Thermoelectricity in Ferrofluids, Ionic Liquids and Colloids – TE-FLIC

In the project TE-FLIC (ThermoElectricity in Ferrofluids, Ionic-Liquids and Colloids) we will investigate liquid based thermoelectric systems. It is an inter-disciplinary fundamental research project that combines concepts and techniques from physics, electrochemistry and physical chemistry. The goal of TE-FLIC is two-fold. First, we intend to experimentally study a hitherto unexplored phenomenon: the thermoelectricity in liquids induced by the diffusion of large charged objects inside (macro-ions, micro-particles and nanoparticles). Second, we aim to identify novel liquid based thermoelectric energy conversion materials that are cost-effective, reliable and environmentally sound.

Low-grade heat (temperature below 150°C) from industrial waste streams, geothermal activity, solar heating, etc., represents a major sustainable energy source. Despite their technological advantages including long life-time, no moving parts, and environmental friendliness etc., the development of thermoelectric generators had been hindered by their low efficiency. To overcome this technological barrier, a great amount of fundamental research effort has been poured into nanostructural control of thermoelectric materials in recent years. Improved efficiency has been reported in these nanostructured thermoelectric generators; however, they are often limited to very small active surface areas and incur huge production costs and often consist of elements with limited global reserves and/or toxic elements. In this respect, thermoelectric liquid systems such as ionic liquids and colloidal suspensions, offer numerous advantages; e.g., material abundance, low material and production costs.

Our theoretical motivation to seek thermoelectric energy generation in liquid systems is quite straight forward. Thermoelectric effects are generally proportional to the entropy transported by the moving particles. We thus expect large Seebeck coefficients in electrolytes containing macroions with many degrees of freedom and large solvation shell. Extending the same argument, even larger thermoelectric effects may exist in colloidal suspensions of charged particles (micelles of copolymers, hydrogels with microparticles, or ferrofluids with magnetic nanoparticles, etc.).
In this project, we will focus our attention on three types of liquids: 1) Pure ionic-liquids and binary mixtures, 2) Aqueous colloidal suspensions with fluorescent thermosensitive charged poly(N-isopropylacrylamide) (PNIPAM) micro particles and 3) Ferrofluids based on ionic liquids and organic solvents. We will investigate their thermoelectric and transport properties. In addition, for colloidal suspensions and ferrofluids, thermodiffusion of heat/charge carriers (i.e., PNIPAM particles and magnetic nanoparticles) will be measured in parallel via florescence microscopy and Forced Rayleigh scattering experiments, respectively. Additionally, in the case of ferrofluids, an application of magnetic field is expected to result in enhanced diffusion of magnetic particles.

Our consortium is composed of two partners with complementary expertise. Partner 1, SPEC (Service de Physique de l’Etat Condensé, CEA) will study thermoelectric and transport property measurements (liquids 1, 2 and 3) and fluorescence microscopy measurements (liquid 2). Partner 2, PECSA (Laboratoire Physicochimie des Electrolytes, Colloïdes et Sciences Analytiques, UPMC) will undertake the tasks on designing tailored ferrofluids (liquid 3) and the Forced Rayley scattering experiments (liquid 3). Together, our project aims to expose the thermodiffusion-thermoelectric link in ionic liquid mixtures and colloidal suspensions. Such a proof-of-concept experimental demonstration should generate renewed interest in liquid conductors as potential a candidate for future thermoelectric material in renewable energy applications.