SEMS Research: Functional Nanomaterials
The development and understanding of nanostructurised materials is currently a major research theme at Queen Mary. These nanomaterials have a range of unique physical and chemical characteristics, and have the potential to be used in a multitude of novel applications from new functional materials and sensors and actuators, materials for energy conversion and storage to biomaterials. It is because of this diversity that the work of this group overlaps with other research groupings within Queen Mary.
A large area of research within the Nanostructured Materials group is in nanocomposites. A major research effort is around the creation of multi-functional polymeric materials based on carbon nanofillers such as carbon nanotubes, graphene and carbon black. Research in carbon nanostructures ranges from synthesis and electrical properties to applications and is studied in collaboration with the Physics Department. A specific area of interest is higher-order fullerenes filled with guest atoms and electronic properties of nanotubes. Extensive research activity involves the application of carbon nanotubes in polymer composites for the creation of multi-functional materials with interesting mechanical, electrical, thermal and optical properties. Specific areas of research are the creation of high strength polymer fibres, sensory fibres for smart textiles, smart rubber, improved flame retardancy of polymers, transparent conductive films and new hierarchical carbon fibre/carbon nanotube composites with localized damage sensing capability. Besides carbon nanoparticles a significant research activity is in the area of electrospun polymer nanofibres, cellulose nanofibres and nanoclays. Cellulose nanofibres such as cellulose whiskers and nanocellulose produced by bacteria are used to create fully biobased nanostructured materials with interesting mechanical and optical properties. Nanospider® technology is used for the creation of electrospun nanofibreous materials for a wide variety of applications such as filtration, textiles, medical and composites.
There is currently also a great interest in size effects in ceramic materials as many properties change dramatically when the grain size or component dimensions are below 100 nm. For the production of these materials the Queen Mary team has unique Spark Plasma Sintering (SPS) facilities that allow densification of nanoceramic powders to be achieved with minimal grain growth. Research is focused on the effect of grain size on the mechanical properties of metals and structural nanoceramics and the electrical properties of ferroelectric, varistors and thermoelectric nanoceramics. Applications of these ferroelectrics are in non-volatile memories, and actuators and sensors in microelectromechanical systems (MEMS). The increasing demand for size reduction in the microelectronics industry is approaching the nanometre scale, where our experimental and theoretical work is showing that the properties of these functional ceramics strongly diverge. Our work on nanoscale metals and structural ceramics involves development of improved tungsten components for fusion reactors and anti-ballistic protection with industrial collaborators, respectively. Next to the creation of nanostructured ceramics the group is also involved in the development of conductive ceramic nanocomposites using carbon nanotubes or graphene as a conductive filler. We have shown that rapid sintering by SPS can preserve the structure of such carbon nanostructures, opening up the possibility to create multi-functional ceramic materials with improved mechanical, electrical and thermal properties.
A very distinctive area of research that has recently been introduced to Queen Mary is that of micro- and nano-encapsulation. This work is based on a layer-by-layer (LbL) adsorption approach utilising oppositely charged polyelectrolytes on colloidal template particles, including emulsions and gas bubbles. A great variety of materials can be encased in capsules with controlled delivery and release properties, sensing, magnetic navigation, light addressing and more functions to meet scientific and industrial interest. Our work on stimuli-responsive nanoparticles and nanocapsules has attracted great interest because of the broad opportunities for in vivo medical applications. Hollow LbL capsules can be refilled with various molecules for drug delivery. Drug release can be activated on demand by local changes in pH or by remote physical stimuli.
Imaging is a strength of both the School and the College with a number of centres of excellence in institutes on all campuses. Within the School, nanoscale imaging is exemplified by the NanoVision Centre that was developed to provide a facility to support nanomaterials research and to develop new imaging platforms. However, research extends beyond these bounds to the use of national and international facilities (e.g. synchrotron X-ray experiments). For routine characterisation of nanostructures the NanoVision Centre is well-equipped in scanning probe techniques and scanning electron microscopy, while having basic facilities in transmission electron microscopy. In this area of research developments in advanced nano-imaging techniques there is a strong emphasis on integration of imaging and nanomechanics, where structure-property relations at the molecular scale are a key theme. There is also considerable overlap with the biomaterials group, since many of the systems studied are biological materials. The development of new techniques has been, to date, associated with 3D imaging of biological tissue and with the integration of different technologies to produce new approaches to imaging and nanomechanics. These developments have been built around mutual partnerships with instrument suppliers, in producing both novel techniques and high profile research publications.
A key element supporting nanostructured materials research is having available the necessary multi-disciplinary approaches to manufacture and, as required, functionalize surfaces at the nano and micro-scales. This is achieved by having staff with chemistry, physics, materials science and engineering backgrounds. The group has the technological capability to pattern surfaces with nanostructure via a variety of routes. These routes include chemical synthesis, photo-embossing, EHD direct writing, solid free forming fabrication of meta materials and tissue engineering scaffold structures and 3D inkjet printing of ceramic and polymeric materials. These techniques continue to be developed to provide enhanced group capability to investigate novel material structures and cost effective manufacture of advanced materials. Genuine disruptive technology skill base includes dry powder dispensing at 10 times speed of competitive technology and EHD deposition with feature resolution 1/10th that of conventional inkjet.
A large research effort is in electrospraying and advanced electrostatic technologies to produce tiny and accurately placed droplets of a wide range of fluids onto various substrates. Drops as small as a few femtolitres or as large as tens of picolitres can be produced by a novel technology with superior capabilities to conventional inkjet. The ability to deposit such small drop volumes in a controlled ‘Drop on Demand’ manner has uses in biological applications such as in Microarrays and Tissue Engineering applications. The technology is also being applied to Microelectronics in displays, flexible circuits, circuit fabrication printing conductive tracks and etching resists for MEMS. [www.emdot.co.uk]
Application of the team's research is significantly enhanced by the creation of Nanoforce Technology Ltd., a wholly-owned QMUL subsidiary devoted to nanomaterials research for exploitation by industry. Nanoforce provides access to a broad range of unique world-class processing facilities, such as spark-plasma sintering for development of nanoceramics and dedicated equipment for production of polymer nanocomposites.