Research Themes
The Institute's research in Soft Materials is undertaken in the School of Chemical and Physical Sciences , Victoria University of Wellington and the Biomaterials Group at Massey.
Theme Leader: Dr Bill (Martin) Williams
Soft matter is where physics meets chemistry, and where physics and chemistry meet biology. Nature elegantly harnesses the special physics of the nano-world and performs ‘bottom-up’ processing with aplomb, generating smart, functional, viscoelastic matrices: from molecules to materials. Soft materials and complex fluids are ubiquitous not only in biology, but also in industrial arenas as diverse as oil recovery, food technology, cosmetics and personal care products, electronic devices, and biotechnologies, such as microfluidics and targeted drug delivery.
Soft materials characteristically exhibit hierarchical structures organized on multiple length-scales, which emerge from molecular and supra-molecular self-assembly. The study of how their macroscopic materials properties emerge as a consequence of the properties and interactions of their constituent molecules promises not only to illuminate Nature’s design rules but to inform us in the design of our own smart soft materials: structure-function understanding par-excellence. The spatial and temporal richness of these hierarchical architectures necessitates the use of varied experimental techniques to address organisational phenomena and dynamics across many orders of magnitude. It is the complementary nature of the available techniques, in addition to theoretical capability, and relevant expertise in the gamut of soft matter systems including emulsions, foams, liquid crystals, polymer and biopolymer solutions and gels, that is the strength of the Theme.
- Uniquely powerful state-of-the-art experimental tools: are being developed, including simultaneous mechanical deformation and spectroscopic investigation of complex fluids via novel rheo-NMR, and rheo-optical methods. These build on pioneering research in rheo-NMR, the amalgamation of nuclear magnetic resonance and its capacity for molecular insight, with rheology, the science of mechanical deformation, and provide the opportunity to monitor molecular properties and macroscopic consequences concurrently. Furthermore, recently developed diffusioncorrelation, -exchange and -spectral-analysis methods have proven powerful in measuring bilayer dynamics and ordering in equilibrium lyotropic liquid crystal phases and are poised to extend our experimental insights regarding flow-induced reorganisation in complex soft matter. These results will now be supplemented with those obtained by small-angle X-ray scattering (SAXS), microscopy, laser diffraction, rheology and ellipsometric techniques to investigate the role of dynamic processes in emulsions and lyotropic liquid crystals.
- Learning and exploiting the tricks that Nature uses in the production of advanced materials is another focus for the Theme. Nature controls the precipitation of inorganic materials to high precision and in doing so manipulates their growth such that the final materials have superior physical (e.g. strength) and chemical properties (e.g. resistance to corrosion) as compared with similar mineral or synthetically grown materials. Investigations are underway into using soft interactions and traits inherent in soft matter systems, such as self assembly, phase separation and surface tension, in order to orchestrate the assembly of hierarchical structures in advanced inorganic materials.
- Mechanical properties of soft materials: will also be directly measured on multiple length- and time-scales by employing microrheological techniques using multiple particle tracking (MTP) and diffusing wave spectroscopy (DWS). In addition, a new optical tweezers set-up will be developed in order to provide unprecedented access into the non-linear regime as well as providing advanced single molecule stretching capability that will supplement ongoing polymeric stretching work carried out presently using atomic force microscopy (AFM).
- Theoretical modelling capability: complements the extensive experimental suite available in the Theme. For example, Flow in nanochannels will be studied using our theoretical and computational expertise. This has relevance far beyond flows in porous materials of reduced dimensions. Indeed, understanding how to manipulate the transport of large molecules under nanofluidic conditions has the potential to revolutionise the way in which molecular biology is done. In addition, the morphologies of surfactant systems that have the ability to naturally self-assemble to form meso-scale structures such as bilayers (membranes), cylinders (worm-like micelles) and spherical structures (micelles) will be investigated.
- Fluid flow in porous media: will also be compared using simulations and experiments. In particular, flow propagators, spatial and temporal correlation functions, the non-local dispersion tensor, and the scaling of the dispersion on the Peclet and Reynolds numbers, will be investigated using an array of gradient NMR methods. These methods will be combined with rapid micro-imaging based on rapid scan echo planar techniques, in order to investigate spatial heterogeneity. Additionally, combined spin-relaxation and gradient diffusion methods will be developed to investigate molecular dynamics using multi-dimensional NMR based on novel inverse Fourier and inverse Laplace methods.
- Spectroscopy and Nano-Scale Structures: is a further active area within the Theme. Vibrational pumping in Surface Enhanced Raman Scattering (SERS), and single molecule SERS, where the enhancement arises from proximity to metallic nano-particles with their plasmon resonances have been convincingly demonstrated. Current work is expanding on this success by investigating SERS for more complex multiple-particle nanostructure geometries.
- Molecular basis of soft material rheology (P.T. Callaghan, K.M. McGrath, M.A.K. Williams)
- Correlating molecular level interactions to the macroscopic properties of soft matter (K.M. McGrath, P.T.Callaghan )
- Controlling hierarchical structure in inorganic materials through soft interactions (K.M. McGrath)
- Bio-inspired pattern formation in 2 and 3 dimensions (K.M. McGrath, M.Alkaisi, R.J. Blaikie)
- State-of-the-art microrheological measurements in soft materials (M.A.K. Williams, P.T. Callaghan, K.M. McGrath,)
- Nanomechanical properties and function of biopolymers (M.A.K. Williams)
- Theory of light-matter interactions, with applications to optical tweezers and spanners (J. Lekner)
- Fluid dispersion and flow in micro-and nano-porous media (P.T. Callaghan)
- Nanofluidic modelling (S.C. Hendy, J. Lekner, U. Zülicke, J. Tallon)
- 4Ultra-sensitive laser spectroscopy (P.G. Etchegoin, R. Tilley)
Objectives 4.1 and 4.2 focus, in the spirit of traditional condensed matter physics, on understanding how the macroscopic properties of soft materials emerge from the chemical composition of, and the interactions between, the molecular components; with the former concentrating on polymeric-type systems where topological entanglements can be important, and the later predominantly on emulsion systems where interfacial properties play a major role. Objective 4.3 seeks to understand the role that such soft matrices play in directing biomineralisation, while 4.4 provides a natural link between the prior two objectives by exploiting the Theme’s expertise in emulsion and liquid crystal-type systems in order to investigate the possibility of templating the growth of designed inorganic structures.
Objectives 4.5 and 4.6 aim to underpin the work of the Theme by providing state-of-the- art experimental capability in the measurement of mechanical properties over a whole range of spatiotemporal scales, including single macromolecule stretching and high frequency microrheology, while 4.7 adds theoretical expertise invaluable in the exploitation of optical tweezers in this regard.Objectives 4.8 and 4.9 respectively bring cutting-edge experimental and theoretical techniques to bear on the study of flow in porous media and nanochannels; and finally the aspects of colloidal, biomolecular and single molecule physics encompassed by the Theme provide objective 4.10, which continues to yield ground-breaking work in the area of SERS, with a natural home.
