Dielectrophoresis And reverse dielectro-Osmosis for Membraneless Sieving: Toward high-throughput multiscale particles tracking – DIADEM

By introducing a new paradigm for filtration, the DIADEM project aims at developing analytical devices for high throughput (> 1ml/min), “membraneless” sieving of colloidal suspensions having a wide range of characteristic sizes (from 10 nm to 10 µm), shapes and compositions (from synthetic particles to marine microorganisms). We will design, fabricate, simulate and characterize a new generation of analytical devices consisting in electrode patterns printed on both the top and the bottom of a microfluidic channel. This will allow us to control the trajectory of the particles composing the colloidal solution via dielectrophoretic (DEP) forces, as well as to induce a new transport process, which we coin reverse dielectro-osmosis. The DIADEM project brings together physicochemists (ITODYS, PHENIX, IFREMER), physicists (ENS-CNRS) and biologists (IFREMER) to challenge on-chip sorting and characterization of (nano-)particles thanks to theory-driven device design. The ambition is to achieve a multiscale understanding of the correlation between the typology of electrode networks and the particles trajectory. Transport processes will be investigated both theoretically (simulation, modelling) and experimentally by coupling to the channel operando particles tracking/characterization techniques such as Dynamic Light Scattering, (DLS), (nano)electrochemistry and interferometry. The resulting insights will lead to the rational design of microchannels with tailored electric field distributions providing a handle to drive particle towards target regions. This original concept allowing to establish and tune new transport processes will allow to go beyond the state of the art in many fields of application relative to (nano-)particle characterization (Issue 1) but may also generate unexpected breakthrough (Issue 2):

1) How to sort and characterize marine microorganisms at high flow rate? Printing fabrication technologies open the way to the production of DEP devices on (very) large areas enabling sieving and analysis of marine samples at unprecedented flow rates. Living marine microorganisms will be sieved according to their polarizability, i.e. their physico-chemical nature, their size and their shape. Therefore, a wide community of microorganisms (from viruses to microalgae) will be analyzed independently of their fluorescence properties (required for conventional cytometer-based analysis) and separated for in operando identification. For the first time, interferometric reflectance imaging for high-throughput marine microorganisms identification will be coupled to DEP sorting. Validated here for algae model systems, our approach will be easily applied to many other materials and reactions (e.g. nanoparticles detection, depollution, new marine pollutants such as micro and nanoplastics).

2) How to induce membraneless osmotic water flows, in order to avoid membrane fouling? DEP electrodes can be also employed in the domain of osmotic processes, as a virtual semi-permeable membrane. Osmotic flows can be created by dielectrophoretic forces acting as a barrier and leading to a new transport process that we coin “reverse dielectro-osmosis” (REDO). Special device architectures allowing the establishment of an electric field gradient barrier will be designed allowing the theoretical and experimental investigation of REDO-induced transport.