Ice Particles Trapped by Temperature Gradients at mbar Pressure
  In laboratory experiments we observe that ice particles (\leq100 \mu m) entrained in a low pressure atmosphere (~1 mbar) get trapped by temperature gradients between three reservoirs at different tempertature. Confining elements are a peltier element at 250 K (bottom), a liquid nitrogen reservoir at 77 K (top) and the surrounding vacuum chamber at 293 K. Particle levitation and trapping is modeled by an interplay of thermophoresis, photophoresis and gravity. A number of ice particles are trapped simultaneously in close spatial distance to each other at least up to minutes and are accessible for further experiments. 
Thorben Kelling and Gerhard Wurm and Christoph D\"urmann
physics.ins-det cond-mat.mtrl-sci cond-mat.other physics.flu-dyn