Affiliation:
1. School of Chemical Engineering University of New South Wales (UNSW) Kensington NSW 2052 Australia
2. School of Mechanical and Manufacturing Engineering University of New South Wales (UNSW) Kensington NSW 2052 Australia
3. School of Chemical and Biomolecular Engineering University of Sydney Darlington NSW 2008 Australia
4. School of Electronics and Computer Science University of Southampton Southampton SO17 1BJ UK
5. Department of Chemical and Biomolecular Engineering North Carolina State University Raleigh NC 27695‐7905 USA
Abstract
AbstractActive droplets play important roles in microfluidics, robotics, and micro‐electromechanical systems. As a special class of active droplets that are conductive, reactive, and of high surface tension, liquid metal droplets (LMDs) can be driven by electric‐field‐induced surface (Marangoni) flows to function as reconfigurable components in actuators, sensors, catalytic reactors, and antennas. Stimulating LMDs using an electric field induces concurrent electro‐hydrodynamic flows and electrochemical surface oxidation (passivation). It is however difficult to decouple these two effects which brings complexity in controlling LMD motions. To address this challenge, pulse time modulation (PTM) signals are used. PTM enables controlled LMD displacement by propelling the droplets forward during the voltage‐on phases and facilitating surface recovery from oxidation during the voltage‐off phases. Counterintuitively, by taking such intermittent “rests”, the LMDs effectively inhibit the unfavorable impact of oxidation, granting high motion controllability. Combining high‐speed imaging, motion tracking, machine learning, and electrochemical analysis, the study reveals how electro‐hydrodynamic flows and surface oxide formation/dissolution interplay to generate well‐defined motion regimes. The study further develops a quasi‐analytical model to describe droplet motions and designs a rotary LMD motor to showcase the versatility of the approach. This work provides the fundamental framework and viable strategy for designing innovative liquid metal‐based systems.
Subject
Electrochemistry,Condensed Matter Physics,Biomaterials,Electronic, Optical and Magnetic Materials
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