Success stories
Ian Hodgkinson: Beetlemania
Although he is now 'officially' retired Ian Hodgkinson's research is as lively as ever. In 'official' terms he studies 'chiral-birefringent composite mediums that exhibit Bragg resonance with elliptically polarised light' but ask him what he studies yourself and he'll say, with a twinkle in his eye, "Beetles!" Around his lab in the Physics Department at Otago University, his small collection of bright metallic green beetles sit on proud display. 'Have you seen this?' he asks and eagerly holds a polarising lens in front of one of the beetles. As he turns the lens around the bright green beetle turns black and then reappears again. The nanoscopic structure on its surface is polarising the light. Guided by these little green gurus of nano-engineering, Ian has developed his own surface coatings that reflect circular and elliptically polarised light. His discoveries have opened new realms of research and could be used in the development of high tech optical devices. In November 2003 he was the joint winner of the RSNZ T.K Sidey medal, which is awarded at irregular intervals for outstanding scientific research concerning electromagnetic radiation.
Polarising light
Light is made up of transverse waves of radiation and its polarisation refers to the direction of vibration as it speeds along. There are two basic polarisations ('up and down' and 'side to side'). Combinations of these, result in circularly and elliptically polarised light that spirals through space like a corkscrew. Ordinary unpolarised white light, such as sunlight or light from a light bulb, is a hocus pocus jumble of wavelengths (colours) and polarisations.
The horizontally polarised light (blue) and vertically polarised light (pink) add together to create circularly polarised light.
Birefringence – Polarising prejudice
Before meeting the beetles, Ian had been investigating the optical properties of nanoscopically structured surfaces. He was depositing clusters of atoms onto substrates and found that when the substrate was held at an angle to the falling clusters, the resulting film structure caused different polarisations of light to travel through it at different speeds - a property called birefringence. He saw potential use for this technique in making polarising surfaces.
Ian meets the beetles
It was at a tea break at a conference in Charleston in 1997 (or thereabouts) that Ian heard about the remarkable optical properties of scarab beetles. Catching the scent of a superior craftsman in his newly discovered art Ian was keen to find these beetles. He tried to get in touch with a beetle expert but never got a reply. He had finally decided to go looking for beetles himself when fate intervened.
Ian was spending Christmas with a relative in Makarora, at the head of Lake Wanaka. Hearing of his interest in beetles his relative took him to a Manuka tree 100 metres up the road, told him to lay a rug beneath and began to shake the tree. Hundreds of bright, green Manuka beetles came hurtling down - just the sort Ian was looking for.
The next piece of good luck took place back over a cup of tea at Otago University. Ian had been lamenting his lack of beetle expertise, when his old friend John Leader from the Physiology Department revealed that he had done his PhD on beetles. That's when the adventure really began. Not only was John a beetle expert, he also had access to the confocal optical microscopes and electron microscopes in Anatomy & Structural Biology. Lakshman De Silva from Physics joined the group and this is what they discovered:
The beetle wing surface is made up of millions of tiny pits, a little like concave mirrors. The pits are lined with layers of long, thin chitin molecules set in a protein matrix. In each layer the molecules are oriented a few degrees different to the layer below so that a left handed spiral staircase of molecules is formed that gives the material chirality (handedness).
Top: Surface of a green beetle illuminated from above. Bottom: Green beetle surface illuminated at an angle
