Newswise The following are brief summaries of papers recently accepted for publication in journals of the American Institute of Physics (AIP): Applied Physics Letters, Journal of Applied Physics, and Physics of Fluids.

1. A Nanoclutch for Nano-bots

Chinese researchers have designed and tested simulations of a nanoclutch, a speed regulation tool for nanomotors. The nanoclutch consists of two carbon nanotubes (CNTs), one inside the other, separated by a film of water. Electrowetting forces control the friction between the water and the inner and outer walls of the CNTs. When the two tubes are electrically charged, the water confined between them can transmit the torque from the inner tube to the outer tube, and the device is said to be in the engaged state. When the CNTs are uncharged, the device is in the disengaged state. In a paper accepted to the American Institute of Physics Journal of Applied Physics, the authors write that their proposed device can perform stepless speed regulation by changing the magnitude of the charge assigned to the CNT atoms. Though further work is needed, they say the model may be helpful in designing and manufacturing nanorobots.

Title: Carbon Nanotube-Based Charge-Controlled Speed-Regulating Nanoclutch Journal: Journal of Applied Physics (jap.aip.org) Authors: Zhong-Qiang Zhang (1), Hong-Fei Ye (2), Zhen Liu (3), Jian-Ning Ding (1), Guang-Gui Cheng (1), Zhi-Yong Ling (1), Yong-Gang Zheng (2), Lei Wang (4), and Jin-Bao Wang (5)

(1) Micro/Nano Science and Technology Center, Jiangsu University, China (2) State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, China (3) School of Naval Architecture and Ocean Engineering, Jiangsu University of Science and Technology, China (4) Department of Engineering Mechanics, College of Mechanics and Materials, Hohai University, China (5) School of Naval Architecture & Civil Engineering, Zhejiang Ocean University, China

2. Sound Increases the Efficiency of Boiling

Scientists at the Georgia Institute of Technology achieved a 17-percent increase in boiling efficiency by using an acoustic field to enhance heat transfer. The acoustic field does this by efficiently removing vapor bubbles from the heated surface and suppressing the formation of an insulating vapor film. As reported in the American Institute of Physics (AIP) journal the Physics of Fluids, bubble removal was enhanced because the acoustic field induces capillary waves on the bubble, causing its contact line to contract and detach the bubble from the surface. The mechanisms associated with these interactions were explored using three acoustic experiments: an air bubble on the underside of a horizontal surface, a single vapor bubble on the top side of a horizontal heated surface, and pool boiling from a horizontal heated surface. The researchers were able to isolate and identify the dominant forces involved in these acoustically forced motions by measuring the capillary waves induced on the bubbles, bubble motion, and heat transfer during boiling. Title: Acoustically Enhanced Boiling Heat Transfer Journal: Physics of Fluids (pof.aip.org) Authors: Zachary Douglas (1), Thomas R. Boziuk (1), Marc K. Smith (1), and Ari Glezer (1)

(1) Georgia Institute of Technology

3. Slip-and-slide Power Generators

Researchers from Vestfold University College in Norway have created a simple, efficient energy harvesting device that uses the motion of a single droplet to generate electrical power. The new technology could be used as a power source for low-power portable devices, and would be especially suitable for harvesting energy from low frequency sources such as human body motion, write the authors in a paper accepted to the American Institute of Physics (AIP) journal Applied Physics Letters. The harvester produces power when an electrically conductive droplet (mercury or an ionic liquid) slides along a thin microfabricated material called an electret film, which has a permanent electric charge built into it during deposition. Cyclic tilting of the device causes the droplet to accelerate across the films surface; the maximum output voltage (and power) occurs when the sliding droplet reaches its maximum velocity at one end of the film. A prototype of the fluidic energy harvester demonstrated a peak output power at 0.18 microwatts, using a single droplet 1.2 millimeters in diameter sliding along a 2-micrometer-thick electret film.

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Journal Tips from the American Institute of Physics: May 24, 2012