ORCID Profile
0000-0003-3784-7494
Current Organisation
Hong Kong University of Science and Technology
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Publisher: Wiley
Date: 08-01-2009
Publisher: Springer Science and Business Media LLC
Date: 20-12-2013
DOI: 10.1007/S10544-013-9832-2
Abstract: 2D imaging of biochips is particularly interesting for multiplex biosensing. Resonant properties allow label-free detection using the change of refractive index at the chip surface. We demonstrate a new principle of Scanning Of Resonance on Chip by Imaging (SORCI) based on spatial profiles of nanopatterns of resonant waveguide gratings (RWGs) and its embodiment in a fluidic chip for real-time biological studies. This scheme allows multiplexing of the resonance itself by providing nanopattern sensing areas in a bioarray format. Through several chip designs we discuss resonance spatial profiles, dispersion and electric field distribution for optimal light-matter interaction with biological species of different sizes. Fluidic integration is carried out with a black anodized aluminum chamber, advantageous in term of mechanical stability, multiple uses of the chip, temperature control and low optical background. Real-time hybridization experiments are illustrated by SNP (Single Nucleotide Polymorphism) detection in gyrase A of E. coli K12, observed in evolution studies of resistance to the antibiotic ciprofloxacin. We choose a 100 base pairs (bp) DNA target (~30 kDa) including the codon of interest and demonstrate the high specificity of our technique for probes and targets with close affinity constants. This work validates the safe applicability of our unique combination of RWGs and simple instrumentation for real-time biosensing with sensitivity in buffer solution of ~10 pg/mm². Paralleling the success of RWGs sensing for cells sensing, our work opens new avenues for a large number of biological studies.
Publisher: IOP Publishing
Date: 08-01-2014
Publisher: Springer Science and Business Media LLC
Date: 02-09-2015
DOI: 10.1038/SREP13673
Abstract: Light traveling in time-dependent media has many extraordinary properties which can be utilized to convert frequency, achieve temporal cloaking and simulate cosmological phenomena. In this paper, we focus on time-dependent axion-type magnetoelectric (ME) media and prove that light in these media always has two degenerate modes with opposite circular polarizations corresponding to one wave vector "Equation missing" and name this effect “time circular birefringence” (TCB). By interchanging the status of space and time, the pair of TCB modes can appear simultaneously via “time refraction” and “time reflection” of a linear polarized incident wave at a time interface of ME media. The superposition of the two TCB modes causes the “time Faraday effect”, namely the globally unified polarization axes rotate with time. A circularly polarized Gaussian pulse traversing a time interface is also studied. If the wave-vector spectrum of a pulse mainly concentrates in the non-traveling-wave band, the pulse will be trapped with nearly fixed center while its intensity will grow rapidly. In addition, we propose an experimental scheme of using molecular fluid with external time-varying electric and magnetic fields both parallel to the direction of light to realize these phenomena in practice.
Publisher: AIP Publishing
Date: 15-05-2006
DOI: 10.1063/1.2199749
Abstract: We demonstrate the role of particle-fluid wetting in inducing the electrorheological (ER) effect. Nanoparticles of barium titanyl oxalate coated with urea (BTRU) were suspended in either silicone oil or hydrocarbon oil. In the former, a high yield stress of more than 250kPa can be attained at an electric field of 5kV∕mm, while for the latter no measurable ER effect can be obtained. The two suspensions exhibit completely different appearances. Whereas the silicone oil suspension has the consistency of light cream, in the case of hydrocarbon oil with the same solid concentration the appearance is that of a lumpy paste. This clear visual distinction is attributed to the wetting characteristic between the solid BTRU particles and the suspending oil. We found that by adding a controlled, small amount of surfactant additive to the hydrocarbon oil suspension (oleic acid), the consistency can change drastically to resemble that of the silicone oil suspension, with a yield stress of 260kPa attained at an electric field of 3kV∕mm. We give a simple physical picture of wetting-induced giant electrorheological effect.
Publisher: Elsevier BV
Date: 08-2012
Publisher: Elsevier BV
Date: 06-2012
Publisher: IEEE
Date: 07-2013
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2SM00176D
Abstract: The synergistic effect of the lipophilic groups on the surface of CDs and the biomimetic chestnut-like structure give Co(OH) 2 @CDs good wettability with silicone oil, great electrorheological efficiency and dynamic shear stress stability.
Publisher: AIP Publishing
Date: 02-09-2005
DOI: 10.1063/1.2042535
Abstract: We present an electrorheological (ER) fluid cylindrical clutch which achieves stable shear stress at high shear rate, and demonstrates superior performance compared with the traditional ER clutches. The design is realized by employing alternate-stripe electrodes on the inner cylinder, with either dielectric or metallic outer rotor. The alternate stripe electrodes generate electric fields with a component parallel to the shearing direction, so that ER particles can form chain structures parallel to shear and thereby bring significant enhanced device performance at a high shear rate. Differences due to the use of dielectric or metallic outer rotor are shown to be compatible with expectations based on simulated electric-field patterns.
Publisher: Springer Science and Business Media LLC
Date: 06-10-2011
DOI: 10.1007/S10544-011-9595-6
Abstract: In this paper, we report the construction of a polymerase chain reaction (PCR) device for fast lification and detection of DNA. This device consists of an interchangeable PCR chamber, a temperature control component as well as an optical detection system. The DNA lification happens on an interchangeable chip with the volumes as low as 1.25 μl, while the heating and cooling rate was as fast as 12.7°C/second ensuring that the total time needed of only 25 min to complete the 35 cycle PCR lification. An optimized PCR with two-temperature approach for denaturing and annealing (Td and Ta) of DNA was also formulated with the PCR chip, with which the lification of male-specific sex determining region Y (SRY) gene marker by utilizing raw saliva was successfully achieved and the genetic identification was in-situ detected right after PCR by the optical detection system.
Publisher: Springer Science and Business Media LLC
Date: 12-10-2010
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1SM05687E
Publisher: AIP
Date: 2013
DOI: 10.1063/1.4811884
Publisher: IOP Publishing
Date: 20-05-2008
Publisher: Springer Science and Business Media LLC
Date: 03-12-2011
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C004744A
Abstract: We report a simple, low-cost and detachable microfluidic chip incorporating easily accessible paper, glass slides or other polymer films as the chip materials along with adhesive wax as the recycling bonding material. We use a laser to cut through the paper or film to form patterns and then sandwich the paper and film between glass sheets or polymer membranes. The hot-melt adhesive wax can realize bridge bonding between various materials, for ex le, paper, polymethylmethacrylate (PMMA) film, glass sheets, or metal plate. The bonding process is reversible and the wax is reusable through a melting and cooling process. With this process, a three-dimensional (3D) microfluidic chip is achievable by vacuating and venting the chip in a hot-water bath. To study the biocompatibility and applicability of the wax-based microfluidic chip, we tested the PCR compatibility with the chip materials first. Then we applied the wax-paper based microfluidic chip to HeLa cell electroporation (EP). Subsequently, a prototype of a 5-layer 3D chip was fabricated by multilayer wax bonding. To check the sealing ability and the durability of the chip, green fluorescence protein (GFP) recombinant Escherichia coli (E. coli) bacteria were cultured, with which the chemotaxis of E. coli was studied in order to determine the influence of antibiotic ciprofloxacin concentration on the E. coli migration.
Publisher: AIP Publishing
Date: 09-2010
DOI: 10.1063/1.3487796
Abstract: We report a simple, low-cost, rapid, and mask-free method to fabricate two-dimensional (2D) and three-dimensional (3D) microfluidic chip for biological analysis researches. In this fabrication process, a laser system is used to cut through paper to form intricate patterns and differently configured channels for specific purposes. Bonded with cyanoacrylate-based resin, the prepared paper sheet is sandwiched between glass slides (hydrophilic) or polymer-based plates (hydrophobic) to obtain a multilayer structure. In order to examine the chip’s biocompatibility and applicability, protein concentration was measured while DNA capillary electrophoresis was carried out, and both of them show positive results. With the utilization of direct laser cutting and one-step gas-sacrificing techniques, the whole fabrication processes for complicated 2D and 3D microfluidic devices are shorten into several minutes which make it a good alternative of poly(dimethylsiloxane) microfluidic chips used in biological analysis researches.
Publisher: AIP
Date: 2013
DOI: 10.1063/1.4812140
Publisher: ACM
Date: 20-06-2011
Publisher: Wiley
Date: 11-03-2013
Abstract: This paper presents a novel dielectrophoresis-based microfluidic device incorporating round hurdles within an S-shaped microchannel for continuous manipulation and separation of microparticles. Local nonuniform electric fields are generated due to the combined effects of obstacle and curvature, which in turn induce negative dielectrophoresis forces exerting on the particle that transport throughout the microchannel electrokinetically. Experiments were conducted to demonstrate the controlled trajectories of fix-sized (i.e. 10 or 15 μm) polystyrene particles, and size-dependent separation of 10 and 15 μm particles by adjusting the applied voltages at the inlet and outlets. Numerical simulations were also performed to predict the particle trajectories, which showed reasonable agreement with experimentally observed results. Compared to other microchannel designs that make use of either obstacle or curvature in idually for inhomogeneous electric fields, the developed microchannel offers advantages such as improved controllability of particle motion, lower requirement of applied voltage, reduced fouling, and particle adhesion, etc.
Publisher: Springer Science and Business Media LLC
Date: 08-04-2014
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8LC00047F
Abstract: In this work, we proposed an amalgamation-assisted lithography technique using liquid metal alloys for the fabrication of complex channels with a simple fabrication process, room-temperature fabrication and low toxicity.
No related grants have been discovered for Weijia Wen.