Physics of tiny hydrodynamical experiments – PtYX

The team Physics of tiny hydrodynamical experiments (PtYX) aims to experimentally approach seemingly simple fluid phenomena at small scale. We define “small scale” as the size of a droplet between 100 µm and 10 mm. However,  the investigation length scale range can be broader. Typically, PtYX primarly focuses on the physics of droplets and antibubbles.

PtYX tool box includes the access to a talented team of technical fellows to build dedicated experiments, high speed cameras, rheometer, Langmuir through, STIL profilometer, a lot of sense of humour and tenacity. Imagination is welcome.

Droplets - The Leidenfrost effect occurs when a droplet approaches a surface heated above the liquid's boiling point, creating a vapor film that prevents direct contact.  The heat transfer must be sufficient to maintain the vapour layer between the droplet and the substrate, and paradoxically, at the same time, the heat transfer decreases due to the presence of the vapour layer. This situation is common to cooling processes, fire extinguishing, cryogenics context, fluid propellant manipulation. The Leidenfrost effect is typically undesirable, as the heat transfer is reduced due to the thermal insulation induced by the vapour film. On the other hand, the Leidenfrost effect can be beneficial in cleaning processes or when considering the droplet as a borderless vessel reactor. In short, the main objective is to address the "undesirable" Leidenfrost effect: to control it and turn it into an advantage.

​Antibubbles - The physics related to the system “antibubble” is now better understood and the community is increasing. The existence of a thin gas film is unique with respect to its long lifetime (from minutes to hours depending on the surrounding conditions; the lifetime can be controlled). We have demonstrated that antibubbles have promising applications, such as acting as gas exchangers with the surrounding fluid. Other research groups have explored their potential for oil-free encapsulation or drug delivery.  A gas film is not simply the inverse of a liquid film; its mechanical properties remain to be fully determined and rationalised.

​Various –

Wetting on “evolutive” substrates - The interaction of a droplet with a fibre network concerns a large variety of domains: face mask, sacrificial and biocompatible scaffold, droplet manipulation, water harvesting, or breath dryer.  A large network of sugar fibres has been shown to be very hygroscopic and is efficient for the water capture. Moreover, the slow collapse of the sugar fibre due to the water results in controlled and small (<1 µm) particles. The situation is totally like the instability observe in nanowires submitted to a thermal stress.

Spray – Nebulizers are used for intraperitoneal aerosolized drug delivery for cancer treatment. The full characterisation of the droplet population and the droplet motion in the cavity must be understood in order to optimise the drug treatment. This is an important collaboration with Pr. Wim Ceelen (UGent).

Art – Droplets are present in art. In particular, the paint is a “special” fluid since there is nearly one recipe per Artist (with evolutions in time). The drying, the spreading, the impregnation,… are a lot of phenomena that have to be approached in the framework of Art. Collaboration C. Defeyt (ULiege).