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Shiho Tokonami, Takuya Iida
For sustainable human life, biosensing systems for contaminants or disease-causing bacteria are crucial for food security, environmental improvement, and disease prevention. With an aim of enhancing the sensitivity and detection speed, many researchers have developed efficient detection methods for target bacteria. In this review, we discuss recent topics related to active and passive bacterial detection methods, including (1) optical approaches with unique functional nano- and micro-structures, and (2) electrical approaches involving mechanical modulation and electrochemical reactions...
October 2, 2017: Analytica Chimica Acta
Sarah Boehm, Lan Lin, Nermina Brljak, Nicole Famularo, Theresa S Mayer, Christine D Keating
We report the effect of topographical features on gold nanowire assemblies in a vertically-applied AC electric field. Nanowires 300 nm in diameter × 2.5 µm long, and coated with ~30 nm silica shell, were assembled in aqueous solution between top and bottom electrodes, where the bottom electrode was patterned with cylindrical dielectric posts. Assemblies were monitored in real time using optical microscopy. Dielectrophoretic and electrohydrodynamic forces were manipulated through frequency and voltage variation, organizing nanowires parallel to the field lines, i...
September 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Cunlu Zhao, Zhengwei Ge, Yongxin Song, Chun Yang
Enrichment of colloidal particles in continuous flow has not only numerous applications but also poses a great challenge in controlling physical forces that are required for achieving particle enrichment. Here, we for the first time experimentally demonstrate the electrokinetically-driven continuous-flow enrichment of colloidal particles with Joule heating induced temperature gradient focusing (TGF) in a microfluidic convergent-divergent structure. We consider four mechanisms of particle transport, i.e., advection due to electroosmosis, electrophoresis, dielectrophoresis and, and further clarify their roles in the particle enrichment...
September 7, 2017: Scientific Reports
Tayloria N G Adams, Alan Y L Jiang, Prema D Vyas, Lisa A Flanagan
Whole cell membrane capacitance is an electrophysiological property of the plasma membrane that serves as a biomarker for stem cell fate potential. Neural stem and progenitor cells (NSPCs) that differ in ability to form neurons or astrocytes are distinguished by membrane capacitance measured by dielectrophoresis (DEP). Differences in membrane capacitance are sufficient to enable the enrichment of neuron- or astrocyte-forming cells by DEP, showing the separation of stem cells on the basis of fate potential by membrane capacitance...
August 29, 2017: Methods: a Companion to Methods in Enzymology
Jie Ding, Christine Woolley, Mark A Hayes
Blood is one of the most important biofluids used for clinical diagnostics. Cells and proteins in the blood can provide a rich source of information for the evaluation of human health. Efficient separation of blood components is a necessary process in order to minimize the interference of unwanted components during sensing, separation, and detection. In this paper, an insulator-based gradient dielectrophoretic device has been applied to separate red blood cells from model protein biomarkers for myocardial infarction in buffer...
August 29, 2017: Analytical and Bioanalytical Chemistry
Justin R Sperling, Steven L Neale, Alasdair W Clark
In the context of micro-electronics, the real-time manipulation and placement of components using optics alone promises a route towards increasingly dynamic systems, where the geometry and function of the device is not fixed at the point of fabrication. Here, we demonstrate physically reconfigurable circuitry through light-induced dielectrophoresis on lithium niobate. Using virtual electrodes, patterned by light, to trap, move, and chain individual micro-solder-beads in real-time via dielectrophoresis, we demonstrate rewritable electrical contacts which can make electrical connections between surface-bound components...
August 29, 2017: Scientific Reports
Gadi Piriatinskiy, Stephen D Atkinson, Sinwook Park, David Morgenstern, Vera Brekhman, Gilad Yossifon, Jerri L Bartholomew, Tamar Lotan
Myxozoa is a diverse, speciose group of microscopic parasites, recently placed within the phylum Cnidaria. Myxozoans are highly reduced in size and complexity relative to free-living cnidarians, yet they have retained specialized organelles known as polar capsules, akin to the nematocyst stinging capsules of free-living species. Whereas in free-living cnidarians the stinging capsules are used for prey capture or defense, in myxozoans they have the essential function of initiating the host infection process...
August 21, 2017: Scientific Reports
Xiangyu Chen, Zhiting Liang, Daobo Li, Ying Xiong, Penghui Xiong, Yong Guan, Shuangyue Hou, Yue Hu, Shan Chen, Gang Liu, Yangchao Tian
Shewanella oneidensis, a model organism for electrochemical activity bacteria, has been widely studied at the biofilm level. However, to obtain more information regarding this species, it is essential to develop an approach to trap and detect S. oneidensis at the cell level. In this study, we report a rapid and label-free microfluidic platform for trapping, counting and detecting S. oneidensis cells. A microfluidic chip was integrated with a modified dielectrophoresis (DEP) trapping technique and hole arrays of different hole sizes...
August 8, 2017: Biosensors & Bioelectronics
Ali Rohani, Bankim J Sanghavi, Armita Salahi, Kuo-Tang Liao, Chia-Fu Chou, Nathan S Swami
Proteomic biomarkers of interest to the early diagnosis of diseases and infections are present at trace levels versus interfering species. Hence, their selective enrichment is needed within bio-assays for speeding binding kinetics with receptors and for reducing signal interferences. While DC fields can separate biomolecules based on their electrokinetic mobilities, they are unable to selectively enrich biomarkers versus interfering species, which may possess like-charges. We present the utilization of AC electrokinetics to enable frequency-selective enrichment of nanocolloidal biomolecules, based on the characteristic time constant for polarization of their electrical double-layer, since surface conduction in their ion cloud depends on colloidal size, shape and surface charge...
August 24, 2017: Nanoscale
Amir Shamloo, Ali Kamali
In this study, a dielectrophoresis field-flow fractionation device was analyzed using a numerical simulation method and the behaviors of a set of different cells were investigated. By reducing the alternating current frequency of the electrodes from the value used in the original setup configuration and increasing the number of exit channels, total discrimination in cell trajectories and subsequent separation of four cell types were achieved. Cells were differentiated based on their size and dielectric response which are represented in their real part of Clausius-Mossotti factor at different frequencies...
August 10, 2017: Journal of Separation Science
Xiaoming Chen, Yukun Ren, Weiyu Liu, Xiangsong Feng, Yankai Jia, Ye Tao, Hongyuan Jiang
Continuous dielectrophoretic separation is recognized as a powerful technique for a large number of applications including early stage cancer diagnosis, water quality analysis, and stem-cell-based therapy. Generally, the prefocusing of a particle mixture into a stream is an essential process to ensure all particles are subjected to the same electric field geometry in the separation region. However, accomplishing this focusing process either requires hydrodynamic squeezing, which requires an encumbering peripheral system and a complicated operation to drive and control the fluid motion, or depends on dielectrophoretic forces, which are highly sensitive to the dielectric characterization of particles...
September 5, 2017: Analytical Chemistry
Jason Bonezzi, Tulashi Luitel, Aliaksei Boika
Electrokinetic phenomena such as dielectrophoresis and electrothermal fluid flow are used to increase the rate of mass transfer of silver and platinum nanoparticles and improve their stochastic electrochemical detection. These phenomena are induced by applying a high frequency alternating current (ac) waveform between a counter electrode and a working disk microelectrode. By recording chronoamperograms at room temperature and various ac powers, it is shown that the ac heating leads to an increase in the collision frequency of studied nanoparticles with working electrode surface by a factor of ∼10(1)-10(3) as well as the increase in the magnitude of the measured faradaic response...
September 5, 2017: Analytical Chemistry
Li Wei, Benjamin S Flavel, Wenshan Li, Ralph Krupke, Yuan Chen
Ultrahigh purity semiconducting single-walled carbon nanotubes (S-SWCNTs) are required for high-performance transistors. Aqueous two-phase (ATP) separation is an attractive method to obtain such SWCNTs due to its simplicity and scalability. This work targeted two questions; namely what is the upper limit of S-SWCNT purity that can be achieved by multiple cycles of ATP separation from the most commonly used polyethylene glycol and dextran system and how accurately can commonly used methods characterize the improvement in purity? SWCNT purity in nanotube dispersions obtained by multi-cycle ATP separation (2, 4, 6 and 8 cycles) was evaluated by three methods, including UV-vis-NIR absorption spectroscopy analysis, performance of thin-film field effect transistors (FETs) prepared by drop casting and short-channel FET devices prepared by dielectrophoresis deposition...
August 3, 2017: Nanoscale
Qianru Wang, Naga Neehar Dingari, Cullen R Buie
Insulator-based dielectrophoresis (iDEP) has emerged as a powerful tool for multiple biomicrofluidic operations, such as cell separation and concentration. The key feature for iDEP systems is the alteration of insulating microchannel geometries to create strong electric field gradients. Under AC electric fields, this strong electric field gradient can affect fluid flow by (at least) two nonlinear electrokinetic phenomena; (a) electrothermal flow due to Joule heating and (b) induced charge electroosmosis (ICEO) near the microchannel constrictions of small (but finite) permittivity and conductivity...
August 1, 2017: Electrophoresis
Zhuoqiang Jia, Stefano Sacanna, Stephanie S Lee
Reversible solid-state phase transitions between open- and close-packed structures in two-dimensional colloidal crystals comprising 1.8 μm dimpled spherical colloids were observed using negative dielectrophoresis. These asymmetrically-shaped colloids adopted lattices with cmm plane group symmetry and a packing fraction, ϕ, of 0.68 at low electric field strengths. At high electric field strengths, the close-packed p6m symmetry was observed, with ϕ = 0.90. The transition between open and close-packed structures was found to be reversible, depending on the applied electric field strength and frequency...
August 30, 2017: Soft Matter
Peng Zhang, Yuxin Liu
Sample enrichment or molecules concentration is considered an essential step in sample processing of miniaturized devices aimed at biosensing and bioanalysis. Among all the means involved to achieve this aim, dielectrophoresis (DEP) is increasingly employed in molecules manipulation and concentration because it is non-destructive and high efficiency. This paper presents a methodology to achieve protein concentration utilizing the combination effects of electrokinetics and low frequency insulating dielectrophoresis (iDEP) generated within a microfluidic device, in which a submicron constricted channel was fabricated using DNA molecular combing and replica molding...
September 1, 2017: Biofabrication
Zhenhao Ding, Hiromichi Kasahara, Michihiko Nakano, Junya Suehiro
In this study, an electrical DNA detection method was applied to bacterial detection. DNA was extracted from bacteria and amplified by polymerase chain reaction. The microbeads were labelled with amplicons, altering their surface conductance and therefore their dielectrophoresis characteristics. Amplicon-labelled microbeads could thus be trapped within a high-strength electric field, where they formed a pearl chain between the electrodes, resulting in an increased conductance between the electrodes. This method reduces the amplicon detection time from 1-2 h to 15 min, compared with the conventional method...
August 2017: IET Nanobiotechnology
Qiaoying Zhang, Paula Arribas, E Marielle Remillard, M Carmen García-Payo, Mohamed Khayet, Chad D Vecitis
Interlaced carbon nanotube electrodes (ICE) were prepared by vacuum filtering a well-dispersed carbon nanotube-Nafion solution through a laser-cut acrylic stencil onto a commercial polyvinylidene fluoride (PVDF) microfiltration (MF) membrane. Dead-end filtration was carried out using 10(7) and 10(8) CFU mL(-1) Pseudomonas fluorescens to study the effects of the electrochemically active ICE on bacterial density and morphology, as well as to evaluate the bacterial fouling trend and backwash (BW) efficacy, respectively...
July 27, 2017: Environmental Science & Technology
Mario A Saucedo-Espinosa, Blanca H Lapizco-Encinas
Dielectrophoresis (DEP) is the motion of particles under the influence of a nonuniform electric field. In insulator-based dielectrophoresis (iDEP), the required nonuniform electric fields are generated with insulating structures embedded in a microchannel. These structures distort the electric field distribution when an electric potential is applied. This contribution presents an experimental characterization of the electrokinetic (EK) and DEP velocities of a set of target particles, under DC potentials, when additional innocuous particles are used as fillers...
July 25, 2017: Analytical Chemistry
Yu-Liang Chen, Hong-Ren Jiang
This article provides a simple method to prepare partially or fully coated metallic particles and to perform the rapid fabrication of electrode arrays, which can facilitate electrical experiments in microfluidic devices. Janus particles are asymmetric particles that contain two different surface properties on their two sides. To prepare Janus particles, a monolayer of silica particles is prepared by a drying process. Gold (Au) is deposited on one side of each particle using a sputtering device. The fully coated metallic particles are completed after the second coating process...
June 23, 2017: Journal of Visualized Experiments: JoVE
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