Many open questions concerning the physics of wetting concern the structure and dynamics of the contact line which governs the spreading of droplets. In particular, the dissipation in the drop wedge, in the vicinity of the contact line is still poorly understood as well as the pinning on surface defects which leads to contact angle hysteresis. Answers to such questions require the development of new methods to probe the physics of contact line at the nanometer scale. With that aim we used several approaches based on advanced microscopy techniques :
- Wetting of graphene monolayers
Does the shape of a liquid droplet only depend on the interactions with the topmost atoms of the substrate or do the underlying atoms also play some role ? In collaboration with colleagues from the Brookhaven National Lab (USA) we brought a quantitative answer by investigating the wetting properties of a graphene monolayer suspended on silicon surfaces bearing nanopillars. The precise control over the nanopillar profile allows us to vary the area fraction of suspended graphene from 0% to 95% which is used to effectively “tune” the liquid-substrate interactions. We could quantify that ca. 80% of the long-range water-substrate interactions are screened by the graphene monolayer.
- Hydrodynamics around micro- and nano-fibers
Three AFM techniques werere combined to investigate hydrodynamics around micro- and nanofibers. Confronting the experimental findings to a classical theoretical model reveals the potential of AFM for quantitative measurement of dissipation processes at the sub-micron scale.
- Shape and spring constant of a nanomeniscus
We investigate the shape and mechanical properties of liquid interfaces down to nanometer scale by atomic force microscopy (AFM) and scanning electron microscopy (SEM). In both cases, the interface is probed with a cylindrical nanofiber with radius of the order of 25-100 nm. The effective spring constant of the nanomeniscus is determined by frequency-modulation FM-AFM modes in unbounded or confined situations. It shows that the lateral size of the meniscus strongly influences the effective spring constant. Electron microscopy allowed to visualize the meniscus profile around the fiber with a lateral resolution of the order of 10 nm and confirmed its catenary shape.
- Contact angle hysteresis at the nanometer scale
Using non conventional AFM tips equipped with a carbon nanocone, we were able to investigate the pinning of the contact line on individual nanometric defects and demonstrated the existence of two types of defects (weak and strong).
The extension of these studies in dynamic FM-AFM mode is currently underway.
- Dynamics of spreading and evaporation at sub-micron scale
By its ability to manipulate ultrasmall liquid volumes (aL to fL), the NADIS technique is a useful tool to preform original wetting experiments at sub-micron scale.
The size of spots as a function of tip contact time or speed allows to study the dynamics of spreading at sub-micron range and millisecond timescale. The measured R t1/4 power law can be interpreted by assuming a spreading under constant pressure condition.
- Evaporation of femtodroplets
The controlled deposition of droplets by NADIS on ultrasensitive mass sensors allowed us to study the evaporation of “femtodroplets” of glycerol which could be interpreted using a macroscopic constant contact angle model.
Collaboration with Francesc Merez-Murano and Julien Arcamone, CNM, Barcelona (Spain)
- Condensation of water on tobacco mosaic viruses
We used environmental electron microscopy (EM) to image the condensation of water onto viruses which is not well-known even though their contact with water is
the basis for all biology. We captured the formation of submicrometer water droplets and filaments on single viral particles. The condensate structures are compatible with capillary condensation between adsorbed virus particlesand with known droplet shapes on patterned surfaces.
Collaboration with Alex Bittner and Txema Alonso, Nanogune, San Sebastian (Spain)
- Pinning of a contact line on nanometric steps
- Interaction d’une ligne de contact avec des marches nanométriques
- © CEMES-CNRS
- Wettability of partially suspended graphene, T. Ondarçuhu, V. Thomas, M. Nuñez, E. Dujardin, A. Rahman, C. Black, A. Checco. Sci. Rep, 6 (2016) 24237.
- AFM study of nanohydrodynamics around micro and nanocylindersJ. Dupré de Baubigny, M. Benzaquen, C. Mortagne, C. Devailly, J. Laurent, A. Steinberger, J.-P. Salvetat, J.-P. Aimé, T. Ondarçuhu, Phys. Rev. Fluids, 1 (2016) 044104.
- Shape and effective spring constant of liquid interfaces probed at the nanometer scale : finite size effect, J. Dupré de Baubigny, M. Benzaquen, L. Fabié, M. Delmas, J.-P. Aimé, M. Legros, T. Ondarçuhu*, Langmuir 31 (2015) 9790-9798
- Contact angle hysteresis at the nanometer scale M. Delmas, M. Monthioux, T. Ondarçuhu* Phys. Rev. Lett. 106 (2011) 136102.
- The condensation of water on adsorbed viruses, J.M. Alonso, F. Tatti, A. Chuvilin, K. Mam, T. Ondarçuhu, A. Bittner, Langmuir, 29 (2013) 14580-14587.
- Writing with liquid using a nanodispenser : spreading dynamics at the sub-micron scale L. Fabié, T. Ondarçuhu, Soft Matter 8 (2012) 4995-5001
- Elasto-capillary fabrication of 3D microstructures, J.W. van Honschonten, J.W. Berenschot, T. Ondarçuhu, R.G.P. Sanders, J. Sundaram, N.R. Tas, Appl. Phys. Lett. 97 (2010) 014103.
- Evaporation of femtoliter sessile droplets monitored with nanomechanical mass sensors J. Arcamone, E. Dujardin, G. Rius, F. Pérez-Murano, T. Ondarçuhu* J. Phys. Chem. B 111 (2007) 13020-13027
- Pinning of a contact line on nanometric steps during the dewetting of a terraced substrate T. Ondarçuhu, A. Piednoir NanoLett. 5 (2005) 1744-1750.
Book chapters :
- Nanomeniscus mechanical properties,JP Aimé, T. Ondarçuhu, R. Boisgard, L. Fabié, M. Delmas, C. Fouché in « Nanoscale liquid interfaces », Eds T. Ondarçuhu, J.P. Aimé (Pan Stanford Publishing) 2013, 307-359 (53 pages).
- Manipulation of liquid nanodrops, E. Dujardin, T. Ondarçuhu, L. Fabié in « Nanoscale liquid interfaces », Eds T. Ondarçuhu, J.P. Aimé (Pan Stanford Publishing) 2013, 441-491 (51 pages)
- Capillary forces in atomic force microscopy and liquid nanodispensing, T. Ondarçuhu, L. Fabié, in “Surface Tension in Microsystems - Engineering Below the Capillary Length”, Ed. P. Lambert (Springer Verlag) 2013, 279-305 (27 pages).
Pan Stanford publishing, Eds Thierry Ondarçuhu, Jean-Pierre Aimé ; March 2013.
19 chapters by S. Jarvis, O. Vinogradova, S. Dietrich, G. Reiter, A.M. Cazabat, A. Checco, D. Lohse, D. Johansmann, JP. Aimé, D. Mattia, N. Tas, E. Dujardin, R. Garcia, F. Biscarini, L. Malaquin, A. Jagota, S. Scheuring, T. Ando, T. Fukuma
ISBN-10 : 9814316458
ANR "NANOFLUIDYN", European integrated project "NaPa", Cnano GSO interregion project , LABEX NEXT, TRAIN², ANR CANAC.