Lab profile: David Simpson, University of Melbourne

Dr Simpson will present the Materials Today 'Materials in Society' lecture at the the 29th International Conference on Diamond and Carbon Materials in September 2018, entitled "Diamond quantum probes for bio-sensing and imaging".

Listen to an interview with Prof Simpson, here.

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Confucius said ‘Better a diamond with a flaw than a pebble without’ and in the new era of quantum technology this is certainly true. Defect centers in diamond are now being used as sensitive quantum probes for a variety of applications.

The rise of quantum technology over the past decade has changed the landscape of sensing technology, particularly at the nanoscale. Quantum sensors based on the nitrogen vacancy (NV) defect in diamond provide exquisite sensitivity and unprecedented spatial resolution. What’s more, these tiny nanoscale sensors have now found their way into the complex world of biology.

David Simpson, who leads a group in the Hollenberg Lab at the University of Melbourne in Australia, was part of the team of scientist that showed NV centers in diamond can be used as an intracellular quantum sensor. This pioneering work was awarded the Australian Eureka Prize for Interdisciplinary Research in 2013.

His research currently focuses on various theoretical and experimental aspects of quantum science and technology, particularly relating to applications in quantum biosensing. Following a PhD in physics at the Victoria University, Simpson became fascinated with biological systems and how they function. He now applies diamond-based quantum sensors to all kinds of interesting biological systems.

David Simpson talked to Materials Today about his current research and future plans.

How long has the lab been running?

I work in the Hollenberg Lab in the School of Physics. The lab was established in 2009 through the support of the Australian Research Council (ARC) and has grown substantially in that time via the ARC Centre of Excellence and Laureate Fellowship schemes.

I was appointed to head the experimental program in Physical Biosciences in 2017, in association with the Thomas Baker initiative.

How many staff makes up the lab?

The Hollenberg Lab currently hosts eight postdoctoral research fellows, six PhD students and 13 MSc students.

What are the major themes of research in your group?

The main goal of my research is to develop new quantum sensing technology for a host of applications in particular, magnetometry and thermometry. My research is focused on a particular atomic-sized defect commonly found in diamond, referred to as the nitrogen vacancy (NV) defect. This defect represents an ideal quantum system that we can manipulate and integrate at room temperature using a simple combination of light and microwave fields.

The electronic structure of the NV defect provides a playground in terms of sensing technology and we can adapt our measurement protocols to determine small changes in magnetic fields, electric fields, temperature, and pressure using a single quantum system. This versatility has given rise to new fields of research in biology and condensed matter physics with many groups around the world exploring the wonders of this system.

My focus is on the application side of this quantum technology, particularly in the biological sciences. We were the first to demonstrate a quantum probe measurement inside a living cell and have since refined this technology to demonstrate intracellular temperature sensing in neurons and nanoscale magnetic sensing in artificial cell membranes.

My current research focus is on detecting and imaging iron in biological systems using widefield quantum sensing microscopes. Iron is a key element of life and is present in all living organisms, but at present our ability to detect iron and related complexes at the single cellular level is lacking. Our research is focused on developing new magnetic sensing techniques based on quantum protocols that can image and identify iron complexes across a host of biological systems.  This includes probing the mineralization properties of chiton teeth, a common sea mollusk, and delving into the inner ear of pigeons to understand the magnetic properties of iron-based cuticulosomes. 

How and why did you come to work in these areas?

I came to work in the physical biosciences in 2010 when we embarked on an interdisciplinary project that set out to perform the first quantum measurement in a living cell. The interdisciplinary team comprised physicists, biologists and chemists. My exposure to the world of biology changed my outlook on science and I became fascinated by biological systems and how they function.

I have since applied nanodiamonds to all kinds of interesting systems from drosophila melanogaster (fruit fly) embryos to primary cortical neurons. This journey has taken many wonderful twists and turns along the way and I am still constantly amazed by the efficiency and complexity of biological structures and systems.

What facilities and equipment does the lab have?

Our lab currently hosts one of the largest concentrations of diamond-based quantum sensing microscopes in the world. We have a number of dedicated quantum-based confocal microscopes that are used for nanoscale nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) using single NV centers and widefield magnetic microscopes for 2D magnetic, current, and temperature imaging. In addition to this, we have a lab at the Florey Institute that currently hosts widefield magnetic microscopes dedicated to bio-sensing and imaging activities. These microscope suites are complemented by state-of-the-art cleanroom facilities within the School of Physics where we can design, fabricate, and characterize a host of interesting devices and materials.  We are also home to two diamond chemical vapor deposition reactors that we use to engineer the next generation of diamond-based quantum sensing devices.

Do you have a favorite piece of kit or equipment?

We have complied an array of quantum sensing systems that we have customized and assembled from scratch. My favorite piece of equipment would have to be the first quantum magnetic microscope I designed and constructed in 2014. It produced our first 2D magnetic image and has been used to image current in 2D materials such as graphene and is currently used to study the biomineralization processes in chiton teeth.

What do you think has been your most influential work to date?

Our most influential work to date was the first demonstration of a quantum measurement in a living cell. This work showed that the NV centers in diamond can be used as an intracellular quantum sensor. This highly cited work was the first in the new field of quantum sensing in biology and was awarded the Australian Eureka Prize for Interdisciplinary Research in 2013. Several groups including our own have gone on to demonstrate the power of this technology including detection of individual electron spin labels in cell membranes through to hyperpolarized molecules. Working at the cutting edge of a new field is a wonderful, fast-paced, and imaginative place to be.

What is the key to running a successful group?

The students play an enormous role in the success of a group and we have been fortunate to attract many outstanding students over the past decade. Our students are encouraged to push the envelope and think creatively to solve complex and challenging questions.

I have personally found interdisciplinary research incredibly fun and rewarding, and I am constantly learning and developing new skills. I aim to instill my inquisitive nature and feeling of excitement into the next generation of researchers.

How do you plan to develop your group in the future?

My plans for the future are to continue to grow the team and establish an interdisciplinary group that can tackle some of the big questions in biology. At the moment, we are looking into the origins of magnetoreception, probing the complex biomineralization processes in sea mollusks and studying the iron storage protein ferritin. We hope, in the future, to be able to answer some of the fundamental questions about the role of iron in biology. If we succeed, we will aim to translate this knowledge into new medical diagnostics and imaging technology that can be accessed by researchers across all areas of science.

Key publications

1. L. P. McGuinness, Y. Yan, A. Stacey, D. A. Simpson, L. T. Hall, D. Maclaurin, S. Prawer, P. Mulvaney, J. Wrachtrup, F. Caruso, R. E. Scholten and L. C. L. Hollenberg. Quantum control and measurement of single-spin fluorescent probes in a living cell. Nature Nanotechnology 6 (2011) 358.
2. D. A. Simpson, E. Morrisroe, J. M. McCoey, A. H. Lombard, D. C. Mendis, F. Treussart, L. T. Hall, S. Petrou, L. C. L. Hollenberg. Non-neurotoxic nanodiamond probes for intraneuronal temperature mapping. ACS Nano 11 (2017) 12077. 
3. S. Kaufmann, D. A. Simpson, L. T. Hall, V. Perunicic, P. Senn, S. Steinert, L. P. McGuinness, B. C. Johnson, T. Ohshima, F. Caruso, J. Wrachtrup, R. E. Scholten, P. Mulvaney, L.C. L. Hollenberg. Detection of atomic spin labels in a lipid bilayer using a single-spin nanodiamond probe. Proc. Natl. Acad. Sci. USA 110 (2013) 10894. 
4. J-P Tetienne, N. Dontschuk, D. A. Broadway, A. Stacey, D. A. Simpson, L. C. L. Hollenberg. Quantum imaging of current flow in graphene. Science Advances 3 (4) (2017) e1602429. 
5. D. A. Simpson, R. G. Ryan, L. T. Hall, E. Panchenko, S. C. Drew, S. Petrou, P. S. Donnelly, P. Mulvaney, L. C. L. Hollenberg. Electron paramagnetic resonance microscopy using spins in diamond under ambient conditions. Nature Communications 8 (2017) 458. 
6. D. A. Broadway, J-P. Tetienne, A. Stacey, J. D. A. Wood, D. A. Simpson, L. T. Hall, L. C. L. Hollenberg. Quantum probe hyperpolarization of molecular nuclear spins. Nature Communications 9 (2018) 1246.