Hot liquid marbles

Area of Science:

• Soft Matter Physics
• Microfluidics
• Biophysics

Background:

• Insects like aphids utilize hydrophobic coatings to manage viscous liquids, inspiring the creation of liquid marbles.
• Liquid marbles offer advantages in microfluidics, biomedical analysis, and chemistry due to their low friction and high mobility.
• The thermal stability and friction of hot liquid marbles remain largely unexplored, limiting their application in temperature-sensitive processes.

Purpose of the Study:

• To investigate the stability and static friction of hot liquid marbles on substrates with a temperature difference (ΔT).
• To understand the mechanisms behind hot liquid marble instability and friction changes at elevated temperatures.
• To identify strategies for preventing hot liquid marble rupture and excessive friction.

Main Methods:

• Experimental analysis of hot liquid marbles placed on substrates with controlled temperature differences (ΔT).
• Observation of liquid evaporation, condensation, and liquid bridge formation beneath the marbles.
• Measurement of static friction on both hydrophilic and hydrophobic substrates under varying temperature conditions.

Main Results:

• Large ΔT leads to liquid evaporation and condensation, forming liquid bridges that cause marble rupture on hydrophilic substrates.
• Increased liquid bridge density due to condensation results in higher static friction on hydrophobic substrates at larger ΔT.
• Static friction transitions from solid friction dominance at small ΔT to liquid pinning force dominance at larger ΔT.

Conclusions:

• Hot liquid marbles are susceptible to rupture and increased friction due to thermal gradients and resulting liquid bridge formation.
• Strategies such as increasing particle size, reducing liquid volatility, or using superhydrophobic substrates can mitigate these issues.
• This research provides crucial insights for the application of hot liquid marbles in temperature-controlled microfluidic systems.