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Special Issue on Microlenses

by Hongrui Jiang

Micromachines 2014, 5(4), 1342-1343; https://doi.org/10.3390/mi5041342 - 8 Dec 2014

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Abstract

The study and application of microscale lenses and lens arrays have been actively researched in recent years; new approaches in the fabrication of microlenses and microlens arrays have emerged. Also, novel applications of these microlenses and microlens arrays have been demonstrated. In an [...] Read more.

The study and application of microscale lenses and lens arrays have been actively researched in recent years; new approaches in the fabrication of microlenses and microlens arrays have emerged. Also, novel applications of these microlenses and microlens arrays have been demonstrated. In an effort to disseminate the current advances in this specialized field of microlenses and microlens arrays, and to encourage discussion on the future research directions while stimulating research interests in this area, a Special Issue of Micromachines has been dedicated to “Microlenses”. [...] Full article

(This article belongs to the Special Issue Microlenses)

Research

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1326 KiB

Open AccessArticle

Simulation Study on Polarization-Independent Microlens Arrays Utilizing Blue Phase Liquid Crystals with Spatially-Distributed Kerr Constants

by Hung-Shan Chen, Michael Chen, Chia-Ming Chang, Yu-Jen Wang and Yi-Hsin Lin

Micromachines 2014, 5(4), 859-867; https://doi.org/10.3390/mi5040859 - 3 Oct 2014

Cited by 1 | Viewed by 6365

Abstract

Polarization independent liquid crystal (LC) microlens arrays based on controlling the spatial distribution of the Kerr constants of blue phase LC are simulated. Each sub-lens with a parabolic distribution of Kerr constants results in a parabolic phase profile when a homogeneous electric field [...] Read more.

Polarization independent liquid crystal (LC) microlens arrays based on controlling the spatial distribution of the Kerr constants of blue phase LC are simulated. Each sub-lens with a parabolic distribution of Kerr constants results in a parabolic phase profile when a homogeneous electric field is applied. We evaluate the phase distribution under different applied voltages, and the focusing properties of the microlens arrays are simulated. We also calculate polarization dependency of the microlenses arrays at oblique incidence of light. The impact of this study is to provide polarizer-free, electrically tunable focusing microlens arrays with simple electrode design based on the Kerr effect. Full article

(This article belongs to the Special Issue Microlenses)

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11155 KiB

Open AccessArticle

An Optofluidic Lens Array Microchip for High Resolution Stereo Microscopy

by Mayurachat Ning Gulari, Anurag Tripathi, Mostafa Ghannad-Rezaie and Nikos Chronis

Micromachines 2014, 5(3), 607-621; https://doi.org/10.3390/mi5030607 - 28 Aug 2014

Cited by 10 | Viewed by 10794

Abstract

We report the development of an add-on, chip-based, optical module—termed the Microfluidic-based Oil-immersion Lenses (μOIL) chip—which transforms any stereo microscope into a high-resolution, large field of view imaging platform. The μOIL chip consists of an array of ball mini-lenses that are assembled onto [...] Read more.

We report the development of an add-on, chip-based, optical module—termed the Microfluidic-based Oil-immersion Lenses (μOIL) chip—which transforms any stereo microscope into a high-resolution, large field of view imaging platform. The μOIL chip consists of an array of ball mini-lenses that are assembled onto a microfluidic silicon chip. The mini-lenses are made out of high refractive index material (sapphire) and they are half immersed in oil. Those two key features enable submicron resolution and a maximum numerical aperture of ~1.2. The μOIL chip is reusable and easy to operate as it can be placed directly on top of any biological sample. It improves the resolution of a stereo microscope by an order of magnitude without compromising the field of view; therefore, we believe it could become a versatile tool for use in various research studies and clinical applications. Full article

(This article belongs to the Special Issue Microlenses)

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16561 KiB

Open AccessArticle

Adaptive Liquid Lens Actuated by Droplet Movement

by Chao Liu, Qiong-Hua Wang, Li-Xiao Yao and Ming-Huan Wang

Micromachines 2014, 5(3), 496-504; https://doi.org/10.3390/mi5030496 - 4 Aug 2014

Cited by 9 | Viewed by 7024

Abstract

In this paper we report an adaptive liquid lens actuated by droplet movement. Four rectangular PMMA (Polymethyl Methacrylate) substrates are stacked to form the device structure. Two ITO (Indium Tin Oxide) sheets stick on the bottom substrate. One PMMA sheet with a light [...] Read more.

In this paper we report an adaptive liquid lens actuated by droplet movement. Four rectangular PMMA (Polymethyl Methacrylate) substrates are stacked to form the device structure. Two ITO (Indium Tin Oxide) sheets stick on the bottom substrate. One PMMA sheet with a light hole is inserted in the middle of the device. A conductive droplet is placed on the substrate and touches the PMMA sheet to form a small closed reservoir. The reservoir is filled with another immiscible non-conductive liquid. The non-conductive liquid can form a smooth concave interface with the light hole. When the device is applied with voltage, the droplet stretches towards the reservoir. The volume of the reservoir reduces, changing the curvature of the interface. The device can thus achieve the function of an adaptive lens. Our experiments show that the focal length can be varied from −10 to −159 mm as the applied voltage changes from 0 to 65 V. The response time of the liquid lens is ~75 ms. The proposed device has potential applications in many fields such as information displays, imaging systems, and laser scanning systems. Full article

(This article belongs to the Special Issue Microlenses)

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2356 KiB

Open AccessArticle

CO₂ Laser Manufacturing of Miniaturised Lenses for Lab-on-a-Chip Systems

by Mazher-Iqbal Mohammed and Marc Phillipe Yves Desmulliez

Micromachines 2014, 5(3), 457-471; https://doi.org/10.3390/mi5030457 - 21 Jul 2014

Cited by 6 | Viewed by 8403

Abstract

This article describes the manufacturing and characterisation of plano-convex miniaturised lenses using a CO₂ laser engraving process in PMMA substrates. The technique allows for lenses to be fabricated rapidly and in a reproducible manner at depths of over 200 µm and for [...] Read more.

This article describes the manufacturing and characterisation of plano-convex miniaturised lenses using a CO₂ laser engraving process in PMMA substrates. The technique allows for lenses to be fabricated rapidly and in a reproducible manner at depths of over 200 µm and for lens diameters of more than 3 mm. Experimental characterisation of the lens focal lengths shows good correlation with theory. The plano-convex lenses have been successfully embedded into capillary microfluidic systems alongside planar microlenses, allowing for a significant reduction of ancillary optics without a loss of detection sensitivity when performing fluorescence measurements. Such technology provides a significant step forward towards the portability of fluorescence- or luminescence-based systems for biological/chemical analysis. Full article

(This article belongs to the Special Issue Microlenses)

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572 KiB

Open AccessArticle

Fabrication and Characterization of Flexible Electrowetting on Dielectrics (EWOD) Microlens

by Chenhui Li and Hongrui Jiang

Micromachines 2014, 5(3), 432-441; https://doi.org/10.3390/mi5030432 - 4 Jul 2014

Cited by 40 | Viewed by 9060

Abstract

We present a flexible variable-focus converging microlens actuated by electrowetting on dielectric (EWOD). The microlens is made of two immiscible liquids and a soft polymer, polydimethylsiloxane (PDMS). Parylene intermediate layer is used to produce robust flexible electrode on PDMS. A low-temperature PDMS-compatible fabrication [...] Read more.

We present a flexible variable-focus converging microlens actuated by electrowetting on dielectric (EWOD). The microlens is made of two immiscible liquids and a soft polymer, polydimethylsiloxane (PDMS). Parylene intermediate layer is used to produce robust flexible electrode on PDMS. A low-temperature PDMS-compatible fabrication process has been developed to reduce the stress on the lens structure. The lens has been demonstrated to be able to conform to curved surfaces smoothly. The focal length of the microlens is 29–38 mm on a flat surface, and 31–41 mm on a curved surface, varying with the voltage applied. The resolving power of the microlens is 25.39 line pairs per mm by a 1951 United States Air Force (USAF) resolution chart and the lens aberrations are measured by a Shack-Hartmann wavefront sensor. The focal length behavior on a curved surface is discussed and for the current lens demonstrated the focal length is slightly longer on the curved surface as a result of the effect of the curved PDMS substrate. Full article

(This article belongs to the Special Issue Microlenses)

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2047 KiB

Open AccessArticle

Bio-Inspired Wide-Angle Broad-Spectrum Cylindrical Lens Based on Reflections from Micro-Mirror Array on a Cylindrical Elastomeric Membrane

by Chi-Chieh Huang and Hongrui Jiang

Micromachines 2014, 5(2), 373-384; https://doi.org/10.3390/mi5020373 - 20 Jun 2014

Cited by 5 | Viewed by 9123

Abstract

We present a wide-angle, broad-spectrum cylindrical lens based on reflections from an array of three-dimensional, high-aspect-ratio micro-mirrors fabricated on a cylindrical elastomeric substrate, functionally inspired by natural reflecting superposition compound eyes. Our device can perform one-dimensional focusing and beam-shaping comparable to conventional refraction-based [...] Read more.

We present a wide-angle, broad-spectrum cylindrical lens based on reflections from an array of three-dimensional, high-aspect-ratio micro-mirrors fabricated on a cylindrical elastomeric substrate, functionally inspired by natural reflecting superposition compound eyes. Our device can perform one-dimensional focusing and beam-shaping comparable to conventional refraction-based cylindrical lenses, while avoiding chromatic aberration. The focal length of our cylindrical lens is 1.035 mm, suitable for micro-optical systems. Moreover, it demonstrates a wide field of view of 152° without distortion, as well as modest spherical aberrations. Our work could be applied to diverse applications including laser diode collimation, barcode scanning, holography, digital projection display, microlens arrays, and optical microscopy. Full article

(This article belongs to the Special Issue Microlenses)

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1048 KiB

Open AccessArticle

Wafer-Level Hybrid Integration of Complex Micro-Optical Modules

by Peter Dannberg, Frank Wippermann, Andreas Brückner, Andre Matthes, Peter Schreiber and Andreas Bräuer

Micromachines 2014, 5(2), 325-340; https://doi.org/10.3390/mi5020325 - 5 Jun 2014

Cited by 38 | Viewed by 12141

Abstract

A series of technological steps concentrating around photolithography and UV polymer on glass replication in a mask-aligner that allow for the cost-effective generation of rather complex micro-optical systems on the wafer level are discussed. In this approach, optical functional surfaces are aligned to [...] Read more.

A series of technological steps concentrating around photolithography and UV polymer on glass replication in a mask-aligner that allow for the cost-effective generation of rather complex micro-optical systems on the wafer level are discussed. In this approach, optical functional surfaces are aligned to each other and stacked on top of each other at a desired axial distance. They can consist of lenses, achromatic doublets, regular or chirped lens arrays, diffractive elements, apertures, filter structures, reflecting layers, polarizers, etc. The suitability of the separated modules in certain imaging and non-imaging applications will be shown. Full article

(This article belongs to the Special Issue Microlenses)

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359 KiB

Open AccessArticle

Fabrication of Polydimethylsiloxane Microlenses Utilizing Hydrogel Shrinkage and a Single Molding Step

by Bader Aldalali, Aditi Kanhere, Jayer Fernandes, Chi-Chieh Huang and Hongrui Jiang

Micromachines 2014, 5(2), 275-288; https://doi.org/10.3390/mi5020275 - 21 May 2014

Cited by 14 | Viewed by 10145

Abstract

We report on polydimethlysiloxane (PDMS) microlenses and microlens arrays on flat and curved substrates fabricated via a relatively simple process combining liquid-phase photopolymerization and a single molding step. The mold for the formation of the PDMS lenses is fabricated by photopolymerizing a polyacrylamide [...] Read more.

We report on polydimethlysiloxane (PDMS) microlenses and microlens arrays on flat and curved substrates fabricated via a relatively simple process combining liquid-phase photopolymerization and a single molding step. The mold for the formation of the PDMS lenses is fabricated by photopolymerizing a polyacrylamide (PAAm) pre-hydrogel. The shrinkage of PAAm after its polymerization forms concave lenses. The lenses are then transferred to PDMS by a single step molding to form PDMS microlens array on a flat substrate. The PAAm concave lenses are also transferred to PDMS and another flexible polymer, Solaris, to realize artificial compound eyes. The resultant microlenses and microlens arrays possess good uniformity and optical properties. The focal length of the lenses is inversely proportional to the shrinkage time. The microlens mold can also be rehydrated to change the focal length of the ultimate PDMS microlenses. The spherical aberration is 2.85 μm and the surface roughness is on the order of 204 nm. The microlenses can resolve 10.10 line pairs per mm (lp/mm) and have an f-number range between f/2.9 and f/56.5. For the compound eye, the field of view is 113°. Full article

(This article belongs to the Special Issue Microlenses)

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Review

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2242 KiB

Open AccessReview

Fast-Response Liquid Crystal Microlens

by Su Xu, Yan Li, Yifan Liu, Jie Sun, Hongwen Ren and Shin-Tson Wu

Micromachines 2014, 5(2), 300-324; https://doi.org/10.3390/mi5020300 - 3 Jun 2014

Cited by 75 | Viewed by 15785 | Correction

Abstract

Electrically tunable liquid crystal microlenses have attracted strong research attention due to their advantages of tunable focusing, voltage actuation, low power consumption, simple fabrication, compact structure, and good stability. They are expected to be essential optical devices with widespread applications. However, the slow [...] Read more.

Electrically tunable liquid crystal microlenses have attracted strong research attention due to their advantages of tunable focusing, voltage actuation, low power consumption, simple fabrication, compact structure, and good stability. They are expected to be essential optical devices with widespread applications. However, the slow response time of nematic liquid crystal (LC) microlenses has been a significant technical barrier to practical applications and commercialization. LC/polymer composites, consisting of LC and monomer, are an important extension of pure LC systems, which offer more flexibility and much richer functionality than LC alone. Due to the anchoring effect of a polymer network, microlenses, based on LC/polymer composites, have relatively fast response time in comparison with pure nematic LC microlenses. In addition, polymer-stabilized blue phase liquid crystal (PS-BPLC) based on Kerr effect is emerging as a promising candidate for new photonics application. The major attractions of PS-BPLC are submillisecond response time and no need for surface alignment layer. In this paper, we review two types of fast-response microlenses based on LC/polymer composites: polymer dispersed/stabilized nematic LC and polymer-stabilized blue phase LC. Their basic operating principles are introduced and recent progress is reviewed by examples from recent literature. Finally, the major challenges and future perspectives are discussed. Full article

(This article belongs to the Special Issue Microlenses)

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5856 KiB

Open AccessReview

The Five Ws (and one H) of Super-Hydrophobic Surfaces in Medicine

by Francesco Gentile, Maria Laura Coluccio, Tania Limongi, Gerardo Perozziello, Patrizio Candeloro and Enzo Di Fabrizio

Micromachines 2014, 5(2), 239-262; https://doi.org/10.3390/mi5020239 - 5 May 2014

Cited by 11 | Viewed by 9746

Abstract

Super-hydrophobic surfaces (SHSs) are bio-inspired, artificial microfabricated interfaces, in which a pattern of cylindrical micropillars is modified to incorporate details at the nanoscale. For those systems, the integration of different scales translates into superior properties, including the ability of manipulating biological solutions. The [...] Read more.

Super-hydrophobic surfaces (SHSs) are bio-inspired, artificial microfabricated interfaces, in which a pattern of cylindrical micropillars is modified to incorporate details at the nanoscale. For those systems, the integration of different scales translates into superior properties, including the ability of manipulating biological solutions. The five Ws, five Ws and one H or the six Ws (6W), are questions, whose answers are considered basic in information-gathering. They constitute a formula for getting the complete story on a subject. According to the principle of the six Ws, a report can only be considered complete if it answers these questions starting with an interrogative word: who, why, what, where, when, how. Each question should have a factual answer. In what follows, SHSs and some of the most promising applications thereof are reviewed following the scheme of the 6W. We will show how these surfaces can be integrated into bio-photonic devices for the identification and detection of a single molecule. We will describe how SHSs and nanoporous silicon matrices can be combined to yield devices with the capability of harvesting small molecules, where the cut-off size can be adequately controlled. We will describe how this concept is utilized for obtaining a direct TEM image of a DNA molecule. Full article

(This article belongs to the Special Issue Microlenses)

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