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Ultrasound Velocity Measurement in a Liquid Metal Electrode
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Acoustic Wave-Driven Liquid Metal Expansion.

Youngbin Hyun1, Jeong-Bong Lee2, Sangkug Chung1

  • 1Department of Mechanical Engineering, Myongji University, Yongin 120-728, Korea.

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|May 28, 2022
PubMed
Summary
This summary is machine-generated.

Acoustic waves cause oxidized liquid metal droplets to expand by drawing in air through oxide cracks. This volume expansion phenomenon, observed in gallium-based liquid metals, was quantified and demonstrated in a simple circuit.

Keywords:
acoustic waveexpansionliquid metal dropletoxidationoxide crack

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Area of Science:

  • Materials Science
  • Acoustics
  • Surface Science

Background:

  • Liquid metal droplets are susceptible to oxidation in ambient environments, forming a surface oxide layer.
  • Acoustic wave excitation is a non-contact method for manipulating materials.

Purpose of the Study:

  • To investigate the volume expansion phenomenon of oxidized liquid metal droplets under acoustic wave excitation.
  • To quantify the expansion ratio and analyze the time-dependent characteristics of the expansion.
  • To demonstrate a practical application of the expanded liquid metal droplet.

Main Methods:

  • An oxidized gallium-based liquid metal droplet was placed on a substrate and excited using a piezo-actuator.
  • A high-speed camera was used to measure the expansion ratio (x and y axes) relative to the initial droplet size.
  • The influence of droplet volume and atmospheric exposure time on expansion was studied.
  • A circuit demonstrating an LED powered by the expanded liquid metal was constructed.

Main Results:

  • Oxidized liquid metal droplets exhibited significant volume expansion when subjected to acoustic waves, attributed to air inflow through oxide cracks.
  • Non-oxidized liquid metal droplets did not show expansion under acoustic excitation.
  • Maximum expansion ratios of 2.4 (x-axis) and 3.8 (y-axis) were achieved.
  • Expansion time was proportional to droplet volume (4-20 s), while maintenance time was inversely proportional (23-2.5 s).

Conclusions:

  • Acoustic wave excitation is an effective method to induce volume expansion in oxidized liquid metal droplets.
  • The expansion is dependent on the presence of an oxide layer and its crack structure.
  • The observed phenomenon has potential applications, such as in switchable electronic circuits.