Measuring Electric Dipole Moments of Trapped Sub-mm Particles

TL;DR

This paper introduces a novel acoustic trapping method to measure electric dipole moments of sub-millimeter particles, revealing their magnitude, aggregation effects, and charge stability over time.

Contribution

It presents a new technique for measuring electric dipole moments of levitated particles in an acoustic trap, including insights into charge stability and aggregation effects.

Findings

Dipole moments are on the order of 10^{-15} to 10^{-14} C·m.

Dipole moments increase with particle aggregation and tribocharging.

No change in dipole moment observed over minutes, indicating charge stability.

Abstract

We present a method for measurements of electric dipole moments on (sub)-mm size (basalt) particles levitated in an acoustic trap and centered within a plate capacitor. If an electric field is applied the particles oscillate with specific frequencies due to their permanent dipole moments. We observe dipole moments on the order of $D_P = 10^{-15} ... 10^{-14} \rm \, C \, m $. The dipole moment increases in small aggregates with the number of grains and is larger for samples vibrated (tribocharged) before trapping. The basalt grains show no sign of change in their dipole moment during measurements, implying a timescale for charge mobility being at least larger than minutes.