What colour would you like your gold or silver? Yellow? White? Red? Green? Blue? Nanotechnology researchers at Southampton University have discovered how to make precious metals appear in any colour you please, by making microscopic changes in the surface that change the way it reflects light.
It has long been possible to change the appearance of a metal through alloying or adding a film to the surface. For example, “red gold” or “rose gold” is traditionally made by adding copper. The Southampton scientists say they are the first to colour metals without coating or chemical treatment.
You might think that the point of gold is to look golden, but the researchers say there are a lot of applications where another colour would be desirable, even for jewellery and watches. You could, for instance, design a gold watch face in which the hours are denoted in different colours, or add coloured banding to a silver ring.
The process involves embossing tiny raised or indented patterns on to the surface. For it to work, each feature on the surface pattern has to be smaller than the wavelength of visible light.
“By embossing metals with patterns only around 100 nanometres across [400 times less than the width of a human hair] we can control which wavelengths of light the metal absorbs and which it reflects,” says Nikolay Zheludev, who led the project.
The process has been demonstrated for gold, silver and aluminium, says his colleague Kevin MacDonald, but it could be applied to many other metals. It is part of a £5m programme at Southampton’s Optoelectronics Research Centre, which uses nanotechnology to change the surface structure of materials. The overall aim is to develop new “meta-materials” with properties not found in nature.
In the lab a technique called ion beam milling – something like sandblasting on an atomic scale – has achieved coloured areas only half a millimetre square, which is just visible to the naked eye. But MacDonald is confident that the concept could be scaled up for industrial production using a process in which large areas are stamped out from a master template, like making DVDs.
“We’ve filed a patent application for our work,” Zheludev says, “and we’re currently talking to a number of organisations about taking our breakthrough towards commercialisation.”
An important application might be security tagging, because the nano-embossed metal surfaces would be extremely hard to forge. But for many people the most exciting prospect will be high-tech jewellery.
How to spot diseases early – and at a glance
Scientists at Imperial College London have developed a sensor to detect early-stage diseases such as prostate cancer and HIV infection with the naked eye, potentially leading to cheaper and simpler diagnoses for patients, writes Ling Ge.
The team reports in the journal Nature Biotechnology that the visual sensor is ten times more sensitive than the best current methods of indicating the onset of the diseases. The test looks at levels of “biomarkers” such as p24, which indicates HIV infection, and prostate specific antigen (PSA), an early indicator for prostate cancer.
The sensor works by analysing the patient’s blood serum in a disposable container. If the result is positive for p24 or PSA, a reaction generates irregular clumps of nanoparticles, which give off a distinctive blue hue in a solution inside the container. If the result is negative, the microscopic particles separate into ball-like shapes, creating a red colour. So both reactions can be detected at a glance with the naked eye.
The test has picked up p24 in samples where patients had extremely low HIV levels that were missed by the existing tests such as the enzyme-linked immunosorbent assay (Elisa) test or the “gold standard” nucleic acid-based test. And according to the researchers, the sensor can be reconfigured for other viruses and diseases where a specific biomarker is known.
“It is vital that patients get periodically tested in order to assess the success of retroviral therapies and check for new cases of infection,” says Molly Stevens, the leader of the project.
The sensor would also benefit countries where sophisticated detection equipment is scarce. “We believe that this test could be significantly cheaper to administer,” adds Roberto de la Rica, Stevens’s colleague and the co-author of the report. “And that could pave the way for more widespread use of HIV testing in poorer parts of the world.”
When photographs get under your skin
Itching and scratching are contagious, like yawning, a study in the British Journal of Dermatology shows. The discovery of a psychological dimension could be useful for treating skin disorders.
Researchers at Manchester and Liverpool John Moores universities showed 30 volunteers pictures that were either itch-related (such as ants, fleas and skin conditions) or neutral (such as butterflies and healthy skin). The experiment confirmed that visual cues alone, without any irritant to the skin, could elicit sensations of itch – and a scratch response. This effect was strongest when the participants were shown pictures of someone scratching a skin irritation.
“Our findings may help improve the efficiency of treatment programmes for people suffering from chronic itch,” says Francis McGlone, the lead author. “Knowing the specific triggers of an individual’s chronic itch and how visual stimuli translate to the physical may also provide insight into the mechanisms of ‘psychosomatic itch’, in which there are no physical triggers.”
“Itch is often the worst symptom for people with skin disorders, and any research into its causes that may lead to new methods of alleviation will be greatly welcomed by the millions of skin patients,” adds Nina Goad of the British Association of Dermatologists. “Combining elements of psychology with dermatology is an increasingly important area of research.”
Does your computer measure up?
A “virtual tape measure”, which gives accurate body measurements from webcam or smartphone pictures, could encourage more people to buy clothes online and cut today’s high level of returns.
The device is under development with a £350,000 grant from the Engineering and Physical Sciences Research Council in collaboration with the University of Surrey, London College of Fashion and Bodymetrics, a company specialising in in-store measurement technology. A commercial launch is expected within two years.
The people working on the project say that online clothes shopping has been held back by uncertainties over whether the garments will fit when they arrive. They estimate that between 30 and 60 per cent of clothes bought on the internet are returned to the retailer.
Under the new system, a participating company will have a logo or button on its website, which home shoppers click to activate the virtual tape measure. They then stand in front of their webcam or smartphone in their underwear, take a full-length photo and type in their height. The software immediately works out their size for that particular retailer and offers only clothes that will fit.
“The potential benefits for the fashion industry and for shoppers are huge,” says Philip Delamore of London College of Fashion. “Currently, it’s common for online shoppers to order two or three different sizes of the same item of clothing at the same time, as they’re unsure which one will fit best.”