This project centers on developing new analytical models for nematic liquid crystals (NLCs) in two basic configurations. The first concerns NLCs "sandwiched" between two solid boundaries, subject to an applied electric field. This geometry is directly relevant to a number of liquid crystal display devices. By investigating the response of the NLC layer to an external electric field, the investigator and her colleage develop new models relevant to the design of bistable LCD devices. Advances here could lead to the development of new, easily-manufactured, energy-saving technologies. The second configuration considers free-surface dynamics of NLC films and drops, relevant to numerous manufacturing processes. Mathematically, the problem is complicated by the need to model carefully the liquid crystal behavior in the vicinity of any contact lines. This, in addition to the known unstable behavior, leads to a very complex problem, about which little is known theoretically. Systematic asymptotic reduction of the complex Ericksen-Leslie equations for nematic media, to the appropriate thin-film geometry, is made. The formulation includes the effects of finite anchoring strength of the liquid crystal director field at the boundaries, and the effects of liquid-solid interaction energy (via a disjoining pressure). The theoretical investigations are augmented by an experimental program, comprising simple table-top experiments carried out by summer students at NJIT, and more sophisticated investigations carried out by an experimental collaborator, Peter Palffy-Muhoray, at Kent State University.
The project has two strands: A theoretical investigation into optimal design of low-energy (so-called "bistable") Liquid Crystal Display (LCD) devices, for use in applications such as e-paper; and an investigation into the dynamics of nematic liquid crystals spreading on surfaces, a process known to be unstable in certain situations. The development of a theoretical base for a workable, easily-manufactured, low-energy LCD device would have undeniable economic and environmental impact if it proved competitive, in terms of cost or performance, with the small number of such low-energy LCD microtechnologies presently available. The investigations into free-surface spreading lead to a better understanding of coating processes and, particularly with the inclusion of an electric field, offer potential for new ways of controlling the evolution of spreading films in manufacturing processes. This project is carried out in coordination with educational efforts that include invaluable research experiences for undergraduate students.
