Glazed new world

One material that can be found sitting quietly and unremarked across the spectrum of engineering achievement is glass.

Glass technology has its roots in ancient history and in its simplest form has become an essential part of daily life.

Glass may be taken for granted but it is far more than a kind of ‘enabling’ technology. It has many unique properties, which over the past 20 years have been developed and coaxed forward by researchers across the globe.

In the US and UK that research is beginning to bear fruit and has created a window on a new world of applications. The US in particular has recently put a significant amount of money into glass research. The International Materials Institute (IMI) for New Functionality in Glass, a collaboration between Lehigh and Penn State Universities, is to receive $3.25m (£1.8m) from the National Science Foundation over the next five years.

Himanshu Jain, professor of materials science and engineering at Lehigh, said: ‘The award will enable the two universities to offer more courses, create educational programmes by world leaders in glass research, and host annual conferences on glass.’

Jain has collaborated with researchers in Germany, Greece, India and the UK, but despite his own efforts he believes the development of new glass technologies has been fragmented, ‘caused over the past 20 years by the elimination of industrial laboratories and the shift of government funding to nanotechnologies and the biosciences’.

‘Today glass research is conducted at many universities, but usually by a solitary faculty member offering a single survey course on the topic,’ said Jain. ‘The result is a larger number of students exposed to glassy materials but with relatively shallow, cursory knowledge that does not prepare them to become professional glass scientists or engineers.’

The Lehigh IMI will seek to reverse this and also redress the balance in terms of making glass a fashionable area of research, much like nanotechnology is today. ‘Glass’s unique properties make it useful for many modern applications,’ said Jain. ‘Because it can transmit light signals for hundreds of miles it is a vital component of the optical fibres used in internet and broadband applications. And because it is easy to shape and does not dissolve or corrode, it can safely store nuclear and radioactive materials.’

Jain believes novel glasses will be useful in a number of burgeoning areas of technology development such as nanocomposites and functional coatings. Engineers could also exploit its ionic functionality — that is the transmission of ions or electric charge — in capacitors; its optical functionality in terms of lasers and data storage, and its biofunctionality.

In his proposal for the IMI, Jain said: ‘Applications include arrays of micro and nanolenses, 3D information storage, optical sensors and displays, glasses engineered for toughness, glass for DNA analysis, glass films for viewing X-rays, micro and nanoelectronics, glasses on which bacteria cannot grow and glasses for hydrogen storage.’

The institute will be overseen by a board of directors representing US universities and laboratories, as well as an international board of directors representing 10 countries, recognising the fact that glass research outside the US has been steadily increasing over recent years. The directors’ role will be to evaluate, research and assess proposals for collaboration on new areas of glass research.

Prof Malcolm Ingram, who recently retired from the department of chemistry at the University of Aberdeen, will represent the UK on the international board. At Aberdeen his research focused on ion transport in glasses and the properties of glass and their application in electrochemical energy storage.

With a team of collaborators including Jain, and others in Germany and Greece, Ingram sought to understand further the ion transport mechanisms in glass, and determine the relationship between its morphology and ion exchange to achieve optimal energy and power densities in practical devices. This underpinned his applied work on electrochemical supercapacitors which was supported by the EPSRC and Dera, now the Dstl.

Other UK universities are increasing their support for research into new glass technologies. The Novel Photonic Glasses Research Group — part of the school of engineering at Nottingham University — last year commissioned a laboratory for making, shaping and testing novel glass fibre and planar waveguides and bulk glass for optical components. It has received funding from the EPSRC, Qinetiq, Nortel Networks and Bookham Technology for the development of chalcogenide (sulphur-based) glass, as well as halide and heavy metal oxide-based glasses and transparent nano-structured glass-ceramics.

These have, among other properties, a wide refractive index which makes them ideal for the new generation of all-optical micro-amplifiers used in telecommunications and infrared communications, and for infrared power delivery in laser surgery.

Meanwhile researchers at Southampton University have taken the ultimate step and decided to spin-out a company, CHG Southampton, to make and supply the chalcogenide glass to a range of industries. Chief technical officer Dr Dan Hewak said: ‘As a glass, chalcogenides have many important characteristics, but most crucially a transmission range which extends to wavelengths far beyond the range of silica and other glasses.‘

'More akin to semiconductors and crystals, chalcogenides can also actively interact with photons and electrons. This combination of passive and active properties makes it unique among optical and electronic materials.'

The Optoelectronics Research Centre at Southampton University has worked for ever purer forms of photonic glasses, reducing silica, metal and other insoluble contaminants.

CHG Southampton will market GLS, a new chalcogenide glass with substantially reduced impurities.

GLS is a radically new product offering an optical transparency from the visible to infrared wavelengths, and thermal stability up to 550ºC. In addition, it can be melted in a large scale without the need for sealed ampoule processing making its production and processing safer and more economical.

Hewak’s team sees an obvious use for chalcogenide in the development of minimally invasive surgery. A natural step, said Hewak, would be to combine laser treatment with keyhole surgery techniques, but this has yet to occur due to the lack of suitable optical fibre.

In many cases the laser that is best suited to carry out many of these surgical procedures cannot be used. Lasers that are used can often damage healthy tissue as well as the target areas.

The ability of GLS and other chalcogenide glasses to transmit further into the infrared spectrum would make it possible to create a much finer, more suitable laser for the surgeon, he said.

The proliferation of novel glasses means that this most versatile of materials is set to form a new strata in the course of technological development. Just as nanotechnology has inspired engineers to think what was once the unthinkable, so glass is set to do the same.

Hewak points to an emerging awareness of the possibilities for glass in the chemical, medical, telecommunications and computing worlds. ‘There exists widespread interest in new, relatively unexplored applications. These include optical data storage using phase change or holography, photonic crystal waveguides and a range of chemical and biological sensors,’ he said.