The active transport of micron sized 4′-pentyl-4-biphenylcarbonitrile (5CB) liquid crystal droplets propelled through an aqueous solution of tetradecyltrimethylammonium bromide (TTAB) as surfactant and glycerol as a solute, is investigated. On addition of glycerol, it was observed that the motion of active 5CB droplets exhibited a transition from smooth to a jittery chaotic motion. The motion was further found to be independent of the droplet size and the nematic state of 5CB. Upon conducting analogous experiments with Polyacrylamide (PAAM) as the solute, it was confirmed that a mere increase in viscosity cannot explain the transition. We propose the physicochemical interactions of glycerol with TTAB and 5CB, as the main cause responsible for the observed jittery motion. Presence of glycerol significantly enhances the rate of solubilization of the 5CB droplets resulting in a quicker re-distribution of the adsorbed TTAB molecules on the interface causing the droplet to momentarily stop and then restart in an independent direction. This hypothesis is supported by the time evolution of droplets size and interfacial velocity measurements in the presence and absence of glycerol. Overall, our results provide fundamental insights into the scheme of complex interactions emerging due to the presence of a non-reactive solute such as glycerol.

Microencapsulation is employed to protect bioactive ingredients in foods and is also used for their controlled release at targeted sites. Hydroxycitric acid ((-)-HCA) is present in the fruits of certain species of Garcinia and it has been studied extensively for its unique regulatory effect on fatty acid synthesis, lipogenesis, appetite, and weight loss. Since hydroxycitric acid is hygroscopic in nature, it is very difficult to convert liquid extract from the fruits of Garcinia into dried powder. Hence, microencapsulation of Garcinia cowa fruit extract was performed in a pilot-scale co-current spray dryer with whey protein isolate as a wall material. In this study, two different wall-to-core ratios (1:1 and 1.5:1) and dryer outlet temperatures (90 and 105 • C) were used for assessing the encapsulation efficiency. The results in this study showed that the microencapsulation efficiency (based on HPLC analysis) and antioxidant properties (based on 2,2-diphenyl-1-picrylhydrazyl assay) were higher at 90 • C outlet temperature of the spray dryer using 1.5:1 wall-to-core ratio feed. Further, the spray-dried powders were incorporated into pasta processing and evaluated its quality characteristics. The results of this study demonstrated that incorporation of powder spray-dried at 90 • C outlet temperature with 1.5:1 wall-to-core pasta exhibited higher antioxidant activity as well as better cooking and sensory characteristics.

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Rheotaxis is a well-known phenomenon among microbial organisms and artificial active colloids, wherein the swimmers respond to an imposed flow. We report the first experimental evidence of upstream rheotaxis by spherical active droplets. It is shown that the presence of a nearby wall and the resulting strong flow-gradient at the droplet level is at the root of this phenomenon. Experiments with optical cells of different heights reveal that rheotaxis is observed only for a finite range of shear rates, independent of the bulk flow rate. We conjecture that the flow induced distortion of an otherwise isotropic distribution of filled/empty micelles around the droplet propels it against the flow. We also show that nematic droplets exhibit elastic stress-induced oscillations during their rheotactic flight. A promising potential of manipulating the rheotactic behavior to trap as well as shuttle droplets between target locations is demonstrated, paving way to potentially significant advancement in bio-medical applications.