Novel thermo-molecular effects at nanoscale interfaces: from nanoparticles to molecular motors

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Nanomaterials provide new opportunities for the conversion of heat into other forms of energy as they can sustain much larger temperature gradients than macroscopic systems, hence producing much stronger non equilibrium effects. These non equilibrium effects can be exploited in the generation of electricity from waste heat, thermoelectricity, one of the most important non equilibrium phenomena associated to temperature gradients, which has enormous practical implications in energy conversion. We have recently reported a novel non equilibrium effect in water, thermo-molecular polarization, where the thermal reorientation of the molecules under temperature gradients leads to sizeable electrostatic fields. This is a novel concept that can provide the basis to design and make new molecular-based devices for energy conversion. Nanomaterials offer many possibilities to exploit this novel effect, but at the same time many challenges, as it is necessary to manage heat dissipation at very small scales. Heat dissipation is a very generic problem, featuring in many different disciplines: biology (molecular motors), physics, chemistry, engineering (chemical reactions at surfaces, microelectronic devices, condensation-evaporation processes) and medical applications ('nanoheaters' for thermal therapy treatments). Energy dissipation in proteins and in particular biological molecular motors has been optimised through a long evolution process. There are lessons we can learn by investigating heat dissipation in such structures, and hence, use them as a template for new biomimetic approaches to make nanomaterials. Realising this objective requires developing appropriate tools to quantify heat transfer in nanoscale materials and biomolecules. One advantage of working at the scales characteristic of nanomaterials is that very large gradients can be achieved with temperature differences of a few degrees. These gradients are strong enough to cause local phase transformations in solids, and even destroy biological cells, a notion that is being exploited in cancer therapies. We have shown that gradients of this magnitude can induce strong polarization effects in polar fluids, of the order of the electrostatic fields needed to operate liquid crystal displays. Hence, the combination of nanomaterials and thermo-molecular effects offers an exciting principle to design novel energy conversion approaches. The investigation of these small materials is not trivial though, since they are small and intricate, making them a difficult target for experimental probes. The limited capability of experimental methods to measure the dependence of thermal transport with size and chemical composition in nanoscale materials limits our ability to develop models and hence design materials that can be exploited in energy conversion devices. Indeed, our understanding of the mechanisms controlling heat transport at the nanoscale is still scarce, but there is evidence that their description requires a molecular approach.In spite of the great advances over the past years in our understanding of heat transport in nanomaterials, there are many challenges to tackle in the near future. In recent work, new and exciting non-equilibrum effects have been reported, showing there is room to explore new principles and possibly exploit them to design energy conversion devices. In the present project we will develop new computational/theoretical approaches to investigate heat transport in nanoscale materials and biomolecules. This methodology will enable us to investigate heat flow at an unprecedented level of detail. This will make possible the development of the microscopic background needed to make the necessary breakthroughs to realise the potential of thermo-molecular effects in new and transformative energy conversion technologies.