Selective Surface Smoothening of Polymer Microlenses by Depth Confined Softening

Chidambaram, Nachiappan; Kirchner, Robert; Fallica, Roberto; Yu, Libo; Altana, Mirco; Schift, Helmut

doi:10.1002/admt.201700018

Cited by 34 publications

(29 citation statements)

References 59 publications

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“…Such polymer substrates are poly(ethylene)terephthalate (PET) and polyethylene naphthalate (PEN), which would melt in too high temperatures and the structures on them would be distorted. By using poly(methyl methacrylate) (PMMA) with lower T g as a substrate (or as a planarization layer on other material substrates), we can apply a heating step to eliminate the sharp Λ‐ridges and grooves, and achieve a flat surface between the lines . Flash lamp annealing (FLA) is presented as an option for both ink sintering and thermal reflow, which enables to reduce both the temperature and exposure time .…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Large Area Sub‐200 nm Conducting Electrode Arrays by Self‐Confinement of Spincoated Metal Nanoparticle Inks

Horváth

Křivová

Bolat

et al. 2019

Adv Materials Technologies

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polar liquid layer on the substrate which serves as a transfer mechanism; therefore they are still costly for high volume manufacturing of transparent electrodes in lowcost applications. Other options, such as randomly distributed metal nanofibers [7] or nanowire networks [8,9] allow no control of the location and pattern of the wires as they are always randomly distributed on the substrate. On a micrometer scale of creating silver wires, inkjet [10] and gravure printing [11,12] are low-cost additive methods used for printed electronics, yet with resolutions often in the range much larger than 10 µm. [13] They are not suitable for applications where sub-micrometer or even sub-100 nm resolutions (e.g., for subwavelength optics) are needed. In order to shrink dimensions without using traditional lithography, the patterning of nanoparticles by self-assembly on pre-patterned substrates is a solution. It has been tested for the generation of dense arrays of 50-80 nm silica particles in V-grooves. [14] Capillary assisted particle assembly (CAPA) is used for the parallel assembly of sub-micrometer particles into hexagonal arrangements by convective or capillary effects. [15,16] However, nanoparticle inks have polydisperse distribution of particle sizes (here between 20 and 80 nm) and therefore typically do not self-assemble but rather form a loose agglomeration, which is merged into a 3D cluster by post-processing (e.g., sintering).The objective of the present paper is to provide a novel method for reducing the width of structures generated by ink deposition on pre-patterned substrates. We aim to achieve resolutions which are not only much smaller than the resolution of the applied additive process, but also smaller than the width of the pre-patterned structures. Pre-patterning the substrates with specific sub-micrometer topography can be done by straightforward replication techniques such as thermal or UV-assisted NIL which can then be covered either locally (e.g., by inkjet printing) or on an entire substrate (by spincoating). This enables the generation of fine structures in the micrometer range down to subwavelength range at low cost and high throughput, and thus satisfies the demand for a technology being less expensive than currently known lithographic processes. In the process proposed here, we use this approach to fill V-groove shaped substrates with silver nanoparticle-based inks, typically with average 50 nm particles dispersed in a suitable solvent. [17] The nature of the V-groove substrates with inclined sidewalls and Λ-ridges between adjacent grooves separates individual lines Here, the fabrication of sub-200 nm metal wires from commercial silver inks with 50 nm particle size, 100 times narrower than with typical low-resolution ink-jet and screen printing in flexible electronics, is demonstrated. Using a combination of spincoating on prepatterned polymer substrates and flash lamp annealing, nanoparticles merge to wires featuring good electrical conductivity. With this method less than 150 nm thin wires can ...

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Section: Introductionmentioning

confidence: 99%

Fabrication of Large Area Sub‐200 nm Conducting Electrode Arrays by Self‐Confinement of Spincoated Metal Nanoparticle Inks

Horváth

Křivová

Bolat

et al. 2019

Adv Materials Technologies

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Section: D Printing Of Bioinspired Optical Devicesmentioning

confidence: 99%

“…To create prototype of optical lenses and devices, traditional fabrication methods are limited by their high cost, time‐consuming, and difficulties in modifying designs. Besides, the postprocessing steps such as sanding, polishing, bead blasting, or vapor smoothing may change the structural details or the overall shape, especially for microscale complex optical structures . 3D printing may provide breakthroughs for the fabrication of smooth optical surfaces (Figure f).…”

Section: D Printing Of Bioinspired Optical Devicesmentioning

confidence: 99%

“…3D printing may provide breakthroughs for the fabrication of smooth optical surfaces (Figure f). For example, a postcuring method was developed by curing the residual material on the surface to eliminate the layer staircase effects . Similarly, smooth surface quality can be achieved using dual exposures by curing the residual resin between neighboring layers .…”

Section: D Printing Of Bioinspired Optical Devicesmentioning

confidence: 99%

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Recent Progress in Biomimetic Additive Manufacturing Technology: From Materials to Functional Structures

et al. 2018

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Nature has developed high-performance materials and structures over millions of years of evolution and provides valuable sources of inspiration for the design of next-generation structural materials, given the variety of excellent mechanical, hydrodynamic, optical, and electrical properties. Biomimicry, by learning from nature's concepts and design principles, is driving a paradigm shift in modern materials science and technology. However, the complicated structural architectures in nature far exceed the capability of traditional design and fabrication technologies, which hinders the progress of biomimetic study and its usage in engineering systems. Additive manufacturing (three-dimensional (3D) printing) has created new opportunities for manipulating and mimicking the intrinsically multiscale, multimaterial, and multifunctional structures in nature. Here, an overview of recent developments in 3D printing of biomimetic reinforced mechanics, shape changing, and hydrodynamic structures, as well as optical and electrical devices is provided. The inspirations are from various creatures such as nacre, lobster claw, pine cone, flowers, octopus, butterfly wing, fly eye, etc., and various 3D-printing technologies are discussed. Future opportunities for the development of biomimetic 3D-printing technology to fabricate next-generation functional materials and structures in mechanical, electrical, optical, and biomedical engineering are also outlined.

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“…It can be operated in ambient, and large area lamps enabling homogeneous irradiation are available. More details will be presented in future publications [20]. Ambient conditions Figure 2.…”

Section: Layering Versus Post-processing For Roughness Reductionmentioning

confidence: 99%

How post-processing by selective thermal reflow can reduce the roughness of 3D lithography in micro-optical lenses

et al. 2017

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Most polymeric refractive micro-optics simultaneously demand ultra-smooth 3D topographies and precise geometry for high optical performance and low stray light. We have established a surface selective smoothening for thermoplastic polymers that does not affect the designed optical geometry. For example, high curvature corners required for a 50 µm tall optical diffuser device were maintained while the surface roughness was reduced to about 10 nm RMS. 3D master structures were fabricated using direct write laser-lithography with two-photon absorption. Master structures were then replicated into poly(methyl methacrylate) through a poly(dimethyl siloxane) intermediate copying step and subsequently smoothed-out by high-energy photon exposure and thermal post-processing. The smoothening results in a lower roughness compared to a direct writing strategy using even about 50 nm vertical discretization steps still enables 10 times faster writing times.

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Selective Surface Smoothening of Polymer Microlenses by Depth Confined Softening

Cited by 34 publications

References 59 publications

Fabrication of Large Area Sub‐200 nm Conducting Electrode Arrays by Self‐Confinement of Spincoated Metal Nanoparticle Inks

Fabrication of Large Area Sub‐200 nm Conducting Electrode Arrays by Self‐Confinement of Spincoated Metal Nanoparticle Inks

Recent Progress in Biomimetic Additive Manufacturing Technology: From Materials to Functional Structures

How post-processing by selective thermal reflow can reduce the roughness of 3D lithography in micro-optical lenses

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