StatementThis is the peer reviewed version of the following article: Song, Y., Wang, C., Li, M., Pan, X. Both authors contributed equally to this work.
2
AbstractA novel method of sheathless particle focusing by induced charge electrokinetic flow (ICEK) in a microchannel is presented in this paper. By placing a pair of metal plates on the opposite walls of the channel and applying an electrical field, particle focusing is achieved due to the two vortex pairs which constrain the flow of the particle solution. As an example, the trajectories of particles under different electrical fields with only one metal plate on one side channel wall were numerically simulated and experimentally validated. Other flow focusing effects, such as the focused width ratio (focused width/channel width) and length ratio (focused length/ half length of metal plate) of sample solution, were also numerically studied. The results show that the particle firstly will pass through the gaps between the upstream vortices and the channel walls. Afterwards, the particle will be focused to pass through the gap between the two downstream vortices which determine the focused particle position. Numerical simulations show that the focused particle stream becomes thin with the increase in the applied electrical field and the length of the metal plates. As regards to the focused length ratio of the focused stream, however, it slightly increases with the increase in the applied electrical field and almost keeps constant with the increase in the length of the metal plate. The size of the focused sample solution, therefore, can be easily adjusted by controlling the applied electrical field and the size of the metal plates.
Bioinspired ionic diodes are widely explored to mimic the controllable ion transport of biological ion channels. However, due to their vertical structures, the integration of conventional ionic diodes into complex ionic circuits is still a challenge. Here, a horizontal ionic diode is developed based on an asymmetric nanochannel network membrane (NCNM) constructed from carbon black nanoparticles. The rectification of ionic current is achieved through the asymmetric concentration polarization of ions at two ends of the asymmetric NCNM. The rectification ratio of the NCNM ionic diode can be modified flexibly by changing the working fluid and the geometry of the NCNM. It is found that with the presence of cationic surfactant in the working fluid, the rectification ratio increases more than 30 times from 3.03 to 109.77. Advanced functions of the developed ionic component, including working as an ionic transistor for current switching and integrating into an ionic diode bridge on a single nanofluidic chip for rectifying alternating current signals, are also demonstrated in this paper. The horizontally arranged NCNM ionic diode possesses the advantages of easy fabrication and integration that can be practically applied in the development of ionic electronics and biocomputing.
The electrokinetic motion of a negatively charged spherical particle at an oil-water interface in a microchannel is numerically investigated and analyzed in this paper. A three-dimensional (3D) transient numerical model is developed to simulate the particle electrokinetic motion. The channel wall, the surface of the particle and the oil-water interface are all considered negatively charged. The effects of the direct current (DC) electric field, the zeta potentials of the particle-water interface and the oil-water interface, and the dynamic viscosity ratio of oil to water on the velocity of the particle are studied in this paper. In addition, the influences of the particle size are also discussed. The simulation results show that the micro-particle with a small value of negative zeta potential moves in the same direction of the external electric field. However, if the zeta potential value of the particle-water interface is large enough, the moving direction of the particle is opposite to that of the electric field. The velocity of the particle at the interface increases with the increase in the electric field strength and the particle size, but decreases with the increase in the dynamic viscosity ratio of oil to water, and the absolute value of the negative zeta potentials of both the particle-water interface and the oil-water interface. This work is the first numerical study of the electrokinetic motion of a charged particle at an oil-water interface in a microchannel.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.