Proceedings Article | 29 August 2008
Proc. SPIE. 7038, Optical Trapping and Optical Micromanipulation V
KEYWORDS: Aerosols, Particles, Chemistry, Raman spectroscopy, Optical tweezers, Chemical analysis, Sodium, Atmospheric particles, Thermodynamics, Liquids
Aerosols play a crucial role in many areas of science, ranging from atmospheric chemistry and physics, to
pharmaceutical aerosols and drug delivery to the lungs, to combustion science and spray drying. The
development of new methods for characterising the properties and dynamics of aerosol particles is of crucial
importance if the complex role that particles play is to be more fully understood. Optical tweezers provide a
valuable new tool to address fundamental questions in aerosol science. Single or multiple particles 1-15 μm in
diameter can be manipulated for indefinite timescales. Linear and non-linear Raman and fluorescence
spectroscopies can be used to probe particle composition, phase, component mixing state, and size. In
particular, size can be determined with nanometre accuracy, allowing accurate measurements of the
thermodynamic properties of aerosols, the kinetics of particle transformation and of light absorption. Further,
the simultaneous manipulation of multiple particles in parallel optical traps provides a method for performing
comparative measurements on particles of different composition. We will present some latest work in which
optical tweezers are used to characterise aerosol dynamics, demonstrating that optical tweezers can find
application in studies of hygroscopicity, the mixing state of different chemical components, including the
phase separation of immiscible phases, and the kinetics of chemical transformation.
