|
From "The Engineer", 2 April 2004 Plugging the gap The UK is ahead of the game in what promises to be one of the most exciting areas of applied technology in the coming decade: the exploitation of TeraHertz imaging. For once Europe in general and the UK in particular rather than the US or Japan are setting the pace in what could turn into a huge new international market with major implications for society and medicine. Advances in physics and laser technology are unlocking the secrets of the TeraHertz (THz) gap, described as the 'final frontier' of the radio and light spectrum (see ‘The TeraHertz gap’ below). Rather like nanotechnology, but without most of the hype or any of the science fiction scaremongering, THz imaging has the potential to enable significant technical advances in many areas. These range from early detection of skin cancer and screening for hidden explosives to a multitude of less high-profile but equally revolutionary applications in industrial processes. The two key pillars of a strong position in any new technology are a healthy academic research base and an active programme of commercialisation. Happily for the UK, things are currently looking good on both counts. A significant chunk of the research impetus will come from the Centre for TeraHertz Photonics at Leeds University. Currently nearing completion, the centre will combine the established expertise and resources of teams at Leeds and Cambridge University into Europe's biggest THz research facility. On the commercial front the UK boasts the world's only company building actual products based on THz technology. Cambridge-based TeraView is developing THz systems for a range of applications in the industrial, medical and security sectors (see 'Commercial Possibilities for THz' below). The company was one of only a handful of European businesses recently to be named as pioneers of potentially world-changing technology by the World Economic Forum. So what is the immediate future for THz in the UK? In Leeds Prof Giles Davies is supervising the final few months of work that will bring some of the world's best THz expertise under one roof in Yorkshire. Formerly part of Cambridge's pioneering THz team, Davies and his colleagues will carry out research into sources, detectors and applications of THz radiation. Davies said the potential applications of THz are extensive, although he stressed the need for caution at what is still a relatively early stage for much of the research. Even so, he has every reason to be excited about the new centre. As well as its size, the facility will have the advantage of the considerable expertise and experience built up over the years in Leeds itself and Cambridge. The two major THz projects mounted by the EU have both been led by UK research teams. There are Teravision, which investigated the use of THz in medicine, and Wanted, a wireless networking initiative. A third may follow soon. 'We're doing phenomenally well and are certainly very much up with the pack. The reason we're leading these things is that we have the credibility, not just running the programmes themselves but in the science behind the programmes,' said Davies. He and his colleagues will spend the next few years exploring numerous potential applications for THz. These include combustion and flame analysis. 'We will be looking at whether THz radiation is capable of investigating the by-products of flames,' said Davies. THz could be useful in specialised fields such as the grain industry. The detection of moisture content and the location of water in a batch of grain would be a valuable tool in the milling process, said Davies. The technology may also have medical applications beyond detection of skin cancer. It could, for example, be used to look through bandages to assess the status of a healing wound. This would avoid having to remove a dressing if the healing process is proceeding well. According to Davies, THz could also become a valuable addition to the panoply of communications technologies. 'As far as communications is concerned you are unlikely to be able to send a THz signal around the world,' he said. 'But it is possible to imagine a local area THz network, perhaps in an office or factory.' The properties of THz would make it suitable for such networks on several counts, said Davies, not least containing the signal within the four walls of the building. 'You would have the advantages of the broad bandwidth, but if any of your industrial competitors was standing outside the window they would not be able to access it because THz is absorbed so heavily.' Other work underway around the world includes the investigation of THz as a means of detecting microscopic flaws in steel. Davies said German researchers were using THz to look at the surface of steel as it left the production process, using it to spot indentations and impurities that remain invisible under other inspection processes. Other specialist inspection activity includes New York-based research to see whether THz can be used to examine the tiles on the Space Shuttle. Defects on the tiles on the outside of the shuttle were identified as a possible cause of the Columbia disaster, and the US researchers hope THz could detect problems on future flights. Research into skin cancer detection will form part of Leeds' investigations, but Davies is anxious not to stoke expectations too early. 'I know what everyone wants to hear is that we are going to use this to detect and cure skin cancer. But we're not there yet, and won't be there for a number of years.' With regard to security, the area that has brought THz to a wider public's attention via the pages of the national press, Davies is especially cautious. The possibility of THz being used to screen people and baggage for hidden weapons and explosives has struck a chord with an increasingly security-obsessed global media. 'There have been some recent articles that haven't perhaps been quite as rigorous as they could have been. It certainly is on the table, because security has obviously been a very important area particularly in the past few years.' Davies does have funding specifically to explore these areas. 'We are going to be looking at things like explosives to see whether we can use THz radiation to locate them, to maybe see whether they are concealed in somebody's clothing. But I really can't say any more until we have done the research, and that's not going to be for another three years.' Industrial process applications could, according to Davies, emerge from among the plethora of research initiatives to be early examples of working THz systems. 'There is a whole range of things that people are trying. The truth is nobody currently knows what the killer application is going to be. It would be great to say that we are going to cure cancer doing this. On the other hand, it could end up looking at something on a conveyor belt in a factory, which could still be a multimillion-pound industry.' Davies's contemporaries at the THz commercial sharp end will certainly hope he is right. TeraView is very much a pioneering venture, not just in THz technology but delivering working commercial products. Unsurprisingly, the company is less cautious than Davies over proclaiming THz as a technology that is very much of the here and now. Its slick website is packed with examples of why medical screening, security and industrial processes could all benefit from the exploitation of the THz gap. One of TeraView's key advantages is its status as a first mover in commercialising the technology. Mick Withers, the company's chief engineer, said this also brings its own special challenges. 'We have to be especially diligent in producing our products because nobody else has done the groundwork for us.' Like its colleagues in academic research, TeraView is looking at the plethora of potential uses for THz systems and trying to assess their merits. As a commercial venture it has to pace itself and be led to a certain extent by its various potential markets. In this respect TeraView has been canny in its development programme, creating a common platform that can be adapted relatively easily to the needs of various applications and industries. 'We have fundamental components that can be used in four completely different markets,' said Withers. Although the core technology is the same, the user interface is unique to the demands of the particular application. 'Customers in each sector would think that they were completely different products,' added Withers. Although TeraView is developing products suitable for each of its core areas - medical, security, pharmaceutical and non-destructive testing - the rate of progress towards full-scale commercialisation will inevitably vary. Medical applications, for example, have more hurdles to jump in terms of gaining regulatory approval. The pharmaceutical industry, however, is particularly interested in THz's potential as an aid to drug discovery, formulation and manufacturing. 'The pharmaceutical industry is quite happy to put its money where its mouth is. It is used to the R&D phase of technology.' Happily for TeraView, a string of heavyweight investors have also been prepared to put their cash behind the potential of THz. TTP Ventures, an investor specialising in early-stage technologies, helped spin TeraView out of Toshiba's Cambridge Research Laboratory and has been a staunch supporter of the company ever since. David Connell, the investment firm's chairman, said TeraView's rapid progress in THz had made it 'the leading company in the field without a shadow of a doubt. It is a firm with the potential to become a very serious business.' In the wider context Connell said the UK was 'in as good a position as it possibly could be' in terms of THz development. 'But the big issue is to ensure it remains at the front of the pack,' said Connell. He claimed that the government had 'a key role to play' in this respect. 'In certain sectors the customers and the big specifiers are from the government, for security applications, for example,' said Connell, who added that the support and involvement of government agencies would be a major boost to the emergence of the technology. 'Fortunately it looks as though that is happening.' Through grants to academics and support for commercial programmes, the police and military are already showing they mean business when it comes to THz. The medical sector, ever cautious when it comes to new technologies, will surely follow. And the industrial sector has never been known to ignore a technology with the potential to boost productivity and efficiency. If the roll-out of THz gathers the momentum that many predict, the UK has a golden opportunity to reap the rewards. The TeraHertz gap The TeraHertz gap, which lies between 100GHz and 10THz, is the last unexplored part of the electromagnetic spectrum, nestling between the microwave and infrared regions. While devices such as mobile phones operate quite happily on one side and TV remote controllers on the other, the THz gap has proved the toughest nut for scientists to crack when it comes to developing electronic systems that are able to generate and detect its radiation. That is changing, thanks to a new generation of ultra-fast pulsed lasers that can generate broad bandwidth THz light. Early versions of these devices tended to be complex, bulky and expensive. So academic and commercial research will concentrate on increasing their performance and reducing their size and cost. The reason for the excitement over THz is the unique properties displayed by radiation in the gap. At THz frequencies common materials such as living tissue and plastic become semi-transparent, yielding a 3D image when targeted by a THz pulse that sweeps across its surface. But THz's uses go well beyond visual inspection. It can reveal the unique THz signatures of different types of substances, allowing users to perform chemical and structural analysis of the objects they are scanning. Because THz is heavily absorbed by water, most of its medical applications are likely to be at or near the body's surface, hence its early application to skin or teeth. With dry substances THz can penetrate deeper, opening the way for scanning of objects such as suitcases at airports. Commercial Possibilities for THz TeraView has grown rapidly since it was spun out from Toshiba Research Europe's laboratory in 2001, following almost a decade of work on source and detector technology relating to THz radiation. Its intention was to bring products to market quickly, and it laid down its marker with a succession of commercial firsts. These included using THz to create images of cancer and tooth decay, producing a portable THz imager and designing a hand-held probe that can be used with THz. TeraView has honed in on what it believes are significant opportunities for THz in four distinct sectors. Security screening has grabbed most of the headlines since September 11 propelled the issue to the top of the global news agenda. THz radiation is particularly good at penetrating clothes and revealing the type of non-metallic objects that X-ray screening would miss during security checks at airports. The technology's ability to carry out analysis of a substance's chemical composition has also proved highly topical, raising the possibility of THz scanners being used to screen incoming mail for terrorist threats such as viruses like anthrax and biochemicals. TeraView has also talked about applying THz to landmine detection. On the medical front the potential for THz to sit alongside other scanning technologies such as X-ray and MRI has been recognised since the earliest days of research in the field. TeraView has carried out trials with clinicians and patients, and although the commercialisation path in the medical sector is long and winding the opportunities are considerable. Because it is non-ionising, THz radiation is safe for medical use and can provide detailed analysis of soft tissue to detect the presence of tumours and other diseases. It has also shown advantages over X-rays for early detection of tooth decay. The pharmaceutical industry may be among the first to benefit from the application of THz. Its ability to analyse chemical composition in detail opens the way for new tools in the development and production of drugs. For example, TeraView has developed techniques to assess the chemical stability of drugs in the purification process prior to preparing them for patients. Non-destructive testing is TeraView's fourth major area of commercial focus. Terahertz pulsed imaging (TPI) techniques developed by the company can be used in industrial applications such as checking the interconnect structures inside semiconductors.
|
