Integrating Biomaterials into Microsystems: Formation and Characterization of Nanostructured Titania
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Integrating Biomaterials into Microsystems: Formation and Characterization of Nanostructured Titania Zuruzi Abu Samah, Blaine C. Butler1, Emily R. Parker, Ayesha Ahmed1, Heather M. Evans1, Cyrus R. Safinya1 and Noel C. MacDonald Materials Department, and Mechanical and Environmental Engineering Department, University of California at Santa Barbara, California, CA 93106, U. S. A 1 Materials Department, Physics Department, and Biomolecular Science and Engineering Program, University of California at Santa Barbara, CA 93106, U. S. A ABSTRACT We demonstrate the facile fabrication of crack-free nanostructured crystalline titania into microsystems. Titania layers were formed by reacting Ti thin films, deposited by evaporation and sputtering, with aqueous H202. Cracks were observed in titania layers formed on blanket Ti films but absent on arrays of patterned Ti pads below a threshold dimension. Nanostructured titania formed from sputtered and evaporated Ti films consists of aligned fibrous and sponge-like nanoporous morphologies, respectively. Rat fibroblasts L-cells cultured on these titania fibers remain viable up to 3 days. These observations demonstrate the feasibility of this technique to integrate nanostructured titania into Nano|Micro-Electromechanical systems (N|MEMS) devices.
INTRODUCTION Porous and nanostructured titania (ns-titania) attract considerable interest because of their diverse technological applications. Hence, various techniques for synthesizing porous titania have been developed such as anodizing, emulsion templating, oxidation, reactive sputtering and sol-gel processing. However, these techniques are not suitable for integration into current procedures for silicon-based N|MEMS device manufacturing. Also, the critical issue of cracking in titania layers remains. Hence, techniques to integrate ns-titania which are compatible with microsystems device manufacturing are required. Oxidation of Ti by aqueous hydrogen peroxide solution (aq. H2O2) had been studied previously. Tengvall [1] reacted titanium powder with aq. H2O2 and obtained transparent titania gel with excellent bioactivity. Wu et. al. [2] investigated the interactions between Ti thick sheets with aq. H2O2 and formed porous titania layers. However, these layers have high crack density and delaminate extensively from the Ti substrate which makes them unsuitable for device applications. Here, we propose the reaction of pre-patterned Ti thin (~1 to 3.5 µm) films with aq. H2O2 for integrating ns-titania into N|MEMS devices. EXPERIMENTAL DETAILS We used 2.5 cm square tabs of N-type Si(100) as substrates. Ti thin films were patterned using either lift-off or selective masking process. In selective masking, Ti film was electron beam evaporated on Si tabs followed by silicon dioxide deposition. Silicon dioxide was
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deposited using plasma-enhanced chemical vapor deposition. Photo resist (PR) was deposited on the silicon dioxide layer and patterned. Pattern on the PR layer was transferred to the silicon dioxide layer by etching with C
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