Analysis of optical trap mediated aerosol coalescence

摘要

The use of optical tweezers for the analysis of aerosols is valuable for understanding the dynamics of atmosphericallyrelevant particles. However to be able to make accurate measurements that can be directly tied to real-world phenomenait is important that we understand the influence of the optical trap on those processes. One process that is seeminglystraightforward to study with these techniques is binary droplet coalescence, either using dual beam traps, or by particlecollision with a single trapped droplet. This binary coalescence is also of interest in many other processes that make useof dense aerosol sprays such as spray drying and the use of inhalers for drug delivery in conditions such as asthma or hayfever. In this presentation we discuss the use of high speed (~5000 frames per second) video microscopy to track thedynamics of particles as they approach and interact with a trapped aqueous droplet and develop this analysis further byconsidering elastic light scattering from droplets as they undergo coalescence. We find that we are able to characterizethe re-equilibration time of droplets of the same phase after they interact and that the trajectories taken by airborneparticles influenced by an optical trap are often quite complex. We also examine the role of parameters such as the saltconcentration of the aqueous solutions used and the influence of laser wavelength.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.