Laser micromachining of high-density optical structures on large substrates

Boehlen, Karl L.; Boehlen, Ines Benigna Stassen

doi:10.1117/12.537827

Cited by 17 publications

(4 citation statements)

References 6 publications

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“…Laser ablation of polymers has been extensively studied for more than 3 decades. − A wide range of shapes can be obtained when optimized mask imaging techniques are used . 3D microstructural features are first laser ablated into polycarbonate by direct mask projection with a KrF (λ = 248 nm) laser and fluences from 100 to 600 mJ cm –2 . Each pulse can ablate layers between 20 and 250 nm depending on the fluence used.…”

Section: Resultsmentioning

confidence: 99%

Surface 3D Micro Free Forms: Multifunctional Microstructured Mesoporous α-Alumina by in Situ Slip Casting Using Excimer Laser Ablated Polycarbonate Molds

Rowthu

Böhlen

Bowen

et al. 2015

ACS Appl. Mater. Interfaces

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Ceramic surface microstructuring is a rapidly growing field with a variety of applications in tribology, wetting, biology, and so on. However, there are limitations to large-area microstructuring and fabrication of three-dimensional (3D) micro free forms. Here, we present a route to obtain intricate surface structures through in situ slip casting using polydimethylsiloxane (PDMS) negative molds which are replicated from excimer laser ablated polycarbonate (PC) master molds. PC sheets are ablated with a nanosecond KrF (λ = 248 nm) excimer laser mask projection system to obtain micron-scale 3D surface features over a large area of up to 3 m(2). Complex surface structures that include 3D free forms such as 3D topography of Switzerland, shallow structures such as diffractive optical elements (60 nm step) and conical micropillars have been obtained. The samples are defect-free produced with thicknesses of up to 10 mm and 120 mm diameter. The drying process of the slip cast alumina slurry takes place as a one-dimensional process, through surface evaporation and water permeation through the PDMS membrane. This allows homogeneous one-dimensional shrinkage during the drying process, independent of the sample's lateral dimensions. A linear mass diffusion model has been proposed to predict and explain the drying process of these ceramic colloidal suspensions. The calculated drying time is linearly proportional to the height of the slurry and the thickness of the negatively structured PDMS and is validated by the experimental results. An experimentally observed optimum Sylgard PDMS thickness range of ∼400 μm to 1 mm has achieved the best quality microstructured green compacts. Further, the model predicts that the drying time is independent of the microstructured areas and was validated using experimental observations carried out with microstructured areas of 300 mm(2), 1200 mm(2), and 120 cm(2). Therefore, in principle, the structures can be further replicated in areas up to 3 m(2) with the same drying time for the same slurry height. The surface-structured ceramics display interesting wetting properties, for example, eicosane-coated mesoporous microstructured alumina shows superhydrophobic behavior. Additionally, ceramic bulk samples could be further used as second-generation very hard and low-wear molds for further microfabrication.

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Section: Resultsmentioning

confidence: 99%

Surface 3D Micro Free Forms: Multifunctional Microstructured Mesoporous α-Alumina by in Situ Slip Casting Using Excimer Laser Ablated Polycarbonate Molds

Rowthu

Böhlen

Bowen

et al. 2015

ACS Appl. Mater. Interfaces

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“…The main functional role attributed to platelets was haemostasis and maintenance of the vessel wall. But there is strong evidence that platelets also affect inflammatory processes and modulate leukocytefunction,endothelium and the surrounding cytokine milieu (23,24). Resting platelets exert anti-inflammatory and anti-thrombotic actions, but upon activation they release pro-inflammatory and pro-thrombotic substances that activate neutrophils,monocytesand endothelial cells (14,25).…”

Section: Discussionmentioning

confidence: 99%

CD40 Ligand-Dependent Maturation of Human Monocyte-Derived Dendritic Cells by Activated Platelets

Kaneider

Kaser

Tilg

et al. 2003

Int J Immunopathol Pharmacol

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Atherosclerosis is defined as an inflammatory immunological disease that is triggered by platelet activation, endothelial injury and consequent innate and adaptive immune processes. Dendritic cells are critical for the cell-mediated arm of the immune response as they activate naïve T cells after maturation. Platelets play a crucial role in thrombus formation in the injured vessel walls. We investigated the role of resting and thrombin-activated platelets in dendritic cell maturation in vitro using platelets and monocyte-derived dendritic cells from healthy donors. Resting platelet supernatants did not affect maturation, whereas supernatants from thrombin-activated platelets induced dendritic cell maturation as demonstrated by FACS analysis of HLA-DR expression. This effect was inhibited by anti CD40 ligand antibody, but not by aspirin pretreatment of platelets. Supernatants of platelet-dendritic cell co-cultures induced augmented monocyte migration when platelets were activated by thrombin, again reversible by blocking CD40 ligand. These data show that activated platelets trigger dendritic cell maturation independent of cyclooxygenase-derived arachidonic acid metabolites by mechanisms involving CD40 ligand, which is also involved in monocyte chemotactic mediator release from platelets and dendritic cells. The results of this study suggest a role of CD40 ligand from activated platelets in connecting innate and adaptive immunity.

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“…The feature is then written by synchronized motion and laser firing in such a way that the firing frequency of the laser corresponds to the spatial pitch of the features. The technique of SIS is explained in depth in three previous papers [2,3,4]. There are virtually no limits to the design of the features as long as there are no undercuts and no details smaller than the resolution of the imaging system.…”

Section: A Short Introductionmentioning

confidence: 98%

Advanced laser micro-structuring of super-large-area optical films

Boehlen¹,

Boehlen²,

Allott³

2005

SPIE Proceedings

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A novel laser micro-machining technique to produce high density micro-structures called Synchronized Image Scanning (SIS) was introduced a couple of years ago. Over this period of time, the technique was refined in a major effort to meet the needs of various industries. There is an increasing demand for micro-structuring of large and super large area optical films, e.g. for Rear Projection TV, anti counterfeit packaging material and 3D displays. Especially in the display industry, where the screens are ever increasing in size, established micro-structuring methods like e-beam milling, diamond turning or the reflow technique struggle to keep up with the development.This paper explains how it is possible to direct laser etch hundreds of millions of lenses into a 2 m x 1.5 m substrate. It looks at the advances made in SIS in recent years regarding seam reduction, overall accuracy and precision when structuring super large area optical films, and it presents the tools and subsystems needed to generate the features in those films. Furthermore, the potential of this exciting laser micro-machining technique for rapid prototyping for all sorts of optical and non-optical structures is mapped out.

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Laser micromachining of high-density optical structures on large substrates

Cited by 17 publications

References 6 publications

Surface 3D Micro Free Forms: Multifunctional Microstructured Mesoporous α-Alumina by in Situ Slip Casting Using Excimer Laser Ablated Polycarbonate Molds

Surface 3D Micro Free Forms: Multifunctional Microstructured Mesoporous α-Alumina by in Situ Slip Casting Using Excimer Laser Ablated Polycarbonate Molds

CD40 Ligand-Dependent Maturation of Human Monocyte-Derived Dendritic Cells by Activated Platelets

Advanced laser micro-structuring of super-large-area optical films

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