Substrate-Confined Lamb Waves Induced Thermal Field Modulation in Microscale Droplet

Area of Science:

• Microfluidics
• Acoustics
• Thermal Engineering

Background:

• Precise temperature control in microfluidic droplets is vital for microreactors.
• Conventional acoustothermal methods require costly piezoelectric substrates.

Purpose of the Study:

• To develop a cost-effective, noncontact droplet thermal regulation method.
• To utilize laterally excited Lamb waves on nonpiezoelectric substrates.

Main Methods:

• Employing laterally excited Lamb waves (1 MHz) on glass substrates.
• Analyzing glycerol-water droplets (20-50 μL) with varying viscosities.
• Conducting coupled numerical simulations to validate thermal fields.

Main Results:

• Achieved a stable droplet temperature plateau of 31.4 °C within 100 s at 1.10 W.
• Demonstrated that increased fluid viscosity enhances thermal dissipation and homogeneity.
• Validated experimental thermal fields with numerical simulations showing acoustic streaming effects.

Conclusions:

• The lateral-excitation methodology offers a tunable, low-cost platform for precise droplet thermal management.
• This approach advances the use of droplets as isolated bioreactors and bioparticle carriers.
• Decoupling acoustic generation from the substrate simplifies and improves scalability.