Transportation Of Beads Research Articles

Isotropic Hedgehog-Shaped-TiO2/Functional-Multiwall-Carbon-Nanotube Micromotors with Phototactic Motility in Fuel-Free Environments.

Directional motion in response to specific signals is critically important for micro/nanomotors in precise cargo transport, obstacle avoidance, collective control, and complex maneuvers. In this work, a kind of isotropic light-driven micromotor that is made of hedgehog-shaped TiO2 and functional multiwall carbon nanotubes (Hs-TiO2@FCNTs) has been developed. The FCNTs are closely entangled with Hs-TiO2 and form a close-knit matrix on the surface of Hs-TiO2, which facilitates the transfer of electrons from Hs-TiO2 to FCNTs. Due to the high redox potential of Hs-TiO2, excellent electron-hole separation efficiency by the addition of FCNTs, and isotropic morphology of the micromotor, these Hs-TiO2@FCNT micromotors show phototactic and fuel-free propulsion under unidirectional irradiation of UV light. It is the first time to demonstrate isotropic micromotors that are propelled by self-electrophoresis. The isotropy of Hs-TiO2@FCNT micromotors makes them immune to the rotational Brownian diffusion and local flows, exhibiting superior directionality. The motion direction of our micromotors can be precisely tuned by light and a velocity of 8.9 μm/s is achieved under 160 mW/cm2 UV light illumination. Photodegradation of methylene blue and active transportation of polystyrene beads are demonstrated for a proof-of-concept application of our micromotors. The isotropic design of the Hs-TiO2@FCNT micromotors with enhanced photocatalytic properties unfolds a new paradigm for addressing the limitations of directionality control and chemical fuels in the current asymmetric light-driven micromotors.

Geometrical optimization of microstripe arrays for microbead magnetophoresis.

Manipulation of magnetic beads plays an increasingly important role in molecular diagnostics. Magnetophoresis is a promising technique for selective transportation of magnetic beads in lab-on-a-chip systems. We investigate periodic arrays of exchange-biased permalloy microstripes fabricated using a single lithography step. Magnetic beads can be continuously moved across such arrays by combining the spatially periodic magnetic field from microstripes with a rotating external magnetic field. By measuring and modeling the magnetophoresis properties of thirteen different stripe designs, we study the effect of the stripe geometry on the magnetophoretic transport properties of the magnetic microbeads between the stripes. We show that a symmetric geometry with equal width of and spacing between the microstripes facilitates faster transportation and that the optimal period of the periodic stripe array is approximately three times the height of the bead center over the microstripes.

Building the isotropic acoustic potential well with strong constraint boundary to improve the stability of ultrasonic transportation

A quantitative analysis of the acoustic potential well has been proposed for the purpose of realizing stability improvement of ultrasonic transportation. It was found that the boundary Rp and elastic constant kl(l,θ) of the acoustic potential well, acoustic radiation force offset ratio βfl, and elastic constant offset ratio βkl are the critical parameters that define the trapping ability. They were made clear both their intrinsic significance. The stability of the ultrasonic transportation using three transducers is theoretically studied. Long range ultrasonic transportation of silica beads with better stability is realized by optimizing the acoustic parameters to get the well-defined acoustic potential wells. No slip-off the equilibrium position has been observed, which proved its strong ability of trapping and transportation. Because of its simplicity, flexibility, and non-destructivity, the ultrasonic transportation offered a competitive micro-manipulation technology and will provide a promising tool for life science, chemistry and micro-assembly.

Centrifugal gas-phase transition magnetophoresis (GTM) – a generic method for automation of magnetic bead based assays on the centrifugal microfluidic platform and application to DNA purification

Transportation of magnetic beads between different reagents plays a crucial role in many biological assays e.g. for purification of biomolecules or cells where the beads act as a mobile solid support. Therefore, usually a complex set-up either for fluidic processing or for manipulation of magnetic beads is required. To circumvent these drawbacks, we present a facile and automated method for the transportation of magnetic beads between multiple microfluidic chambers on a centrifugal microfluidic cartridge "LabDisk". The method excels by requiring only one stack of stationary permanent magnets, a specific microfluidic layout without actively controlled valves and a predefined frequency protocol for rotation of the LabDisk. Magnetic beads were transported through three fluidically separated chambers with a yield of 82.6% ± 3.6%. Bead based DNA purification from a dilution series of a Listeria innocua lysate and from a lambda phage DNA standard was demonstrated where the three chambers were used for binding, washing and elution of DNA. Recovery of L. innocua DNA was up to 68% ± 24% and for lambda phage DNA 43% ± 10% compared to manual reference purification in test tubes. Complete purification was conducted automatically within 12.5 min. Since all reagents can be preloaded onto the LabDisk prior to purification, no further hands-on steps are required during processing. Due to its modular and generic character, the presented method could also be adapted to other magnetic bead based assays e.g. to immunoassays or protein affinity purification, solely requiring the adjustment of number and volumes of the fluidic chambers.

A Planar Conducting Micro-Loop Structure for Transportation of Magnetic Beads: An Approach Towards Rapid Sensing and Quantification of Biological Entities

A Planar Conducting Micro-Loop Structure for Transportation of Magnetic Beads: An Approach Towards Rapid Sensing and Quantification of Biological Entities

Nanostructure-enhanced laser tweezers for efficient trapping and alignment of particles.

We propose and demonstrate a purely optical approach to trap and align particles using the interaction of polarized light with periodic nanostructures to generate enhanced trapping force. With a weakly focused laser beam, we observed efficient trapping and transportation of polystyrene beads with sizes ranging from 10 μm down to 190 nm as well as cancer cell nuclei. In addition, alignment of non-spherical dielectric particles to a 1-D periodic nanostructure was achieved with low laser intensity without attachment to birefringent crystals. Bacterial cells were trapped and aligned with incident optical intensity as low as 17 μW/μm2.

APPLICATION OF ADAPTIVE PREDICTIVE CONTROL TO A SHAKER CONVEYOR FOR TRANSPORTATION OF PLASTIC BEADS

After having briefly portrayed the basic principles of predictive control, three adaptive predictive control algorithms–the GPC algorithm and two new modifications of it proposed by the authors, called the MGPC (modified GPC) algorithm and the DGPC (direct GPC) algorithm—will be discussed. The main disadvantage of the GPC algorithm, namely the noise sensitivity, will be highlighted, when the real-time application to a plant with variable dead-time, a shaker conveyor system for transportation of plastic beads, will be studied. Both new algorithms proposed here show good behaviour in reducing the computational burden and achieving a better disturbance rejection than the direct application of the GPC algorithm. © 1997 by John Wiley & Sons, Ltd.