Dust suspended in low-temperature plasma as an analogue to soft matter phenomena

Dusty (complex) plasmas are multiphase suspensions of solid, charged, micron-scale particles in a partially ionized gas. These systems contain up to one million dust particles and have been used to investigate waves, diffusion, self-assembly, phase transformation, and other collective effects. The dust cloud can be resolved at the level of individual particles allowing the study of these soft condensed matter phenomena on local and global interaction scales. In microgravity environments—like the International Space Station (ISS)—the charged dust particles fill the quasineutral plasma bulk providing access to large, three-dimensional, coupled systems with tunable electrostatic interactions. Data from both ground- and ISS-based plasma laboratories have recently been used to investigate varying degrees of anisotropy and crystallinity in these systems. In the present work, we show preliminary analysis from these experiments and discuss different methods to characterize the structure of the dust clouds, including bond orientational order, the Minkowski structure metric, and local nematic order. Comparisons between dusty plasma and crystals, liquid crystals, and electrorheological fluids are discussed.