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  • Cantilevered actuator using magnetostricitive thin film, Kazushi Ishiyama et al. (2008)
    TitleCantilevered actuator using magnetostricitive thin film
    AuthorsKazushi Ishiyama, Chikako Yokota
    PublicationJournal of Magnetism and Magnetic Materials
    VolumeIn Press, Accepted Manuscript
    DateApril 2008
  • Development of Ni-Zn nanoferrite core material with improved saturation magnetization and DC resistivity, A. Mahesh Kumar et al. (2008)
    TitleDevelopment of Ni-Zn nanoferrite core material with improved saturation magnetization and DC resistivity
    AuthorsA. Mahesh Kumar, M. Chaitanya Varma, Charu Lata Dube, K.H. Rao, Subhash C. Kashyap
    PublicationJournal of Magnetism and Magnetic Materials
    VolumeIn Press, Accepted Manuscript
  • MEMS-based fabrication and microfluidic analysis of three-dimensional perfusion systems, Choi et al. (2008)
    TitleMEMS-based fabrication and microfluidic analysis of three-dimensional perfusion systems
    Authors Choi, Vukasinovic, Glezer, Allen
    PublicationBiomedical Microdevices
    AbstractThis paper describes fabrication and fluidic characterization of 3D microperfusion systems that could extend the viability of high-density 3D cultures in vitro. High-aspect ratio towers serve as 3D scaffolds to support the cultures and contain injection sites for interstitial delivery of nutrients, drugs, and other reagents. Hollow and solid-top tower arrays with laser ablated side-ports were fabricated using SU-8. Appropriate sizing of fluidic ports improves the control of agent delivery. Microfluidic perfusion can be used to continuously deliver equal amount of nutrients through all ports, or more media can be delivered at some ports than the others, thus allowing spatial control of steady concentration gradients throughout the culture thickness. The induced 3D flow around towers was validated using micro particle image velocimetry. Based on experimental data, the flow rates from the characteristic ports were found to follow the analytical predictions.
  • Statistical inference for particle size distribution of magnetic nanoparticles, Gang Lei et al. (2008)
    TitleStatistical inference for particle size distribution of magnetic nanoparticles
    AuthorsGang Lei, K.R. Shao, G.Y. Yang
    PublicationJournal of Magnetism and Magnetic Materials
    VolumeIn Press, Accepted Manuscript
  • Shrinky-Dink microfluidics: 3D polystyrene chips, C. Chen et al. (2008)
    TitleShrinky-Dink microfluidics: 3D polystyrene chips
    Authors C. Chen, D.N. Breslauer, J.I. Luna, A. Grimes, W. Chin, L.P. Lee, M. Khine
    PublicationLab on a Chip
    AbstractWe present a novel approach for the ultra-rapid direct patterning of complex three-dimensional, stacked polystyrene (PS) microfluidic chips. By leveraging the inherent shrinkage properties of biaxially pre-stressed thermoplastic sheets, microfluidic channels become thinner and deeper upon heating. Design conception to fully functional chips can thus be completed within minutes.
  • Nanoimprinting of conductive tracks using metal nanopowders, Seok-min Kim et al. (2007)
    TitleNanoimprinting of conductive tracks using metal nanopowders
    AuthorsSeok-min Kim, Jinsu Kim, Jiseok Lim, Minseok Choi, Shinill Kang, Sukwon Lee, Hyuk Kim
    PublicationApplied Physics Letters
    DateOctober 01, 2007
  • Tunable Poly(dimethylsiloxane) Topography in O2 or Ar Plasmas for Controlling Surface Wetting Properties and Their Ageing, K. Tsougeni et al. (2007)
    TitleTunable Poly(dimethylsiloxane) Topography in O2 or Ar Plasmas for Controlling Surface Wetting Properties and Their Ageing
    AuthorsK. Tsougeni, A. Tserepi, Vassilios Constantoudis, E. Gogolides
    PublicationJapanese Journal of Applied Physics
    DateFebruary 8, 2007
    AbstractA plasma-based methodology to fabricate ultraviolet (UV) curable poly(dimethylsiloxane) (PDMS) surfaces with controlled nano-texturing and wettability is described. The surface topography of photo-sensitive PDMS is modified in oxygen and argon plasmas. Plasma treatment of photo-crosslinked PDMS produces spontaneously-formed wavy structures with high nano-scale amplitude and with periodicity of a few 100's nm. With increasing plasma treatment duration, roughness increased while periodicity decreased, resulting in surfaces of enhanced surface area exploited for the enhancement and control of surface hydrophilicity and hydrophobicity. The mechanisms responsible for the plasma-induced PDMS surface nanotexturing are discussed. The beneficial effect of this nanotopography on retarding ageing of PDMS hydrophilicity is demonstrated. Possible applications in sensors and bio-microsystems are outlined.
  • A virtual hair cell: I. Addition of gating spring theory into a 3-D bundle mechanical model, Jong-Hoon Nam et al. (2007)
    TitleA virtual hair cell: I. Addition of gating spring theory into a 3-D bundle mechanical model
    AuthorsJong-Hoon Nam, John R. Cotton, Wally Grant
    PublicationBiophysical Journal
    DateJanuary 5, 2007
    AbstractWe have developed a virtual hair cell that simulates hair cell mechano-electrical transduction (MET) in the turtle utricle. This study combines a full 3-D hair bundle mechanical model with a gating spring theory. Previous mathematical models represent the hair bundle with a single degree of freedom system which, we have argued, cannot fully explain hair bundle mechanics. In our computer model, the tip link tension and fast adaptation modulator kinetics determine the opening and closing of each channel independently. We observed the response of individual transduction channels with our presented model. The simulated results showed three features of hair cells in vitro: First, a transient rebound of the bundle tip appeared when fast adaptation dominated the dynamics. Second, the dynamic stiffness of the bundle was minimized when the response-displacement (I-X) curve was steepest. Third, the hair cell showed "polarity", i.e. activation decreased from a peak to zero as the forcing direction rotated from the excitatory to inhibitory direction.
  • Arrayed pH-responsive microvalves controlled by multiphase laminar flow, Chenwei Liu et al. (2007)
    TitleArrayed pH-responsive microvalves controlled by multiphase laminar flow
    AuthorsChenwei Liu, Joong Yull Park, Yugong Xu, SangHoon Lee
    PublicationJournal of Micromechanics and Microengineering
    AbstractIn chemical and biological assays, the synchronized control of multiple valves is very important. Currently there is no control scheme for the use of a large number of valves without adopting bulky peripheral control devices such as pumps or electrical equipment. Therefore, we propose a simple pH-responsive microvalve array system and a new multiplexing technology that, through its reliance on multiphase laminar flow, facilitates the operation of arrayed multiple microvalves. For the fabrication of the microvalve arrays, we have used pH-responsive hydrogel microspheres produced by a microfluidic chip. By incorporating these microspheres inside an arrayed microvalve polydimethylsiloxane (PDMS) platform, we produced pH-responsive arrayed microvalves with 'open' and 'close' operations carried out by the multiphase laminar streams of pH solutions. The constructed arrayed microvalves were adequately controlled by the multiphase pH buffer; the pressure of the pH-buffer solutions controlled the widths of the sample flow. Based on the simplicity and reliability of the operating principles, this new arrayed-valve system will decrease the need for complicated peripheral lines and will remove the need for many solenoid valves, which are currently used for the individual control of arrayed valves.
  • A decade of microfluidic analysis coupled with electrospray mass spectrometry: An overview, Sander Koster et al. (2007)
    TitleA decade of microfluidic analysis coupled with electrospray mass spectrometry: An overview
    AuthorsSander Koster, Elisabeth Verpoorte
    PublicationLab on a Chip
    AbstractThis review presents a thorough overview covering the period 1997-2006 of microfluidic chips coupled to mass spectrometry through an electrospray interface. The different types of fabrication processes and materials used to fabricate these chips throughout this period are discussed. Three 'eras' of interfaces are clearly distinguished. The earliest approach involves spraying from the edge of a chip, while later devices either incorporate a standard fused-silica emitter inserted into the device or fully integrated emitters formed during chip fabrication. A summary of microfluidic-electrospray devices for performing separations and sample pretreatment steps before sample introduction into the mass spectrometer is also presented.
  • CRC Handbook of Chemistry and Physics, Internet Version, (2007)
    TitleCRC Handbook of Chemistry and Physics, Internet Version
    PlaceBoca Raton, Fl, USA
    PublisherTaylor and Francis
  • Process and formulation variables in the preparation of injectable and biodegradable magnetic microspheres, Hong Zhao et al. (2007)
    TitleProcess and formulation variables in the preparation of injectable and biodegradable magnetic microspheres
    AuthorsHong Zhao, Jeffrey Gagnon, Urs Hafeli
    PublicationBioMagnetic Research and Technology
    AbstractThe aim of this study was to prepare biodegradable sustained release magnetite microspheres sized between 1 to 2 mum. The microspheres with or without magnetic materials were prepared by a W/O/W double emulsion solvent evaporation technique using poly(lactide-co-glycolide) (PLGA) as the biodegradable matrix forming polymer. Effects of manufacturing and formulation variables on particle size were investigated with non-magnetic microspheres. Microsphere size could be controlled by modification of homogenization speed, PLGA concentration in the oil phase, oil phase volume, solvent composition, and polyvinyl alcohol (PVA) concentration in the outer water phase. Most influential were the agitation velocity and all parameters that influence the kinematic viscosity of oil and outer water phase, specifically the type and concentration of the oil phase. The magnetic component yielding homogeneous magnetic microspheres consisted of magnetite nanoparticles of 8 nm diameter stabilized with a polyethylene glycole/polyacrylic acid (PEG/PAA) coating and a saturation magnetization of 47.8 emu/g. Non-magnetic and magnetic microspheres had very similar size, morphology, and size distribution, as shown by scanning electron microscopy. The optimized conditions yielded microspheres with 13.7 weight% of magnetite and an average diameter of 1.37 mum. Such biodegradable magnetic microspheres seem appropriate for vascular administration followed by magnetic drug targeting.
  • Transient behaviour of magnetic micro-bead chains rotating in a fluid by external fields, Ioannis Petousis et al. (2007)
    TitleTransient behaviour of magnetic micro-bead chains rotating in a fluid by external fields
    AuthorsIoannis Petousis, Erik Homburg, Roy Derks, Andreas Dietzel
    PublicationLab on a Chip
    AbstractMagnetic micro-beads can facilitate many functions in lab-on-a-chip systems, such as bio-chemical labeling, selective transport, magnetic sensing and mixing. In order to investigate potential applications of magnetic micro-beads for mixing in micro fluidic systems, we developed a pin-jointed mechanism model that allows analysing the behaviour of rotating superparamagnetic bead chains. Our numerical model revealed the response of the chains on a rotating magnetic field over time. We could demonstrate that the governing parameters are the Mason number and number of beads in the chain. The results are in agreement with the simplified analytical model, assuming a straight chain, but also allow prediction of the transient chain shape. The modelled chains develop an anti-symmetric S-shape that is stable, if the Mason number for a given chain length does not surpass a critical value. Above that value, rupture occurs in the vicinity of the chain centre. However, variations in bead susceptibility can shift the location of rupture. Moreover, we performed experiments with superparamagnetic micro-beads in a small fluid volume exposed to a uniform rotating magnetic field. Our simulation could successfully predict the observed transient chain form and the time for chain rupture. The developed model can be used to design optimised bead based mixers in micro fluidic systems.
  • Magnetic Field-Responsive Smart Polymer Composites, Genovéva Filipcsei et al. (2007)
    TitleMagnetic Field-Responsive Smart Polymer Composites
    AuthorsGenovéva Filipcsei, Ildikó Csetneki, András Szilágyi, Miklós Zrínyi
    AbstractThe combination of polymers with nano- or microsized solid materials displays novel and often enhanced properties compared to the traditional materials. They can open up possibilities for new technological applications. Materials whose physical properties can be varied by application of magnetic fields belong to a specific class of smart materials. The broad family of magnetic field-controllable soft materials includes ferrofluids, magneto-rheological fluids, magnetic gels, and magnetic elastomers. The magnetic gels and elastomers (magnetoelasts) represent a new type of composite and consist of small magnetic particles, usually in the nanometer to micron range, dispersed in a highly elastic polymeric matrix. The magnetic particles can be incorporated into the elastic body either randomly or in ordered structure. If a uniform magnetic field is applied to the reactive mixture during the cross-linking process, particle chains form and become locked into the elastomer. The resulting composites exhibit anisotropic properties. Combination of magnetic and elastic properties leads to a number of striking phenomena that are exhibited in response to impressed magnetic fields. The magnetic particles couple the shape and the elastic modulus with the external magnetic field. Giant deformational effects, high elasticity, anisotropic elastic and swelling properties, and quick response to magnetic fields open new opportunities for using such materials for various applications. Since the magnetic fields are convenient stimuli from the point of signal control, the magnetoelasts are promising smart materials in engineering due to their real-time controllable elastic properties. More recently, increasing interest has been devoted to exploration of multiresponsive magnetic polymers, which exhibit sensitivity to several external stimuli. Micro- and nanospheres that combine both magnetic, temperature, and pH sensitivity were also elaborated and studied. These new results provide novel possibilities for preparation of more complex magnetic field-responsive materials like membranes with on/off switching control. In this article, we review recent advances in mechanical and swelling behavior of magnetic field-responsive soft materials, including flexible polymer networks and gels.
  • Atomic force microscope based nanofabrication of master pattern molds for use in soft lithography, Matthew S. Johannes et al. (2007)
    TitleAtomic force microscope based nanofabrication of master pattern molds for use in soft lithography
    AuthorsMatthew S. Johannes, Daniel G. Cole, Robert L. Clark
    PublicationApplied Physics Letters
    AbstractThe authors have developed a technique that couples nanolithographic patterning using an atomic force microscope with the parallel patterning abilities of soft lithography. Master pattern generation is accomplished using local anodic oxidation as a mask pattern for anisotropic wet etching of Si(110). The resulting nanostructures are then used as master patterns for the molding of polymeric stamps to be used for microcontact printing of alkanethiols. Analysis of the resulting patterns demonstrates the validity of this method as a simple, effective, and low cost alternative to conduct and prototype nanoscale patterning in a parallel fashion.
  • Characterization of laterally deformable elastomer membranes for microfluidics, S. J. Lee et al. (2007)
    TitleCharacterization of laterally deformable elastomer membranes for microfluidics
    AuthorsS. J. Lee, J. C.-Y. Chan, K. J. Maung, E. Rezler, N. Sundararajan
    PublicationJournal of Micromechanics and Microengineering
    AbstractThis work presents experimental characterization and numerical modeling of laterally deflecting polydimethylsiloxane (PDMS) membranes under pneumatic actuation. The device for this study is a membrane valve seat that partially closes a perpendicular fluid microchannel, fabricated using single-layer soft lithography. Membranes with thickness between 8 and 14 µm have been experimentally tested up to 207 kPa, and maximum lateral displacement beyond 20 µm has been demonstrated. Investigation of geometric parameters by factorial design shows that the height of the membrane is more dominant than the width and thickness, and this is attributed to the zero-displacement boundary condition at the foot of the membrane where it is bonded to a flat substrate. A numerical model that incorporates hyperelastic material testing data shows close agreement with the deflection behavior of experimental samples, accurately predicting that a membrane of 10 µm thick, 100 µm wide and 45 µm tall deflects approximately 13 µm at 207 kPa. Simulation further shows that sidewall effects from bulk compression of the elastomer material in the actuation cavity have a significant effect, reducing maximum displacement by as much as 15% over predictions based on deformation that is limited strictly to the membrane only. Experimental yield, SEM imaging and stress simulations emphasize that the membrane foot region requires the greatest attention in terms of process development.
  • A novel metal-protected plasma treatment for the robust bonding of polydimethylsiloxane, Natasha Patrito et al. (2007)
    TitleA novel metal-protected plasma treatment for the robust bonding of polydimethylsiloxane
    AuthorsNatasha Patrito, Jessica Mary McLachlan, Sarah Nicole Faria, Jayna Chan, Peter R. Norton
    PublicationLab on a Chip
    AbstractWe describe a method for the irreversible bonding of PDMS-based microfluidic components by exploiting the first reported "shelfable" plasma treatment of PDMS. Simultaneous plasma activation and protection of PDMS surfaces are achieved via RF magnetron sputtering of thin aluminium films in the presence of an argon plasma. In this process, Ar plasma exposure generates a hydrophilic, silanol-enriched polymer surface amenable to irreversible bonding to glass, PDMS or silicon substrates, while the aluminium film functions as a capping layer to preserve the surface functionality over several weeks of storage in ambient conditions. Prior to bonding, this protective aluminium layer is removed by immersion in an aqueous etchant, exposing the adhesive surface. Employing this technology, PDMS-glass and PDMS-PDMS microfluidic devices were fabricated and the adhesive strength was quantified by tensile and leakage testing. Bonding success rates in excess of 80% were demonstrated for both PDMS-glass and PDMS-PDMS assemblies sealed 24 h and 7 days following initial polymer surface activation. PDMS-glass microdevices performed optimally, displaying maximum adhesive strengths on the order of 5 MPa and burst flow rates of [similar]1 mL min-1 (channel dimensions: l = 25 mm; w = 300 [micro sign]m; h = 20 [micro sign]m). These data demonstrate a significant improvement in performance over previously reported bonding technologies, resulting in the production of more robust, longer-lasting microfluidic systems that can withstand higher pressures and flow rates.
  • Development of a miniaturised drug delivery system with wireless power transfer and communication, S. Smith et al. (2007)
    TitleDevelopment of a miniaturised drug delivery system with wireless power transfer and communication
    AuthorsS. Smith, T.B. Tang, J.G. Terry, J.T.M. Stevenson, B.W. Flynn, H.M. Reekie, A.F. Murray, A.M. Gundlach, D. Renshaw, B. A10 - Dhillon Dhillon, A. A11 - Ohtori Ohtori, Y. A12 - Inoue Inoue, A.J. A13 - Walton Walton
    PublicationNanobiotechnology, IET
  • Electromagnetic actuation and microchannel engineering of a polymer micropen array integrated with microchannels and sample reservoirs for biological assay patterning, Maesoon Im et al. (2007)
    TitleElectromagnetic actuation and microchannel engineering of a polymer micropen array integrated with microchannels and sample reservoirs for biological assay patterning
    AuthorsMaesoon Im, Il-Joo Cho, Kwang-Seok Yun, Euisik Yoon
    PublicationApplied Physics Letters
  • Magnetic field driven nanowire rotation in suspension, K. Keshoju et al. (2007)
    TitleMagnetic field driven nanowire rotation in suspension
    AuthorsK. Keshoju, H. Xing, L. Sun
    PublicationApplied Physics Letters
  • A versatile surface channel concept for microfluidic applications, M. Dijkstra et al. (2007)
    TitleA versatile surface channel concept for microfluidic applications
    AuthorsM. Dijkstra, M. J. de Boer, J. W. Berenschot, T. S. J. Lammerink, R. J. Wiegerink, M. Elwenspoek
    PublicationJournal of Micromechanics and Microengineering
    AbstractMEMS fluidic devices often require the integration of transducer structures with freely suspended microchannels. In this paper a versatile microchannel fabrication concept is presented, allowing for easy fluidic interfacing and integration of transducer structures in close proximity to the fluid. This is achieved by the reliable fabrication of completely sealed microchannels directly below the substrate surface. The resulting planar substrate surface allows for the deposition of transducer material and pattern transfer by lithography. The microchannels are subsequently released and fluidic entrance holes are created, while the transducer structures can be protected by photoresist. Several monolithic microfluidic device structures have been fabricated, demonstrating the versatility of the concept. Fabricated surface microchannel devices can optionally be vacuum sealed by anodic bonding.
  • From superhydrophobic to superhydrophilic surfaces tuned by surfactant solutions, Feng-Ming Chang et al. (2007)
    TitleFrom superhydrophobic to superhydrophilic surfaces tuned by surfactant solutions
    AuthorsFeng-Ming Chang, Yu-Jane Sheng, Hui Chen, Heng-Kwong Tsao
    PublicationApplied Physics Letters
  • A bonding technique using hydrophilic SU-8, Yu-Tzu Chen et al. (2007)
    TitleA bonding technique using hydrophilic SU-8
    AuthorsYu-Tzu Chen, Denz Lee
    PublicationJournal of Micromechanics and Microengineering
    AbstractIn this study, we present a bonding technique for fabricating microfluidic devices with surfactant-added SU-8 (hydrophilic SU-8) as the structure. The technique is based on an adhesive wafer bonding process. The hydrophilic SU-8 plays the roles of both an adhesive layer (glue) as well as a structural layer. Due to its special feature, bonding with hydrophilic SU-8 could be conducted without pressurizing equipment. The material could define structure satisfactorily and it has a hydrophilic surface in a cured state, and has a good adhesion capability with various substrates (glass, silicon or PDMS) after oxygen plasma treatment. The performance of the material was verified by using the Raman spectroscopy to analyze the possible changes in chemical structure, measuring contact angle to characterize hydrophilicity and several tests to confirm the bonding capability. The effect of different parameters on the bonding has also been explored. 2D (one-layer hydrophilic SU-8) and 3D (two-layer hydrophilic SU-8) sandwich configurations were constructed using this bonding technique. The tests showed the bonding strength to be in the range of 2-14 kg cm[?]2 measured by the pull test, and the microchannels could stand up to 0.4 atm pressure drop in the hydrodynamic testing. The present material has good properties in bonding, and the procedure is fast, compatible and easily implementable with a standard photolithography. It is suitable for microstructure and microelectronics integration, and highly involved three-dimensional (3D) microstructures.
  • Microfabricated solenoids and Helmholtz coils for NMR spectroscopy of mammalian cells, Klaus Ehrmann et al. (2007)
    TitleMicrofabricated solenoids and Helmholtz coils for NMR spectroscopy of mammalian cells
    AuthorsKlaus Ehrmann, Nicolas Saillen, Franck Vincent, Matthieu Stettler, Martin Jordan, Florian Maria Wurm, Pierre-Andre Besse, Radivoje Popovic
    PublicationLab on a Chip
    AbstractNMR-microprobes based on solenoids and Helmholtz coils have been microfabricated and NMR-spectra of mammalian cells have successfully been taken. The microfabrication technology developed for these probes consists of three electroplated copper levels for low resistance coils and three SU-8 layers for the integration of microchannels. This technology allows fabricating solenoids, Helmholtz and planar coils on the same wafer. The coils have inner diameters in the range of 160 to 400 [micro sign]m and detection volumes of 5 to 22 nL. The solenoid and Helmholtz coils show improved RF-field characteristics compared to a planar coil fabricated with the same process. The fabricated solenoid has a particularly low resistance of only 0.46 [capital Omega] at 300 MHz. Moreover, it is very sensitive and has a very uniform RF-field, but shows large line width. The Helmholtz coils are slightly less sensitive, but display a far narrower line width, and are therefore a good compromise. With a Helmholtz coil, a SNR of 620 has been measured after one scan on 9 nL pure water. An NMR-microprobe based on a Helmholtz coil has also been used to take spectra of CHO cells that have been concentrated in the sensitive region of the coil with a mechanical filter integrated into the channel.
  • Magnetic nanoparticles with surface modification enhanced gene delivery of HVJ-E vector, Norio Morishita et al. (2005)
    TitleMagnetic nanoparticles with surface modification enhanced gene delivery of HVJ-E vector
    AuthorsNorio Morishita, Hironori Nakagami, Ryuichi Morishita, Shin-ichi Takeda, Fumihito Mishima, BungoTerazono, Shigehiro Nishijima, Yasufumi Kaneda, Noriaki Tanaka
    PublicationBiochemical and Biophysical Research Communications
    DateSeptember 9, 2005
    AbstractTo enter the realm of human gene therapy, a novel drug delivery system is required for efficient delivery of small molecules with high safety for clinical usage. We have developed a unique vector "HVJ-E (hemagglutinating virus of Japan-envelope)" that can rapidly transfer plasmid DNA, oligonucleotide, and protein into cells by cell-fusion. In this study, we associated HVJ-E with magnetic nanoparticles, which can potentially enhance its transfection efficiency in the presence of a magnetic force. Magnetic nanoparticles, such as maghemite, with an average size of 29 nm, can be regulated by a magnetic force and basically consist of oxidized Fe which is commonly used as a supplement for the treatment of anemia. A mixture of magnetite particles with protamine sulfate, which gives a cationic surface charge on the maghemite particles, significantly enhanced the transfection efficiency in an in vitro cell culture system based on HVJ-E technology, resulting in a reduction in the required titer of HVJ. Addition of magnetic nanoparticles would enhance the association of HVJ-E with the cell membrane with a magnetic force. However, maghemite particles surface-coated with heparin, but not protamine sulfate, enhanced the transfection efficiency in the analysis of direct injection into the mouse liver in an in vivo model. The size and surface chemistry of magnetic particles could be tailored accordingly to meet specific demands of physical and biological characteristics. Overall, magnetic nanoparticles with different surface modifications can enhance HVJ-E-based gene transfer by modification of the size or charge, which could potentially help to overcome fundamental limitations to gene therapy in vivo.
  • Evaluation of polydimethylsiloxane scaffolds with physiologically-relevant elastic moduli: interplay of substrate mechanics and surface chemistry effects on vascular smooth muscle cell response, Xin Q. Brown et al. (2005)
    TitleEvaluation of polydimethylsiloxane scaffolds with physiologically-relevant elastic moduli: interplay of substrate mechanics and surface chemistry effects on vascular smooth muscle cell response
    AuthorsXin Q. Brown, Keiko Ookawa, Joyce Y. Wong
    DateJune 2005
    AbstractPolydimethylsiloxane (PDMS) is used extensively to study cell-substrate interactions because its mechanical properties are easily tuned in physiologically relevant ranges. However, changes in mechanical properties also modulate surface chemistry and cell response. Here, we correlate the mechanical and surface properties of PDMS to vascular smooth muscle cell (VSMC) behavior. We find that a 5-fold increase in base:crosslinker ratio leads to ~40-fold decrease in elastic modulus but no significant differences in surface wettability. However, when polyelectrolyte multilayers are adsorbed to promote cell adhesion, wettability varies inversely with substrate stiffness. Despite these differences in hydrophobicity, the amount of adsorbed protein remains the same. In the absence of serum, there is a 39% decrease in cell attachment and a 42% decrease in spreading as the elastic modulus decreases from 1.79 to 0.05�MPa. In the presence of serum or adsorbed fibronectin, the differences in attachment and spreading are diminished. This is not the case for the rate of serum-stimulated cell proliferation, which remains inversely dependent on crosslinker concentration. We conclude that for the range of crosslinker concentrations investigated, the surface properties dominate the initial cell attachment and spreading, whereas the mechanical properties influence the long-term cell growth.
  • Magnetization processes in magnetotactic bacteria systems, Tatyana Polyakova et al. (2005)
    TitleMagnetization processes in magnetotactic bacteria systems
    AuthorsTatyana Polyakova, Vitalii Zablotskii
    PublicationJournal of Magnetism and Magnetic Materials
    DateMay 2005
    AbstractIn low fields, the magnetization of magnetotactic bacteria (MTB) culture is affected by chemotaxis and can be described by the Langevin function which depends on magnetic field strength and chemotaxis energy. In moderate fields, bacteria magnetization switching occurs as the second-order phase transition induced by increasing the field applied opposite the MTB magnetic moments. For bacteria containing one or two chains of magnetosomes we calculated the switching field as a function of the gap between magnetic particles.
  • Magnetic susceptibility studies of single-crystalline zinc ferrites under pressure, A. Wiechec et al. (2005)
    TitleMagnetic susceptibility studies of single-crystalline zinc ferrites under pressure
    AuthorsA. Wiechec, R. Zach, Z. Ka[cedilla]kol, Z. Tarnawski, A. Kozlowski, J.M. Honig
    PublicationPhysica B: Condensed Matter
    DateApril 30, 2005
    AbstractMagnetic susceptibility measurements of magnetite and zinc ferrite (Fe3-xZnxO4, x=0.0174, 0.049) single-crystal samples were performed under pressure up to 1.2 GPa in the temperature range close to the Verwey transition TV. The application of pressure p decreases TV linearly. The [chi]AC signal is not affected above TV, but rises below TV with p; this was explained by increasing domain wall movement. Finally, the isotropy point TIP increases with pressure indicating that magnetism does not actively participate in the Verwey transition.
  • Biomimetic Autoseparation of Leukocytes from Whole Blood in a Microfluidic Device, S.S. Shevkoplyas et al. (2005)
    TitleBiomimetic Autoseparation of Leukocytes from Whole Blood in a Microfluidic Device
    AuthorsS.S. Shevkoplyas, T. Yoshida, L.L. Munn, M.W. Bitensky
    PublicationAnalytical Chemistry
    DateFebruary 1, 2005
    AbstractLeukocytes comprise less than 1% of all blood cells. Enrichment of their number, starting from a sample of whole blood, is the required first step of many clinical and basic research assays. We created a microfluidic device that takes advantage of the intrinsic features of blood flow in the microcirculation, such as plasma skimming and leukocyte margination, to separate leukocytes directly from whole blood. It consists of a simple network of rectangular microchannels designed to enhance lateral migration of leukocytes and their subsequent extraction from the erythrocyte-depleted region near the sidewalls. A single pass through the device produces a 34-fold enrichment of the leukocyte-to-erythrocyte ratio. It operates on microliter samples of whole blood, provides positive, continuous flow selection of leukocytes, and requires neither preliminary labeling of cells nor input of energy (except for a small pressure gradient to support the flow of blood). This effortless, efficient, and inexpensive technology can be used as a lab-on-a-chip component for initial whole blood sample preparation. Its integration into microanalytical devices that require leukocyte enrichment will enable accelerated transition of these devices into the field for point-of-care clinical testing.
    DOI10.1021/ac049037i S0003-2700(04)09037-7
  • Recent developments in single-cell analysis, Xin Lu et al. (2004)
    TitleRecent developments in single-cell analysis
    AuthorsXin Lu, Wei-Hua Huang, Zong-Li Wang, Jie-Ke Cheng
    PublicationAnalytica Chimica Acta
    DateMay 17, 2004
    AbstractCells play a significant role in life activities such as metabolism and signal transduction and so on. The development of cellular research puts forward a severe challenge to analyst, and the study of single-cell has already become the focus of the frontiers in analytical chemistry. Combining capillary electrophoresis (CE) with detection methods such as laser-induced fluorescence (LIF) and electrochemical detection (ED), and mass spectrometry (MS) have particular description for single-cell analysis. Due to extensive research on objects and complex characteristic in the single-cell, scientists have developed more methods and technologies for application in single-cell analysis. Here we reviewed the current approach of technologies of single-cell analysis in manipulation, injection and lysis of single-cell, capillary electrophoresis, imaging analysis, temporal and spatial monitoring on dynamics of single-cells, and the application.
  • Nanoparticles probe biosystems, Paula Gould (2004)
    TitleNanoparticles probe biosystems
    AuthorPaula Gould
    PublicationMaterials Today
    DateFebruary 2004
  • Two-Photon Three-Dimensional Microfabrication of Poly(Dimethylsiloxane) Elastomers, C. A Coenjarts et al. (2004)
    TitleTwo-Photon Three-Dimensional Microfabrication of Poly(Dimethylsiloxane) Elastomers
    AuthorsC. A Coenjarts, C. K Ober
    PublicationChem. Mater
  • Adhesion and friction of PDMS networks: molecular weight effects, A. Galliano et al. (2003)
    TitleAdhesion and friction of PDMS networks: molecular weight effects
    AuthorsA. Galliano, S. Bistac, J. Schultz
    PublicationJournal of Colloid and Interface Science
    DateSeptember 15, 2003
    AbstractThe objective of this work is to find relations between adherence and friction behaviors of elastomer networks. The chosen approach is based on the parallel study of the initial molecular weight (i.e., the degree of cross-linking) dependence of both adherence and friction. The polymers used are cross-linked polydimethylsiloxane (PDMS) and the substrate is a smooth glass plate. The experimental procedure uses both friction (pin on disk tribometer) and adhesion (tack test) measurements, associated with surface analysis and mechanical and rheological characterizations. Tack results show that high molecular weight PDMS exhibits the greater adherence energy. This can be explained by the role of both chain length and free and pendant chains: more numerous and longer free chains favor the substrate wetting (at a molecular scale) and increases the energy dissipation during separation (extraction and reptation mechanisms). However, friction results indicate a higher friction resistance for low molecular weight PDMS. This result could be quite surprising. An explanation based on interfacial sliding properties of free and pendant chains can be proposed. Elsewhere, for the lower molecular weight polymer, elastic contact present during friction is able to act as a forced wetting, constraining the network and consequently leading to a greater energy dissipation.
  • Smart nanocomposite polymer gels, Zsolt Varga et al. (2003)
    TitleSmart nanocomposite polymer gels
    AuthorsZsolt Varga, J�zsef Feh�r, Genov�va Filipcsei, Mikl�s Zr�nyi
    PublicationMacromolecular Symposia
    AbstractThe combination of polymers with nanomaterials displays novel and often enhanced properties compared to the traditional materials. They can open up possibilities for new technological applications. The magnetic polymer gel represents a new type of composites consisting of small magnetic particles, usually from the nanometer range to the micron range, dispersed in a highly elastic polymeric gel matrix. Combination of magnetic and elastic properties leads to a number of striking phenomena that are exhibited in response to impressed magnetic fields. Giant deformational effects, high elasticity, anisotropic properties, temporary reinforcement and quick response to magnetic field open new opportunities for using such materials for various applications.
  • Hemocompatibility, biocompatibility, inflammatory and in vivo studies of primary reference materials low-density polyethylene and polydimethylsiloxane: A review, Yves Marois Marie-Claire Bélanger (2001)
    TitleHemocompatibility, biocompatibility, inflammatory and in vivo studies of primary reference materials low-density polyethylene and polydimethylsiloxane: A review
    AuthorYves Marois Marie-Claire Bélanger
    PublicationJournal of Biomedical Materials Research
    AbstractIn 1984, low-density polyethylene (LDPE) and polymethylsiloxane (PDMS), two primary reference materials (PRM), were made available by the National Heart, Lung, and Blood Institute (NHLBI) as discriminatory tools for the validation of standardized and novel in vitro and in vivo tests in the evaluation of biomaterials. This article reviews the results and conclusions obtained by several studies investigating the hemocompatibility, in vitro biocompatibility, inflammatory response, and in vivo tissue reactions of these two reference materials. Variable results obtained with LDPE and PDMS in ex vivo hemocompatibility studies were attributed to the type of animal model used, the flow velocity of the circulating blood, the time of exposure, and the methodology used to measure blood cell adhesion or activation at the surface of the materials. In contrast, both the LDPE and PDMS appeared to be suitable reference materials when used in in vitro biocompatibility, inflammatory response, and in vivo studies. However, caution must be taken when interpreting the results, because gamma sterilization of these two materials as well as their origin (for example PDMS) are two critically important factors. In conclusion, we see a definite need for standardized hemocompatible parameters and better high-quality hemocompatibility studies on PRM. This review also suggests other materials as potential PRM candidates, namely, Biomer® and IntramedicTM polyethylene. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 467-477, 2001
  • Shaped Ceramics with Tunable Magnetic Properties from Metal-Containing Polymers, Mark J. MacLachlan et al. (2000)
    TitleShaped Ceramics with Tunable Magnetic Properties from Metal-Containing Polymers
    AuthorsMark J. MacLachlan, Madlen Ginzburg, Neil Coombs, Thomas W. Coyle, Nandyala P. Raju, John E. Greedan, Geoffrey A. Ozin, Ian Manners
    DateFebruary 25, 2000
  • Surface oxidation of nickel thin films, Kumari et al. (1992)
    TitleSurface oxidation of nickel thin films
    Authors Kumari, Natarajan, Vaidyan, Koshy
    PublicationJournal of Materials Science Letters
    DateJanuary 01, 1992
  • Organic polymer: Ferromagnetism or antiferromagnetism, Daping Chu et al. (1990)
    TitleOrganic polymer: Ferromagnetism or antiferromagnetism
    AuthorsDaping Chu, Sen Liu, Zhong-can Ou-Yang
    PublicationPhysics Letters A
    DateNovember 5, 1990
    AbstractHere we propose a structure model of quasi-one-dimensional polymers with antiferromagnetic exchange interaction between radicals, which will show ferromagnetic behavior in an applied field. Break down units are suggested for easy calculation. Some analytical and numerical results are given.
  • Magnetic susceptibility of strongly magnetic ores at different magnetic field intensities, Rychkov et al. (1978)
    TitleMagnetic susceptibility of strongly magnetic ores at different magnetic field intensities
    Authors Rychkov, Lomovtsev
    PublicationJournal of Mining Science
    DateNovember 11, 1978
    AbstractConclusions 1. At a given intensity, the magnetic susceptibility of strongly magnetic ores is directly proportional to the maximum susceptibility, proportional to the fourth root of the magnetic field intensity corresponding to the susceptibility maximum, and inversely proportional to the fourth root of the given magnetic field intensity. 2. The proposed procedure for determining the specific force of magnetic attraction (5) of strongly magnetic particles to the separator poles, which takes account of the dependence of the susceptibility on the field intensity, the textural-structural chracteristics of the ore, and the ferromagnetic phase content of the intergrowth can be used to calculate the operating conditions of the separator and of apparatus for dry magnetic beneficiation of crushed strongly magnetic ores.