Brussels, 12 Sep 2005
Researchers from the University of Edinburgh, UK, the University of Groningen in the Netherlands, and the University of Bologna, Italy, have succeed in making the first synthetic molecular machine able to perform a relatively large-scale mechanical task.
The results of their research were published in the last issue of Nature Materials and presented last week at the BA Festival of Science in Dublin, Ireland. The researchers say their technique could have applications in lab-on-a-chip environments, in performing chemical reactions on a tiny scale without reaction vessels, and in drug delivery, smart materials and artificial muscles.
Molecular machines are usual in biology, helping to perform biological functions ranging from moving muscles in the body to photosynthesis. Many scientists are already working with so-called 'molecular machines', a process which involves making molecules move in a controlled fashion. Making tiny artificial machines is not easy though because the physics governing the behaviour of things at the molecular level differs from conventional physics. The breakthrough of the Edinburgh-led team is that for the first time, scientists were able to make these tiny nanoscale machines, two millionths of a millimetre high, interact with objects visible to the naked eye, bringing them into contact with the real world around us.
The research team has developed a technique for covering a gold surface with a single layer of rotaxane molecules, synthetic molecular 'shuttles' that change the properties of the surface to which they were attached in response to light, moving up and down by a millionth of a millimetre when exposed to light. To make a liquid droplet move, the team focused a light beam on one side of the drop: this created a gradient in the surface free energy along the length of the drop, resulting in motion of a one microlitre droplet not just across a flat surface, but also up a one millimetre, 12 degree slope against the force of gravity. Although the movement is tiny, the efficiency of the phenomenon in terms of scale is huge, being equivalent of a conventional mechanical machine using a millimetre displacement of pistons to lift an object twice the height of the world's tallest building.
David Leigh, Forbes Professor of organic chemistry and leader of the University of Edinburgh team, says: 'Nature uses molecules as motors and machines in all kinds of biological and chemical processes. Although man's understanding of how to build and control molecular machines is still at an early stage, nanoscale science and engineering could have a life-enhancing impact on human society comparable in extent to that of electricity, the steam engine, the transistor and the Internet.'
To download the abstract of the Nature Materials paper, please consult the following web address: http:///www.nature.com/nmat/journal/v4/ n9 /abs/nmat1455.html
Remarks: Reference document: Macroscopic transport by synthetic molecular machines. J. Berná, A.Leigh, M Lubomska, SM Mendoza, EM Pérez, P. Rudolf, G Teobaldi and F Zerbeto. Nature Materials 4, 704-710; doi:10.1038/nmat1455. September 2005