David Quéré’s research while affiliated with ESPCI Paris and other places

... The pH range in the nasal mucus is associated 60 with a distinct hydrophilic behavior, which justifies the assumption of the airway walls to be perfectly absorbing via surface tension forces. The absorbed droplets will spread on impact [61][62][63][64] , and mechanistically, the virions embedded in the droplets could be conjectured to disperse over and percolate through the top gel-like layer of mucus. ...

Reference:

Computational characterization of inhaled droplet transport to the nasopharynx

... In most previous work where MFS has been used to probe forces in soft and/or living mesoscale systems (e.g., Refs. (32)(33)(34)(44)(45)(46)), the measurements were deemed quasi-static and the cantilever drag and inertia was neglected. In such case, the force was determined as = , where is the elastic spring constant of the cantilever. ...

Reference:

Forces and symmetry breaking of a living meso-swimmer

... They measured the thickness of these plastrons and applied a model of the process of withdrawing plates from a liquid by modifying the Landau-Levich-Derjaguin theory. 11 Additionally, Erbil and McHale have synthesized the research on droplet evaporation on superhydrophobic surfaces to date, focusing on the theory of droplet evaporation on smooth and patterned superhydrophobic surfaces and the practical applications by exploiting the dynamics of droplet evaporation. 12 Hoque et al. have discussed important recent advancements and challenges to the development of durable superhydrophobic surfaces, including scalable fabrication, efficacy with low surface tension fluids, and the absence of standardized durability testing methods. ...

Reference:

Superhydrophobic surfaces: Fundamentals, manufacture, and applications

... The We influence on the impact force also warrants further exploration, especially in the regime We 1 for arbitrary Oh (Chevy et al. 2012;Moláček & Bush 2012) and drop impact on compliant surfaces (Alventosa et al. 2023;Ma & Huang 2023). Another potential extension of this work is to non-Newtonian fluids (Martouzet et al. 2021;Agüero et al. 2022;Bertin 2024;Jin et al. 2023). ...

Reference:

The role of viscosity on drop impact forces on non-wetting surfaces

... This alters the bubble temperature and surface tension, which can enhance or weaken bubble drainage. 7,71 Specifically, when Ta > Tw, the cap film temperature increases, which leads to a downward flow u Dr that thickens the film [ Fig. 5(a)]. When T a < T w , the cap film cools, which leads to an upward flow u Dr that thins the film [ Fig. 5(b)]. ...

Reference:

Bubble floatation, burst, drainage, and droplet release characteristics on a free surface: A review

... Although drops begin to move at low tilt angles on LIS, they still experience significantly more friction during motion than on superhydrophobic surfaces (by around 1-2 orders of magnitude) [18][19][20][21][22] . On LIS, friction arises due to the complex interplay between capillary forces and viscous forces acting inside the drop and in the lubricant meniscus (called wetting ridge) surrounding the drop [23][24][25][26][27][28] . Previous works have suggested that most energy is dissipated in the wetting ridge and possibly in the lubricant film underneath the drop, rather than in the drop itself when the lubricant is more viscous than the drop [23][24][25]29,30 . ...

Reference:

Direct visualization of viscous dissipation and wetting ridge geometry on lubricant-infused surfaces

... Typically, the liquid-vapor interface at the bottom of the droplet ehibits higher temperatures compared to the liquid-air interface at the apex, potentially triggering thermobuoyant currents and Marangoni flows within the Leidenfrost droplet. These dynamics can lead to heightened horizontal and vertical rotation (Chakraborty et al., 2022;Yim et al., 2022), as shown in Figs. 3(a) and (b). ...

Reference:

Recent advances in strategies for inhibiting Leidenfrost effect

... While the grinding temperature exceeded than saturation point of biodegradable fluid, the mist droplets boiled, evaporated, and formed a significant number of bubbles. Further, these bubbles accumulate heat and move aside from the primary grinding region due to leidenfrost effect [37]. However, the impression of this emulsion was visible on the micro-glass slide. ...

Reference:

Investigation of biodegradable oil–based MQL parameters for sustainable grinding of H13 die steel using MCDM techniques

... 6 In addition, Leidenfrost droplets are able to self-propel on a flat substrate with a thermal gradient, which was originally demonstrated theoretically by Sobac et al., 26 and was further confirmed experimentally. 27,28 The propulsion of Leidenfrost droplets on hot liquid surfaces exhibits distinct motion modes compared with that on solid surfaces. Janssens et al. 29 reported the self-propulsion of acetone drops on heated water surfaces in straight line trajectories at constant speed of about 18 cm/s, and such motion was attributed to the solutocapillary Marangoni flow. ...

Reference:

Curvilinear self-propulsion of Leidenfrost droplets on an immiscible liquid layer with Bénard–Marangoni cells

... For large puddle-like droplets, the vapour pocket grows until it eventually pops up as a central 'chimney' due to a Rayleigh-Taylor mechanism (Biance et al. 2003;Snoeijer et al. 2009). Instability of large droplets can also occur (either spontaneously or forced) in the form of 'star-faceted' shapes when azimuthal surface oscillations develop along the periphery of the droplets (Brunet & Snoeijer 2011;Ma et al. 2017;Ma & Burton 2018;Bergen et al. 2019;Bouillant et al. 2021a). Selfinduced spontaneous oscillations can also occur in the vertical plane, yielding the recently reported bobing, bouncing or trampolining dynamics when Leidenfrost droplets reach moderate and small sizes with R c (Liu & Tran 2020;Graeber et al. 2021). ...

Reference:

Small Leidenfrost droplet dynamics