A senior member of the British Royal family has asked the Royal Society to investigate the dangers of nanotechnology to society. This follows similar clarion calls in the past months. As in any field of scientific endeavor, the arguments must be balanced and a careful distinction made between the rightful, curiosity-driven endeavor of the scientist and the uptake of that endeavor in terms of technology. It is never simple. The atom was split by scientists interested in the properties of atoms and subatomic particles. Technology turned this into weapons of mass destruction and nuclear power; the first to be abhorred, the second to be grappled with in terms of environmental impact and energy requirements. Any debate must be well-informed, but can only achieve a snapshot view, as the science knowledge base is continually expanding. Care must also be exercised in not damning a generic technology when only subsets may pose significant problems to society.

What of the nano-world? For someone like me, interested in both fundamental and applied aspects of magnetic materials, it is relatively easy to see the impact of nanotechnology. But in fact, nanotechnology is nothing new to those of us who have spent the last 20 years working on magnetic materials. The magnets in your headphones or the motor in your PC disk drive or cordless power tool all depend on nanostructured magnets. The NdFeB alloys that are used to give high efficiency at low power consumption only do so because the magnetic grains are a few tens of nanometers in size. It is this that allows powerful magnetic interactions, such as exchange coupling, to prevail. The head reading a computer’s hard disk comprises magnetic and nonmagnetic layers only a few nanometers thick, where the layer thicknesses and spacing dictate the overall magnetic properties of the structure — the ‘spin-valve’. This advance has allowed the significant increases seen recently in data storage density for the PC market.

The subtlety of the magnetic properties of these nanomagnets is nowhere better seen than in a simple change of composition. If we go from the archetypal Nd2Fe14B to Fe73.5Cu1Nb3Si13.5B9, we do not change the essentials of the nanostructure, but we do move from the best hard magnetic material to the best soft magnetic material. The science base underpinning both sets of materials is now relatively well developed, and is certainly sufficient to see technological exploitation. Nature, in the form of magneto-tactic bacteria for example, has used nanoscale permanent magnetic materials for navigation for as long as we can tell.

The benefits of nanomagnets in terms of greater energy efficiency in motors and drives has been clearly established, and is allowing significant technological progress in areas where motor size and weight for a given volume is important. In my view, this is a ‘safe’ and socially beneficial subset of nanotechnology.

The science base is not resting on its laurels. Once the significance of the nanostructure in controlling magnetic properties was understood, scientists have been seeking ways to create nanostructures artificially. Self-assembly is one of the core fabrication routes in many areas of nanotechnology. Recent success in terms of hard magnets has been reported where self-assembly techniques are used to mimic the bulk alloy synthesis used for NdFeB. This produces a new permanent magnet material with properties only 50% down on the best NdFeB [Zeng, H., et al., Nature (2002) 420, 395]. This step has the potential to produce small volume, synthesized magnets for a range of technologies. Thought is already being given to developing self-assembled nanomagnetic systems for smart drug delivery, tissue engineering, and image enhancement in magnetic resonance imaging. Sensors based on nanomagnetic materials (e.g. the spin-valve) may be used in diagnostic testing, where a given chemical is tagged magnetically and then its relative content detected in a sample taken from a patient. This may open up the possibility of greater and cheaper testing and screening for many diseases. If nanomagnetic technology is coupled with microelectromechanical systems, then further opportunities arise. In Sheffield, we have already got to the proof-of-concept stage for a cochlear implant for the profoundly deaf.

Much of the science base for these new areas remains to be developed, but it is possible to see the potential benefits. In the medical field, we already have stringent guidelines for testing before widespread use. We have to trust that these can adapt to these new opportunities in order to protect society. We must not stop the progress of science, but it is always appropriate to assess any resulting technology for social or environmental impact carefully. Above all, in the present climate, we must avoid the condemnation of all nanotechnology as inherently dangerous, and applaud those areas from which we may safely benefit.

[1] Mike Gibbs is professor of functional magnetic materials at the University of Sheffield and director of the Sheffield Centre for Advanced Magnetic Materials and Devices, UK.

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DOI: 10.1016/S1369-7021(03)00764-8