The forces between two molecularly smooth mica surfaces are measured in monovalent and divalent cations electrolyte solutions by a surface force apparatus (SFA). The properties of K+, Na+, and Mg2+ between molecu...
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The forces between two molecularly smooth mica surfaces are measured in monovalent and divalent cations electrolyte solutions by a surface force apparatus (SFA). The properties of K+, Na+, and Mg2+ between molecularly smooth mica surfaces are investigated. The Derjagui-Landau- Verwey-Overbeek (DLVO) force and the hydration force are detected in the experiment. The results show that in lower concentrations of a monovalent electrolyte solution (about 10-4 mol/L), the force curves are completely in good agreement with those computed by the DLVO theory. However, additional short-range repulsive forces which deviate from the DLVO theory are observed when the concentrations of cations are above the critical bulk concentration, which is different for each electrolyte. The results show the properties of these cations on both the screening effect adsorbed on the mica surface and the hydration in solution. From the results, the interaction energy between two hydrated ions of potassium or sodium can also be estimated.
To realize automatic manipulation of micro-particles by light-induced dielectrophoresis (LDEP), a path-planning scheme based on the improved artificial potential field (APF) for micro light pattern movements is pr...
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To realize automatic manipulation of micro-particles by light-induced dielectrophoresis (LDEP), a path-planning scheme based on the improved artificial potential field (APF) for micro light pattern movements is proposed. An algorithm combining guided target and point obstacle based on a new local minimum judging criterion is specially designed, which can solve the local minimum problems encountered by the traditional APF. Experiments of real-time particle manipulation based on this algorithm are implemented and the experimental results show that the proposed approach can overcome the local minimum problems of the traditional APF method, and it is validated to be highly stable for intensive particle obstacles during LDEP manipulation. Consequently, this method can realize real-time manipulation of micro-nano particles with safety, decrease the difficulty of manual manipulation, and thus improve the efficiency of manipulation of micro-particles.
Experiments of poly(dT)20 electrophoresis throughα-hemolysin nanopores were performed to unveil the electrophoretic transport mechanism of DNA through nanopores in high concentration potassium chloride solution. It...
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Experiments of poly(dT)20 electrophoresis throughα-hemolysin nanopores were performed to unveil the electrophoretic transport mechanism of DNA through nanopores in high concentration potassium chloride solution. It is found that there are two obvious current blockades induced by poly(dT)20 translocation and collision events. Both blockade currents increase linearly with the applied bias voltage. However, the normalized blockade currents are almost kept the same although variable bias voltages are applied. The collision time of poly(dT)20 in the luminal site of the pore remains constant for different voltages. The translocation speed of poly(dT)20through the nanopore decreases with the increase of bias voltage. It is because as the potential increases, the drag force on the homopolymer helps it to crumple into a cluster much easier due to the poor stacking of thymine residues compared with homopolymers consisting of other nucleotides. Molecular dynamics simulations further confirm the experimental results. Increasing the applied bias voltage can slowdown the translocation velocity of the flexible poly(dT)20, which favors increasing the precision of single molecule detection by using nanopores.
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