Using new experimental techniques, we have looked at the light production on a single-cell level. The study reveals the light production is a function of both strain and strain-rate: the cell produces more lights when the deformation is higher and faster.

Read the preprint here: https://arxiv.org/abs/2003.08427

Video: The marine organism P. Lunula under repeated deformation (~10 microns) between two micropipettes.

Together with Babak Vajidi and Corina Maas we studied the motion of active droplet in a viscous medium. We simultaneously measured the fuel consumption of these self-propelled droplets and the flow field around the1m to explain different behaviour. Writing in progress! a draft is expected by end of summer 2019.

Together with Hai Le The and Alvaro Marin we studied the gravitaxis and active motion of Janus particles next to interfaces. Using a 3D measurement technique we showed how the dynamics of the particles change in the vicinity of a free surface. Papers to be on arXive soon!

We studied the small deformation of a thin film ahead of the contact line of a spreading droplet. We use an imaging technique based on digital holographic microscopy that allows for height resolution up to a nanometer. We found a critical point (a critical capillary number) that the thin film undulation suddenly vanishes. Using linear stability analysis we found the same critical value! a preprint available HERE.

We are now studying the motion of unicellular algae in a crowded environment. We are interested in algae-algae interaction and how they collectively response to stimuli.

In collaboration with Devaraj van Der meer and Anthony Wachs we study how the entanglement of non-convex particles affect the flow. The aim is to model cohesive granular systems such as snow avalanches :)

With Vatsal Sanjay we studied how a bubble collapse at a free surface of a complex fluid. We show how yield stress can dominate and prevent the jet formation; moreover how significantly the flow inside the bath changes. The big aim is to take steps toward modelling mud volcanos :)

Watch the video above! or read our (picked-by-editor) article HERE!

We are studying the impact of viscoplastic fluids (a.k.a yield stress materials) on an air-water interface. The project extends the classic problem of solid water entry for elasto-viscoplastic material.

Together with Utkarsh Jain, we are experimentally and theoretically study the impact of an oil droplet on a water surface. We found that, if the Weber number is high enough, the oil-water-air contact line becomes unstable and forms fingers. The fingers can later determine the final size distribution of droplets. Publication no online HERE! Also on the cover of Soft Matter :)

Together with Vamsi Spandan, we are studying the highly non-linear deformation of elastic plates and fibres in a turbulent field. To do so, we are using direct numerical simulations. We are now starting the experiments in collaboration with the Max-Planck institute in Gottingen.

Together with Martin Klein Schaarsberg, we are studying the interaction of a high power laser with a thin film of complex fluids. In collaboration with our industrial partners, we aim to develop a technique for 3D printing of flexible electronics.

Using a unique optical technique based on optical coherence tomography and speckle patterns due to the Brownian particle, we studied the gel formation inside a sessile droplet and also a spreading one. The picture above shows the growth of gel phase (white area) inside a droplet heating from the bottom. Our JFM paper is recently accepted and should be available online sometime soon.

We extended the classic problem of Bretherton to a viscoplastic version, where a long bubble is displaced down a tube or a slot. We provided lubrication solutions and numerical simulations of the problem and highlight the effect of yield stress on the flow pattern. In the picture above, the grey region is the bubble, and the color map shows the magnitude of the deformation rate in the fluid. If interested see this paper. Also this paper of Laborie et al. provides some experimental counterpart of the problem.