Liquid crystalline‐based actuators containing azobenzene photoswitches have been used to demonstrate light‐responsive motion in soft actuator systems. Understanding the mechanical performance of ...these light‐responsive actuators as a function of the polymer chemistry as well as the nature and concentration of the photoswitches is crucial for developing advanced applications. A systematic study is presented here that clarifies the role of azobenzene photoswitches and the liquid crystalline networks in generating the desired photomechanical performance. Through measurement of photo stimulated mechanical behavior, in particular generated force and strain, a generalized set of guidelines concerning the appropriate subset of polymer chemistry and photoswitches required to achieve the desired performance for actuator design is derived.
Light‐responsive motion has been demonstrated in soft actuator systems using liquid crystalline‐based actuators with azobenzene photoswitches. Understanding the mechanical performance of these light‐responsive actuators as a function of polymer chemistry and the concentration of photoswitches is critical for developing advanced applications. A systematic study that clarifies the role of azobenzene photoswitches and liquid crystalline networks in achieving the desired photomechanical performance is presented here.
We present a detailed investigation of the effect of lens size on the focusing performance of plasmonic lenses based on metallic nanoslit arrays with variable widths. The performance parameters ...considered include the focal length, depth of focus (DOF), full-width half-maximum (FWHM) and the maximum intensity of the focal point. 2D FDTD simulation was utilized. The results show that all the lens parameters are greatly affected by the lens size. A larger lens size, with a total phase difference of at least 2π, will produce a better focusing behavior and a closer agreement with the design. The Fresnel number and diffraction theory can be used to explain the effect of lens size. Suggestions are provided for realization of a practical plasmonic lens using the existing nanofabrication techniques.
Whispering gallery resonators made out of lithium niobate allow for optical parametric oscillation and frequency comb generation employing the outstanding second-order nonlinear-optical properties of ...this material. An important knob to tune and control these processes is, e.g., the linear electro-optic effect, the Pockels effect via externally applied electric fields. Due to the shape of the resonators a precise prediction of the electric field strength that affects the optical mode is non-trivial. Here, we study the average strength of the electric field in z-direction in the region of the optical mode for different configurations and geometries of lithium niobate whispering gallery resonators with the help of the finite element method. We find that in some configurations almost 100% is present in the cavity compared to the ideal case of a cylindrical resonator. Even in the case of a few-mode resonator with a very thin rim we find a strength of 90%. Our results give useful design considerations for future arrangements that may benefit from the strong electro-optic effect in bulk whispering gallery resonators made out of lithium niobate.
The design of a novel anamorphic optofluidic imaging system based on a pair of liquid lenses whose toroidal surfaces create different optical powers in the symmetry-axes is presented. Using ...electrowetting-ondieletrics for actuation, a cylindrical fluidic system is actuated by 32 azimuthally-distributed electrodes allowing the definition of non-rotationally-symmetric surface shapes. We present the design and simulation of this optical system and show that an anamorphic ratio of 1.43 at a maximum field of view of 6:82° is attainable.
Presenting state-of-the-art research into the dynamic field of tunable micro-optics, this is the first book to provide a comprehensive survey covering a varied range of topics including novel ...materials, actuation concepts and new imaging systems in optics. Internationally renowned researchers present a diverse range of chapters on cutting-edge materials, devices and subsystems, including soft matter, artificial muscles, tunable lenses and apertures, photonic crystals, and complete tunable imagers. Special contributions also provide in-depth treatment of micro-optical characterisation, scanners, and the use of natural eye models as inspiration for new concepts in advanced optics. With applications extending from medical diagnosis to fibre telecommunications, Tunable Micro-optics equips readers with a solid understanding of the broader technical context through its interdisciplinary approach to the realisation of new types of optical systems. This is an essential resource for engineers in industry and academia, and advanced students working on optical systems design.
Tunable multi-chamber microfluidic membrane microlenses with achromaticity over a given focal length range are demonstrated. In analogy to a fixed-focus achromatic doublet lens, the multi-lens system ...is based on a stack of microfluidic cavities filled with optically optimized liquids with precisely defined refractive index and Abbe number, and these are independently pneumatically actuated. The membranes separating the cavities form the refractive optical surfaces, and the curvatures as a function of pressure are calculated using a mechanical model for deformation of flexible plates. The results are combined with optical ray tracing simulations of the multi-lens system to yield chromatic aberration behavior, which is verified experimentally. A focal length tuning range of 5-40 mm and reduction in chromatic aberration of over 30% is demonstrated, limited by the availability of optical fluids.
We describe a microelectromechanical systems-based actuator for three-dimensional (3D) positioning of a polymer microlens implemented using silicon-on-glass technology. The actuator combines comb ...drives for lateral tracking with electrostatic parallel plates for out-of-plane focusing as well as tilting of a polymer microlens, yielding fully 3D actuation. The complete actuator is fabricated using wafer bonding of silicon and pyrex wafers; the lens is integrated using polymer dispensing techniques. The 3 DOF positioning of the lens for focusing, tracking, and tilting are experimentally characterized, furthermore, the layout and symmetry would allow 4 DOF movement, demonstrating how this actuation system combined with an integrated lens may be particularly useful for new generations of optical pickups.
For the development and routine characterization of optical devices used in medicine, tissue-equivalent phantoms mimicking a broad spectrum of human skin properties are indispensable.
Our work aims ...to develop a tissue-equivalent phantom suitable for photoplethysmography applications. The phantom includes the optical and mechanical properties of the three uppermost human skin layers (dermis, epidermis, and hypodermis, each containing different types of blood vessels) plus the ability to mimic pulsation.
While the mechanical properties of the polydimethylsiloxane base material are adjusted by different mixing ratios of a base and curing agent, the optical properties are tuned by adding titanium dioxide particles, India ink, and synthetic melanin in different concentrations. The layered structure of the phantom is realized using a doctor blade technique, and blood vessels are fabricated using molding wires of different diameters. The tissue-mimicking phantom is then integrated into an artificial circulatory system employing piezo-actuated double diaphragm pumps for testing.
The optical and mechanical properties of human skin were successfully replicated. The diameter of the artificial blood vessels is linearly dependent on pump actuation, and the time-dependent expansion profile of real pulse forms were mimicked.
A tissue equivalent phantom suitable for the
testing of opto-medical devices was demonstrated.
Simulation of light interaction with seedless grapes Jenne, Sophie; Zappe, Hans
Journal of the Science of Food and Agriculture/Journal of the science of food and agriculture,
15 January 2023, Volume:
103, Issue:
1
Journal Article
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