Optical Control of Emulsion Drops for Nanofluidics and Microfabrication

Ground-breaking discoveries at the STFC's Central Laser Facility showed that optical traps can be used to control the shape of micron-sized emulsion droplets, to create droplets connected by stable threads of oil a thousand times thinner than a human hair and to pump liquids from one drop to another through these nanothreads. This project will explore the science behind these discoveries and develop prospective applications. First, we will develop a robust experimental and theoretical framework for manipulating emulsion drops and for creating nanofluidic networks with laser beams. Second, we will use this platform to reveal the physical and chemical principles governing the structure and dynamics of these nanothreads and use the nanothreads to explore the physics of transport in nanofluidic networks. Third, optical deformation of polymerisable emulsions will be developed as a technology for microfabrication of polymer objects with complex 3-D shapes. Such microparticles have potential applications in medical devices, drug delivery, MEMS, photonic materials and ion sources. Finally, we will establish the principles for using these nanofluidic networks to carry out chemical reactions on the attolitre scale.

Academic beneficiaries are an important set of intermediaries in the long-term economic and societal impact of this project. This project starts virtually 'from scratch' and aims to establish a firm experimental and theoretical grounding for droplet deformation and transport. While we have identified two areas of application that we will develop in our project - microfabrication of complex plastic objects and chemical reactions in nanofluidics networks - the full potential of this work will only be realised when other academic groups adopt our ideas and methods and apply them to a broad range of applications. We have described the academic communities we believe will benefit from this project in the previous section. In commercial applications, microscopic plastic shapes with appropriate mechanical properties could be used as components in micromechanical systems, for example as valves, gears or actuators, and as tissue engineering scaffolds. Polymer components have the advantage over ceramics of lower coefficients of friction. A specific application of shaped polymer particles is the fabrication of targets for ion beam production, which is being developed as part of the Basic Technology LIBRA consortium. Self-assembly of shaped particles into regular arrays could have applications as photonic bandgap materials in optoelectronics; to date most colloidal self-assembly has been limited to spheres. Micromechanical components have applications in medical devices, both for microbiological research and potentially in microsurgery. Chemical and biochemical reactions in femtolitre vessels is of particular interest in pharmacological and radiological research, where the high toxicity of materials (or limited availability) favours reactions on the smallest practical scale - this is one of the drivers for current lab-on-a-chip research. The future development of new ultra-small-scale technologies that combine chemical reactions at the attolitre scale with solid-state technology will require an understanding of how complex chemical and physical phenomena occur at these previously unattainable levels of detail. Membrane nanotubular connections have recently been identified as dynamic junctions between cells that provide a new route for HIV-1 transmission, vesicular transport between macrophages and long distance communication between killer cells and target cells. Unfortunately progress in this field is hampered by our understanding of material transfer at this length scale and a lack of tools with which to generate these connections in-vitro. This project will directly address both these technological bottlenecks. Current proteomic technologies are limited with respect to absolute quantification of protein levels and drug efficacy assays including toxicological responses often miss rare but important events as result of working with large populations and limited control of spatial delivery. Researchers at IC have already demonstrated that nanotube connections between microdroplets and target cells can be used as platforms for undertaking proteomics ( Nanodigestion ) - in effect performing biopsies at the single cell level. This work in this proposal will make it possible to deliver material to a spatially defined location of a single cell by using the trapping lasers to pump material from the microdroplet to the cell. Such single cell tools are indispensible to the study of rare cells such as stem cells and progenitor cells that do not lend themselves to high throughput protocols.