Toward optical-tweezers-based force microscopy for airborne microparticles.

Area of Science:

• Physics
• Physical Chemistry
• Aerosol Science

Background:

• Optical tweezers are crucial for measuring pN forces in condensed phases.
• Aerosol-phase force measurements are lacking, hindering the study of particle coagulation kinetics.

Purpose of the Study:

• To develop and validate methods for measuring interparticle forces in the aerosol phase using optical tweezers.
• To overcome challenges associated with aerosol particle manipulation and measurement.

Main Methods:

• Utilized bright-field microscopy for unambiguous measurement of particle position and trap stiffness.
• Exploited challenges of dynamic aqueous particles to observe size-dependent phenomena.
• Integrated cavity-enhanced Raman spectroscopy for comprehensive analysis.

Main Results:

• Achieved resolution comparable to condensed-phase measurements for aerosol optical tweezers.
• Observed size-dependent phenomena in aerosol optical tweezers.
• Demonstrated a method to probe trapping forces across a continuum of particle sizes and refractive indices.

Conclusions:

• Developed robust methods for aerosol optical tweezers measurements.
• Established a foundation for measuring pairwise interaction forces in aerosols.
• Provided a new probe for fundamental airborne particle trapping dynamics.