Manipulation of monodisperse emulsions in microchannels

The manipulation of monodisperse gel emulsions confined in a microfluidic channel network has been investigated. Monodisperse gel emulsions were organized by spatial confinement as a function of dispersed phase volume fraction and manipulated using fixed ("passive") and switchable ("active") channel geometries. Furthermore, quasi two-dimensional structural transitions of static emulsion topologies have been studied as a function of lateral force. The controlled droplet formation, targeted electrocoalescence of pairs of droplets, and manipulation of the droplets using the channel geometry has been used to study fibrin network formation and manipulation within the droplet.Transitions between certain arrangements in an emulsion flowing through a channel can be induced, e.g. by varying the geometry of the channel along its length. Due to the finite energy required to change a certain droplet arrangement, these transitions are inherently hysteretic and depend not only on the droplet size but also on the volume fraction of the dispersed phase. We studied these droplet rearrangements for various channel geometries including constrictions and corners as a function of volume fraction and droplet size. The stability of certain droplet arrangements and their transitions are discussed for static droplet arrangements. We studied the influence of dispersed phase volume fraction and drop size by applying lateral force to the emulsion.To actively manipulate the emulsion arrangements in a microchannel we used a ferrofluid as the continuous phase of the emulsion. By applying external magnetic fields to the confined arrangement, we could observe a transition between two droplet arrangements. In this case, a temporarily created ferrofluid plug caused by inhomogeneous magnetic field changes the channel geometry which leads to the transition.In combination with a technique to coalesce targeted pairs of droplets, we performed in situ measurements of the formation, manipulation, and structure of droplet-encapsulated fibrin networks. In the dynamic case, where droplets were travelling continuously through the channels, we observed fibrin network aggregation due to the velocity distribution of the flow field inside the droplet. However, when the droplet is parked in the reaction chamber until the fibrin network is fully developed, then controllably deformed, we observed elastic recovery of the fibrin network

Quecksilberexposition von Goldbergarbeiterinnen in der Mongolei. Humanes Biomonitoring von 15–45 Jahre alten Frauen

Steckling N, Böse-O'Reilly S, Gradel C, et al. Quecksilberexposition von Goldbergarbeiterinnen in der Mongolei. Humanes Biomonitoring von 15–45 Jahre alten Frauen. Umweltmedizin in Forschung und Praxis. 2010;15(5):252