This title appears in the Scientific Report : 2023 
Electric-field induced phases/states in suspensions of highly charged rod-like colloids
Dhont, Jan K. G. (Corresponding author)
Kang, Kyongok
Biomakromolekulare Systeme und Prozesse; IBI-4
2023
Honorary doctorate by the Faculty of Science at Lund University, Lund (Sweden), 2023-05-25 - 2023-05-25
Talk (non-conference)
Information Processing in Distributed Systems


After a short introduction to colloids and liquid crystals, I will discuss the response of concentrated suspensions of highly charged, very long and thin, rod-like colloids to external electric fields. Fd-virus particles are used as a model system for such rod-like colloids. These virus particles consist of a dsDNA strand of a length of 880 nm, which is covered by 2700 coat proteins, leading a core thickness of 7 nm. The coat proteins give rise a very large surface charge density of the fd-virus particles, which results in a large number of condensed ions close to the surface of the particles. Depending on the amplitude and frequency of the external field, transitions from a nematic to chiral nematic, and from a chiral nematic to a homeotropic phase are found. In addition, a field-induced dynamical state can be induced, where nematic domains persistently melt and reform. The time scale on which melting and reforming of nematic domains occurs, and the size of the domains, both diverge at what could be identified as a “non-equilibrium critical point”. An explanation of these phenomena is presented, both on an intuitive level and based on appropriate equations of motion for the orientational order parameter, where the field-induced dissociation/associated of condensed ions plays an important role.