Active nematic vesicles
Science 345, 1135 (2014)
Active nematics exhibit a wealth of interesting behaviour not observed in their ‘inactive’ counterparts. Now Keber and colleagues investigate the properties of active nematic films within a lipid vesicle [Citation1]. The authors created their active nematics by encapsulating microtubules, kinesin motor clusters, and a non-adsorbing polymer within a lipid vesicle and imaged them using confocal microscopy. It was found that, whereas the stable configuration of such defects in an inactive system is typically four +1/2 defects arranged tetrahedrally, the four defects in an active system can oscillate between a tetrahedral and a co-planar configuration and, further, that such defect motion can drastically affect the shape of the vesicles.
Chiral rafts
Nature 513, 77 (2014)
Colloidal membranes formed from chiral rod-like viruses continue to prove to be a fertile area of research. Previous editions of Liquid Crystal Research Highlights featured articles on the effect of chirality on membrane shape [Citation2,Citation3] and the coalescence of multiple membranes [Citation4,Citation5]. Now Sharma and colleagues report on the behaviour of such membranes formed from two types of colloidal rods with opposite chirality [Citation6]. The authors found that, in addition to regimes where the two types of rods are either homogeneously mixed or completely separated, there exist intermediate states in which thermodynamically stable ‘rafts’ of one rod-type form in a background of the other rod type. Using a range of experimental techniques the authors investigated the repulsive raft–raft interactions and the propensity of the rafts to organise into two-dimensional cluster crystals.
Elastomer iris
Advanced Materials (advance online publication)
Motivated by an apparent lack of suitable technology for tuneable apertures in cell phone cameras, Schuhladen et al. report the fabrication of a tuneable aperture using liquid-crystal elastomers that mimics the action of a human iris [Citation7]. The authors used a magnetic field to induce a radial director configuration in an annulus-shaped layer of liquid crystal elastomer. By incorporating resistive heating wires, it was shown that the width of the aperture could be reversibly modified by an applied voltage. Though the time required to switch the device is currently a few seconds, the authors suggest the mechanism may have potential for use in miniaturised photographic optics.
References
- Keber FC, Loiseau E, Sanchez T, DeCamp SJ, Giomi L, Bowick MJ, Marchetti MC, Dogic Z, Bausch AR. Topology and dynamics of active nematic vesicles. Science. 2014;345:1135–1139. doi:10.1126/science.1254784.
- Gibaud T, Barry E, Zakhary MJ, Henglin M, Ward A, Yang Y, Berciu C, Oldenbourg R, Hagan MF, Nicastro D, Meyer RB, Dogic Z. Reconfigurable self-assembly through chiral control of interfacial tension. Nature. 2012;481:348.
- Castles F. Liquid crystal research highlights: chiral control. Liq Cryst Today. 2012;21:49–50. doi:10.1080/1358314X.2012.673913.
- Zakhary MJ, Gibaud T, Kaplan CN, Barry E, Oldenbourg R, Meyer RB, Dogic Z. Imprintable membranes from incomplete chiral coalescence. Nat Commun. 2014;5:3063. doi:10.1038/ncomms4063.
- Castles F. Liquid crystal research highlights: chiral coalescence. Liq Cryst Today. 2014;23:67. doi:10.1080/1358314X.2014.912385.
- Sharma P, Ward A, Gibaud T, Hagan MF, Dogic Z. Hierarchical organization of chiral rafts in colloidal membranes. Nature. 2014;513:77–80. doi:10.1038/nature13694.
- Schuhladen S, Preller F, Rix R, Petsch S, Zentel R, Zappe H. Iris-like tunable aperture employing liquid-crystal elastomers. Adv Mater. (advance online publication). 2014. doi:10.1002/adma.201402878.