Fluidic Microassembly with Surface Tension Effects

Par Pierre Lambert, Université Libre de Bruxelles

Mardi 10 Avril, 14h, Salle des séminaires (215), 2ème étage, Bâtiment A4N

Abstract :

This talk relates to fluidic assembly relying on surface tension effects, based on examples developed these last years: capillary gripping [1], capillary self-alignment [2], assembly platform supported by droplets or bubbles [3, 4]. It will be built along two axis.
Firstly, we will present the underlying capillary forces models, emphasizing current research challenges: dynamics of surface tension effects, coupling between the degrees-of-freedom of a liquid meniscus, reliability and repeatability issues due to evaporation, contact angle hysteresis, control of surface tension effects.
Secondly, recent results will be shown on a new approach of thermo-capillary micromanipulation [5,6]. This consists in creating a laser-controlled temperature gradient on a liquid-air interface, leading to a surface tension gradient field which is used to move 500µm components along trajectories located at the interface. This technique is considered to be complementary to capillary self-assembly patterns (Cheerios effect), since it can move individual components.  Similar to but unlike natural or Marangoni convection, this technique does not rely on any thermodynamic instability (ie. neither Rayleigh nor Marangoni numbers thresholds are required). Moving particles can be triggered with a 37mW laser power, leading to a temperature difference smaller than 5°C degrees while leading to velocities up to 5 mm/s. The current results include the open loop proof of concept, the experimental characterization of the particle velocity as a function of the laser-particle distance, which is then used to closed-loop control the particle trajectory until a target location. These results are supported by simulation results (Comsol, solving the coupled thermal and flow physics). Recent development on use of light patterns as well as control of particles against a perturbation induced by a neighboring particle.
The new results presented in this abstract on thermocapillary micromanipulation are based on the work of R. TERRAZAS, joint PhD student between my team and FEMTO-ST, Besançon (M. GAUTHIER and A. BOLOPION). This research has been funded by the Belgian Science Policy Office (IAP 7/38 MicroMAST), by the Labex ACTION project (contract « ANR-11-LABX-01-01 »), by the French Agence Nationale de la Recherche, through the LEMA project (contract « ANR 12 BS03 007 01 »), by the PHC Tournesol (contract « FR 2015 project 34237PC « ) and by the Franche-Comté Région.

[1]    P. Lambert et al. J Micromech. Microengin. 16:1267-1276. 2006
[2]    P. Lambert et al. Microfluid. Nanofluid.9:797-807. 2010
[3]    C. Lenders et al. IEEE Transactions on Robotics. 10.1109/TRO.2012.2199009. 2012
[4]    N. Majcherczyk et al. IEEE AIM Conference, Besançon, July 8-11, 2014
[5] E. Munoz et al. Optimizing the speed of single infrared-laser-induced thermocapillary flows micromanipulation by using design of experimentsSource of the Document Journal of Micro-Bio Robotics 12 (1-4), pp. 65-72 (2017)
6] R. Terrazas et al, Laser-Induced thermocapillary convective flows: A new approach for noncontact actuation at microscale at the fluid/gas interfaceIEEE/ASME Transactions on Mechatronics , 22 (2), 7782755, pp. 693-704