Foldable and Cytocompatible Sol-gel TiO2 Photonics
Date
2015-09-07
Journal Title
Journal ISSN
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Publisher
Nature Publishing Group
Abstract
Integrated photonics provides a miniaturized and potentially implantable platform to manipulate
and enhance the interactions between light and biological molecules or tissues in in-vitro and in-vivo
settings, and is thus being increasingly adopted in a wide cross-section of biomedical applications
ranging from disease diagnosis to optogenetic neuromodulation. However, the mechanical rigidity
of substrates traditionally used for photonic integration is fundamentally incompatible with soft
biological tissues. Cytotoxicity of materials and chemicals used in photonic device processing imposes
another constraint towards these biophotonic applications. Here we present thin film TiO2 as a viable
material for biocompatible and flexible integrated photonics. Amorphous TiO2 films were deposited
using a low temperature (<250 °C) sol-gel process fully compatible with monolithic integration on
plastic substrates. High-index-contrast flexible optical waveguides and resonators were fabricated
using the sol-gel TiO2 material, and resonator quality factors up to 20,000 were measured. Following
a multi-neutral-axis mechanical design, these devices exhibit remarkable mechanical flexibility, and
can sustain repeated folding without compromising their optical performance. Finally, we validated
the low cytotoxicity of the sol-gel TiO2 devices through in-vitro cell culture tests. These results
demonstrate the potential of sol-gel TiO2 as a promising material platform for novel biophotonic
devices.
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Citation
Li, L. et al. Foldable and Cytocompatible Sol-gel TiO2 Photonics. Sci. Rep. 5, 13832; doi: 10.1038/srep13832 (2015).