Liquid crystal lasers could move diagnostics closer to the patient
Fast and accurate medical diagnosis can save lives, and COSMOS Lasers hopes to turn diagnostic laser technology from laboratory based systems into portable field devices.
Accurate medical diagnostics for diseases such as malaria often require laser-based spectroscopic or visible image analysis of thin microscopic samples. These techniques can be improved using tuneable lasers, which are unfortunately large and expensive, and are beyond the means of most hospitals in malarial zones. The lack of access to such tests, and therefore the inability to differentiate between different viral species, means that malaria and indeed other diseases are often misdiagnosed. Using liquid crystals, COSMOS has produced a compact and low-cost laser, which is tuneable to any spectral wavelength, from the near Ultra Violet to Infra-Red. This broadband technology could make diagnosis tests affordable, portable and easy to perform at any time.
The COSMOS Lasers project, which was funded by the EPSRC, is taking place at Cambridge University, with a multidisciplinary team led by Professor Harry Coles in the Department of Engineering. One of the leading investigators, Dr Philip Hands, says: “Most lasers work at one fixed wavelength, but the ability to tune a laser to emit a different part of the light spectrum is desirable for many hospital and laboratory tests. However, the tuneable commercial lasers available at the moment are prohibitively expensive for many of the organisations which could benefit from them. Also, of the few main types of tuneable lasers, most are highly complex to operate and take up an entire room, whilst others rely on high-pressure streaming of liquid carcinogenic dyes and high-powered mains electricity supplies.”
COSMOS Lasers’ patented technology uses liquid crystals, not too dissimilar to those used in TV displays, but Harry adds: “Our liquid crystal lasers emit light of any wavelength or colour and this is controlled by the structure of the liquid crystal. Liquid crystals automatically organise themselves into a twisted helical structure, rather like DNA, but by adjusting the tightness of the helix it is possible to alter the wavelength of the laser.”
The liquid crystal laser needs an energy input to excite it, which comes from a green or violet light source, usually a miniature laser beam. This beam is passed through the liquid crystal, which converts it into a tuneable laser of any desired colour. Dr Damian Gardiner, a leading device scientist in the team, says: “The liquid crystals are available in glass or plastic ‘cells’ –in thin microscopic layers, thinner than a human hair, trapped between the glass or on the plastic surface, a bit like microscope slides. These cells are very cheap to produce. They can be printed onto surfaces, but can be made to emit light at any wavelength from 450nm (UV/blue light) to 850nm (near-infrared). Also, cells can contain mixtures of crystals which produce simultaneously different colours. By changing the point at which the laser hits the cell you can chose whatever wavelength you require or combine beams to form “white” laser light.”
The COSMOS tuneable laser is designed to be small and cheap to manufacture. It currently fits in a small briefcase, and with further research the team hope to reduce this to a handheld device including analytics. A hand-held device from COSMOS Lasers would mean medical diagnostics in general, of which malaria tests might be one, could be done on-site by a clinician, taking minutes not days and rather than being sent away for lab analysis.
COSMOS Lasers have a wide range of medical and laboratory applications and beyond. Potential uses outside the lab include holographic laser displays. As well as being cheaper and more practical than conventional tuneable lasers, the COSMOS laser can give multiple simultaneous emissions, both in one beam or two dimensional arrays. This means it can produce many colours simultaneously, create intricate patterns or be used in combinatorial analysis. To do this at the moment would require multiple large and expensive lasers or complex displays. As Harry summarises: “Our laser gives us complete control over light – we’re getting it to do whatever we want it to. For researchers in the lab this means they can do faster and more detailed analyses, with any colour, anytime and anywhere.”
Written by Claire Lynn