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Proceedings Paper

Tunable liquid microlens array driven by pyroelectric effect: full interferometric characterization
Author(s): Lisa Miccio; Simonetta Grilli; Veronica Vespini; Pietro Ferraro
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Paper Abstract

Liquid lenses with adjustable focal length are of great interest in the field of microfluidic devices. They are, usually, realized by electrowetting effect after electrodes patterning on a hydrofobic substrate. Applications are possible in many fields ranging from commercial products such as digital cameras to biological cell sorting. We realized an open array of liquid lenses with adjustable focal length without electrode patterning. We used a z-cut Lithium Niobate crystal (LN) as substrate and few microliters of an oily substance to obtain the droplets array. The spontaneous polarization of LN crystals is reversed by the electric field poling process, thus enabling the realization of periodically poled LN (PPLN) crystals. The substrate consists of a two-dimensional square array of reversed domains with a period around 200 μm. Each domain presents an hexagonal geometry due to the crystal structure. PPLN is first covered by a thin and homogeneous layer of the above mentioned liquid and therefore its temperature is changed by means of a digitally controlled hot plate. During heating and cooling process there is a rearrangement of the liquid layer until it reaches the final topography. Lenses formation is due to the superficial tension changing at the liquid-solid interface by means of the pyroelectric effect. Such effect allows to create a two-dimensional lens pattern of tunable focal length without electrodes. The temporal evolution of both shape and focal length lenses are quantitatively measured by Digital Holographic Microscopy. Array imaging properties and quantitative analysis of the lenses features and aberrations are presented.

Paper Details

Date Published: 25 September 2008
PDF: 6 pages
Proc. SPIE 7102, Optical Fabrication, Testing, and Metrology III, 710205 (25 September 2008); doi: 10.1117/12.797695
Show Author Affiliations
Lisa Miccio, Istituto Nazionale di Ottica Applicata, CNR (Italy)
Simonetta Grilli, Istituto Nazionale di Ottica Applicata, CNR (Italy)
Veronica Vespini, Istituto Nazionale di Ottica Applicata, CNR (Italy)
Pietro Ferraro, Istituto Nazionale di Ottica Applicata, CNR (Italy)

Published in SPIE Proceedings Vol. 7102:
Optical Fabrication, Testing, and Metrology III
Angela Duparré; Roland Geyl, Editor(s)

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