Michael P. Tate

An electrochemical fabrication process for the assembly of anisotropically oriented collagen bundles

Controlled assembly of collagen molecules in vitro remains a major challenge for fabricating the next generation of engineered tissues. Here we present a novel electrochemical alignment technique to control the assembly of type-I collagen molecules into highly oriented and densely packed elongated bundles at the macroscale. The process involves application of electric currents to collagen solutions which in turn generate a pH gradient. Through an isoelectric focusing process, the molecules migrate and congregate within a plane. It was possible to fabricate collagen bundles with 50-400 microm diameter and several inches length via this process. The current study assessed the orientational order, and the presence of fibrillar assembly in such electrochemically oriented constructs by polarized optical microscopy, small angle X-ray scattering, second harmonic generation, and electron microscopy. The mechanical strength of the aligned crosslinked collagen bundles was 30-fold greater than its randomly oriented-crosslinked counterpart. Aligned crosslinked collagen bundles had about half the strength of the native tendon. Tendon-derived fibroblast cells were able to migrate and populate multiple macroscopic bundles at a rate of 0.5mm/day. The anisotropic order within biocompatible collagenous constructs was conferred upon the nuclear morphology of cells as well. These results indicate that the electrochemically oriented collagen scaffolds carry baseline characteristics to be considered for tendon/ligament repair.

Fabrication of continuous mesoporous carbon films with face-centered orthorhombic symmetry through a soft templating pathway

Preparation of well-ordered continuous mesoporous carbon films without the use of an intermediate inorganic template was achieved by spin coating of a thermosetting phenolic resin, resorcinol/phloroglucinol/formaldehyde, and a thermally-decomposable organic template, Pluronic F127 (PEO106–PPO70–PEO106). The carbon films were deposited onto silicon, platinum/silicon, copper, glass, and quartz substrates. Afterwards, decomposition of the organic template and solidification of the carbon precursors are simultaneously performed through a carbonization process. The resulting films referred to as CKU-F69, are (010)-oriented, and possess a face-centered orthorhombic Fmmm symmetry. Film periodicity is maintained even after a 68% uniaxial contraction perpendicular to the substrate brought on by carbonization at 800 °C. This method could facilitate the mass-production and creation of new carbon and carbon–polymer porous films that find broad potential applications in catalysis, separation, hydrogen storage, bioengineering, nanodevices, and nanotemplates.

Characterization of Lipid-Templated Silica and Hybrid Thin Film Mesophases by Grazing Incidence Small-Angle X-ray Scattering

The nanostructure of silica and hybrid thin film mesophases templated by phospholipids via an evaporation-induced self-assembly (EISA) process was investigated by grazing-incidence small-angle X-ray scattering (GISAXS). Diacyl phosphatidylcholines with two tails of 6 or 8 carbons were found to template 2D hexagonal mesophases, with the removal of lipid from these lipid/silica films by thermal or UV/O3 processing resulting in a complete collapse of the pore volume. Monoacyl phosphatidylcholines with single tails of 10-14 carbons formed 3D micellular mesophases; the lipid was found to be extractable from these 3D materials, yielding a porous material. In contrast to pure lipid/silica thin film mesophases, films formed from the hybrid bridged silsesquioxane precursor bis(triethoxysilyl)ethane exhibited greater stability toward (both diacyl and monoacyl) lipid removal. Ellipsometric, FTIR, and NMR studies show that the presence of phospholipid suppresses siloxane network formation, while actually promoting condensation reactions in the hybrid material. 1D X-ray scattering and FTIR data were found to be consistent with strong interactions between lipid headgroups and the silica framework.

Vapor phase synthesis of mesoporous silica thin films with a 3D pore structure

Abstract Ordered mesoporous silica thin films were prepared using non-ionic alkyl poly(oxyethylene) surfactants (Brij56: C18EO10) by a vapor phase method. First, a Brij56/H2SO4 composite was deposited on a silicon substrate by spin-coating. The Brij56 film was treated with a tetraethoxysilane (TEOS) and hydrochloric acid (HCl) vapors in a closed vessel. The TEOS and HCl vapors were infiltrated into the film, resulted in a formation of the silica network. Results of a grazing angle of incidence small angle X-ray scattering (GISAXS) show that the films have an ordered structure with an Fmmm symmetry. From an Field emission scanning electron microscope (FESEM) observations, the film has a 3D pore structure.

Synthesis of ordered mesoporous carbons in film morphology using organic-organic interaction approach

Preparation of ordered mesoporous carbon films without the use of an intermediate inorganic silica template was achieved from organic-organic assembly of thermally-decomposable triblock copolymer and thermosetting phenolic resin precursors. The films were formed by spin-coating followed by an evaporation-induced self-assembly. Afterwards, decompositon of the organic template and solidification of the carbon precursors are simultaneously performed through a direct carbonization process. Adjusted condition in the ratio of phenolic resin precursors and triblock copolymer allows one to tailor the final mesostructure which include 2D hexagonal phase (c2mm) and 3D face-centered orthorhombic symmetry (Fmmm). These film periodicity uniaxially-contracted normal to the film surface.