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We have created a family of water-soluble block copolymers of acrylamide and N-alkylacrylamides that are designed to selectively remove proteins from DNA via microchannel electrophoresis. It was hypothesized that the inclusion of hydrophobic subunits in the polymer chain, in sufficient concentration, could lead to protein adsorption due to hydrophobic interactions. A series ofN-alkylacrylamide comonomers with varying alkyl chain lengths (C4, C6, C8) and also an N,N-dialkyl group (C6-C6) were synthesized via reactions between acryloyl chloride and the respective alkylamines. Copolymers were synthesized using an aqueous "micellar" polymerization technique, which involves dissolving acrylamide in the aqueous phase while hydrophobic monomers are solubilized in sodium dodecyl sulfate micelles. Copolymers comprising up to 4 mol % of a hydrophobic subunit (as verified by (1)H NMR) were synthesized. Polymer molecular weights were determined by tandem gel permeation chromatography-multiangle laser light scattering, and ranged from 1.5 x 10(6) to 4.3 x 10(6). Capillary electrophoresis analysis of bovine serum albumin and beta-lactoglobulin migration in these matrixes revealed that the octylacrylamide and dihexylacrylamide copolymers show the most significant extent of protein adsorption while butylacrylamides show no noteworthy adsorption trend. All copolymer matrixes studied allowed the passage of a dsDNA digest, and displayed some DNA sieving ability at 0.5% (w/w) in TTE (50 mM Tris, 50 mM TAPS, 2 mM EDTA, pH 8.4) buffer. These matrixes are demonstrated in on-chip experiments to adsorb protein, in a step toward meeting the front-end processing goals of mu-TAS for genetic analysis applications.

The macroscopic mechanical performance of additive manufactured structures is essential for the design and application of multiscale microlattice structure. Performance is affected by microstructure and geometrical imperfection, which are strongly influenced by the size of the struts in selective laser melting (SLM) lattice structures. In this paper, the effect of size on microstructure, geometrical imperfection, and mechanical properties was systemically studied by conducting experimental tests. A series of AlSi10Mg rod-shaped samples with various diameters were fabricated using SLM. The uniaxial tensile test results show that with the decrease in build diameter, strength and Young’s modulus of strut decreased by 30% more than the stable state. The main reasons for this degradation were investigated through microscopic observation and micro X-ray computed tomography (μ-CT). In contrast with large-sized strut, the inherent porosity (1.87%) and section geometrical deviation (3%) of ponysize strut is greater because of the effect of thermal transform and hydrogen evolution, and the grain size is 0.5 μm. The discrepancy in microstructure, geometrical imperfection, and mechanical properties induced by size effect should be considered for the design and evaluation of SLM-fabricated complex structures.

We review the variety of thermo-responsive and shear-responsive polymer solutions with "switchable" viscosities that have been proposed for application as DNA sequencing matrices for capillary and microfluidic chip electrophoresis. Generally, highly entangled polymer solutions of high-molar mass polymers are necessary for the attainment of long DNA sequencing read lengths (> 500 bases) with short analysis times (< 3 h). However, these entangled polymer matrices create practical difficulties for microchannel electrophoresis with their extremely high viscosities, necessitating high-pressure loading into capillaries or chips. Shear-responsive (shear-thinning) polymer matrices exhibit a rapid drop in viscosity as the applied shear force is increased, but still require a high initial pressure to initiate flow of the solution into a microchannel. Polymer matrices designed to have thermo-responsive properties display either a lowered (thermo-thinning) or raised (thermo-thickening) viscosity as the temperature of the solution is elevated. These properties are generally designed into the polymers by the incorporation of moderately hydrophobic groups in some part of the polymer structure, which either phase-separate or hydrophobically aggregate at higher temperatures. In their low-viscosity states, these matrices that allow rapid loading of capillary or chip microchannels under low applied pressure. The primary goal of work in this area is to design polymer matrices that exhibit this responsive behavior and hence easy microchannel loading, without a reduction in DNA separation performance compared to conventional matrices. While good progress has been made, thermo-responsive matrices have yet to offer sequencing performance as good as nonthermo-responsive networks. The challenge remains to accomplish this goal through the innovative design of novel polymer structures.

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