Optical Trapping for Aerosol Science and Applications: Advances and Perspectives

CHUJI WANG, Mississippi State University

     Abstract Number: 24
     Working Group: Plenary Lecture Invited by Conference Chair

Abstract
Optical trapping (OT) has evolved significantly over the past few decades, transforming from the early optical tweezers approach—using a single, tightly focused laser beam to levitate dielectric or absorbing micron-sized spheres—into a versatile technique capable of trapping, manipulating, and studying single aerosols without using a substrate. Among recent developments in OT, the Universal Optical Trap (UOT) has demonstrated to be a powerful tool, capable of stably confining single particles of arbitrary chemical and physical properties, including variations in size, morphology, optical absorbance, and material composition, in diverse trapping media such as solutions, gases, and plasmas, under both atmospheric and reduced-pressure conditions. This capability has enabled in-depth investigations of a wide variety of aerosols, including droplets, solid particles, complex organic-inorganic mixtures, chemical and bioaerosols, sea-spray particles, and interplanetary dust particles.

A major breakthrough in optical trapping research has been the integration of an optical trap with advanced laser spectroscopic methods, allowing for near-real-time, in situ, single-particle study. This plenary talk will highlight the latest advances in optical trapping-cavity ringdown spectroscopy, optical trapping-Raman spectroscopy, and optical trapping-elastic light scattering, which have been applied to characterize aerosol physical, chemical, optical, and surface properties and studying aerosol formation and growth, hygroscopicity, phase transitions, photochemical and aging processes, heterogeneous chemical reactions, and surface chemistry. Recent studies using these techniques have revealed time- and structure-dependent fundamental processes occurring in single aerosols levitated in controlled reactive environments.

Building on these capabilities, I will explore the potential for developing single-aerosol spectrometers, a next-generation tool that could provide high-temporal and spatial resolution chemical characterization of individual airborne particles. These instruments would allow time- and space-resolved studies of aerosol surface chemistry and transient processes. While ensemble-based measurements provide bulk properties of aerosols, single-particle studies offer a unique and complementary perspective by capturing intrinsic heterogeneity, transient processes, and microphysical transformations that are often masked in averaged ensemble data. Such tools could bridge single aerosol studies and aerosol ensemble measurements, significantly advancing our understanding and modeling of aerosol behavior in the native atmospheric state (e.g., freely suspended in the atmosphere) and environmental contexts. As optical trapping continues to evolve, especially in combination with other techniques, its applications will extend beyond aerosol science into environmental monitoring and sensing, material synthesis, biomedical research, planetary science, and more, positioning it as a cornerstone technique for single-particle studies across a wide range of disciplines.