Shan-Chi Tsai is currently a PhD student under the guidance of Professor Eric Lee. She has a journal paper published in Langmuir in 2016, “Electrophoretic and Electroosmotic Motion of a Charged Spherical Particle within a Cylindrical Pore Filled with Debye–Bueche–Brinkman Polymeric Solution. Langmuir.”
Emulsion droplet is involved in many important processes in the colloid industry, especially in microfluidic and nanofluidic applications. The tiny drops in microfluidic flows are almost ideal chemical reactors characterized by fast thermal transfer, efficient mixing, narrow residence time, and an absence of hydrodynamic dispersion. Well-confined small volume droplets have been utilized as microcapsules, microreactors, micromixers, and bioassay media. The lab-on-a-chip and emulsion electrokinetic chromatography (EKC) are other potential fields for its application. Traditionally there are two major manipulation methods for moving droplets in a microfluidic device: electrowetting(EWOD), the modification of the wetting properties of a surface with an applied electric field, and dielectrophoresis(DEP), a phenomenon in which a force is exerted on a dielectric particle when it is subjected to a nonuniform electric field. Recently, numerous possibilities and advantages have been found by adopting electrophoresis, the movement of a charged particle relative to the surrounding fluid in response to an applied electric field, as a new droplet manipulating method in view of its various merits as follows: First of all, electrophoresis is free from surface contamination. Second, electrophoresis is simpler and more straightforward in principle than EWOD and DEP. Third, the coalescence of droplets can be easily controlled. As a result, electrophoresis is viewed as a novel method and believed to have great potential in the manipulation of droplets. Numerous experimental works have been reported on the electrophoresis of liquid droplets in a finite medium, for either dilute or concentrated suspensions. We considered here the electrophoretic motion of a droplet normal to a charged solid plane to investigate the boundary effect both in the electrostatic and hydrodynamic aspects. It is found, among other things, that the mobility is affected drastically once the double layer surrounding the droplet touches the planar boundary. Moreover, the electroosmotic flow induced by the charged wall has a profound impact upon the particle motion, especially when the plane is highly charged and the droplet is close to it.
The use of herbal products has significantly increased in recent decades. One of the main factors leading to this trend is that consumers assumed that use of herbal products is safer and natural alternative to traditional medical treatments. It has been found that many of such so called natural products have been counterfeited by addition of active pharmaceutical ingredients. One of the groups of products of our interest was herbal dermatological products. The aim of the study was to find the most appropriate extraction solution for the best recovery of added synthetic corticosteroids in topical preparations before assay determination by chromatographic method. Four different extraction solutions were used and nine corticosteroids were determined, namely: alclometasone dipropionate, betamethasone dipropionate, betamethasone valerate, dexamethason, hydrocortisone acetate, clobetasol propionate, methylprednisolone acetate, mometasone fuorate and triamcinolone acetonide. For that purpose, validated analytical chromatographic method was used that was developed previously for assay determination of above mentioned compounds. Results show that 0.1% V/V acetic acid in methanol is the most appropriate extraction solution for 4 compounds namely, alclometasonezon dipropionate, clobetasol propionate, mometasone furoate and betamethasone dipropionate. Further, it can be seen that methanol gave the best recovery for 3 compounds - betamethasone dipropionate, mometasone froate and hydrocortisone acetate, and also acetonitrile was the best choice for 3 compounds - methylprednisolone acetate, betamethasone valerate and dexamethasone. Finally, in ethanol as extraction solution only 1 compound had the best recovery, triamcinolone acetonide. It can be seen from all of the obtained results that the best compromise extraction conditions, if one would like to extract most of above mentioned corticosteroids, would be accomplished by using acetonitrile as the extraction solution. Following acetonitrile, second choice for extraction more than half of mentioned corticosteroids would be both methanol or 0,1 % V/V acetic acid in methanol. The results suggest that addition of acetic acid changes the type of compounds that are extracted and efficiency of extraction procedure.