How it works!

Nanomachines and nanotechnology

Designing molecular-level systems that employ motion in a useful manner teaches us much about the fundamental mechanical behaviour of matter at small length scales. This in turn helps scientists to unravel how the sophisticated and complicated biomachines of the cell work – crucially important because of the central role they play in many disease states. But the ultimate goal for synthetic molecular machines is to harness their abilities for our own technological use; the creation of artificial nanotechnology. Many believe that a working artificial nanotechnology will ultimately have an impact on our economy and our society that is comparable in scale and scope to the steam engine, electricity, the transistor, and the internet. The realisation of that vision is still some way off, but this new motor-mechanism represents a useful step along the road towards it.^[8]

Footnotes and references

[1] (a) B. Mahon, The Man Who Changed Everything: The Life of James Clerk Maxwell, John Wiley & Sons, Chichester, 2004. (b) The year 2006 marked the 175^th anniversary of Maxwell’s birth, see http://www.maxwellyear2006.org/index.html.

[2] The first (a) private and (b) public written discussions of the ‘temperature demon’ were: a) J. C. Maxwell, Letter to P. G. Tait, 11 December 1867. Quoted in C. G. Knott, Life and Scientific Work of Peter Guthrie Tait, Cambridge University Press, London, 1911, pp. 213-214; and reproduced in The Scientific Letters and Papers of James Clerk Maxwell Vol. II 1862-1873 (Ed.: P. M. Harman), Cambridge University Press, Cambridge, 1995, pp. 331-332. b) J. C. Maxwell, Theory of Heat, Longmans, Green and Co., London, 1871, Chapter 22. c) Maxwell introduced the idea of a ‘pressure demon’ in a later letter to Tait (believed to date from early 1875). Quoted in C. G. Knott, Life and Scientific Work of Peter Guthrie Tait, Cambridge University Press, London, 1911, pp. 214-215; and reproduced in The Scientific Letters and Papers of James Clerk Maxwell Vol. III 1874-1879 (Ed.: P. M. Harman), Cambridge University Press, Cambridge, 2002, pp. 185-187. “Concerning Demons.... Is the production of an inequality of temperature their only occupation? No, for less intelligent demons can produce a difference in pressure as well as temperature by merely allowing all particles going in one direction while stopping all those going the other way. This reduces the demon to a valve.”. More formally, a pressure demon would operate in a system linked to a constant-temperature reservoir with the sole effect of using energy transferred as heat from that reservoir to do work. This is in conflict with the Kelvin–Planck form of the Second Law whereas the temperature demon challenges the Clausius definition.

[3] For reprints of key papers and commentary on some of the main issues regarding Maxwell’s Demon, see: Maxwell's Demon 2. Entropy, Classical and Quantum Information, Computing (Eds.: H. S. Leff, A. F. Rex), Institute of Physics Publishing, Bristol, 2003.

[4] V. Serreli, C.-F. Lee, E. R. Kay and D. A. Leigh. A molecular information ratchet. Nature, 445, 523-527 (2007).

[5] C. H. Bennett. The thermodynamics of computation – a review. Int. J. Theor. Phys. 21, 905-940 (1982).

[6] R. Landauer. Irreversibility and heat generation in the computing process. IBM J. Res. Dev. 5, 183-191 (1961).

[7] (a) R. A. Bissell, E. Córdova, A. E. Kaifer and J. F. Stoddart. A chemically and electrochemically switchable molecular shuttle. Nature 369, 133-137 (1994). (b) A. M. Brouwer, et al. Photoinduction of fast, reversible translational motion in a hydrogen-bonded molecular shuttle. Science 291, 2124-2128 (2001). (c) Y. Liu, et al. Linear artificial molecular muscles. J. Am. Chem. Soc. 127, 9745-9759 (2005). (d) J. Berná, et al. Macroscopic Transport by Synthetic Molecular Machines. Nature Mater. 4, 704-710 (2005).

[8] (a) E. R. Kay, D. A. Leigh. Lighting Up Nanomachines. Nature 440, 286-287 (2006). (b) E. R. Kay, D. A. Leigh and F. Zerbetto. Synthetic molecular motors and mechanical machines. Angew. Chem. Int. Ed. 46, 72-191 (2007).

[9] M. Schliwa (ed) Molecular Motors (Wiley-VCH, Weinheim, 2003).

[10] (a) D. A. Leigh, J. K. Y. Wong, F. Dehez and F. Zerbetto. Unidirectional rotation in a mechanically interlocked molecular rotor. Nature 424, 174-179 (2003). (b) J. V. Hernández, E. R. Kay, and D. A. Leigh. A reversible synthetic rotary molecular motor. Science 306, 1532-1537 (2004). (c) M. N. Chatterjee, E. R. Kay and D. A. Leigh. Beyond switches: ratcheting a particle energetically uphill with a compartmentalized molecular machine. J. Am. Chem. Soc. 128, 4058-4073 (2006).

[11] (a) N. Koumura, R. W. J. Zijlstra, R. A. van Delden, N. Harada and B. L. Feringa. Light-driven monodirectional molecular rotor. Nature 401, 152-155 (1999). (b) S. P. Fletcher, F. Dumur, M. M. Pollard and B. L. Feringa. A reversible, unidirectional molecular rotary motor driven by chemical energy. Science 310, 80-82 (2005).

[12] T. R. Kelly, H. De Silva and R. A. Silva. Unidirectional rotary motion in a molecular system. Nature 401, 150-152 (1999).

‘A demonic rotaxane’. Click on image to download high resolution version (jpeg).
[This illustration by Peter Macdonald – Edmonds UK.]