Nano-Demonstrations, Deutsches Museum, Munich, Germany
05.7.2011In this document are various nano-demonstrations which have been shown in the Open Research Laboratory of the Deutsches Museum.
Soap Bubble
A simple and easy-to-understand demonstration which is ideal as an introduction into the nano-world is by means of a soap bubble. When a soap bubble thins out, interference stripes emerge in different colours. The final stripe is bright white, after which the soap bubble appears completely black. In this black area, the soap bubble is below 100nm thick (explanation below), thus demonstrating that it is possible to 'see' nano-sized structures with the naked eye.
The coloured stripes are caused by light waves interfering with each other within the bubble. Some of the light entering from above is reflected by the surface of the bubble, as is some of the light entering from below. The minimum thickness for this to occur is half the wave-length of light (½ in + ½ out = 1 wavelength). However, these light waves interfere with each other at down to half of this distance (¼ the wavelength of light). For blue light (i.e. diffuse light) with a wavelength of 460 nm, this means that interference is visible down to 115 nm. When this figure is divided by the optical coefficient of soapy water (around 1,2), this means that the final interference limit is just below 100 nm.
Ferrofluid
Ferrofluid is a liquid substance consisting of iron oxide nanocrystals (approx. 10 nm in size) suspended in a carrier liquid, usually oil or water. The crystals are covered by a so-called surfactant, which isolates the individual nanoparticles and prevents them from clumping together. This also ensures that each individual partner has a coating of the carrier liquid. Above a certain concentration of particles, all the liquid is bonded to the surface of a particle. Thus, by influencing the nanocrystals you can influence the whole liquid. As the nanocrystals react to a magnetic field, the result is that the liquid can be magnetically influenced. When an external magnetic field is applied to a ferrofluid it responds immediately, with the particles orienting themselves according to the field lines.
Ferrofluid is an example of how materials at a nanoscopic scale show different behaviours and overall physical properties. Making a reactive ferrofluid is not a trivial process. To achieve the small size, the ferrofluid particles need to be precipitated out of a solution by means of a chemical reaction. They then immediately require coating with the surfactant to prevent aggregation into larger units. Finally, they have to be mixed into the carrier liquid.
Nano Glass Powder
Nano glass powder is commercially used in paints (increased scratch resistance) and plastics (reduced flammability), and thus is mass-produced. It is created by dispersing silicic acid in an oxyhydrogen flame, with the nano glass powder precipitating from the flame. It is available in various specifications, with the 'Aerosil 200' used in the Open Research Lab having an average particle size of ~12 nm and a specific surface area of 200m2 / per gram.
Due to the small particle size nano glass powder has various physical properties which differ from macroscopic powders. These can be demonstrated as described below.
» news archive «
« back print
TIME for Nano is a project funded by the European Commission. The views expressed on this site are entirely those of the Authors and do not engage or commit the European Commission in any way.The Community is not liable for any use that may be made of the information contained therein.
Copyright © Time for Nano 2009 art & design by BridA