Lasers put objects into a spin

University of St. Andrews scientists have designed a novel way of spinning the most delicate microscopic objects without damaging them.

University of St. Andrews scientists have designed a novel way of spinning the most delicate microscopic objects – from a hamster chromosome to a glass bead – without damaging them.

Using special lasers, the project could give researchers an unprecedented amount of control for manipulating objects in living cells or components of micro-machines.

The technique, developed by Dr Kishan Dholakia of the School of Physics and Astronomy and his colleagues, could allow researchers to rotate biological structures in living cells, potentially revealing new drug targets by rotating enzymes and proteins to align the active sites where they latch onto each other.

So far, the scientists have demonstrated their technique with glass beads just one micron across (a human hair is approximately 100 microns thick) and a miniscule glass rod which could be potentially useful for stirring minute amounts of liquid. They also rotated a Chinese hamster chromosome, showing the potential for studying many other structures inside a cell.

Dr Dholakia said, ‘We’ve only just begun to realise the possibilities for what we might do with this technology,’ he said.

The research adds an extremely useful twist to optical tweezer technology in which particles trapped in a tightly focused laser beam can be moved from one spot to another. Researchers currently use optical tweezers to insert genes into cells and assist with, for example, in-vitro fertilisation but, just as someone assembling a jigsaw needs to rotate the pieces as well as move them across the table, scientists using optical tweezers would gain much more control if they could turn objects as well.

Dr Dholakia added, ‘The beauty of our technique is that we can dictate how far we want the spiral pattern to go around and at what speed. That means we can fully control the rotation of that one particle.’

Researchers previously developed two other methods for rotating objects but they did not allow as much control, nor were they as gentle on the objects and could only be used on certain types of materials.

‘Our technique is potentially more applicable than the others. We’ve rotated several different structures to show the range of things one can do,’ Dr Dholakia said.

The research was funded by the Engineering and Physical Sciences Research Council.

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