Paper Number
FE13
Session
Foams, Emulsions & Interfacial Rheology
Title
Interfacial viscoelasticity of the native oxide layer on gallium based liquid metal alloys
Presentation Date and Time
October 17, 2018 (Wednesday) 2:45
Track / Room
Track 6 / Tanglewood
Authors
- Jacob, Alan R. (North Carolina State University, Department of Chemical and Biomolecular Engineeirng)
- Parekh, Dishit (North Carolina State University, Department of Chemical and Biomolecular Engineeirng)
- Dickey, Michael (North Carolina State University, Department of Chemical and Biomolecular Engineeirng)
- Hsiao, Lilian C. (North Carolina State University, Department of Chemical and Biomolecular Engineeirng)
Author and Affiliation Lines
Alan R. Jacob, Dishit Parekh, Michael Dickey, and Lilian C. Hsiao
Department of Chemical and Biomolecular Engineeirng, North Carolina State University, Raleigh, NC 27606
Speaker / Presenter
Jacob, Alan R.
Text of Abstract
Gallium and its alloys form a native oxide layer, which acts like a skin that encapsulates the liquid metal. There has been a surge in interest on investigation of gallium and its alloys as electronic materials for their potential applications, in flexible and stretchable electronics, due to low toxicity, high metallic conductivity, and its compatibility with soft materials such as organic polymers during processing. Despite the immense potential of liquid metals, there is a lack of understanding of the viscoelastic nature of the oxide skin. In this work, we characterize the oxide skin at liquid metal-air interfaces using a Du Noüy ring attached to a stress-controlled rheometer. A systematic study of the interfacial oxide layer is performed by following the linear elastic and viscous moduli for pristine gallium, its alloys with indium and tin, eutectic gallium indium and galinstan. Additionally, the pristine liquid metals when doped with aluminum at a weight percent as low as 0.45%, modifies the liquid metal-air interface. Our results show a time evolution of the liquid metal-air interface when aluminum diffuses from the bulk liquid metal matrix and migrates to the liquid metal-air interface replacing gallium to form an oxide layer with elastic moduli that is larger than the undoped liquid metal alloys. Finally, using imaging and analytical characterization tools such as scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy, qualitative and quantitative insights are gained into the skin texture and composition of elements in pristine as well as doped oxide layers of gallium that leads to the change in viscoelasticity of the skin. This work could provide a pathway to modifying the rheology of liquid metal for printing as well as tuning the chemistry of the interface of the metal for use as soft electrodes.