Economics Education across Borders and Cultures

Soper, John C. 한국경제교육학회 2003 경제교육연구 Vol.10 No.2

Polymer-based dense fluidic networks for high throughput screening with ultrasensitive fluorescence detection

Okagbare, Paul I.,Soper, Steven Allan WILEY-VCH Verlag 2010 Electrophoresis Vol.31 No.18

<P>Microfluidics represents a viable platform for performing high throughput screening (HTS) because of its ability to automate fluid handling and generate fluidic networks with high number densities over small footprints appropriate for the simultaneous optical interrogation of many screening assays. While most HTS campaigns depend on fluorescence, readers typically use point detection and serially address the assay results significantly lowering throughput or detection sensitivity due to a low duty cycle. To address this challenge, we present here the fabrication of a high-density microfluidic network packed into the imaging area of a large field-of-view (FoV) ultrasensitive fluorescence detection system. The fluidic channels were 1, 5 or 10 μm (width), 1 μm (depth) with a pitch of 1–10 μm and each fluidic processor was individually addressable. The fluidic chip was produced from a molding tool using hot embossing and thermal fusion bonding to enclose the fluidic channels. A 40× microscope objective (numerical aperture=0.75) created an FoV of 200 μm, providing the ability to interrogate ∼25 channels using the current fluidic configuration. An ultrasensitive fluorescence detection system with a large FoV was used to transduce fluorescence signals simultaneously from each fluidic processor onto the active area of an electron multiplying charge-coupled device. The utility of these multichannel networks for HTS was demonstrated by carrying out the high throughput monitoring of the activity of an enzyme, apurinic Endonuclease 1, used as a model-screening assay.</P>

Staphylococcus aureus extracellular vesicles (EVs): surface-binding antagonists of biofilm formation

Im, H.,Lee, S.,Soper, S.,Mitchell, R. Royal Society of Chemistry 2017 Molecular bioSystems Vol.13 No.12

Flexible fabrication and applications of polymer nanochannels and nanoslits

Chantiwas, Rattikan,Park, Sunggook,Soper, Steven A.,Kim, Byoung Choul,Takayama, Shuichi,Sunkara, Vijaya,Hwang, Hyundoo,Cho, Yoon-Kyoung Royal Society of Chemistry 2011 Chemical Society reviews Vol.40 No.7

<P>Fluidic devices that employ nanoscale structures (<100 nm in one or two dimensions, slits or channels, respectively) are generating great interest due to the unique properties afforded by this size domain compared to their micro-scale counterparts. Examples of interesting nanoscale phenomena include the ability to preconcentrate ionic species at extremely high levels due to ion selective migration, unique molecular separation modalities, confined environments to allow biopolymer stretching and elongation and solid-phase bioreactions that are not constrained by mass transport artifacts. Indeed, many examples in the literature have demonstrated these unique opportunities, although predominately using glass, fused silica or silicon as the substrate material. Polymer microfluidics has established itself as an alternative to glass, fused silica, or silicon-based fluidic devices. The primary advantages arising from the use of polymers are the diverse fabrication protocols that can be used to produce the desired structures, the extensive array of physiochemical properties associated with different polymeric materials, and the simple and robust modification strategies that can be employed to alter the substrate's surface chemistry. However, while the strengths of polymer microfluidics is currently being realized, the evolution of polymer-based nanofluidics has only recently been reported. In this <I>critical review</I>, the opportunities afforded by polymer-based nanofluidics will be discussed using both elastomeric and thermoplastic materials. In particular, various fabrication modalities will be discussed along with the nanometre size domains that they can achieve for both elastomer and thermoplastic materials. Different polymer substrates that can be used for nanofluidics will be presented along with comparisons to inorganic nanodevices and the consequences of material differences on the fabrication and operation of nanofluidic devices (257 references).</P> <P>Graphic Abstract</P><P>The fabrication of nanochannels in thermoplastics and elastomers is critically reviewed along with their potential applications. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0cs00138d'> </P>

Hydrodynamic shearing of DNA in a polymeric microfluidic device

Nesterova, I.,Hupert, M.,Witek, M.,Soper, S. Royal Society of Chemistry 2012 Lab on a chip Vol.12 No.6

Discrete geometry optimization for reducing flow non-uniformity, asymmetry, and parasitic minor loss pressure drops in Z-type configurations of fuel cells

Jackson, J.M.,Hupert, M.L.,Soper, S.A. Elsevier Sequoia 2014 Journal of Power Sources Vol.269 No.-

Parallel channel configurations, such as Z-type, used to distribute reagents in planar fuel cells provide lower overall pressure drop as compared to other channel designs. However, due to their inherent characteristics, flow maldistribution in parallel configurations is commonly observed and leads to starvation of reagents in middle channels. In addition, the Reynolds number dependent minor losses at branching tee junctions may cause asymmetric flow non-uniformity and reagent imbalance between the cathode and anode. Herein, we present a universal and simple optimization method to simultaneously reduce flow maldistribution, asymmetry, and parasitic pressure in Z-type parallel configurations of fuel cells or fuel cell stacks that has improved scalability relative to previous methods. A discrete model's governing equations were reduced to yield geometric ratios between headers. Increasing header widths to satisfy these ratios reduced flow maldistribution without modifying parallel channel geometry as validated by computation fluid dynamics (CFD) simulations. Furthermore, decreased Reynolds numbers throughout the headers reduced minor pressure drops and flow distribution asymmetry. We offer several methods to reduce the optimized geometry's footprint, including an adaptation of the discontinuous design.

Ultra-fast two-dimensional microchip electrophoresis using SDS μ-CGE and microemulsion electrokinetic chromatography for protein separations

Osiri, John K.,Shadpour, Hamed,Soper, Steven A. Springer-Verlag 2010 ANALYTICAL AND BIOANALYTICAL CHEMISTRY Vol.398 No.1

Characterization of activated cyclic olefin copolymer: effects of ethylene/norbornene content on the physiochemical properties

O'Neil, Colleen E.,Taylor, Scott,Ratnayake, Kumuditha,Pullagurla, Swathi,Singh, Varshni,Soper, Steven A. The Royal Society of Chemistry 2016 The Analyst Vol.141 No.24

<P>The ethylene/norbornene content within cyclic olefin copolymer (COC) is well known to affect the chemical and physical properties of the copolymer, such as the glass transition temperature (<I>T</I>g) and transparency. However, no work has been reported evaluating the effects of the ethylene/norbornene content on the surface properties of COC following UV/O3 or O2 plasma activation. Activation with either O2 plasma or UV/O3 is often used to assist in thermal assembly of fluidic devices, increasing the wettability of the surfaces, or generating functional scaffolds for the attachment of biological elements. Thus, we investigated differences in the physiochemical surface properties of various ethylene/norbornene compositions of COC following activation using analytical techniques such as water contact angle (WCA), ATR-FTIR, XPS, TOF-SIMS, UV-VIS, AFM and a colorimetric assay utilizing Toluidine Blue O (TBO). Results showed that increased norbornene content led to the generation of more oxygen containing functionalities such as alcohols, ketones, aldehydes and carboxyl groups when activated with either UV/O3 or O2 plasma. Specifically, COC with ∼60% norbornene content showed a significantly higher -COOH functional group density when compared to COC with a 50% norbornene content and COC with a 35% norbornene content following UV/O3 or O2 plasma activation. Furthermore, COC with large norbornene contents showed a smaller average RMS roughness (0.65 nm) when compared to COC containing low norbornene contents (0.95 nm) following activation making this substrate especially suited for nanofluidic applications, which require smooth surfaces to minimize effects arising from dielectrophoretic trapping or non-specific adsorption. Although all COC substrates showed >90% transparency at wavelengths >475 nm, COC possessing high norbornene contents showed significantly less transparency at wavelengths below 475 nm following activation, making optical detection in this region difficult. Our data showed distinct physiochemical differences in activated COC that was dependent upon the ethylene/norbornene content of the thermoplastic and thus, careful selection of the particular COC grade must be considered for micro- and nanofluidics.</P>

Simple room temperature bonding of thermoplastics and poly(dimethylsiloxane)

Sunkara, Vijaya,Park, Dong-Kyu,Hwang, Hyundoo,Chantiwas, Rattikan,Soper, Steven A.,Cho, Yoon-Kyoung Royal Society of Chemistry 2011 Lab on a chip Vol.11 No.5

<P>We describe a simple and versatile method for bonding thermoplastics to elastomeric polydimethylsiloxane (PDMS) at room temperature. The bonding of various thermoplastics including polycarbonate (PC), cyclic olefin copolymer (COC), polymethylmethacrylate (PMMA), and polystyrene (PS), to PDMS has been demonstrated at room temperature. An irreversible bonding was formed instantaneously when the thermoplastics, activated by oxygen plasma followed by aminopropyltriethoxysilane modification, were brought into contact with the plasma treated PDMS. The surface modified thermoplastics were characterized by water contact angle measurements and X-ray photoelectron spectroscopy. The tensile strength of the bonded hybrid devices fabricated with PC, COC, PMMA, and PS was found to be 430, 432, 385, and 388 kPa, respectively. The assembled devices showed high burst resistance at a maximum channel pressure achievable by an in-house built syringe pump, 528 kPa. Furthermore, they displayed very high hydrolytic stability; no significant change was observed even after the storage in water at 37 °C over a period of three weeks. In addition, this thermoplastic-to-PDMS bonding technique has been successfully employed to fabricate a relatively large sized device. For example, a lab-on-a-disc with a diameter of 12 cm showed no leakage when it spins for centrifugal fluidic pumping at a very high rotating speed of 6000 rpm.</P> <P>Graphic Abstract</P><P>We report a simple, versatile, instantaneous and irreversible method for bonding thermoplastics to elastomeric polydimethylsiloxane (PDMS) at room temperature. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0lc00272k'> </P>

Solid-phase extraction and purification of membrane proteins using a UV-modified PMMA microfluidic bioaffinity μSPE device

Battle, Katrina N.,Jackson, Joshua M.,Witek, Małgorzata A.,Hupert, Mateusz L.,Hunsucker, Sally A.,Armistead, Paul M.,Soper, Steven A. The Royal Society of Chemistry 2014 The Analyst Vol.139 No.6

<P>We present a novel microfluidic solid-phase extraction (μSPE) device for the affinity enrichment of biotinylated membrane proteins from whole cell lysates. The device offers features that address challenges currently associated with the extraction and purification of membrane proteins from whole cell lysates, including the ability to release the enriched membrane protein fraction from the extraction surface so that they are available for downstream processing. The extraction bed was fabricated in PMMA using hot embossing and was comprised of 3600 micropillars. Activation of the PMMA micropillars by UV/O<SUB>3</SUB> treatment permitted generation of surface-confined carboxylic acid groups and the covalent attachment of NeutrAvidin onto the μSPE device surfaces, which was used to affinity select biotinylated MCF-7 membrane proteins directly from whole cell lysates. The inclusion of a disulfide linker within the biotin moiety permitted release of the isolated membrane proteins <I>via</I> DTT incubation. Very low levels (∼20 fmol) of membrane proteins could be isolated and recovered with ∼89% efficiency with a bed capacity of 1.7 pmol. Western blotting indicated no traces of cytosolic proteins in the membrane protein fraction as compared to significant contamination using a commercial detergent-based method. We highlight future avenues for enhanced extraction efficiency and increased dynamic range of the μSPE device using computational simulations of different micropillar geometries to guide future device designs.</P> <P>Graphic Abstract</P><P>We present a novel microfluidic solid-phase extraction (μSPE) device for the affinity enrichment of biotinylated membrane proteins from whole cell lysates. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3an02400h'> </P>