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

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.

*Knowledge and Techniques: This Project focuses on a novel physical effect, thermo-molecular orientation, which is relevant to processes concerned with energy conversion under temperature gradients, e.g., thermoelectricity. The project will produce new ideas to make technological devices for energy conversion, and it will provide new concepts that will expand our understanding on how matter behaves under non equilibrium conditions. The relevance of thermal gradients in biology has also been underlined recently with investigations of heat transfer in ATPase molecular motors, hence the Project will be of interest to scientists (physics, chemistry, biology) and engineers. This work will contribute to the general understanding and control of heat transfer in nanomaterials. This is an important technological problem, which is difficult to investigate experimentally. The simulation techniques to be developed in the project will provide new tools to investigate heat transfer at the nanoscale. Our simulation methods will be of interest to researchers working on computer simulations. We will make our codes available for implementation in other codes, e.g., the CCP5 code DL_POLY 4.

*People: The Fellowship will directly benefit all the Researchers (the PI, two PhDs and two PDRAs) who will be working in a highly stimulating environment through interactions with the Thomas Young Center, the Energy Futures Lab, the Doctoral Training Center (DTC) for Theory and Simulation of Materials and the Project Partners and internal collaborators, who are experts in non equilibrium processes, energy conversion or nanomaterials synthesis. The Chemistry Department has a strong mentoring programme for PDRAs. The ECRA Award, recognises Postdocs who have contributed to the departmental 'community'. In addition, the PDRAs will benefit from attendance at specialised workshops (communication, grant writing skills,..., etc), so that they enhance their employability in industry and academia. The PhD students will take part in the activities of the Graduate School of Engineering and Physical Sciences, attending course relevant to their research (e.g., Science, Engineering and DTC courses). Also they will attend workshops to improve personal and transferable skills. The objective is to form highly trained individuals, with the ability to use their knowledge across different disciplines. Such individuals will enjoy exciting prospects in energy research, materials science and engineering.

*Economy and Society: Thermal gradients are responsible for a number of non equilibrium effects; thermoelectricity is no doubt one of the most important ones, and exemplifies the power of a physical principle to make 'clean' energy conversion devices. We have shown that the molecular response to thermal gradients can result in sizeable electrostatic fields. This provides a new idea to design 'thermo-molecular' devices that could produce clean energy from waste heat. The results of our work will be relevant in thermal management problems, design of high performance fluids and efficient materials for heat dissipation of nanostructures (microelectronic industry). Ultimately, our work will provide new physical principles that may enable new energy conversion technologies. To enable this knowledge transfer, we will collaborate with the Energy Futures Lab and the Chemical Engineering Department at Imperial College, who have experience in setting up companies in the energy conversion sector.
Thermal management has a direct impact on Society through improvement of quality of life (microelectronics, the car industry, or personal devices that produce electricity). The project will benefit Society through the development of novel ideas and high performance materials for energy conversion. Also, current approaches on thermal therapy treatments of cancer rely on the selective generation of thermal gradients using nanoparticles, hence the project should have an impact on Health.