Wider perspective

From smart contact lenses that help diabetics monitor their glucose levels to labels that indicate if food is bad to pathogen detectors, the hologram has come of age. Christopher Sell reports.


Last week Visa announced a new card with enhanced security features that will, it claimed, make counterfeiting more difficult. Underpinning its design is a holographic metallic strip that, while being easy for readers to recognise, is also much harder to reproduce.



Although this should not be considered a panacea to fraud or counterfeiting, it is a demonstration of the increasing use of holograms, which until now have perhaps been perceived as best suited to produce an exclusive sticker collection or a sophisticated finish to the latest bestseller.



A new branch of hologram technology has the potential to offer solutions across a broad spectrum — from biosensors in the eye that can read glucose levels to smart labels that tell you when your meat has gone off and devices that can read alcohol and pathogen levels.



One of the most interesting advances is the work of Prof Christopher Lowe, director of the Institute of Biotechnology at Cambridge University, who has developed the concept of smart holograms.



Speaking at this month’s Alfred Franks Memorial Lecture at the Royal Society, Lowe outlined how the use of smart polymers could impact on numerous aspects of everyday life.



The technology is based on interactive holograms that can be engineered to change wavelength, image, brightness or position in response to a range of biological, chemical and physical stimuli. Whereas conventional holograms simply reflect light back, smart holograms are built to contain a 5–10 micron polymer layer. By putting different kinds of receptors into the polymer the reflected light can be altered in the presence of whatever stimulus you want to measure.



Lowe explained that when the polymer with the chosen receptor binds with the complementary ligand (a molecule that binds to the receptor protein) a change in pH, hydration or other parameter will instigate a change in colour.



Formed in 2002 as a spin-out from CambridgeUniversity, Smart Holograms, of which Lowe is co-founder, is working on several applications of this technique. Although medical diagnostics is the company’s main focus, Lowe is aware of the potential the technology offers in other areas such as security and authentication.



The firm’s biggest project so far is a hologram within a contact lens to measure glucose levels in the body and act as a diabetes monitoring system. With a smart hologram approximately 2mm in diameter placed in the lens, it will change colour to show the glucose level in the wearer’s tears as it sits over the eye. ‘Using a receptive device like a hologram you can measure what is going on in the tear fluid, which can give you an indication of what your metabolism is doing,’ said Lowe.



It is important for diabetics to monitor their blood sugar level, especially as they age. Traditionally this requires a small blood sample to be put into a portable testing kit which is time consuming and, for those with Type 1 diabetes, can be necessary several times a day.



Glucose is by no means the only substance in the body that could be monitored, however. Lowe conceded that there are still a number of issues to surmount with the holographic contact lenses, such as compatibility for wearers, calibration and the fact that the polymers need to be more highly sensitive to glucose than blood tests as concentrations of the substance are much lower in tear fluid than in blood. But Lowe was quick to point out that holographic devices could also diagnose levels of potassium for hypertension and calcium for cystic fibrosis.



Another potential application will be to help athletes in their quest for greater fitness. Athletes’ threshold level (the point at which lactic acid starts to accumulate in the muscle) is currently measured as they train by taking a blood sample from the ear in between runs of 400m. This is inconvenient on two counts: the blood has to be sent off for tests and to have blood flowing from the ear is hardly conducive to good training. Lowe suggests that using his holographic sensor to provide lactate monitoring could match training to analysis in real time, allowing the athlete to push him/herself further.



Smart Holograms has produced around 50 other different polymers that are sensitive to various stimulants. These include organic compounds and individual bacteria, with the latter a key area of the company’s research. Lowe said that from an early stage he was interested in bioterrorism and applying spore morphology to smart hologram technology. He has developed a handheld pathogen detection device called PathoTester which is at prototype stage.



‘We have had a lot of interest from certain government departments,’ said Lowe, who added this was an area the US attempted to develop but achieved little. The device will be fitted with the appropriate hologram and a swab from a patient or sample will be read to test for specific bacteria or pathogens. It will give the result in a matter of minutes, as opposed to current methods where growing cultures to test for the presence of bacteria can take weeks.



In an application that carries huge commercial possibility smart holograms can also be used to ascertain whether milk has gone off, food has been contaminated or meat has not thawed out properly. Consumers will be able to tell the condition of food simply from the colour of its label. Holograms placed on fresh fruit and vegetables could similarly provide clear indication of their ripeness.



A holographic breathalyser is a another idea that Lowe’s company has pursued. This would change colour to warn drivers when they are over the alcoholic limit to drive. ‘We contacted the police and the Home Office but they weren’t overly interested,’ said Lowe. ‘They were concerned that people would keep drinking until the device began to change colour and then drive home — they would rather people didn’t drink at all. But while we didn’t pursue it, it was a good indicator of what can be done with this technology.’



Smart Holograms have numerous other ideas in the melting pot, according to Lowe. ‘One of the things that interests me greatly is monitoring patients.’ A diabetic could frequently take digital pictures of his/her eyes to record the colour of the hologram. The photographs could then be compared to a SIM-stored database and the results transmitted to a GP.



There is no doubt that smart holograms will become part of the fabric of our future lives. From smart swimsuits that tell you the strength of the chlorine in a pool, to ’living’ architecture where holograms can indicate humidity and temperature, these are just some of examples of just how far this technology can go, said Lowe.