Research

Research for the CLST is contributed by three physics research groups at UChicago -  Chin group (thermophoretic levitation), Jaeger group (acoustic levitation), and Witten group (theory of levitation phenomena).

Chin Group: Thermophoretic Levitation

Levitation of small, granular materials is achieved at the Chin group by means of thermophoresis -- a little-known effect in which the force exerted on a particle by a surrounding air temperature gradient is found to scale as pressure decreases. As the levitation vacuum chamber pressure approaches ~ 10 torr (nearly 3 orders of magnitude rarer than atmospheric pressure), this force becomes strong enough to overcome gravity for certain granular materials and other materials with a high surface-area to mass ratio. The exact effect of theromophoresis on generic materials is poorly understood, as observation of the phenomenon so far has been limited in scope to simple cases. The thermophoretic levitation project at Chin group aims to study such thermophoretic forces under more complex circumstances, such as dynamics of particles due to their composition and topology, levitation of water droplets, and large-scale object levitation. The project currently uses two student-built experimental vacuum chambers for levitation, with a third model planned for construction during 2018.

Jaeger Group: Acoustic Levitation

As sound is a result of vibrations in air pressure, acoustics can be used to generate wavefronts of condensed air that are capable of pushing on objects. If a wavefront is loud enough (i.e has strong changes in air density for very slight displacements), this force can overcome gravity and hold an object at one of the nodes in the acoustic standing wave. In granular materials science, this method of levitation is a convenient means for determining the charge imparted on some particle by impacting both other grains of the same material and other materials (known as 'tribocharging'), since it can be used to observe the effects of electric fields on the particles in the acoustic trap. To find the displacement of a material in a known electric field is to determine this charge, thus allowing for study of tribocharging.

Witten Group: Theory of Levitation Phenomena

In sympathy with the experimental findings of the CLST, the Witten group provides theoretical modeling of levitation phenomena. This cooperation enables a more comprehensive understanding of the observed levitation systems, as current literature on the field is often limited in scope.