Non-linear response of dipolar colloidal gels to external fields

Dipolar colloids can be made to gel by forming a reversible but persistent network of chain-like aggregates at very low volume fractions. Using the model of charged soft dumbbells in molecular dynamics simulations, we find that, under the effect of an external electric field, this gel displays a highly non-linear dielectrical susceptibility. We show that the latter is caused by a switch from a network to a structure of bundling chains when the field is strong enough. Such dramatic structural transformation upon applying external fields could allow to control the mechanical and dielectric response of these complex fluids, pointing to new applications of dipolar colloids as smart materials.