Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Noise put to work

17.04.2002


Random vibrations can generate rotation.


This converts noise to one-way spin.
©AIP/Y.Zolotaryuk



A simple top converts foghorn noise to one-way spin. The device raises the hope that useful energy could be collected from ambient sounds. Normally, random vibrations, which physicists and engineers call noise, produce useless random motion. You can’t move a cart from A to B by shoving it randomly in every direction.

But in the new device, made by Yaroslav Zolotaryuk of the Technical University of Denmark in Lyngby and colleagues, a flat plate encounters more friction when it spins in one direction than in the other, meaning it always rotates predictably1.


The top is surprisingly simple, like something from a child’s construction set. Two horizontal rectangular plates are connected by a set of springs. A vertical rod in the centre of the lower plate passes through the centre of the upper plate, and two springs threaded onto this rod hold the plates apart. Two other springs link the ends of the upper and lower plates. The upper plate is rotated relative to the lower one, giving the entire structure a screw-like twist.

The direction of this twist determines the direction of rotation. When the upper plate is given a series of taps from random directions, the lower plate rotates in a single direction, pulling the rest of the device with it.

The twist doesn’t actually cause this biased rotation. If the springs were replaced with rigid rods, for instance, random taps would produce random rotation in both directions. The bias occurs because there is more friction between the lower plate and the surface on which it sits when the upper plate is pressed down than when it is pressed up. The springs convert this difference into a preference to rotate in just one direction.

On the bias

It has been known for about 90 years that noise can be used to induce directional motion. The trick is, as in the case of this latest device, to set up some kind of bias in one direction.

During the 1990s, physicists began to study ’brownian ratchets’. In these models, random pushes - such as a dust particle receives from colliding air molecules, which normally induce erratic or ’brownian’ motion - propel a particle in a predictable direction.

In a brownian ratchet, bias is introduced by having the particle move over a set of sawtooth ridges, which slope more gently in one direction than in the other.

References
  1. Norden, B., Zolotaryuk, Y., Christiansen, P.L. & Zolotaryuk, A.V. Ratchet device with broken friction symmetry. Applied Physics Letters, 80, 2601 - 2603, (2002).


PHILIP BALL | © Nature News Service

More articles from Physics and Astronomy:

nachricht A tale of two pulsars' tails: Plumes offer geometry lessons to astronomers
18.01.2017 | Penn State

nachricht Studying fundamental particles in materials
17.01.2017 | Max-Planck-Institut für Struktur und Dynamik der Materie

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

A big nano boost for solar cells

18.01.2017 | Power and Electrical Engineering

Glass's off-kilter harmonies

18.01.2017 | Materials Sciences

Toward a 'smart' patch that automatically delivers insulin when needed

18.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>