Thursday, 16 October 2014

Talk - 3D printing with atoms?

A recent University of Nottingham Science Lecture featured a fascinating talk by Prof Philip Moriarty. The talk was entitled "3D printing with atoms?" and looked at how researchers can now image and manipulate individual atoms to create rudimentary atomic scale structures. This post is based on the talk, with some added linkage thrown in...

Prof Moriarty began by explaining that the "?" in the talk title was important - and that the answer was no, we cannot currently "print" with individual atoms - but that some of the enabling technologies and science is being developed in labs around the world.

One direction that technology might take is to develop machines that take one material, for example grass, and turn it into something else, such as steak. This vision of the future was developed and publicised by Eric Drexler in the 1990s, most notably in his 1992 presentation to Congress, who wondered if such technologies might eliminate world hunger and result in whole populations being able to live a life of leisure, with nanomachines doing all the hard work.

Prof Moriarty moves around a lot, this is about as clear as it got...

Whilst Drexler's vision proved controversial, and he had many critics, the dream of a nanofactory lives on in organisations such as the Nanofactory Collaboration. It is this idea of autonomous nanomachines that has resulted in concerns such as the world being overwhelmed by "Grey Goo". There is continuing discussion on the viability of Drexlers ideas, for example this discussion by Prof Moriarty and this debate between Drexler and Richard Smalley. See also this Wikipedia article.

And of course, Richard Feynman started the whole ball rolling with his famous "There is plenty of room at the bottom" presentation way back in 1959.

Moving back to the talk, it was interesting to see that the audience had been given "clickers" with which they could answer multiple choice questions posed by Prof Moriarty, some of which are shown below :

1) What is the wavelength of red light?
0.6nm 6nm 60nm 600nm 6000nm
(nm=nanometer, a millionth of a millimetre)

2) What is the size of a red blood cell?
50,000nm 5000nm 500nm 50nm 5nm

3) What is the size of a single Gold atom?
3nm 0.3nm 0.03nm 0.003nm

(Answers at the end of the post)

Liked the clicker, loved the grafitti on the left

Prof Moriarty continued by explaining that one of the key concepts of nanotechnology was that simply by changing the size of an object, we can change it's physical, chemical and biological properties.

For example, the element Gold has its characteristic colour because of the way electrons in its structure collectively form waves, known as plasmons - but when gold is in the form of nanoparticles, there is not enough room on each particle for these plasmons to form, and hence a dispersion of gold nanoparticles in water has a red colour.

Differing sizes of gold nanoparticles have different colours

Prof Moriarty then showed a beautiful image (shown below) which he described as the "most important image in the history of science". Called the "Corral", it was created by Don Eigler and colleagues at the IBM Almaden Research Centre in 1993 using the tip of a scanning tunneling microscope (STM) to position 48 iron atoms into a circle on a copper surface. The wave patterns in the image are formed by copper electrons confined by the iron atoms. It

The waves are electrons reflecting of the "corral"

The Prof pointed out that, incredibly, the patterns formed by the electron waves could be described by exactly the same maths as used to define wave patterns on a drum skin.

More examples of atomic manipulation were given, the Nanoputians, and "A Boy and His Atom" - a stop motion movie of atoms !

The talk then moved onto an explanation of how it is that researchers can image and manipulate atoms, given that light has a wavelength hundreds of times larger than the size of atoms and so cannot be used as an imaging technique.

The answer turns out to be the Scanning Probe Microscope (SPM), which is described by Prof Moriarty here (albeit in a font that could perhaps most charitably described as "unhelpful"). In essence, a probe with a very fine tip is used to scan across a flat surface. An electrical force is built up between the probe tip and the surface. The probe scans across the surface and detects variation in the electrical force when the probe encounters changes in the surface, such as steps, holes or the presence of atoms lying on the surface.

You'll be wanting your atomic force probe to be just one atom wide at the tip..

As the probe scans across the material, it detects the changes
in electrical force as the surface dips or rises

A paper entitled "Mapping the force Field of a hydrogen bonded assembly" by Prof Moriarty's group has been published in Nature, no less, and the Prof showed an image from the paper which showed how actual images of molecules correlated very well with the representations of molecules that chemists had been using for many years. Its a fascinating paper and well worth looking at.

Incredible to see correlation between actual image (left) and theoretical model (right)

Another paper entitled "Toggling Bistable Atoms via Mechanical Switching of Bond Angle" describes how the group used SPM to "toggle" molecules between two states, simply by applying an electrical force.

To close out the talk, a few more questions revealed that there are as many atoms in a sugar cube as there are stars in the observable universe (10 to the power 22, since you ask) - just imagine how much memory storage a sugar cube sized volume could hold if even a small fraction of those atoms could be used to store data.....

You can read more about the nanotechnology research being undertaken by the UoN physics department at their webpage

Update 19 Oct: By the magic that is Twitter, NSB has been informed that Dr Drexler is currently at Oxford University

Update 19 Oct: Have also been informed of the existence of and, where you can see just how awesome the state of the art actually is.

Related Posts
NTU Talk by Dr Philip Breeder on Smart Materials
Royal Society Summer Science Display on Biological Nano-Motors
UoN's Clive Roberts talk on Nanotechnology in Healthcare
Cambridge Uni's Prof Ian Hutchings on Inkjet Printing
UoExeter's Prof Roy Sambles talk at NTU on Butterflies and Battleships

Unrelated Posts
Interview with Eben Upton of Raspberry Pi
Fee - An autobiography

Image Sources
Corral (Don Eigler, IBM Almaden Research Center and NISE Network)
Scanning Atomic Force Probe
Colloidal Gold

Answers to the questions:1) 600nm, 2)5000nm, 3) 0.3nm

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