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Electrically tunable micro-lens with a strain-enhanced polymer nanocomposite actuator

: Costache, Florenta; Pawlik, Boscij; Rieck, Andreas


Piyawattanametha, W. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
MOEMS and Miniaturized Systems XVI : 30 January-1 February 2017, San Francisco, California, United States
Bellingham, WA: SPIE, 2017 (Proceedings of SPIE 10116)
ISBN: 978-1-5106-0673-9
ISBN: 978-1-5106-0674-6
Paper 101160D
Conference "MOEMS and Miniaturized Systems" <16, 2017, San Francisco/Calif.>
Fraunhofer IPMS ()

A fluid-filled micro-lens concept with an electrically driven polymer actuator was developed in view of optimization of its variation in focal length. The high strain electrostrictive terpolymer P(VDF-TrFE-CFE) was first used in the actuator design for this purpose. Our study showed that the electric field-induced strain in polymer thin films could be even further enhanced by mixing high-k BaTiO3 nanoparticles in the terpolymer. A newly developed nanocomposite P(VDF-TrFE-CFE) / BaTiO3 ring-shaped actuator was implemented into the 3 mm aperture, liquid-filled micro-lens concept. The micro-lens was fabricated in a wafer-level process flow, which included micromachining of fluidic chambers on silicon wafers, thin film nanocomposite actuator processing, assembly through wafer bonding and chip filling with liquids. Particular characteristics of the nanocomposite were taken into account such as the homogeneous nanoparticle dispersion into the thin film with impact on thin film dielectric breakdown, electrode adherence as well as nanocomposite film etching. Variable focal length micro-lenses conceps with a single fluidic chamber but also with two fluidic chambers (a design, which can potentially improve the lens membrane stability) were fabricated and characterized. We could demonstrate a wide focal length variation of tens of diopters first for a single chamber plano-convex micro-lens obtained by adjusting the voltage applied on the integrated actuator.