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| DVD trick makes for cheap boost to imaging and sensing | DVD trick makes for cheap boost to imaging and sensing |
| (about 2 hours later) | |
| Researchers in the US have hugely boosted the sensitivity of a widespread imaging and sensing technique, using an off-the-shelf DVD. | Researchers in the US have hugely boosted the sensitivity of a widespread imaging and sensing technique, using an off-the-shelf DVD. |
| Fluorescence spectroscopy is used to diagnose disease, image inside cells or detect toxins - but signals are weak. | Fluorescence spectroscopy is used to diagnose disease, image inside cells or detect toxins - but signals are weak. |
| A report in Nanotechnology has outlined how to boost those signals 200-fold, making use of a DVD's ready-made pits and grooves. | A report in Nanotechnology has outlined how to boost those signals 200-fold, making use of a DVD's ready-made pits and grooves. |
| That could help put the technique in far more labs - or hands - worldwide. | That could help put the technique in far more labs - or hands - worldwide. |
| Fluorescence describes the process in which the energy of light put into a molecule is redistributed, leading to a relatively long-lasting "glow" - it is at work in fluorescent lamps and many things that seem to glow under a "blacklight". | |
| This has turned out to be a tremendously successful way to examine the world down at the molecular level. Scientists can "tag" molecules with a part that fluoresces and then use microscopes to see exactly what it is doing. | This has turned out to be a tremendously successful way to examine the world down at the molecular level. Scientists can "tag" molecules with a part that fluoresces and then use microscopes to see exactly what it is doing. |
| Some of these tags only switch on when a particular chemical is present - for instance a toxin or an explosive. | Some of these tags only switch on when a particular chemical is present - for instance a toxin or an explosive. |
| Lightning rods | Lightning rods |
| At that molecular level, the light signals are profoundly weak. One way to boost them developed in recent years is to make use of what are called surface plasmons - the propensity of light waves from a sample to excite electrons in a surface beneath it, thereby boosting the signal. | At that molecular level, the light signals are profoundly weak. One way to boost them developed in recent years is to make use of what are called surface plasmons - the propensity of light waves from a sample to excite electrons in a surface beneath it, thereby boosting the signal. |
| This surface plasmon resonance is itself improved when the surface has nanometre-scale structure - tiny bumps or features of a size not too different from the wavelength of the light. | This surface plasmon resonance is itself improved when the surface has nanometre-scale structure - tiny bumps or features of a size not too different from the wavelength of the light. |
| Making these nanometre-scale features for the task has been an inherently complex and expensive business, but there is one industry in which the costs of such precision-made structures have plummeted: DVDs. | Making these nanometre-scale features for the task has been an inherently complex and expensive business, but there is one industry in which the costs of such precision-made structures have plummeted: DVDs. |
| Shubhra Gangopadhyay of the University of Missouri-Columbia and her colleagues started with commercial DVDs - sourced from a nearby store for $10 - and removed the protective outer layer to expose the nano-structure beneath. | Shubhra Gangopadhyay of the University of Missouri-Columbia and her colleagues started with commercial DVDs - sourced from a nearby store for $10 - and removed the protective outer layer to expose the nano-structure beneath. |
| They coated the DVDs with a stretchy polymer that dries to form something like a rubber stamp with an almost-perfect imprint of the DVD's surface, which can be ink-stamped onto any surface and then coated with a thin layer of metal. | They coated the DVDs with a stretchy polymer that dries to form something like a rubber stamp with an almost-perfect imprint of the DVD's surface, which can be ink-stamped onto any surface and then coated with a thin layer of metal. |
| "Almost-perfect" because the process of peeling the stamp from the DVD creates tiny imperfections, what the team call nano-gaps, just billionths of a metre wide. | "Almost-perfect" because the process of peeling the stamp from the DVD creates tiny imperfections, what the team call nano-gaps, just billionths of a metre wide. |
| Prof Gangopadhyay said that these gaps act like "lightning rods", drawing together and intensifying the fluorescence signal, making it easier to detect. | Prof Gangopadhyay said that these gaps act like "lightning rods", drawing together and intensifying the fluorescence signal, making it easier to detect. |
| In recent experiments, she said, DVD-stamped surfaces have shown a 30-fold jump in light from the molecules of interest - analytes - whereas the nano-gaps boost that signal by 200 times. | In recent experiments, she said, DVD-stamped surfaces have shown a 30-fold jump in light from the molecules of interest - analytes - whereas the nano-gaps boost that signal by 200 times. |
| "Usually when people try to look for low concentrations of analytes, they have to use very expensive microscopes, costing over a million dollars," she told BBC News. | "Usually when people try to look for low concentrations of analytes, they have to use very expensive microscopes, costing over a million dollars," she told BBC News. |
| "The interesting thing is that this can be integrated with simple microscopes - that's what we're using." | "The interesting thing is that this can be integrated with simple microscopes - that's what we're using." |
| The team is pursuing a two-fold goal with the new technique. | The team is pursuing a two-fold goal with the new technique. |
| "One is to give it to researchers, so everyone who has a simple microscope can utilise it to do great science - including high school kids," Prof Gangopadhyay said. | "One is to give it to researchers, so everyone who has a simple microscope can utilise it to do great science - including high school kids," Prof Gangopadhyay said. |
| Secondly the team aims to put the idea to use in simple, cheap diagnostics for use in the developing world - looking for the molecular markers for the HIV virus, toxins, even explosives. | Secondly the team aims to put the idea to use in simple, cheap diagnostics for use in the developing world - looking for the molecular markers for the HIV virus, toxins, even explosives. |
| "This field can go far in the future," she said. "I think it has big implications." | "This field can go far in the future," she said. "I think it has big implications." |