Sessile Drop in Microgravity: Creation, Contact Angle and Interface

Abstract

We present in this paper the results obtained from a parabolic flight campaign regarding the contact angle and the drop interface behavior of sessile drops created under terrestrial gravity (1g) or in microgravity (μg). This is a preliminary study before further investigations on sessile drops evaporation under microgravity. In this study, drops are created by the mean of a syringe pump by injection through the substrate. The created drops are recorded using a video camera to extract the drops contact angles. Three fluids have been used in this study : de-ionized water, HFE-7100 and FC-72 and two heating surfaces: aluminum and PTFE. The results obtained evidence the feasibility of sessile drop creation in microgravity even for low surface tension liquids (below 15 mN m −1 ) such as FC-72 and HFE-7100. We also evidence the contact angle behavior depending of the drop diameter and the gravity level. A second objective of this study is to analyze the drop interface shape in microgravity. The goal of the these experiments is to obtain reference data on the sessile drop behavior in microgravity for future experiments to be performed in an French-Chinese scientific instrument (IMPACHT).

Evaporation of Ethanol Drops on a Heated Substrate Under Microgravity Conditions

“…Under microgravity, the drop is maintained on the surface mainly due to surface tension forces and is slightly influenced by the gravity fluctuations. We previously confirmed that under microgravity conditions for low surface tension fluids, the drop does not detach from the surface even if the vibration level is high (Brutin et al 2009). The experiments are performed at the plane cabin pressure which is regulated at 835 ± 2 mbar.…”

“…The injection mass flow rate is a parameter which has been determined experimentally in microgravity during a previous campaign (Brutin et al 2009), to avoid jet formation at a high mass flow rate. If the mass flow rate is too low, the drop creation time will be important in comparison to the microgravity time (20 s).…”

“…Experiments were performed to confirm the sessile drop creation feasibility in microgravity even for very low surface tension fluids (FC-72 and HFE-7100) in a previous campaign (Brutin et al 2009). Here, only pure ethanol at 99.9% is used.…”

Sessile Axisymmetric Drops in Microgravity Conditions

“…The research of interfacial phenomena in microgravity focuses on how an interface acquires and maintains its shape [8][9][10]. For instance, we can see that in the condition of a reduced gravity, droplets assume a spherical shape (see the Figure 1).…”

Influence of Bond Number on Behaviors of Liquid Drops Deposited onto Solid Substrates

“…In above mentioned literatures, all the experimental and numerical research are carried out under normal gravity. Actually, a different drop spreading behavior in microgravity has been found (Brutin et al 2009). A better understanding and clear knowledge of the physical mechanism of drop spreading in microgravity could widen the applications of liquids drops with the development of space industry.…”