Professor Derek Abbott

T-rays to the rescue!

Professor Derek Abbott describes the fascinating and largely untapped potential of T-rays, discussing why this exciting electromagnetic radiation has been little exploited and sharing his ambitions for novel future applications

Can you open with a short introduction to whole host of metamaterial structures for How has the ability to produce T-rays in the terahertz radiation? manipulating THz radiation. laboratory been advanced?

Terahertz (or T-ray) radiation is considered Could you explain the ways in which Microwaves are generated by using high-speed to be a part of the spectrum between 0.1 and T-rays are being explored for use in oscillating devices, while infrared is generated 10 terahertz (THz). It’s sandwiched between disease identification? thermally or by other light sources. Infrared the world of microwaves and that of infrared. sources become very dim as we approach Traditionally, this part of the spectrum was In the field, THz radiation is being used to the THz region and, to this day, high-speed called the submillimetre wave region and was non-invasively detect diseases, from the plant electronic devices struggle to generate waves used for passive detection by astronomers. kingdom through to humans. For example, in much above 500 gigahertz. However, recent However, active in-lab experiments did not the timber industry there has been interest advances in femtosecond laser technology have take off until the mid-1990s, as it was then that in detecting nematode disease in pinewood. facilitated the convenient generation of short efficient techniques for THz generation were In humans, THz has been used to detect the bursts of THz radiation, thus opening up a new developed using femtosecond lasers. pathology of the human cornea, cirrhosis of the part of the spectrum for further study. liver, misfolded proteins, moisture content and What have been your most significant various carcinomas, among others. In terms of You are Founder of the National T-ray accomplishments to date? cancer, our group has performed fundamental Facility at the University of . Can you studies on detection of skin cancer (via direct elaborate on the history of the Facility? Together with our collaborators, we have scanning of the skin) and detection of cancer demonstrated a number of sensing applications; biomarkers in human saliva. I had not heard of T-rays until 1995. I was for example, label-free avidin-biotin bioaffinity quickly inspired and began to collaborate with detection; sensitive liquid spectroscopy; non- Does their application extend the Rensselaer Polytechnic Institute (RPI) in contact discrimination of RNA polytypes; anthrax beyond healthcare? New York, which at the time had the premier detection; detection of racemic mixtures, THz lab in the world. Then, in 1997, I applied which is of importance for quality control of My team has contributed to security applications for an Australian Research Council grant in pharmaceuticals; discrimination between ranging from checking envelopes for anthrax, the area, which was summarily rejected – the monomeric and fibrillar structures – of interest through to detecting explosives in plastic governing panel had never even heard of for vaccine quality control; and detection of GP2 moulded suitcases. More broadly, T-rays can T-rays! It probably sounded like fiction back peptides, which is of significance as a convenient be used for sensitive gas detection, which then. However, in 1998, after some judicious cancer biomarker within human saliva. can forewarn a security hazard. The detection rewording, I reapplied and won. That grant of a broad range of biohazardous materials commenced in January 1999 and since that In terms of hardware, alongside our is possible. Screening for weapons such as time I have continuously won grants in the collaborators we have demonstrated THz ceramic knives and plastic 3D-printed guns, for area. It was in 2005 that I won about AUS $3 computed tomography, THz functional imaging, example, is where X-rays fail, but T-rays can million in one year and was able to establish porous fibres for THz propagation and a save the day. the National T-ray Facility. This was the

60 INTERNATIONAL INNOVATION Between two worlds The is home to the Adelaide T-ray Group; an expert team of researchers responsible for ’s first T-ray imaging programme. Going from strength to strength in a number of ongoing projects, the team is working towards exciting and impactful future applications in areas as diverse as healthcare and security first fully fledged THz laboratory in the Imagine being able to photocopy a book T-ray Facility and Head of the Adelaide T-ray Southern Hemisphere. without even opening it. Sounds like science Group Professor Derek Abbott. “The Adelaide fiction but the seemingly limitless potential of team has contributed to this effort, including Are you able to reveal any exciting projects T-rays could make this vision a future reality. a patented approach for producing compact on the horizon? Although terahertz (THz or T-ray) technology reflective T-ray systems.” is not new and T-rays have been detected The ongoing Holy Grail project is high- for many years, it has taken scientists a long Novel prospects throughput label-free scanning of biochips, time to be able to generate T-rays in the lab. Since 1997, the talented team, based in the and achieving this will require a number of new The elusive nature of T-rays is due to their University’s School of Electrical and Electronic innovations. Aside from this, a new exciting position on the electromagnetic spectrum, Engineering, has been working to unlock direction is enhanced biosensing at THz where they bridge microwaves and infrared the potential of T-rays in diverse and novel frequencies by exploiting surface plasmons light, constituting a gap in the science of light applications. Realising the great promise on graphene. We also have our sights on and energy; the THz gap. The challenge has T-rays hold in a range of areas, Abbott and his extending the work on carbon-based graphene been first generating enough light in the T-ray collaborators are striving to better understand to silicon-based silicene. frequency band and, second, creating a detector and exploit them. The Group runs a range sensitive enough to react with the T-ray and of THz research programmes that primarily with high enough resolution for imaging. encompass biosensing, security, short-path communications. “I first read about T-rays in The T-ray region became more 1995, and was inspired straight away by their accessible to scientists in the 20th potential to perform direct spectroscopy based Century thanks to time-domain on resonances of the whole molecule,” Abbott spectroscopy with ultrashort- enthuses. “It is this ability that gives rise to The fact that many materials are pulse laser sources and detectors exciting prospects of biosensing.” The Group’s based on pulsed laser excitation, investigations follow two paths: the study of transparent to terahertz radiation which generate and detect free metamaterials to manipulate THz radiation in space T-ray radiation. “In the late new ways; and experiments to detect biological means it has use in a number of 1980s Columbia University was the substances. first to generate coherent pulses quality control and biosecurity of THz energy, but the field did Key connections not take off until the mid-1990s Over the course of their work, the Group applications, where a substance can when AT&T Bell Laboratories has been engaged in a number of crucial successfully demonstrated THz partnerships. Their first collaboration, in 1995, be detected through its packaging pulsed imaging (TPI), coining the was with Rensselaer Polytechnic Institute term ‘T-rays’,” explains founder (RPI), and the team’s ongoing ties with the of Adelaide University’s National organisation have enabled Abbott to send

www.internationalinnovation.com 61 INTELLIGENCE a number of PhD students there, including different vibrational frequencies. “It turns out two Fulbright Scholars. Another important that the frequency range of THz is in the region BIOSENSING WITH TERAHERTZ RADIATION collaboration is with Cambridge University, with where resonances of many biomolecules lie. OBJECTIVES whom the Group successfully demonstrated Thus, it is an ideal modality for spectroscopic • To manipulate terahertz radiation in new ways to T-ray computed tomography using a quantum identification of biomolecules,” details Abbott. explore the fundamentals of the technology cascade laser. The researchers have also been The frequency range of T-rays, 0.1-10 THz, working with the City University of Hong Kong has been shown to be useful for, among other • To perform experiments with terahertz radiation to (CUHK) on several fundamental studies on things, probing biological substances and detect biological substances THz interaction with the peptide GR2, which detecting them for medical applications. KEY COLLABORATORS is derived from a protein marker for cancer. Professor Xi-Cheng Zhang, University of Rochester, “In addition, we have collaborated with the Health applications USA • Professor Lynn Gladden, University of University of Freiburg, RWTH Aachen University, In addition to sensing parts of the body that Cambridge, UK • Dr Bernd M Fischer, French-German Technical University of Denmark, University of X-rays cannot, penetrating thin layers of Research Institute of Saint-Louis, France • Professor Leeds and Osaka University, to name a few,” skin and producing high-resolution images, Willie J Padilla, Duke University, USA • Professor Abbott explains. “Key domestic collaborations T-ray photons are non-ionising and therefore, Emma Pickwell- MacPherson, Chinese University have been with the University of Queensland, unlike X-rays, do not damage cells. As an of Hong Kong, Hong Kong, China • Professor where we have studied the interaction between example, THz technology could be useful in Masayoshi Tonouchi, University of Osaka, Japan THz and monomeric versus fibrillar protein skin cancers, eliminating the need for tissue • Professor Anton P J Middelberg, University of structures with a view to quality control of biopsies. “The photon energy of X-rays is too Queensland, Australia • Dr Martin Nagel, Institut für artificial vaccines. With RMIT University we high for shallow surface layers on the human Halbleitertechnik, RWTH Aachen University, Germany collaborated on numerous metamaterial body and also for laboratory biochips, and • Professor Peter Uhd Jepsen, Technical University of structures in the THz range.” this results in no contrast,” Abbott elaborates. Denmark, Denmark “T-rays on the other hand cannot penetrate The team was awarded a large Australian the depths achieved by X-rays, but provide PARTNERS Research Council (ARC) grant in 1999, which good contrast in thin layers. Thus T-rays Royal Melbourne Institute of Technology enabled them to develop Australia’s first and X-rays are complementary rather than FUNDING T-ray imaging programme. Later, in 2005, competing modalities.” Australian Research Council (ARC) the researchers won a major infrastructural ARC grant to develop the world’s first laser- It will be some time before skin cancers can CONTACT based T-ray user facility – a facility that has be scanned in situ using T-rays due to the Professor Derek Abbott been in high demand. “A recent realisation is complexity and variability of the problem. Founder, National T-ray Facility and that the feature sizes of THz metamaterials However, Abbott and his team see great and Head, Adelaide T-ray Group are in the submillimetre region and thus almost tangible potential for them to be used School of Electrical & Electronic Engineering can be readily manufactured using standard in scanning dental caries or imaging the The University of Adelaide lithographic techniques or even high-end 3D human cornea, for example, as there is greater South Australia 5005 printers,” Abbott reveals. “This has led to a homogeneity in these areas. Australia whole host of metamaterial-based resonators and components for manipulating THz waves First place T +61 8 8313 5748 in clever ways, to enhance their sensitivity The Adelaide T-ray Group has encountered E [email protected] for biosensing.” challenges associated with the large www.eleceng.adelaide.edu.au/Personal/dabbott wavelength of T-rays that makes it impossible Making the invisible visible to resolve the spot size on a near conventional http://bit.ly/MathematicsGenealogyProject The vast potential of T-rays comes from their DNA biochip. “My team has been working on http://neurotree.org/neurotree/tree.php?pid=14808 combined properties. Owing to their short exploiting metamaterials and near-field effects wavelength they are able to pass through dry, where the physics fundamentally changes and www.researcherid.com/rid/E-8352-2011 non-polar objects that are opaque at visible the conventional wavelength resolution limit http://orcid.org/0000-0002-0945-2674 wavelengths. The fact that many materials are is broken,” explains Abbott. Looking ahead, he transparent to THz radiation means it has use and his team see important future applications http://bit.ly/Abbottcitations in a number of quality control and biosecurity for T-rays, notably in customised medicine in www.researchgate.net/profile/Derek_Abbott applications, where a substance can be the area of label-free screening of biochips, detected through its packaging. Importantly, which the researchers predict will be possible www.linkedin.com/profile/view?id=4995859 T-rays can distinguish between different in the mid-term future. The goal will be to use DEREK ABBOTT received a chemical compositions inside a material, THz to rapidly scan for thousands of genetic BSc (Hons) in Physics from and information about the properties of the diseases at once, which will be a huge step Loughborough University, UK, and material can be gleaned by measuring how an forward for customised medicine. a PhD in Electrical and Electronic object absorbs the THz radiation. For example, Engineering under K Eshraghian the radiation can discriminate anthrax from and B R Davis from the University of Adelaide, salt in an envelope, as anthrax molecules have Australia, in 1982 and 1995, respectively. He was with the GEC Hirst Research Centre, , UK, from 1978- 86, and Austek Microsystems, South Australia, from 1986-87. Since 1987, he has been with the University of Adelaide, where he is currently a professor with the School of Electrical and Electronic Engineering. He was awarded an ARC Future Fellowship in 2012.

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