Dynamics of Emulsion Droplet Interactions in Low Gravity Conditions (Low-G-Emulsion)

Contact Person: Angeliki Chondrou aggeliki1811@gmail.com; Sotiris Evgenidis sevgenid@chem.auth.gr

This study refers to the investigation of the dynamic behavior and stability of emulsions under low gravity conditions evolving during parabolic flights. Emulsions are systems consisting of two immiscible liquids. On earth, buoyancy makes an emulsion separate rapidly into two distinct layers and, as a result the motion of droplets and droplet-droplet interactions (coalescence and aggregation) that strongly affect emulsion destabilization cannot be investigated in depth. Low gravity environment, eliminates gravity effects enabling the study of droplets interactions.

An experimental setup is manufactured for the production and dynamic behavior/stability study of emulsions. The core of the device is the emulsification unit, which is based on a miniature pulsating emulsification setup already developed and successfully tested by Multiphase Dynamics Group (see Research Project: Development of an Innovative miniature emulsification device). The most important part of the emulsification unit is an aluminum experimental cell. Two of the parallel cell walls are made of glass offering ports for optical recordings and lighting. The other two (parallel) plexiglass walls have flush-mounted metallic electrodes for performing electrical measurements. A cylindrical piston is integrated to the lid of the cell. The tip of the piston ends to a thin aluminum plate which covers almost the entire cross section. During emulsification, the piston moves continuously up and down along the perpendicular axis, scavenging the total internal volume of the cell. The piston plate has orthogonal shape of uniform height. The height is 1.62 mm while the gap between the plate and the cell walls is 0.66 mm. The design of the device to be used during the Parabolic Flights includes the frame of the emulsification unit in which the motor is integrated and a case that supports five identical experimental cells.

Fig 1. a) Experimental cell, b) Plexiglass walls with flush-mounted metallic electrodes for conducting electrical measurements; c) Glass cell walls for optical recordings and lighting; d) Piston

Fig 2. Case supporting five identical experimental cells

Produced emulsions are experimentally studied by means of: a) Two cameras, a high speed and a still high resolution one, for monitoring droplets’ motion and interactions and estimating droplet size distribution, respectively and b) I-VED EU patented electrical impedance spectroscopy technique for the determination of oil volumetric fraction evolution and validation of droplet size distribution. Examined parameters during testing include surfactant concentration, piston stroke frequency, oil to water ratio and duration of emulsification.

Fig 3. Schematic representation of the experimental setup