A joyride through the nanoscale

13 November 2009


An atomic finger

Rather than seeing what is going on at the nanoscale, an atomic force microscope (AFM) can '"feel" what is happening. An AFM consists of a silicon cantilever with a sharp tip, just a few atoms wide, as shown in the photo.

This brushes over the surface of a sample, feeling the individual atoms. Contact forces, van der Waals forces, capillary forces, electrostatic forces and magnetic forces in the sample can be detected by changes in laser light reflected from the top of the cantilever.

This picture of an AFM tip was taken with a scanning electron microscope and then coloured.

(Image: Felice Frankel)

The new book

The page of an e-book consists of a sheet of plastic laid on top of tiny electrodes. The plastic layer contains microcapsules of oppositely charged black and white ink.

To make a pixel black, negatively charged electrodes repel the black ink to the surface, and when the electrode is positive the colour changes from black to white. Shades of grey can also be reproduced using a mixture of electrodes and inks.

Simple electronics converts the original text of the book into patterns of charge on electrodes.

This image is the "paper" currently used for e-books, made by E-Ink Corporation, Cambridge, Massachusetts.

New colour displays, with each pixel split into four subpixels showing red, green, blue and white are being developed.

(Image: Felice Frankel)

Antisocial water

The flow of fluids in tiny channels follows different rules from those followed by macroscale bodies of liquid. These lines show different coloured water flowing from the top right of the picture in microchannels 200 microns wide – the width of a human hair.

Rather than combining with each other in swirling eddies or other complex processes when they meet, these miniscule tributaries don't tend to mix, or if they do, they do so extremely slowly. This is shown in the image : the fluids exit the channels at the bottom left of the picture, in parallel, unmixed streams.

This behaviour is known as laminar flow and is also seen in glaciers and even in groups of people walking through a narrow corridor. It's important to understand how tiny volumes of liquids flow and mix as microfluidic systems are vital to lab-on-a-chip diagnostic devices.

(Image: Felice Frankel)

Under pressure

This image shows a cross-section of a reverse osmosis membrane which is used to separate mixtures of liquids. In reverse osmosis, pressures typically greater than 1000 times atmospheric pressure are used to force water molecules through the membrane, leaving minerals and ions on the other side.

The membrane itself has a complex internal structure with a number of differently sized pores that distinguish between the molecules and the ions and help the membrane withstand the high pressures required.

These kinds of membranes are used in desalination plants, water purification devices and kidney dialysis machines.

However, generating the pressures involved requires money and energy. More economic alternatives include a salt-gobbling microbial fuel cell and ion-blocking nanotube membranes.

(Image: Felice Frankel)

Sun catchers

This is a close-up of the top side of a photovoltaic solar cell. The cell converts the energy from the sun's photons into electrical energy by taking advantage of the photo-electric effect. This cell is made of a wafer of crystalline silicon.



(Image: Felice Frankel)

All the lonely people

Even the most committed Beatles fan might fail to spot the classic track in this image. It's a chunk of a vinyl copy of the Revolver album, specifically part of Eleanor Rigby, as seen through a Nomarski microscope , which uses differences in the record’s refractive index to emphasise its surface structure.

Read a review of the book No Small Matter here.

(Image: Felice Frankel)

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