24 Nov 2016 : Peter Metaxas

Thu 24 Nov 2016 – 3:30 pm (Murdoch University, Postgrad Suite ECL2.031)

Towards frequency-based electronic bio-detection at the nano-scale

Dr Peter Metaxas — School of Physics, University of Western Australia

Magnetic biosensing exploits chemically functionalised magnetic nanoparticles for labelling and subsequent detection of analytes of interest in biological samples, opening routes to new technologies for point-of-care medical diagnostics [1]. Many solid state nanoparticle detection techniques are voltage-level based. For example, in conventional magnetoresistive sensors, the magnetic configuration within the device is modified by the nanoparticles’ stray magnetic fields, generating a change in the device resistance (and thus the voltage across the device). In contrast, electrically probed, field-dependent magnetisation dynamics in magnetic nanostructures offer a route towards intrinsically frequency-based electronic biosensing. This resonance-based approach potentially offers high speed sensing with nano-scale devices [2] which can operate under very large magnetic field ranges [3]. We demonstrate the potential of this approach first using large area, periodically nanostructured ferromagnets (“magnonic crystals”) [3,4]. These systems enable us to probe the effect of nanoparticles on ferromagnetic resonances that are confined to regions in the crystal with lateral dimensions on the order of 100 nm. Secondly we look at nanoparticle sensing exploiting the “gyrotropic” resonance of ferromagnetic vortices. We show how the localized field of a nanoparticle can stiffen the vortex, leading to field sensitivities exceeding those conventionally measured in uniform fields [5]. Finally, we experimentally demonstrate spintronic, frequency-based detection of superparamagnetic beads and discuss future directions of this work (e.g. [5]).

This work would not have been possible without contributions from collaborators at the the Unité Mixte de Physique CNRS/Thales (France), University of Southampton (UK), the National University of Singapore and AIST (Japan).

[1] Gaster et al., Nat. Med., 15, 1327 (2009). [2] Braganca et al., Nanotechnol., 21, 235202 (2010). [3] Sushruth et al., Phys. Rev Appl., 6, 044005 (2016).  [4] Metaxas et al., Appl. Phys. Lett. 106, 232406 (2015).  [4] Fried and Metaxas, Phys. Rev. B, 93, 064422 (2016). [5] Albert et al., Nanotechnol. 27, 455502 (2016).


9 Nov 2016: Peter Harrowell

Wed 9 Nov 2016 – 2:30*pm (Murdoch University, Senate Room)

Rethinking Structure in Amorphous Materials: From Geometry to Statistics

Peter Harrowell — School of Chemistry, University of Sydney

Despite a long history, there remain many important open questions about, not just the best description of structure in liquids and glasses, but what use these structures provide in terms of understanding the properties of amorphous materials. This talk will introduce the basic questions concerning the role of structure in materials science, how that structure is characterised and then present recent results on how the geometry of the locally stable structures in an amorphous materials influence the stability of the material with respect to crystallization.2016_11_10_peterharrowell_imageA central conclusion of this research is that advances in the study of amorphous structure will involve abandoning the traditional descriptive geometrical approach to structure in favour of regarding structure in terms of the statistical correlations between local structural elements. It is hoped that the description of this exciting open problem will be both accessible to and of interest for mathematicians.

(* Peter’s talk will be at 4pm, but is part of a mini-workshop that starts at 2:30 *)

9 Nov 2016: Julian Gale

Wed 9 Nov 2016 – 2:30pm (Murdoch University, Senate Room)

Exploring the Nucleation of Biominerals: When Hard Rocks Meet Soft Matter

Paolo Raiteri, Raffaella Demichelis, Wen Zhao, Kasia Koziara, Alicia Schuitemaker and Julian D. Gale

Curtin Institute for Computation/The Institute for Geoscience Research (TIGeR), Department of Chemistry, Curtin University, PO Box U1987, Perth, WA 6845

2016_11_10_juliangale_imageThe nucleation of minerals from ions in aqueous solution underpins important processes from biomineralisation to scale formation and carbon sequestration. All this begins with ion pairing, but what happens next is still a matter that is hotly debated for systems such as calcium carbonate, where the classical nature of nucleation has been called into question [1,2,3]. Therefore it is vital to use both experiment and simulation to fill in the missing details as to how crystalline minerals form. In this presentation we will examine the possible pathways by which two common biominerals, calcium carbonate and calcium oxalate, nucleate in order to try to explain how proteins may influence and control this process. Based on simulation results it will be demonstrated that hard rocks and soft matter are perhaps not as different as they might seem during their earlier stages of formation.


[1] D. Gebauer, A. Völkel, H. Cölfen, Science, 322, 1819 (2008).

[2] R. Demichelis, P. Raiteri, J.D. Gale, D. Quigley, D. Gebauer, Nature Comm., 2, 590 (2011).

[3] A.F. Wallace, L.O. Hedges, A. Fernandez-Martinez, P. Raiteri, J.D. Gale, G.A. Waychunas, S. Whitelam, J.F. Banfield and J.J. De Yoreo, Science, 341, 885-889 (2013)

6 Oct 2016 : Sandy Peterhaensel

Detection of nanometer size differences through human color vision

Speaker : Sandy Peterhänsel, Stuttgart University

Venue    : Thu 6 Oct 2016, 3pm (Murdoch University, Senate Room)

We study how accurately a naked human eye can determine the thickness of thin films and the geometric parameters (height and width) of optical gratings from the observed color. Our approach is based on color-matching experiments, where a sample with unknown parameters is observed next to a reference field of same size. The study of the limits of color discrimination and their dependence
on surrounding conditions for human eyes are one of the major trends in color science [1]. For thin lms this is done by placing the  sample in direct contact to a LCD display, see Fig. 1. For matching of gratings the setup is more complex, as shown in gure 2. This is due to the fact, that only the zeroth order should be observed, as higher orders will lead to an angular dispersion of the wavelengths present in the spectrum of the light source.

In both cases, the color of the reference field is matched by several test persons. From their selection the geometric properties of the thin films, as well as of the gratings are reconstructed via rigorous simulation. We found that the human color observation provides an extremely accurate evaluation of the lm thickness and is comparable to sophisticated instrumental methods in this case. Even for the more complex reconstruction of the grating parameters an accuracy in the range of much more sophisticated methods like scanning  electron microscopy could be observed. Our results suggest that for a wide range of structures, the  color observation may help to get quick, but still accurate, results, without any sophisticated instrumentation.
[1] R.G. Kuehni, Color Res. Appl. 33(324), (2008).
[2] S. Peterhänsel, H. Laamanen, J. Letholahti, M. Kuittinen, W. Osten and J. Tervo, Optica 2(7), (2015)
[3] S. Peterhänsel, H. Laamanen, M. Kuittinen, J. Turunen, C. Pruss, W. Osten and J. Tervo, Opt. Lett. 39(3547), (2014)

13 Oct 2016 : Karol Miller

Paradigm shift in biomechanics: no more research on mechanical properties of tissues

Speaker : Winthrop Professor Karol Miller – University of Western Australia

Venue    : Thu 13 Oct 2016, 4pm (Murdoch University, Senate Conference Room)

It is now recognised that the most urgent task of biomechanists is to devise methods for clinically-relevant patient-specific modelling. A large proportion of the biomechanics community believes that the main obstacle in creating patient-specific models is the difficulty (or impossibility?) of measuring patient-specific properties of tissues to be used in biomechanical models.

For about ten years Intelligent Systems for Medicine Laboratory has advocated a complete refocus of biomechanical research away from describing mechanical properties of tissues. We postulate that instead we need to reformulate computational mechanics problems in such a way that the results are weakly sensitive to the variation in mechanical properties of simulated continua. This suggestion constitutes a paradigm shift in the field and has encountered strong resistance of the more traditionally inclined members of the biomechanics community.

In this seminar I will describe briefly how ISML members’ thinking on this completely new approach to biomechanics has evolved over the years. I will also demonstrate the success of our new approach using examples from the fields of image-guided neurosurgery and vascular biomechanics.

(This talk was previously given as the Hamlyn Distinguished lecture at Imperial and recently at Harvard School of Engineering)


5 Sept 2016 : Benjamin Winter

Quantitative Electron Tomography of Functional Nanomaterials

Speaker : Dr Benjamin Winter, Friedrich-Alexander University Erlangen-Nuremberg

Venue    : Monday 5 Sept 2016, 3:30pm (Murdoch University, ECL1.031)

Functional nanomaterials owe their unique properties to structures on the nanometer scale and feature widespread applications ranging from optics, electronics, catalysis and sensor technology, to bionics and biomedical engineering. Since the development of these materials during the last years steadily led to more complex morphologies, novel techniques have to be employed that enable the characterization of these materials in three dimensions. Here, the potential of such a technique, namely electron tomography (ET), is demonstrated by applying it to a variety of technologically relevant nanoparticulate and nanoporous functional materials.

Detailed structural analyses are essential for the understanding of fundamental physical and chemical properties, which is necessary for the further optimization and development of these materials. Transmission electron microscopy (TEM) offers many different imaging and spectroscopic techniques allowing for comprehensive materials characterization. In the course of this, ET enables the three-dimensional (3D) reconstruction of the analyzed material derived from many individual projections recorded from different viewing angles. The realistic 3D representations of the samples with high spatial resolutions down to (1 nm)3, or even below, enable the examination of important structural properties. Each studied material system requires to devise and apply individually tailored characterization approaches, ranging from conventional TEM to advanced techniques like 360° ET.

On the one hand, quantum dot (QD)/low-dimensional hybrid materials with application in optoelectronics are characterized using TEM and ET techniques to unravel important material properties like QD size and morphology or interface cleanliness [1,2]. Furthermore, a novel routine to determine the approximate 3D atom distribution of nanoparticles within beam-sensitive hybrid structures is presented.

On the other hand, mesoporous titania thin films used as catalyst support [3] and nanoporous zeolite [4] and hematite particles are investigated. ET is employed to determine important parameters of these nanoporous functional materials such as pore size distribution, interconnectivity and porosity. Moreover, ET reconstructions can directly be used to understand and model physical and chemical properties and processes within catalysts, e.g., the mass transport and chemical reaction of gases. Here, the integration of ET into a so-called virtual prototyping process for mesoporous titania thin films is demonstrated, which combines experimental and computational approaches for an optimization of the pore system.

Furthermore, ET shows excellent applicability to investigate µm-thick and porous biological structures by revealing the coexistence of both gyroid chiralities and specific crystallographic texture of naturally occurring photonic crystals in wing scales of the butterfly Callophrys rubi [5].

The presented analyses combine different characterization techniques, whereat TEM and ET show their exceptional strength exclusively allowing for the examination of important structural properties. The resultant findings essentially contribute to a detailed understanding of the studied materials and, beyond this, are key to their further development and application.

1. J. Schornbaum, B. Winter, S. P. Schießl, B. Butz, E. Spiecker, J. Zaumseil. Controlled in situ PbSe quantum dot growth around single-walled carbon nanotubes: a noncovalent PbSe-SWNT hybrid structure. Chemistry of Materials, 25(13):2663-2669, 2013.

2. J. Schornbaum, B. Winter, S. P. Schießl, F. Gannott, G. Katsukis, D. M. Guldi, E. Spiecker, J. Zaumseil. Epitaxial growth of PbSe quantum dots on MoS2 nanosheets and their near-infrared photoresponse. Advanced Functional Materials, 24(37):5798-5806, 2014.

3. V. Novák, E. Ortel, B. Winter, B. Butz, B. Paul, P. Kočí, M. Marek, E. Spiecker, R. Kraehnert. Prototyping of catalyst pore-systems by a combined synthetic, analytical and computational approach: application to mesoporous TiO2. Chemical Engineering Journal, 248(0):49-62, 2014.

4. A. G. Machoke, A. M. Beltrán, A. Inayat, B. Winter, T. Weissenberger, N. Kruse, R. Güttel, E. Spiecker,
W. Schwieger.
Micro/macroporous system: MFI-type zeolite crystals with embedded macropores. Advanced Materials, 27(6):1066-1070, 2015.

5. B. Winter, B. Butz, C. Dieker, G. E. Schröder-Turk, K. Mecke, E. Spiecker. Coexistence of both gyroid chiralities in individual butterfly wing scales of Callophrys rubi. PNAS, 112(52):12911-12916, 2015.

Acknowledgement: German Research Foundation (DFG) Cluster of Excellence “Engineering of Advanced Materials” (EXC 315), DFG SPP 1570.

11 Aug 2016 : Julien Dumortier

Image-based Phenotyping of Cereal Crops

Speaker : Mr Julien Dumortier – Murdoch University (visiting student)

Venue    : Thu 11 August 2016, 4pm (Murdoch University, Senate Room)

In this talk, I will review the importance of image processing techniques for phenotyping cereal plants and discuss their potential application in breeding programs. I will then focus on the work I have done during my two-month internship at Murdoch University. I will particularly discuss the use of recent machine leaning techniques and present some preliminary results.

15 Sept 2016 : Adil Mughal

Phyllotaxis, disk packing and Fibonacci numbers

Speaker : Dr Adil Mughal – Aberystwyth University, Wales

Venue    : Thu 15 Sept 2016, 3pm (Murdoch University, Senate Room)

Phyllotaxis (the arrangement of buds or branches on a stem, or  flowerets on a flower) has long been debated [1, 2], particularly in regard to the widespread occurrence of spiral structures that are related to the Fibonacci sequence [3-7]. Over the years hundreds of papers, and several books, have attempted to provide explanations of this phenomenon using models of varying complexity, sophistication and ad hoc inventiveness.

Here we off er a theoretical model which relates the problem to disk packings, extending previous work [8, 9] that seeks explanations in that way. Our method
is to adapt the closely related problem of the dense packing of hard disks on a cylinder [10{12], where helical symmetry arises naturally, to the present case of
buds on a gradually enlarging stem.

The figure shows the evolving arrangement of buds on a “bullet shaped” surface (i.e. the stem) at an initial time T1, and subsequent times T2 and T3. Towards the top the arrangement is characterised in phyllotactic notation [l = m+n; m; n] by the structure [1; 1; 0]. With increasing diameter this structure evolves into more complex arrangements – i.e. [2; 1; 1] followed by [3; 2; 1]. This is precisely the rule of progression in the Fibonacci sequence. The images on the left show the pattern “rolled out” onto the plane while the corresponding figures on the right show the arrangement wrapped seamlessly onto the stem.

Buds are introduced at the top of a “bullet-shaped” surface – roughly representative of a plant stem, see Fig (1) – and migrate downwards, while conforming to three principles: dense packing, homogeneity and continuity. Typical results are presented in a video. We show that spiral structures characterised by the Fibonacci sequence (1,1,2,3,5,8,13…), as well as related structures, occur naturally under such rules.

A. M. acknowledges fi nancial support through Aberystwyth University Research Fund.

[1] H. Airy, Proceedings of the Royal Society of London 21, 176 (1872).
[2] D. Hofstadter and C. Teuscher, Alan Turing: Life and legacy of a great thinker (Springer Science & Business Media, 2013).
[3] L. Levitov, JETP letters 54, 542 (1991).
[4] L. Levitov, EPL (Europhysics Letters) 14, 533 (1991).
[5] S. Douady and Y. Couder, Physical Review Letters 68, 2098 (1992).
[6] P. Atela, C. Gole, and S. Hotton, Journal of Nonlinear Science 12, 641 (2002).
[7] M. Pennybacker and A.C. Newell, Physical Review Letters 110, 248104 (2013).
[8] G.J. Mitchison, Science (1977).
[9] G. Van Iterson, Mathematische und mikroskopisch-anatomische Studien uber Blattstellungen: nebst Betrachtungen über den Schalenbau der Miliolinen, Ph.D. thesis, TU Delft, Delft University of Technology (1907).
[10] A. Mughal, H. Chan, and D. Weaire, Physical Review Letters 106, 115704 (2011).
[11] A. Mughal, H. Chan, D. Weaire, and S. Hutzler, Physical Review E 85, 051305 (2012).
[12] A. Mughal and D. Weaire, Physical Review E (2014).

2 Sept 2016 : David Henry

Soil Water Repellence: A Molecular Dynamics Study of Amphiphilic Compounds on Mineral Surfaces

Speaker : Dr David Henry – Murdoch University

Venue    : Fri 2 Sept 2016 @ 3pm (Murdoch University, Senate Room)

This talk describes joint work with Nicholas Daniel, S. M. Mijan Uddin, Richard. J. Harper from the School of Veterinary and Life Sciences, Murdoch University, 90 South Street, Murdoch WA. 6150 Australia.

Hydrophobic soils have been observed around the world, under different climates and land uses1. It is estimated that southern Australia alone has between two and five million hectares affected by hydrophobic soils2. Non-wettable soils cause both environmental and economic problems including increased surface runoff, enhanced erosion rates and chemical leaching, decreased nutrient storage and plant-available water and reduced crop yields.3 This hydrophobicity is caused by amphiphilic organic compounds deposited in the soil that originate from plant materials.4 Our experimental investigation of this phenomenon is complemented by computer modelling of the structuring and interaction of organic species, on different soil types, to identify key driving forces. This study examines intermolecular interactions of monolayers of hexadecanol (CH3(CH2)15OH) and hexadecanoic acid (CH3(CH2)14COOH) on quartz, silica and kaolinite as a function of surface density, using classical molecular dynamics simulations. The computer simulations clearly indicate quite different packing and interfacial interactions between wax molecules on sand/quartz (Fig. 1a) and clay/kaolinite surfaces (Fig. 1b), respectively.5 Consequently, higher levels of wax material are required to render clay particles hydrophobic compared with sand particles.

Figure 1. Alignment of CH3(CH2)15OH on (a) Quartz and (b) Kaolinite

Analysis of the trajectories also reveals that acid mobility is greatest on the quartz surface, and lowest on the silica surface. While the interactions between the surface and acid chains are of primary interest, the interactions between acid chains are also important in determining the structure of the layers formed. Hydrogen-bonding is dominant between the acidic hydrogen and carbonyl oxygen atoms of the neighbouring acid chains. The structuring of water around the functional groups of the surfaces and the waxes also provides insight into the susceptibility of different surfaces to develop water repellence.


1 S. H. Doerr, C. J. Ritsema, L. W. Dekker, D. F. Scott, D. Cater, D. Hydrological Procs. 2007, 21, 2223-2228.

2 R. J. Harper, I. McKissock, R. J. Gilkes, D. J. Carter, P. S. Blackwell, J. Hydrology 2000, 231-232, 371-383.

3 S. H. Doerr, R. A. Shakesby, R. P. D. Walsh, Earth-Sci. Revs. 2000, 51, 33-65.

4 F. A. Hansel, C. T. Aoki, C. M. B. F. Maia, A. Cunha Jr, R. A. Dedecek, R.A. Geoderma 2008, 148, 167-172.

5 L. Walden, R. Harper, D. Mendham, D. Henry, J. Fontaine, Soil Res. 2015, 53, 168-177.

18 Aug 2016 : Ben Fabry

Cancer cell migration in 3D biological matrices

Speaker : Prof Ben Fabry – Friedrich-Alexander-Universität Erlangen-Nürnberg

Venue    : Thu 18 Aug 2016, 4pm (Murdoch University, Senate Conference Room)

In cancer metastasis and other physiological processes, cells that migrate through the 3-dimensional (3D) extracellular matrix of the connective tissue must overcome the steric hindrance posed by small pores. It is currently assumed that low cell stiffness promotes cell migration through confined spaces. In my talk I will present data showing that a host of other factors such as adhesion and traction forces may be at least equally important. I will also present new assays that we recently developed to quantify cell migration and traction forces in 3D matrices.

This image, taken by Julian Steinwachs, shows a breast carcinoma cell migrating through a collagen gel. Collagen fibers are shown in blue, the actin network of the cell in red, and the cell’s nucleus in green.