Electrified matter at the mesoscale: from windblown dust to jumping parasites

Electrostatic forces are naturally present in the environment. This is mostly due to flow and friction, such as water droplets in clouds or the movement of animals and insects. At large scales, electrostatic forces are often negligible compared to gravity, but can drive transport for sub-millimeter objects in air. In this talk I will discuss how electrostatic forces are important in two distinct systems. First, we experimentally investigated the lifetime of charge on acoustically-levitated, millimetric particles. The particles were charged up and suspended for more weeks, while their charge was measured through non-contact methods. In dry conditions, the charge decayed over several days, and we show how this can be important for the transport of unexpectedly large particles in the atmosphere. Second, we investigated how charge can facilitate host attachment in jumping, parasitic nematodes. These worms jump when the vibrations of a nearby insect (fly) are detected, and often the insects are charged. In experiments, we inferred the charge on different worms by fitting their trajectories to a hydrodynamic model with drag, gravity, and electrostatic forces, and found that the charge can be estimated using Maxwell’s model for a sphere touching a charged plane. Lastly, I will touch on related, ongoing projects in our lab investigating electrostatic forces in the environment.