Effects of surfactant adsorption and lipid coating on the chaining of ferrofluid droplets in nematic liquid crystals

Dispersing ferrofluids in liquid crystals (LCs) creates unique systems with magnetic properties that exhibit fascinating phenomena, such as droplet chaining. The system of dispersed ferrofluid droplets resembles LC-microparticle dispersions, and the droplet chaining is facilitated by the defects in the LC director field induced by the dispersed ferrofluids. This work explores how coating the dispersed ferrofluid droplets with surfactants or lipids stabilizes the droplet chain formation in LCs. The creation and behaviour of ferrofluid droplet chains in nematic 5CB, (4-Cyano-4′-pentylbiphenyl), with the addition of the individual surfactants and lipids was compared to those created in their absence. The effectiveness of a surfactant was determined by the director field disturbance around the chain and the effectiveness in the formation of consistent droplet chains. The translation of these chains on application of external magnetic field is examined. The boundary layer, which is formed at the interface between the ferrofluid and the LC, is estimated for the various surfactants and lipids. Integrating liquid crystals (LCs), ferrofluids, and amphiphilic compounds, along with specific functional elements, can lead to novel materials and new applications. • Surfactants and lipids help establish homeotropic anchoring conditions on the ferrofluid droplets and stabilize the interface between droplets and the LC. A comparative analysis between ionic and non-ionic surfactants and lipids was conducted to determine which compound was most suitable in stabilizing droplets and chain structures against Ostwald ripening. • Variation of non-ionic and zwitterionic surfactants, as well as anionic and zwitterionic lipids indicates best materials for stabilization. • Shorter chain surfactants and zwitterionic surfactants are more efficient than non-ionic materials. • Effects of droplet surface area coverage was studied by varying the surfactant and lipid concentrations. • Effects on magnetic field induced motion and viscosity were investigated. These show that neither the viscosity not the surface boundary layer of the chain varies with type and length of surfactant or lipid.