microfluidic-fabrication-polymeric-biohybrid-fibers-with-predesigned

Microfluidic Fabrication of Polymeric and Biohybrid Fibers with Predesigned Size and Shape

A &#8220;sheath&#8221; fluid passing through a microfluidic channel at low Reynolds number can be directed around another &#8220;core&#8221; stream and ...

US Naval Research Laboratory

Diruthenium compounds bearing one (3) and two (4) ferrocene carboxylate ligands were prepared and characterized, and the electronic coupling between two equatorially adjacent Fc centers in compound 4 is significant, but weaker than those between Fc centers placed on the opposite axial sites.

Fc-Fc Electronic interaction through equatorial pathways of a diruthenium core.

Previously, the synthesis of compounds Ru(2)(D(3,5-Cl(2)Ph)F)(4-n)(O(2)CFc)(n)Cl (n = 1, 3a; 2, 4a), where D(3,5-Cl(2)Ph)F is N,N'-di(3,5-dichlorophenyl)formamidinate, from the carboxylate exchange reactions between Ru(2)(D(3,5-Cl(2)Ph)F)(4-n)(OAc)(n)Cl and ferrocene carboxylic acid was communicated. Reported herein is the preparation of analogous compounds Ru(2)(DmAniF)(4-n)(O(2)CFc)(n)Cl (n = 1, 3b; 2, 4b), where DmAniF is N,N'-di(3-methoxyphenyl)formamidinate, from Ru(2)(DmAniF)(4-n)(OAc)(n)Cl. Compounds 3 and 4 were characterized with various techniques including X-ray structural determinations of 3a and 4a. Voltammetric behaviors of compounds 3 and 4 were investigated, and stepwise one-electron ferrocene oxidations were observed for both compounds 4a and 4b. Spectral analysis of the monocations [4](+) indicated that they are the Robin-Day class II mixed valent [Fc···Fc](+) species. Measurement and fitting of magnetic data (χT) of 4a between 2 and 300 K revealed a typical zero-field splitting of a S = 3/2 center with D = 77 cm(-1), while those of [4a]BF(4) are consistent with the presence of S = 3/2 (Ru(2)) and S = 1/2 (Fc(+)) centers that are weakly coupled (zJ = -0.76 cm(-1)).

Diruthenium compounds bearing equatorial fc-containing ligands: synthesis and electronic structure.

Hydrodynamic focusing in microfluidic channels is used to produce highly uniform, shaped polymer fibers at room temperature and under "green" conditions. Core streams of thiol-ene and thiol-yne prepolymer solutions were guided using a phase-matched sheath stream through microfluidic channels with grooved walls to determine shape. Size was dictated by the ratio of the flow rates of the core and sheath streams. Thiol click reactions were initiated using UV illumination to lock in predesigned cross-sectional shapes and sizes. This approach proved to be much more flexible than electrospinning in that highly uniform fibers can be produced from prepolymer solutions with varying compositions and viscosities with made-to-order sizes and shapes. Furthermore, a very simple manipulation of the composition provided reactive groups on the fiber surface for attachment of active ligands and biological components. A proof-of-principle experiment demonstrated that biotin attached to thiol groups on the fiber surface could specifically bind a fluorescent protein.

Hydrodynamic shaping, polymerization, and subsequent modification of thiol click fibers.

Microfluidic systems have advantages that are just starting to be realized for materials fabrication. In addition to the more common use for fabrication of particles, hydrodynamic focusing has been used to fabricate continuous polymer fibers. We have previously described such a microfluidics system which has the ability to generate fibers with controlled cross-sectional shapes locked in place by in situ photopolymerization. The previous fiber fabrication studies produced relatively simple round or ribbon shapes, demonstrated the use of a variety of polymers, and described the interaction between sheath-core flow-rate ratios used to control the fiber diameter and the impact on possible shapes. These papers documented the fact that no matter what the intended shape, higher flow-rate ratios produced rounder fibers, even in the absence of interfacial tension between the core and sheath fluids. This work describes how to fabricate the next generation of fibers predesigned to have a much more complex geometry, as exemplified by the "double anchor" shape. Critical to production of the pre-specified fibers with complex features was independent control over both the shape and the size of the fabricated microfibers using a two-stage hydrodynamic focusing system. Design and optimization of the channels was performed using finite element simulations and confocal imaging to characterize each of the two stages theoretically and experimentally. The resulting device design was then used to generate thiol-ene fibers with a unique double anchor shape. Finally, proof-of-principle functional experiments demonstrated the ability of the fibers to transport fluids and to interlock laterally.

Darryl A. Boyd

Center for Bio/Molecular Science & Engineering

US Naval Research Laboratory

Microfluidic Fabrication of Polymeric and Biohybrid Fibers with Predesigned Size and Shape

Darryl A. Boyd

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Center for Bio/Molecular Science & Engineering

US Naval Research Laboratory

Microfluidic Fabrication of Polymeric and Biohybrid Fibers with Predesigned Size and Shape

Center for Bio/Molecular Science & Engineering