C. Bailey

Cholesteric Liquid-Crystal Laser as an Optic Fiber-Based Temperature Sensor

In this work, we have studied the temperature dependence of a cholesteric liquid-crystal laser coupled to an optical fiber, with a view towards optical fiber sensor applications. To stabilize the laser emission, we developed a procedure to align the liquid crystal placed in the fiber. Unexpected oscillations in the laser emission were observed as the temperature was varied, which can be understood in terms of the competition between bulk and surface anchoring torques.

Rheological properties of bent-core liquid crystals

We show that bent-core liquid crystalline materials exhibit non-Newtonian flow in their optically isotropic liquid phase. We conjecture that this behavior is due to the existence of nanostructured, fluctuating clusters composed of a few smectic-like layers. Shear alignment of these clusters explains the shear thinning observed in bent-core liquid crystals having either a nematic phase or non-modulated smectic phase. By contrast, smectogens having a modulated smectic phase do not shear thin at low shear rates, but even show a slight shear thickening which may be due to entanglements of wormlike and/or helical clusters.

Piezoelectricity of phospholipids: a possible mechanism for mechanoreception and magnetoreception in biology

We show that phospholipids, which are the main constituents of cell membranes, are piezoelectric. This was done by periodically shearing and compressing films of hydrated l‐α‐phosphatidylcholine, inducing a tilt of the molecules with respect to the bilayer’s normal, which produced an electric current perpendicular to the tilt plane, corresponding to a polarisation of about 300 nC cm−2 at 5° of tilt. We also measured electric currents induced by an alternating magnetic field of less than 100 G in hydrated phospholipids doped with 0.5 wt% of ferrofluid of magnetite (Fe3O4) nanoparticles. A discussion of possible implications of these effects on biophysical processes is also provided.