Harvest usable energy with each step

Tom Krupenkin and J. Ashley Taylor reported the application of a unique electrostatic capacitor. In this study, conducting droplets are suspended between electrodes coated with a thin dielectric film. A capacitor is formed between the electrodes and conducting droplets with an insulating gap on the order of 10-50 nanometers. When incorporated into the sole of a shoe, this "reverse electrowetting" approach was shown to produce up to 1000 times more power than comparable methods. The researchers have formed a company, InStep NanoPower, to help bring the technology to market. Read more at Science NOW.

Abstract
Over the last decade electrical batteries have emerged as a critical bottleneck for portable electronics development. High-power mechanical energy harvesting can potentially provide a valuable alternative to the use of batteries, but, until now, a suitable mechanical-to-electrical energy conversion technology did not exist. Here we describe a novel mechanical-to-electrical energy conversion method based on the reverse electrowetting phenomenon. Electrical energy generation is achieved through the interaction of arrays of moving microscopic liquid droplets with novel nanometer-thick multilayer dielectric films. Advantages of this process include the production of high power densities, up to 103 W m−2; the ability to directly utilize a very broad range of mechanical forces and displacements; and the ability to directly output a broad range of currents and voltages, from several volts to tens of volts. These advantages make this method uniquely suited for high-power energy harvesting from a wide variety of environmental mechanical energy sources.

Krupenkin, T. and Taylor, J.A. Reverse electrowetting as a new approach to high-power energy harvesting. Nature Communications, 2:448 (2011). (Link)

Using velocimetry to extract DEP mobility from electrokinetic particles

In this report, Weiss et al. use a streak-based velocimetry technique to determine the electrokinetic properties of polystyrene particles. This can be a useful manner of characterizing suspended particles without manual tracking.

Abstract
Insulator-based dielectrophoresis (iDEP) is a powerful tool for separating and characterizing particles, yet it is limited by a lack of quantitative characterizations. Here, this limitation is addressed by employing a method capable of quantifying the DEP mobility of particles. Using streak-based velocimetry the particle properties are deduced from their motion in a microfluidic channel with a constant electric field gradient. From this approach, the DEP mobility of 1 μm polystyrene particles was found to be −2±0.4 10⁻⁸ cm⁴/(V² s). In the future, such quantitative treatment will allow for the elucidation of unique insights and rational design of devices.

Weiss N. G., Jones P. V., Mahanti P., Chen K. P., Taylor T. J. and Hayes M. A., Dielectrophoretic mobility determination in DC insulator-based dielectrophoresis. Electrophoresis. 2011, 32 (page numbers undetermined as of 8/23/11). [Link]