Single Droplet Levitation


Cloud microphysical processes are explored by means of microscopy, light scattering and Raman microscopy on single droplets are stored for long periods of time under well controlled atmospheric conditions in home built levitation chambers.

Single water droplets are created by a piezoelectric nozzle, charged by induction and injected into an electrodynamic balance, where they are stabilized and trapped by electric forces at well defined temperature, humidity and atmospheric composition. Their phase, size and index of refraction is monitored continuously by analyzing the light scattered from a monochromatic laser beam onto a CCD detector, while their chemical composition may be probed by Raman spectroscopy. Fast droplet processes may be analyzed by high speed video-microscopy.

Paul Trap

With this general setup, we have been probing: 

frozen drop

frozen droplet


  •  homogeneous freezing of water and solution droplets

het freeze

scattering upon freezing


  • heterogeneous immersion freezing on mineral dust and bacteria

 het freeze

scattering upon freezing


  • heterogeneous contact freezing with various mineral dust aerosols


efflorescing salt crystal


  • trace gas uptake into droplets

 coulomb instability

coulomb instability (jets)


  • electrical stability of cloud droplets

 bubble freezing

dissolved gas is expelled from freezing droplet


  • microsecond dynamics of droplet freezing