Models and microfluidic experiments are presented of an electrophoretic separation technique in which charged particles whose mobilities exceed a tunable threshold are trapped between the crests of a longitudinal electric wave traveling through a stationary viscous fluid. The wave is created by applying periodic potentials to electrode arrays above and below a microchannel. Predicted average velocities agree with experiments and feature chaotic attractors for intermediate mobilities. DOI: 10.1103/PhysRevLett.102.076103 PACS numbers: 82.45.Àh, 05.45.Ac, 82.40.Bj, 87.15.Tt Separations of charged substances are important in proteomics, molecular biology, cell biology, genetics, materials synthesis, and bioengineering, and are integral to microfluidic lab-on-a-chip devices that are being developed for rapid clinical and forensic analysis [1]. Over the last 25 years, capillary electrophoresis (CE) has set the standard for high-efficiency separations in solution [2]. This technique employs static, uniform electric fields to separate ions with different charge-to-size ratios into distinct zones for analysis, with zone dispersion limited ultimately by molecular diffusion.In this Letter, we study an electrophoretic separation technique that differs from CE by trapping ions whose mobilities exceed a tunable threshold between the crests of longitudinal electric field waves traveling through a stationary solution. These waves are created by applying oscillating potentials to interdigitated arrays of stationary electrodes above and below a microfluidic channel (Fig. 1). The trapping threshold depends on the ion mobility, the electrode spacing, and the potential frequency and amplitude, and allows modulation between separative and nonseparative transport by simply varying the frequency. Separations by traveling-wave electrophoresis (TWE) (Fig. 2) apply to ions, charged biomolecules, and micronsized charged particles, and might reduce zone dispersion to below the diffusion limit.Others use interdigitated electrode arrays on a single surface to transport charged species via electrophoresis, imposing static perpendicular gravitational or electric fields to draw particles to the surface [3][4][5]. Our sandwich architecture precludes such fields by bounding a microfluidic channel by electrode-bearing surfaces above and below. This design allows the use of low applied voltages to avoid unwanted electrochemical effects while keeping the electric field high to achieve rapid separations. Singlesurface architectures can also transport charged particles via ac electroosmotic pumping [6,7] and neutral bioparticles via dielectrophoresis [8].We consider the motion of ions of charge q, hydrodynamic radius r, and velocity v through a stationary electrically conducting solution of viscosity and mass density in response to oscillating electric potentials applied to periodic arrays of electrodes. In contrast with studies of oscillator synchronization [9], TWE potentials are external functions of time. In contrast with electron trapping by p...

No abstract

Plotly.js is a declarative JavaScript data visualization library built on D3 and WebGL that supports a wide range of statistical, scientific, financial, geographic, and 3-dimensional visualizations. Support for creating Plotly.js visualizations from Python is provided by the plotly.py library. Version 3 of plotly.py integrates ipywidgets support, providing a host of benefits to plotly.py users working in the Jupyter notebook. This paper describes the architecture of this new version of plotly.py, and presents examples of several of these benefits.

No abstract

No abstract