Polymer Lens Research Articles

Focusing Acoustic Beams with a Ball-Shaped Lens beyond the Diffraction Limit

The authors explore the concept of ``acoustic jets'' for the superfocusing of sound waves. Compared to conventional diffraction-limited systems, 50% better spatial resolution of ultrasound images can be achieved using a ball-shaped polymer lens. Excellent agreement is found between the experimental data and both analytical and numerical predictions. Potential applications extend beyond medical ultrasound to nondestructive testing, acoustic microscopy and sensing, microparticle manipulation, and sonar.

Modelling of Surface Roughness in Ultra-High Precision Turning of an RGP Contact Lens Polymer

Contact lens manufacture requires high accuracy and surface integrity. Surface roughness an important response because it has direct influence toward the part performance and the production cost. Hence, choosing optimal cutting parameters will not only improve the quality measure but also the productivity. This research work is therefore aimed at developing a predictive surface roughness model and investigate a finish cutting conditions of ONSI-56 contact lens polymer with a monocrystalline diamond cutting tool. In this work, a novel surface roughness prediction model, in which the feed rate, cutting speed and depth of cut are considered is developed. This combined process was successfully modeled using a Box–Behnken design (BBD) with response surface methodology (RSM). The effects of feed rate, cutting speed and depth of cut were investigated. Analysis of variance (ANOVA) showed that the proposed quadratic model effectively interpreted the experimental data with coefficients of determination of R2 = 0.89 and adjusted R2 = 0.84. The worse surface value was obtained at high feedrate and low spindle speed.

Automatized Control of Polymer Optical Parts

The manufacturing of polymer optical parts is a technologically complicated process because of a high precision of optical surfaces. Every responsible part has to be checked for homogeneity due to its high effect on optical properties. Thus, the creation of an area for automatized part control after injection molding is a pertinent goal. The study has applied the concept “Industry 4.0” to create a model of automatized area for polymer lens control. A photoelasticity control method for photosensitive materials was chosen.

Nanoparticle Modified Drug Loaded Biodegradable Polymeric Contact Lenses for Sustainable Ocular Drug Delivery.

Glaucoma, a chronic eye condition caused by progressive degeneration of retinal ganglion cells may result in permanent blindness. The restricted efficiency of currently available glaucoma treatments has awakened a global need for designing a novel anti-glaucoma drug delivery mechanism that targets the drug to the site of action in a sustained manner with less toxicity and side effects. With reference to this global problem in the present study, we have fabricated a biodegradable transparent polymeric material loaded with minimum amount of anti-glaucoma drug, acetazolamide. The drug was modified using a suitable nanocarrier for its sustained drug release. The efficient modification of nanocarrier encapsulated drug as well as the drug loaded polymeric film was studied using various characterization techniques such as UV-visible spectrophotometry, spectroflurimetry, polarizing optical microscope, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), X-ray diffraction (XRD), thermogravimetric analysis and differential scanning calorimetry (TGA/DSC). The characterization techniques indicated efficient transformation of the crystalline drug in to amorphous during nanocarrier encapsulation. The in-vitro drug release study in simulated tear fluid (STF) showed prolonged release of the drug from the nano drug complex for 3 h with the complete degradation of the polymer matrix within 5 min. The fabricated biomaterial showed excellent potential to be developed in to a drug loaded contact lens for sustained glaucoma drug delivery with benefits of low drug content and fewer drug induced side effects.

Simple and low-cost polymer lens fabrication using a pressure-driven micro chamber.

In this paper, a low-cost lens fabrication method using a micro chamber produced by a three-dimensional (3-D) printer is presented. The shape of polydimethylsiloxane (PDMS) membrane was controlled by adjusting the pressure inside the chamber. On top of the shaped membrane, an ultraviolet-curable resin was poured. Depending on the pressure inside the chamber and the shape of the chamber lid, three types of lenses could be made: a bi-convex lens, a plano-convex lens, and a concave lens. This method can reduce the cost of making pilot or evaluation devices in healthcare service.

Simple Nanodroplet Templating of Functional Surfaces with Tailored Wettability and Microstructures

Recently, solvent exchange has been demonstrated as a simple solution-based approach for the controlled formation of surface nanodroplets over large areas. The as-formed surface nanodroplets provide new opportunities for a wide range of droplet-based applications. Herein, it is demonstrated that surface nanodroplets can be used as versatile structural templates for the fabrication of functional surfaces with tailored wettability and morphology. Guided by the microstructural and wetting properties of desert beetle's back and cactus spine, two types of functional surfaces have been prepared. The first biomimetic surface of desert beetle's back, with hydrophilic lumps on a hydrophobic background, was obtained by independent selective surface modification of polymerized surface nanodroplets and the background surface. The second surface, with anisotropic wetting microstructures, was fabricated by controlled deposition of droplets on the rim of polymer lenses. The results showed systematic improvement of wettability and efficiency of water collection by using the as-prepared biomimetic surfaces, compared with substrates without the designed microstructures. This work demonstrates surface nanodroplets as a new type of template in the design and preparation of functional surfaces with controlled wettability and morphology.

Low-power focused-laser-assisted remote ignition of nanoenergetic materials and application to a disposable membrane actuator

Ignition of nanoenergetic materials (nEMs) has great potential for various portable and disposable actuator applications due to the unique ability to release pressure in a controllable manner. The development of highly efficient low-power igniters is very important in this context. Here we present a focused-laser-assisted nEMs igniter that can be remotely operated at low power with a portable laser pointer. The proposed optical igniter is monolithically integrated with a polymeric lens and prepared by a very simple, fast, and reproducible single-step soft-lithographic replication process using polydimethylsiloxane (PDMS). The polymeric lens plays a crucial role in greatly enhancing the laser power density on a target area by efficiently concentrating the incident laser beam, generating thermal energy enough to ignite nEMs. A pressure-driven membrane actuator is fabricated by integrating a thin PDMS membrane to the nEMs-coated optical igniter, and the actuation behavior is characterized in response to pressure released by nEMs ignition with different numbers of nEMs coats. Finally, the pressure-driven membrane actuator is demonstrated in an alarm switch to trigger stable operation of an electric buzzer with a blinking light-emitting diode as a potential application.

Rapid fabrication of various molds for replication of polymer lens arrays

This article proposes a rapid fabrication method for the production of various molds for the replication of polymer lens arrays. The method involves ultrasonic vibration embossing with a polymer substrate and small steel ball array. Only one embossing step is required in which a concave lens array pattern is directly fabricated onto the polymer substrate. The total processing cycle time is less than 20 s. The polymer substrate with a concave lens array pattern can then be used as a mold for the replication of a polymer lens array through a polydimethylsiloxane casting process. In addition, the diameter and depth of the concave lens array pattern on the surface of the polymer substrate can be changed and controlled by adjusting the processing conditions of the ultrasonic vibration embossing process. Hence, various molds with different concave lens array patterns and thus polymer lens arrays, can be effectively fabricated at very low cost and with high throughput. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

Optically isotropic microlens arrays using nanoencapsulated liquid crystals

ABSTRACTWe propose an optically isotropic switchable microlens array (MLA) based on nanoencapsulated liquid crystals (LCs). In its initial state, the encapsulated LC layer has an refractive index intermediate to that of the LC and capsule shell polymer even if the LC molecules' structure has any alignment, because the nanocapsules are much smaller than the wavelengths of the incident visible light. Applying a voltage causes the LC molecules to align vertically within the LC capsules, changing their refractive index from that of the initial state. The MLA can be designed to have switching characteristics by means of index matching between the encapsulated LC layer and the polymer lens structure. The proposed switchable MLA shows high light efficiency and true optical isotropy.

Endowing a plain fluidic chip with micro-optics: a holographic microscope slide

Lab-on-a-Chip (LoC) devices are extremely promising in that they enable diagnostic functions at the point-of-care. Within this scope, an important goal is to design imaging schemes that can be used out of the laboratory. In this paper, we introduce and test a pocket holographic slide that allows digital holography microscopy to be performed without an interferometer setup. Instead, a commercial off-the-shelf plastic chip is engineered and functionalized with this aim. The microfluidic chip is endowed with micro-optics, that is, a diffraction grating and polymeric lenses, to build an interferometer directly on the chip, avoiding the need for a reference arm and external bulky optical components. Thanks to the single-beam scheme, the system is completely integrated and robust against vibrations, sharing the useful features of any common path interferometer. Hence, it becomes possible to bring holographic functionalities out of the lab, moving complexity from the external optical apparatus to the chip itself. Label-free imaging and quantitative phase contrast mapping of live samples are demonstrated, along with flexible refocusing capabilities. Thus, a liquid volume can be analyzed in one single shot with no need for mechanical scanning systems.

폴리머 안경렌즈의 반사방지 코팅효과 연구

폴리머 안경렌즈를 제조할 때 가시광선 영역에서 투과되는 빛을 증가시키고, 안경렌즈 표면에 형성되는 허상을 방지하는 반사방지 기능은 매우 중요하다. 본 연구에서는 굴절률 1.56, 1.60 및 1.67을 갖는 안경렌즈를 폴리머 렌즈 모노머 및 이염화 이부틸 주석 촉매제, 알킬 인산 에스터 이형제 등의 혼합물을 인젝션 몰드 방법으로 열중합 공정을 적용하여 제조하였다. 폴리머 안경렌즈 표면에서의 반사방지 효과를 조사하기 위하여 다층 박막 반사방지 코팅 구조(양면 또는 단면 코팅), 3층 박막의 Gaussian gradient-index profile 불연속 근사 반사방지 코팅 구조, 3층 박막의 quarter-wavelength 근사 반사방지코팅 구조 등 다양한 반사방지 코팅 구조를 설계하였고, E-beam 증착 시스템을 이용하여 열중합공정으로 제조된 폴리머 안경렌즈에 각각 코팅하였다. 폴리머 안경렌즈의 광학적 특성은 UV-visible spectrometer로 분석하였다. 반사방지 코팅 층을 구성하는 박막의 굴절률, 표면 거칠기 등의 소재 특성은 Ellipsometer와 원자힘 현미경(AFM)으로 분석하였다. 분석결과, 굴절률 1.56의 낮은 굴절률을 갖는 폴리머 안경렌즈에서 가장 효과적인 반사방지 코팅 구조는 다층 박막 반사방지 코팅 구조의 양면코팅이었다. 하지만 굴절률 1.67의 고굴절률 안경렌즈에 대해서는 3층 박막의 Gaussian gradient-index profile 불연속 근사반사방지 코팅 구조의 양면 코팅도 다층박막 반사방지 코팅구조의 양면코팅에 상응하는 반사방지 효과를 나타내었다. Reducing optical reflection in the visible light range, in order to increase the share of transmitted light and avoid the formation of ghost images in imaging, is important for polymer lens applications. In this study, polymer lenses with refractive indices of n=1.56, 1.60, and 1.67 were fabricated by the injection-molding method with a polymer lens monomer, dibutyltin dichloride as the catalyst and an alkyl phosphoric ester as the release agent. To investigate their anti-reflection (AR) effects, various AR coating structures, viz. a multi-layer AR coating structure, tri-layer AR coating structure with a discrete approximation Gaussian gradient-index profile, and tri-layer AR coating structure with a quarter-wavelength approximation, were designed and coated on the polymer lens by an E-beam evaporation system. The optical properties of the polymer lenses were characterized by UV-visible spectrometry. The material properties of the thin films, refractive index and surface roughness, were analyzed by ellipsometry and AFM, respectively. The most effective AR coating structure of the polymer lens with low refractive index, n=1.56, was the both side coating of multi-layer AR coating structure. However, both side coating of the tri-layered discrete approximation Gaussian gradient-index profile AR coating structure gave comparable results to the both side coating of the multi-layer AR coating structure for the polymer lens with a high refractive index of n=1.67.

Correlation between Experimental and Simulated Shape Deformation of a Bio-inspired Tunable Polymer Lens

Correlation between Experimental and Simulated Shape Deformation of a Bio-inspired Tunable Polymer Lens

Compact and high-power dye-sensitized solar system integrated with low-cost solar-concentrating polymer lens

A dye-sensitized solar cell (DSSC) is integrated monolithically with a polymer lens to demonstrate a compact, low-cost and high-power solar energy harvesting system. The proposed polymer lens is composed of a plano-convex lens for concentrating light and a supporting layer for controlling the distance between the lens and DSSC according to its thickness. A single-step polymer replication process with a glass-based lens mold makes it possible to fabricate the polymer lens in a simple and reproducible manner. The power conversion performance of the polymer lens-integrated dye-sensitized (PLD) solar system is optimized by simply controlling the height of the supporting layer. The maximum output power of DSSC is improved by ~50.2% after monolithically integrating with the polymer lens with a 3-mm-thick supporting layer. Finally, the PLD solar system is packaged with a self-cleanable polymer film to protect the lens from the environment and to make the system robust to contamination. Through a simple self-cleaning test, it is found that the PLD system can recover ~95.2% of its original output power.

Large-Area Sub-Wavelength Optical Patterning via Long-Range Ordered Polymer Lens Array.

Fabrication of large-area, highly orderly, and high-resolution nanostructures in a cost-effective fashion prompts advances in nanotechnology. Herein, for the first time, we demonstrate a unique strategy to prepare a long-range highly regular polymer lens from photoresist nanotrenches based templates, which are obtained from underexposure. The relationship between exposure dose and the cross-sectional morphology of produced photoresist nanostructures is revealed for the first time. The polymer lens arrays are repeatedly used for rapid generation of sub-100 nm nanopatterns across centimeter-scale areas. The light focusing properties of the nanoscale polymer lens are investigated by both simulation and experiment. It is found that the geometry, size of the lens, and the exposure dose can be deployed to adjust the produced feature size, spacing, and shapes. Because the polymer lenses are derived from top-down photolithography, the nearly perfect long-range periodicity of produced nanopatterns is ensured, and the feature shapes can be flexibly designed. Because this nanolithographic strategy enables subwavelength periodical nanopatterns with controllable feature size, geometry, and composition in a cost-effective manner, it can be optimized as a viable and potent nanofabrication tool for various technological applications.

Simulation of imperfections in plastic lenses – transferring local refractive index changes into surface shape modifications

Abstract Injection molded plastic lenses have continuously improved their performance regarding optical quality and nowadays are as usual as glass lenses in image forming devices. However, during the manufacturing process unavoidable fluctuations in material density occur, resulting in local changes in the distribution of refractive index, which degrade the imaging properties of the polymer lens. Such material density fluctuations correlate to phase delays, which opens a path for their mapping. However, it is difficult to transfer the measured variations in refractive index into conventional optical simulation tool. Thus, we propose a method to convert the local variations in refractive index into local changes of one surface of the lens, which can then be described as a free-form surface, easy to introduce in conventional simulation tools. The proposed method was tested on a commercial gradient index (GRIN) lens for a set of six different object positions, using the MTF sagittal and tangential cuts to compare the differences between the real lens and a lens with homogenous refractive index, and the last surface converted into a free-form shape containing the internal refractive index changes. The same procedure was used to reproduce the local refractive index changes of an injected plastic lens with local index changes measured using an in-house built polariscopic arrangement, showing the capability of the method to provide successful results.

Quantitative characterization of X-ray lenses from two fabrication techniques with grating interferometry.

Refractive X-ray lenses are in use at a large number of synchrotron experiments. Several materials and fabrication techniques are available for their production, each having their own strengths and drawbacks. We present a grating interferometer for the quantitative analysis of single refractive X-ray lenses and employ it for the study of a beryllium point focus lens and a polymer line focus lens, highlighting the differences in the outcome of the fabrication methods. The residuals of a line fit to the phase gradient are used to quantify local lens defects, while shape aberrations are quantified by the decomposition of the retrieved wavefront phase profile into either Zernike or Legendre polynomials, depending on the focus and aperture shape. While the polymer lens shows better material homogeneity, the beryllium lens shows higher shape accuracy.

Fabrication of polymer lenses and microlens array for lab-on-a-chip devices

Microlenses and microlens arrays are assuming an increasingly important role in optical devices and communication systems. In response to their extended use in different fields of technology, a great emphasis is being placed on research into simple manufacturing approaches for these micro-optical components as well as on the characterization of their performance. This paper provides an overview of the recent emerging technologies for the fabrication of polymer microlenses by electrical, mechanical, chemical, and pyro-electrical methods. Attention is mainly focused on polymer molding and self-assembling for microlens arrays, while ink-jet printing is proposed for on-demand printing of lenses with high resolution. Among all the emerging techniques proposed, the pyro-electrodynamic approach has recently achieved great interest as an easy multiscale approach for the fabrication of polymer microlens arrays through a flexible process driven by electrohydrodynamic pressure. As each processing method has distinct advantages and limitations, the most significant characteristic parameters and the measurements of these parameters are discussed for each method.

Zoom optical system using tunable polymer lens

This paper demonstrated a zoom optical system with variable magnification based on the tunable polymer lens. The designed system mainly consists of two polymer lenses, voice coil motors, a doublet lens and CMOS chip. The zoom magnification can be adjusted by altering the focal length of the two elastic polymer lenses synergistically through controlling the output displacement of the voice coil motor. A static doublet lens in combination with the polymer lenses stabilize the image plane at the CMOS chip. The optical structure of the zoom system is presented, as well as a detailed description including the lens materials and fabrication process. Images with each zoom magnification are captured, and the Spot diagram and MTF are simulated using Zemax software. A change in magnification from 0.13×to 8.44×is demonstrated within the tiny 0.4 mm variation of the displacement load, and produce a 16.1×full range of magnification experimentally. Simulation analyses show that all the radii of the spot diagram under different magnifications are less than 11.3 um, and the modulation transfer function reaches 107 line pairs per mm. The designed optical system shows the potential for developing stable, integrated, and low-cost zoom systems with large magnification range.

Fabrication and Analyses of Bionic Polymer Lens System

In this paper, we design and fabricate a bionic solid tunable lens which is mainly made of polymer materials. The lens focal length can be changed flexibly by pressing the lens surface to alter the curvature radius. A detailed description of the lens structure, materials and fabrication process is presented. The lens mechanical properties and deformation process are simulated and analyzed using Ansys software. A precise experimental device based on a stepping motor is fabricated to measure and analyze the relationship between the displacement load and focal length. The lens focal length can be reversibly changed from 31.8 to 14.1 mm under 1 mm variation of displacement load. This paper offers a feasible way for the design, fabrication, and actuation of the solid tunable lens, which can be used in various machine vision apparatus.

Nonlinear absorption measurements of intraocular lens polymers by integrating Z-scan

An ultrashort pulsed laser processing knowledge of the amount and distribution of the absorbed energy in the workpiece is essential. For transparent dielectrics, energy input by ultrashort laser pulses occurs by nonlinear absorption in the bulk material. Even at high intensities, the penetration depth is high and for most cases decays with an unknown function. Additionally, nonlinear absorptivity dramatically changes depending on the number of incident pulses due to incubation of the workpiece. This is usually attributed to chemical modifications or generated voids inside the workpiece. Particularly, polymers are strongly influenced by incubation preventing full understanding of ablation at industrial processes. Especially, the Polymethylmethacrylate (PMMA) copolymer analyzed in this paper is of high interest for ophthalmic applications and requires high processing quality and efficiency. To gain detailed insight into interaction of polymers with multiple subsequent picosecond laser pulses, investigations on nonlinear absorptivity have to be carried out. Therefore, the determination of nonlinear transmittance and reflectance by a modified Z-scan setup is presented. Laser pulses at 1064 nm wavelength, which are commonly used for production, are applied with pulse energies up to 130 μJ. Measuring the absorptivity depending on the pulse number is enabled by integrating spheres included in the setup. Up to 100 lasers pulses which are scattered by the rough surface, caused by ablation of previous pulses, are taken into account by collecting the scattered proportion by the spheres. A significant change of transmittance and reflectance is observed depending on the pulse energy and pulse number. The influence of incubation on nonlinear absorption is quantified by fitting the recorded data to the models known from literature. The analytical model of three-photon absorption shows best agreement and is considered as the dominant absorption process. The corresponding nonlinear absorption coefficients are quantified in dependence of the pulse number showing significant increase for the first six pulses.