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

Lead Research Organisation: Imperial College London
Department Name: Dept of Chemistry

Abstract

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.

Planned Impact

*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.

Publications

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Armstrong J (2016) Heads or tails: how do chemically substituted fullerenes melt? in Physical chemistry chemical physics : PCCP

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Armstrong J (2015) Temperature inversion of the thermal polarization of water. in Physical review. E, Statistical, nonlinear, and soft matter physics

 
Description My fellowship focused on the investigation of fluids and materials in temperature gradients. We have expanded significantly this research area, leading the development of computational methods to quantify thermal transport and non-equilibrium thermodynamics theories to explain he response of suspensions and fluids to thermal gradients. Our work was published in ~50 articles in international peer reviewed journals and presented at conferences and seminars around the world. Further, our group set up a school and a conference in the research area of the fellowship.

Thermally induced effects are fascinating. When heat flows in a fluid or a material, a thermal gradient is established. The gradient can drive the motion of solutes (thermophoresis), establish concentration gradients (thermodiffusion), or induce electric currents (thermoelectricity). All these physical effects are used in technological applications: analytical devices, thermometers, energy conversion devices to power spaceships or to recover energy from exhaust systems. During my fellowship I investigated the response of complex fluids to thermal gradients. We showed that the orientation of nanoparticles and solvent molecules can be controlled with temperature and density fields. We reported the first evidence of such effect in water, but we have been able to prove its generality in other fluids as well as in nanoparticles.

-We developed algorithms to compute for the first time the Seebeck coefficient (SC) of aqueous solutions at finite concentrations. The SC defines the strength of the thermoelectric effect, as well as the thermophoretic transport in suspensions. The only available values for this coefficient before we started our work were those obtained from theories at infinite dilution. We were able to compute the Seebeck coefficient at experimentally relevant conditions, and showed that thermal polarisation (TP) of water plays a key role in determining the SC of solutions. This result represents a paradigm change.

-We used our non-equilibrium algorithms to explain how heat flows across interfaces, between fluids and across nanomaterial-fluid interfaces. We were able to compute the thermal resistance at interfaces and to identify its structural origin using novel algorithms. We have also established how the interplay between curvature and hydrophilicity enhances the thermal conduction of nanoparticles-fluid interfaces, showing that nanoscale interfaces are better conductors.

-We established the dependence of the TP of water and fluid suspensions with temperature and density, and explained the role of water-solute interactions under non-equilibrium conditions in determining thermodiffusion. We found that the thermally induced polarization is enhanced significantly near a critical point, and predicted conditions for the generation of strong TP fields for energy conversion. We also established using experiments and simulations a method to quantify solute -water interactions using thermodiffusion. We used the method to identify the onset of hydrophobicity of urea-water mixtures, and correlated this effect with protein denaturation.

-Our work on non-equilibrium simulations led to unexpected developments. We reported the electrotunable lubricity effect, whereby electric fields and ionic liquids can be used to generate super-lubricity states. This physical effect is a proof of principle for the controllable variation of friction.
Exploitation Route We are now on a position to choose thermodynamic conditions to convert a thermal gradient into a polarisation field of different magnitude, varying the molecular properties (molecular mass, geometry and charge distribution) and thermodynamic states (pressure, temperature or density) of complex fluids and solutions. We expect that our will be used by researchers interested in thermally induced effects, and help to rationalise existing experiments and promote new ones in the area of thermoelectric and thermophoretic effects in complex fluids. On the technical side the algorithms developed in the project will be of interest in academic and industry, to obtain thermophysical properties of materials and complex fluids.

From a practical point of view I envisage that our fundamental studies may have future impact in Society through a) the development of devices and improvement of treatments that rely on heating of nanomaterials, e.g., hyperthermia. The Thermal orientation effect might impact on thermoelectric effects for charge storage and energy conversion, thermal-transport of colloids and biomolecules in solution, which is of current interest in the development of analytical devices, as well as in the area of dissipative processes at the nanoscale, such as those takin place in nano-triblogy.
Sectors Chemicals,Energy,Healthcare,Pharmaceuticals and Medical Biotechnology

URL https://www.imperial.ac.uk/people/f.bresme
 
Description Electrotuneable lubricity
Amount £237,563 (GBP)
Funding ID RPG-2016-223 
Organisation The Leverhulme Trust 
Sector Academic/University
Country United Kingdom
Start 01/2017 
End 01/2020
 
Description Funding for workshop
Amount € 10,000 (EUR)
Organisation European Centre of Atomic and Molecular Computation (CECAM) 
Sector Academic/University
Country Switzerland
Start 04/2016 
End 04/2016
 
Description Leverhulme Visiting Professorship
Amount £18,000 (GBP)
Funding ID VP2-2012-009 
Organisation The Leverhulme Trust 
Sector Academic/University
Country United Kingdom
Start 09/2013 
End 04/2014
 
Description The Leverhulm Trust "Active nano-heaters: new approaches to rectify hyperthermia"
Amount £219,111 (GBP)
Organisation Imperial College London 
Sector Academic/University
Country United Kingdom
Start 05/2019 
End 04/2022
 
Title Non equilibrium simulations 
Description We developed computational techniques to compute thermal transport in fluids and fluid mixtures, which have expanded our capability and that of other researchers to perform non-equilibrium simulations of materials under thermal gradients. The approach relies on the computation of thermal conductivity and thermal conductance properties from the analysis of explicit thermal gradients. 
Type Of Material Computer model/algorithm 
Year Produced 2012 
Provided To Others? Yes  
Impact The algorithm has been applied to a wide range of systems: pure fluids and mixtures, as well as nanoparticles, allowing us to uncover the dependence of thermal conductance with particle curvature and particle hydrophilicity. We have also been able to investigate fluids near critical conditions establishing a magnification of the thermal polarisation effect, studied in the project , near critical conditions, and providing information on the dependence of the thermal polarisation with temperature and density in a wide range of thermodynamic states. 
 
Description Collaboration with Professor Miguel Rubi, Universidad de Barcelona 
Organisation University of Barcelona
Department Faculty of Physics
Country Spain 
Sector Academic/University 
PI Contribution We collaborated together in an investigation of thermal transport across fluid interfaces. We contributed with our expertise on computer simulation of heat fluxes under equilibrium and non-equilibrium conditions.
Collaborator Contribution The partner brought expertise on non-equilibrium theory and knowledge on configurational temperatures, which is the main focus of the article we published.
Impact -An article with Niall Jackson was published last year in Molecular Simulation. The collaboration with Prof Rubi has extended to other topics. Prof Bresme is collaborating with Rubi on the writing of a review of thermal transport, and a joined ITN European project was submitted last January 2017.
Start Year 2012
 
Description Collaboration with the Universidad Autonoma de Madrid 
Organisation Autonomous University of Madrid
Country Spain 
Sector Academic/University 
PI Contribution A collaboration with the Universidad Autonoma de Madrid with Prof. Enrique Chacon and Pedro Tarazona has been set up to investigate heat transfer across interfaces. We contribute with out expertise on non-equilibrium simulations of heat transfer in fluids.
Collaborator Contribution The partners in Madrid contributed with their expertise in the structural analysis of interfaces.
Impact An article where we propose the structural origin of the thermal resistance of fluid interfaces has now been submitted for publication
Start Year 2015
 
Description Computer simulation and neutron spectroscopy of materials for energy applications 
Organisation Rutherford Appleton Laboratory
Department Molecular Spectroscopy
Country United Kingdom 
Sector Public 
PI Contribution We have brought our expertise of computer simulation of materials to investigate fullerene derivatives, PCBM nanoparticles, which are widely used in energy applications. The simulations have been used to interpret experimental data obtained from experiments at ISIS-RAL via the award of beam time following the submission of a joint proposal.
Collaborator Contribution Our partners have brought expertise on molecular spectroscopy using neutrons. One member of my group (JA) has been trained in experimental techniques and subsequently he has performed experiments obtaining novel results on structure and dynamics of the fullerene nanoparticles derivatives.
Impact *One member of my group, JA, has been appointed as staff members at ISIS-RAL, with effect April-2016 *One joint article has now been submitted for publication: Jeff Armstrong,Sangamitra Mukhopadhyay, Fernando Bresme and Felix Fernandez-Alonso, "Heads or tails: How do chemically substituted fullerenes melt? *Awarded beam time at TOSCA via TOSCA XPRESS: XB1391013; INS spectrum of [6,6]-Phenyl C61 butyric acid methylester PC61BM sample *Awarded beam time at OSIRIS RB1510601: A new plastic phase in PCBM from low-energy inlelastic neutron scattering Another two proposals that have been funded are: *RB1520126 on Nimrod, "Understanding the structure of PCBM in the amorphous and liquid state". *RB1520393 on TOSCA, "A deuteration study aiming to highlight side chain dynamics in crystaline PCBM" *We submitted proposal to organise the workshop: Chemical Energy at the Nanoscale: Simulation Meets Experiment. This workshop is being organised with Prof. Fernandez-Alonso hear of molecular spectroscopy at ISIS-RAL. Our proposal was funded and the workshops will take place in April 5-7 2016.
Start Year 2014
 
Title Fix spatial average -lammps 
Description An algorithm was developed and implemented a tool to perform analysis of density profiles in 3D geometries. This has been implemented in the open source LAMMPS as a new "fix": fix ave/spatial/sphere (Niall Jackson, Imperial College), which is a parallel code widely used to simulate materials. 
Type Of Technology Software 
Year Produced 2014 
Open Source License? Yes  
Impact This module has added a new functionality to LAMMPS to perform statistical averages of density profiles in three dimensional geometries. LAMMPS is a widely ope source code developed at Sandia National Labs (http://lammps.sandia.gov), hence the implementation of this method will be of direct benefit users in the UK and elsewhere, working on computer simulation of materials. 
URL http://lammps.sandia.gov/history.html
 
Description Chemical Energy at the Nanoscale 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The primary aim of this workshop was to bring together current computational and experimental efforts aimed at exploring the transport, conversion, and storage of chemical energy at the nanoscale. We defined and established the state-of-the-art and associated challenges in the field, and delineated short- and medium-term objectives for the development and subsequent deployment of versatile simulation tools to assist the design and interpretation of increasingly complex experimental studies, with an emphasis on particle-scattering techniques. We identified new avenues for further theoretical and computational developments that can be deployed to analyse scattering experiments, hence expanding the applicability of the latter to face the increasingly demanding challenges associated with the rational design of next-generation energy materials.
Year(s) Of Engagement Activity 2016
URL https://www.cecam.org/workshop-1287.html
 
Description Heat transfer at the nanocale 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact I gave a talk on our research as part of the Doctoral Training Center on Theory and Simulation of Materials summer school, informing student about the capabilities of computer simulation to quantify thermal properties of materials

New contacts were made and new scientific articles were written as a consequence
Year(s) Of Engagement Activity 2012
 
Description IIC (Irene) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Talk by Irene Iriarte Carretero at Sutton Trust Summer School, where she gave a talk on the general topic of Computational Chemistry
Year(s) Of Engagement Activity 2015
 
Description NESC (Non equilibrium simulation conference) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I set up jointly with Dr Travis (Sheffield) the first conference on non-equilibrium simulations and theory. The first conference of the series took place in London- Imperial College in 2014, gathering about 70 people. We are organising the second event in July 2016.
Year(s) Of Engagement Activity 2013,2016
URL http://www.rsc.org/Membership/Networking/InterestGroups/StatisticalMechanics/2013Workshop.asp?CFID=7...
 
Description NESS School on Non-Equilibrium simulations 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact This is a new school I have co-funded which focuses on the teaching of non-equilibrium computer simulation techniques to professionals in industry and postgraduate students. It highlighted the importance of this technique in practical applications.

A proposal with NNL has been submitted to the NDA agency.
Year(s) Of Engagement Activity 2014
 
Description Non Equilibrium Thermodynamics sessions at the Thermophysics Conference Boulder Colorado USA 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I have been involved in organising the non-equilibrum sessions that are part of the thermophysics conference series that takes place in Boulder, Colorado, USA. The conference attracts hundreds of researchers, and it has been a forum focusing on key aspects of the fellowships regarding non-equilibrium phenomena.This activity has contributed to make other researchers aware of the relevance of non equilibrium theory and simulations in the investigation of thermophysical properties.
Year(s) Of Engagement Activity 2015,2018
URL http://thermosymposium.nist.gov