Formation of Spherical and Non-Spherical Eutectic Gallium-Indium Liquid-Metal Microdroplets in Microfluidic Channels at Room Temperature

Reference: Adv. Funct. Mater., 2012, 22(12), 2624–2631.

Title: Formation of Spherical and Non-Spherical Eutectic Gallium-Indium Liquid-Metal Microdroplets in Microfluidic Channels at Room Temperature

Authors: T. Hutter, W.-A. C. Bauer, S. R. Elliott, W. T. S. Huck

Review by: Sergii Rudiuk

The authors prepared eutectic Gallium-Indium (EGaIn) liquid metal microdroplets in microfluidic channels and showed the possibility to control their shape via the nature of carrier phase.

By using a common flow focusing device and water as carrier phase, the authors succeeded to form the spherical EGaIn microdroplets having volume from 0.5 to 4 nL.

Very interestingly, when silicon oil was used as carrier phase, the liquid metal droplets having, a rod-like shape in the narrow part of the microchannel retained this geometry after passing the channel expansion, giving non-spherical stable "rice-shaped" droplets. 

This effect was attributed to the formation of an oxide film at the surface of metal droplets at the moment of the contact with oxygen dissolved in the silicone oil. Moreover, when deoxygenated silicon oil was used as carrier phase, "normal" spherical droplets were obtained.

By varying flow rates and microchannel width, the authors show the possibility to modulate the form and the size of the obtained "rice-shaped" liquid metal microdroplets.