We report a new approach for performing DNA electrophoresis. Using experimental studies and molec... more We report a new approach for performing DNA electrophoresis. Using experimental studies and molecular dynamics simulations, we show that a perfectly flat silicon wafer, without any surface features, can be used to fractionate DNA in free solution. We determine that the ability of a flat surface to separate DNA molecules results from the local friction between the surface and the adsorbed DNA segments. We control this friction by coating the Si surface with silane monolayer films and show that it is possible to systematically change the size range of DNA that can be separated.
The evaporation rate of buffer droplets containing small amount of DNA is strongly dependent on t... more The evaporation rate of buffer droplets containing small amount of DNA is strongly dependent on the adsorption rates of the DNA chains to the air/solid/liquid interface. The adsorption kinetics is greatly affected by the DNA substrate interactions and the presence of external electric fields. Here we study the adsorption kinetics using confocal microscopy of the DNA as a function of applied external electric fields and DNA/surface interactions. Different surface patterning techniques are used to produce chemically inhomogeneous surfaces with correlation length ranging from a few hundred angstroms to several microns. The contact angle and morphology of the drops were monitored using a KSV contact angle gomiometer. The evaporation rates were found to be drastically varied on different patterned surfaces and increased in the presence of electrical fields. The results will be interpreted in terms of the morphology of the DNA on the surfaces.
Functional nanofibrous scaffolds produced by electrospinning have great potential in many biomedi... more Functional nanofibrous scaffolds produced by electrospinning have great potential in many biomedical applications, such as tissue engineering, wound dressing, enzyme immobilization and drug (gene) delivery. For a specific successful application, the chemical, physical and biological properties of electrospun scaffolds should be adjusted to match the environment by using a combination of multi-component compositions and fabrication techniques where electrospinning has often become a pivotal tool. The property of the nanofibrous scaffold can be further improved with innovative development in electrospinning processes, such as two-component electrospinning and in-situ mixing electrospinning. Post modifications of electrospun membranes also provide effective means to render the electrospun scaffolds with controlled anisotropy and porosity. In this review, we review the materials, techniques and post modification methods to functionalize electrospun nanofibrous scaffolds suitable for biomedical applications.
Scattering Study on Self-Assembly of Block Copolymer in Supercritical Carbon Dioxide
Photon Correlation and Scattering
Both pressure- and temperature-induced micellization processes of a diblock copolymer of poly(1,1... more Both pressure- and temperature-induced micellization processes of a diblock copolymer of poly(1,1-dihydroperfluorooctyl acrylate) and poly(vinyl acetate) in supercritical carbon dioxide were studied by using high-pressure laser light scattering.
The journal of physical chemistry. B, Feb 16, 2017
Nanocellulose extracted from wood pulps using TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical... more Nanocellulose extracted from wood pulps using TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation and sulfuric acid hydrolysis methods was characterized by small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and dynamic light scattering (DLS) techniques. The dimensions of this nanocellulose (TEMPO-oxidized cellulose nanofiber (TOCN) and sulfuric acid hydrolyzed cellulose nanocrystal (SACN)) revealed by the different scattering methods were compared with those characterized by transmission electron microscopy (TEM). The SANS and SAXS data were analyzed using a parallelepiped-based form factor. The width and thickness of the nanocellulose cross section were ∼8 and ∼2 nm for TOCN and ∼20 and ∼3 nm for SACN, respectively, where the fitting results from SANS and SAXS profiles were consistent with each other. DLS was carried out under both the VV mode with the polarizer and analyzer parallel to each other and the HV mode having them perpendicula...
A magnetic sphere rheometer which is fully controlled by a personal computer has been developed. It is capable of measuring viscosities in the range of 0.1-5 X 10
High Flux High Efficiency Nanofiber Membranes and Methods of Production Thereof
Separation medium for capillary electrophoresis
Method of cell storage in a delivery system
Complexation of Slightly Cross-Linked Gels of Poly(diallyl-d imethylammonium chloride) with Sodium Alkyl Sulfates
Aps March Meeting Abstracts, Mar 1, 1996
Nanocomposite Fibers and Films Containing Polyolefin and Surface-Modified Carbon Nanotubes
Synchrotron SAXS and WAXD Studies of Cellulose Nascent Crystals: Experiment and Structure Analysis
Aps March Meeting Abstracts, Feb 1, 2012
ABSTRACT Cellulose nascent crystals extracted from biomass (wood pulp, jute and cotton)by combine... more ABSTRACT Cellulose nascent crystals extracted from biomass (wood pulp, jute and cotton)by combined chemical and mechanical treatments are low cost, environmentally friendly and high performance materials to form the barrier layer in ultrafiltration membranes. This research project is aimed at using the synchrotron X-ray scattering methods to characterize the nascent crystalline nanofibers in different formats. The SAXS (Small Angle X-ray Scattering) data of cellulose nanofiber suspensions was analyzed and the polydisperse ribbon model with rectangular cross section fit the data well. The 2D and 3D simulations of WAXD (Wide Angle X-ray Diffraction) pattern of jute cellulose fibers solved the contents ratio of cellulose I-alpha and I-beta and Hermans' orientation parameter P2.
Apparatus and method for electro-blowing or blowing-assisted electro-spinning technology
Water-ιnduced micellar structure change in pluronic P103/water/o-xylene ternary system
Journal of Polymer Science Part B Polymer Physics, 1998
J. GLIMCHER 5 , Harvard Medical School-The three-dimensional packing of collagen molecules in bon... more J. GLIMCHER 5 , Harvard Medical School-The three-dimensional packing of collagen molecules in bone collagen fibrils has been largely unknown because even in moderately mineralized bone tissues, the organic matrix structure is severely perturbed by the deposition of mineral crystals. During the past decades, the structure of tendon collagen (e.g. rat tail)-a tissue that cannot mineralize in vivo, has been assumed to be representative for bone collagen fibrils. Small-angle X-ray diffraction analysis of the native, uncalcified intramuscular fish bone has revealed a new molecular packing scheme, significantly different from the quasi-hexagonal arrangement often found in tendons. The deduced structure in bone collagen fibrils indicates the presence of spatially discrete microfibrils, and an arrangement of intrafibrillar space to form "channels", which could accommodate crystals with dimensions typically found in bone apatite.
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Papers by Benjamin Chu