Minimizing convection effects to measure diffusion in liquid droplets during high-temperature electrostatic levitation

Abstract

We present an approach to reduce the convective flow in an electrostatically levitated liquid droplet to such an extent that diffusion is the dominant mechanism for mass transport, thus enabling direct measurements of atomic diffusion in reactive liquids at elevated temperatures. Convection is minimized by containerless processing, and reducing temperature variations in the sample. The diffusion tracer is deposited in situ in the electrostatic levitation device used for containerless processing. Uniform noncontact heating of the sample is achieved by laser heating with multiple beams arranged symmetrically, e.g., in a tetrahedral geometry. The expected temperature variations and the resulting convection flows are estimated for a Zr-based glass-forming alloy. The analysis suggests that diffusion experiments are possible throughout the entire undercooled liquid temperature range of this alloy and, in microgravity, up to 50 K above the liquidus temperature.

Application of Superhydrophobic Surface with High Adhesive Force in No Lost Transport of Superparamagnetic Microdroplet

“…However, some technological difficulties were also encountered: delivered materials might be adsorbed on the solid walls due to the nature of the contact, leading to contamination or clogging of channels; transport of liquid was confined in permanent microchannels and, hence, limited maneuverability and had poor fault-tolerance capability; abrupt changes in channel direction might cause turbulence and shear. Recent reports have partially overcome these problems through levitation of microdroplets by optical, electrostatic, or electromagnetic techniques, or manipulation of microdroplets freely suspended in fluorocarbon oil by applying an alternating (ac) electric field …”