title: Liquid metal enabled microfluidics.
abstract: Several gallium-based liquid metal alloys are liquid at room temperature. As 'liquid', such alloys have a low viscosity and a high surface tension while as 'metal', they have high thermal and electrical conductivities, similar to mercury. However, unlike mercury, these liquid metal alloys have low toxicity and a negligible vapor pressure, rendering them much safer. In comparison to mercury, the distinguishing feature of these alloys is the rapid formation of a self-limiting atomically thin layer of gallium oxide over their surface when exposed to oxygen. This oxide layer changes many physical and chemical properties of gallium alloys, including their interfacial and rheological properties, which can be employed and modulated for various applications in microfluidics. Injecting liquid metal into microfluidic structures has been extensively used to pattern and encapsulate highly deformable and reconfigurable electronic devices including electrodes, sensors, antennas, and interconnects. Likewise, the unique features of liquid metals have been employed for fabricating miniaturized microfluidic components including pumps, valves, heaters, and electrodes. In this review, we discuss liquid metal enabled microfluidic components, and highlight their desirable attributes including simple fabrication, facile integration, stretchability, reconfigurability, and low power consumption, with promising applications for highly integrated microfluidic systems.
authors.affiliation: School of Engineering, RMIT University, Melbourne, Victoria, Australia. Khashayar.khoshmanesh@rmit.edu.au.
authors.forename: Khashayar
authors.identifier: 0000-0001-6036-7371
authors.initials: K
authors.lastname: Khoshmanesh
authors.affiliation: Department of Bioengineering and Therapeutic Sciences, Schools of Medicine and Pharmacy, University of California, San Francisco, California, USA.
authors.forename: Shi-Yang
authors.initials: SY
authors.lastname: Tang
authors.affiliation: School of Engineering, RMIT University, Melbourne, Victoria, Australia. Khashayar.khoshmanesh@rmit.edu.au.
authors.forename: Jiu Yang
authors.initials: JY
authors.lastname: Zhu
authors.affiliation: Department of Applied Chemistry, Reutlingen University, Reutlingen, Baden-Wuerttemberg, Germany.
authors.forename: Samira
authors.initials: S
authors.lastname: Schaefer
authors.affiliation: School of Engineering, RMIT University, Melbourne, Victoria, Australia. Khashayar.khoshmanesh@rmit.edu.au.
authors.forename: Arnan
authors.initials: A
authors.lastname: Mitchell
authors.affiliation: School of Engineering, RMIT University, Melbourne, Victoria, Australia. Khashayar.khoshmanesh@rmit.edu.au.
authors.forename: Kourosh
authors.initials: K
authors.lastname: Kalantar-Zadeh
authors.affiliation: Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Dickey