the whispering gallery modes inside individual microspheres and the propagation modes of the entire photonic molecule structures. We show that Fano-like resonances in photonic molecules can be engineered by tuning the coupling between the resonant and radiative modes when the structures are illuminated with simple dipole radiation.
Microscale Janus emulsions represent a versatile material platform for dynamic refractive, reflective, and light-emitting optical components. Here, we present a mechanism for droplet actuation that exploits thermocapillarity. Using optically induced thermal gradients, an interfacial tension differential is generated across the surfactant-free internal capillary interface of Janus droplets. The interfacial tension differential causes droplet-internal Marangoni flows and a net torque, resulting in a predictable and controllable reorientation of the droplets. The effect can be quantitatively described with a simple model that balances gravitational and thermal torques. Occurring in small thermal gradients, these optothermally induced Marangoni dynamics represent a promising mechanism for controlling droplet-based micro-optical components.
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