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Design, simulation, and fabrication of three-dimensional microsystem components using grayscale photolithography

Summary

Grayscale lithography is a widely known but underutilized microfabrication technique for creating three-dimensional (3-D) microstructures in photoresist. One of the hurdles for its widespread use is that developing the grayscale photolithography masks can be time-consuming and costly since it often requires an iterative process, especially for complex geometries. We discuss the use of PROLITH, a lithography simulation tool, to predict 3-D photoresist profiles from grayscale mask designs. Several examples of optical microsystems and microelectromechanical systems where PROLITH was used to validate the mask design prior to implementation in the microfabrication process are presented. In all examples, PROLITH was able to accurately and quantitatively predict resist profiles, which reduced both design time and the number of trial photomasks, effectively reducing the cost of component fabrication.
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Summary

Grayscale lithography is a widely known but underutilized microfabrication technique for creating three-dimensional (3-D) microstructures in photoresist. One of the hurdles for its widespread use is that developing the grayscale photolithography masks can be time-consuming and costly since it often requires an iterative process, especially for complex geometries. We discuss...

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Microsputterer with integrated ion-drag focusing for additive manufacturing of thin, narrow conductive lines

Published in:
J. Phys. D.: Appl. Phys., Vol. 51, 2018, 165603.

Summary

We report the design, modelling, and proof-of-concept demonstration of a continuously fed, atmospheric-pressure microplasma metal sputterer that is capable of printing conductive lines narrower than the width of the target without the need for post-processing or lithographic patterning. Ion drag-induced focusing is harnessed to print narrow lines; the focusing mechanism is modelled via COMSOL Multiphysics simulations and validated with experiments. A microplasma sputter head with gold target is constructed and used to deposit imprints with minimum feature sizes as narrow as 9 μm, roughness as small as 55 nm, and electrical resistivity as low as 1.1 mu Omega · m.
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Summary

We report the design, modelling, and proof-of-concept demonstration of a continuously fed, atmospheric-pressure microplasma metal sputterer that is capable of printing conductive lines narrower than the width of the target without the need for post-processing or lithographic patterning. Ion drag-induced focusing is harnessed to print narrow lines; the focusing mechanism...

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Electrically switchable diffractive waveplates with metasurface aligned liquid crystals

Published in:
Opt. Express, Vol. 24, No. 21, 17 October 2016, 24265-24273.

Summary

Diffractive waveplates and equivalent metasurfaces provide a promising path for applications in thin film beam steering, tunable lenses, and polarization filters. However, fixed metasurfaces alone are unable to be tuned electronically. By combining metasurfaces with tunable liquid crystals, we experimentally demonstrate a single layer device capable of electrically switching a diffractive waveplate design at a measured peak diffraction efficiency of 35%, and a minimum switching voltage of 10V. Furthermore, the nano-scale metasurface aligned liquid crystals are largely independent of variations in wavelength and temperature. We also present a computational analysis of the efficiency limits of liquid crystal based diffractive waveplates, and compare this analysis to experimental measurements.
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Summary

Diffractive waveplates and equivalent metasurfaces provide a promising path for applications in thin film beam steering, tunable lenses, and polarization filters. However, fixed metasurfaces alone are unable to be tuned electronically. By combining metasurfaces with tunable liquid crystals, we experimentally demonstrate a single layer device capable of electrically switching a...

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Switchable electrowetting of droplets on dual-scale structured surfaces

Published in:
J. Vac. Sci. Technol. B, Microelectron. Process. Phenon., Vol. 30, No. 6, November 2012, 06F801.

Summary

The authors report on the development of surfaces containing artificially fabricated structures of dual nanometer and micrometer surfaces that allow an aqueous droplet to be reversibly switched by electrowetting from a Cassie state with low adhesion to a Wenzel state with high adhesion. A variety of geometries were fabricated to study parameters that affect switchable wetting-dewetting. Nanometer parallel corrugations, posts, and holes were fabricated and combined with micrometer features consisting of parallel corrugations, streets, and checkerboard patterns of varying widths and pitches. It was observed that many combinations of the dual-textured surfaces produced superhydrophobic wetting states and aqueous droplets on these surfaces could be electrically controlled to switch from a Cassie state to a Wenzel state. Reversible switching between these wetting states occurred on specific combinations of surface geometries, namely surfaces that had parallel corrugations.
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Summary

The authors report on the development of surfaces containing artificially fabricated structures of dual nanometer and micrometer surfaces that allow an aqueous droplet to be reversibly switched by electrowetting from a Cassie state with low adhesion to a Wenzel state with high adhesion. A variety of geometries were fabricated to...

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Reversible electrowetting on dual-scale-patterned corrugated microstructured surfaces

Published in:
J. of Microeletromechanical Systems, Vol. 21, No. 5, October 2012, pp. 1261-71.

Summary

The ability to reversibly switch between a hydrophobic Cassie state and a hydrophilic Wenzel state is often not possible on textured surfaces because of energy barriers which result from the geometry of the microstructure. In this paper, we report on a simple microstructure geometry that allows an aqueous droplet to be reversibly switched between these states by the application of electrowetting. We demonstrate reversible electrowetting in air on microstructured surfaces consisting of parallel corrugations and show that this geometry can be engineered to produce a Cassie state and can be electrically controlled to switch to a Wenzel wetting state having high adhesion. When the electric field was removed, we observed spontaneous dewetting along the corrugations as the droplet transitioned from the Wenzel state back to a Cassie state.
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Summary

The ability to reversibly switch between a hydrophobic Cassie state and a hydrophilic Wenzel state is often not possible on textured surfaces because of energy barriers which result from the geometry of the microstructure. In this paper, we report on a simple microstructure geometry that allows an aqueous droplet to...

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