Abstract
Organically modified ceramic polymers (ORMOCERs) have attracted substantial interest in biomicrofluidic applications owing to their inherent biocompatibility and high optical transparency even in the near-ultraviolet (UV) range. However, the processes for metallization of ORMOCERs as well as for sealing of metallized surfaces have not been fully developed. In this study, we developed metallization processes for a commercial ORMOCER formulation, Ormocomp, covering several commonly used metals, including aluminum, silver, gold, and platinum. The obtained metallizations were systematically characterized with respect to adhesion (with and without adhesion layers), resistivity, and stability during use (in electrochemical assays). In addition to metal adhesion, the possibility for Ormocomp bonding over each metal as well as sufficient step coverage to guarantee conductivity over topographical features (e.g., over microchannel edges) was addressed with a view to the implementation of not only planar, but also three-dimensional on-chip sensing elements. The feasibility of the developed metallization for implementation of microfluidic electrochemical assays was demonstrated by fabricating an electrophoresis separation chip, compatible with a commercial bipotentiostat, and incorporating integrated working, reference, and auxiliary electrodes for amperometric detection of an electrochemically active pharmaceutical, acetaminophen.
Highlights
Owing to the low cost of the materials and the straightforward microfabrication protocols, photolithography of polymer-based photoresists is often considered the most feasible approach for fabrication of high-resolution microfluidic devices
Organically modified ceramic polymers (ORMOCERs) have attracted substantial interest in biomicrofluidic applications owing to their inherent biocompatibility and high optical transparency even in the near-ultraviolet (UV) range
Modified ceramics (ORMOCERs) are a new class of organic-inorganic hybrid polymers that can be patterned by a variety of techniques, including ultraviolet (UV) embossing, UV laser ablation, and UV lithography in proximity mode [1,2,3,4]
Summary
Owing to the low cost of the materials and the straightforward microfabrication protocols, photolithography of polymer-based photoresists is often considered the most feasible approach for fabrication of high-resolution microfluidic devices. The UV exposure of ORMOCERs is typically conducted in proximity mode (instead of contact mode), which facilitates straightforward fabrication of rounded, concave cross-section profile upon controlled overexposure [9] It has been demonstrated with the help of a commercial ORMOCER formulation, Ormocomp, that the microchannel cross-section shape can be flexibly tuned in a single lithographic step by adjusting the UV exposure dose, the distance of the proximity gap (between the photomask and the photoresist), and the layer thickness [9]. For custom polymers, even zero adhesion is sometimes reported necessitating either wet chemical treatment or plasma etching prior to metal deposition [20]
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