Hazards detected at low cost

An essentially simple and very low cost technology allows the rapid determination of parts per million moisture contents in petrochemicals, is sensitive to various chemicals and reagents, and allows the detection of hazardous organisms (whether bio-weapon derived or from natural hazards) in minutes instead of hours or days. Despite its simplicity, it is based on ideas that have been the subject of academic research for at least ten years but have hitherto defied attempts to exploit them as commercial sensors. The technology has vast potential applications in the petrochemical industry, the medical devices and diagnostics market (including bio-military) and drug packaging. The technology is called, "sensor holograms" and the spin-off company to exploit it, Smart Holograms, was co-founded by Professor Chris Lowe, Director of the Institute of Biotechnology in Cambridge in 2002. Dr Frank Craig, the present CEO, joined it in July 2003. The sensing devices are made by directing a spread laser beam onto a polymer coated, transparent strip in a trough containing chemicals. In its simplest form, the strip is mounted at a slight angle to and vertically just above a plane mirror. The laser light interferes with light returning from the mirror to form a standing wave pattern with the anti-nodes or fringes half a wavelength apart. Inclining the strip relative to the mirror prevents the finished hologram from diffracting the viewing light at exactly the same angle as specularly-reflected light. The hologram of the plane mirror consists of a series of bars made up of silver grains with an average diameter of less than 20nm. Used as a sensor, it relies on the substance of interest making the polymer expand or contract and change the spacing of the diffraction pattern bars. If the polymer matrix swells, the spacing between the fringes increases and longer wavelengths are diffracted. Sensor holograms can be made that change brightness, colour, or perceived image according to the chemicals with which the polymer is interacting. Speaking at a recent seminar, "Commercialising research for bio- and medical photonics", organised by the Institute of Physics in London, Professor Lowe revealed the development of sensors to measure the quality of petrochemicals that go from green to red in the presence of water. He also discussed the development of novel chemical and biological sensors for the biomilitary market. The former react to some of the chemicals released due to pathogen metabolism. The company's hand-held, bio-chip based 'PathoTester' can detect the growth of microbial pathogens within a few minutes using 'NanoCartridges' that include microbe-specific sensor holograms and has wireless connectivity for ease of data transfer. The "Nano" in the name refers to an ability to work with nanolitre quantities of fluid. Because the basic sensors can be made cheaply on rolls of film, they are also eminently suitable for other applications in consumer markets. For example, by reacting to changes in pH, it is possible to have internal labels for containers of whole milk that change colour when it is spoiled but not before. On the other hand, sensors for pH measuring peak diffraction grating reflection wavelengths can be devised that are accurate to 4 or 5 decimal places - making them the most accurate sensors on the market. Professor Lowe's group has developed disposable breathalyser strips that respond to alcohol, and which could be made cheap enough to sell or even give away to pub customers as well as the police. Holographic sensors responsive to glucose could be built into contact lenses so that diabetes sufferers could interact with an optical instrument without having to take blood samples. Holograms and holographic gratings can be devised to work at any light wavelength from ultra-violet to infra-red. The current list of demonstrated sensor technologies includes potassium ions in the presence of sodium, calcium, rubidium, barium, magnesium and lithium. Heavy metal ion concentrations can be measured including copper and nickel as can sulphides. Carbonates and bicarbonates can be measured for physiological purposes. Development of a lactate sensor has been completed. Other metabolites are under investigation. Penicillin and other beta-lactams can be detected from the presence of beta-lactamase coupled to a pH sensor. Urea can be detected from the presence of urease coupled to a pH sensor. Amylase can be detected by using the polymer film as a substrate for the enzyme. Specificity has been demonstrated with various proteases. Sensors for oxygen, carbon dioxide and ammonia are at an early stage of development. A nanophysiometer, in which multiple parameters are monitored simultaneously has been developed and is already being used with microbial and human cell lines. The feasibility of a temperature sensor has been demonstrated with utility for "smart packaging" for drugs or vaccines. The feasibility of simultaneously detecting multiple parameters is now being investigated through the use of hologram arrays and also using multiple sensors within a single hologram. Attempts to develop new commercial holographic systems goes back many years. Research to try to develop holographic vision inspection systems were under investigation at Imperial College in the 1970s. We have reported a number of systems down the years since, but the Cambridge University and Smart Holograms link-up is the first development that we have encountered that has made a major commercial breakthrough by applying holograms as sensors. Smart Holograms received first round funding in July 2004 and now employs 27 people. £17 million has been raised so far and another injection of funds is about to be finalised. The company presently has offices in Cambridge and San Ramon, California and is about to open a second US office in Boston. Some 30 patents have either been applied for or granted. The Company has five Blue Chip partnerships and will start manufacturing this year. Smart Holograms Institute of Physics Emerging Technology Programme Eureka says: This is one of those real breakthroughs in sensor technology that looks likely to have a major impact on personal safety in both a civilian, military and consumer setting Pointers * The sensors can be made inexpensively. * They can on the other hand form part of high performance precision measuring instruments * First commercial applications are for detecting contamination of petrochemicals and biohazards.