A recipe for the crystallization of enzymes

A recipe for the crystallization of enzyme

Droplet deformation and pumping in AC electro-osmotic micropumps

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.This contribution deals with the pumping and deformation of oil in water droplets in alternating-current electro-osmotic micropumps. These micropumps are used to transport lowly conductive fluids through micro channels by means of a harmonically driven electrode array on the channel bottom. The periodic formation of an electric double layer above the electrodes results in an electro-osmotic flow, which carries along adjacent fluid layers. In experiments we observed that droplets immersed in the carrier fluid are transported by the channel flow and periodically deformed when passing the electrodes. Due to the different polarizability and conductivity of the droplet and the carrier fluid, dielectrophoretic forces act on the fluid droplet interface. These forces that are described by the Maxwell stress tensor increase with the electric field strength and attract the droplet towards the electrode. This contribution analyses the mechanisms of droplet pumping and deformation numerically by means of solving for the electric and the flow field to the two phases in the channel and by evaluating the dielectrophoretic forces on the droplet. A conservative level-set method is used to track the droplet surface accurately

Feasibility of Miniaturized Viscosity Sensors for the Characterization of Suspensions

AbstractFor many applications the viscosity of a complex fluid sample is interesting to control the process and reactions. These fluids can for instance be suspensions of different types of microorganisms, e.g., bacteria or fungi. Macroscopic viscosity measurement systems would only be able to measure the global, averaged viscosity. Miniaturized TSM resonators, however, are probing only a very thin fluid film (typically only a few μm thick, depending on frequency and viscosity) on their surface. Earlier investigations with water-in-oil micro-emulsions have shown that the influence of water droplets in oil is dependent of their size. In this paper we focus on a similar effect, i.e. the influence of the surface roughness. It turns out that the sensor behaves differently if the dimension of the inclusions or particles is in the order of the surface roughness

Electrically tuned microwave devices using liquid crystal technology

An overview of liquid crystal technology for microwave and millimeter-wave frequencies is presented. The potential of liquid crystals as reconfigurable materials arises from their ability for continuous tuning with low power consumption, transparency, and possible integration with printed and flexible circuit technologies. This paper describes physical theory and fundamental electrical properties arising from the anisotropy of liquid crystals and overviews selected realized liquid crystal devices, throughout four main categories: resonators and filters, phase shifters and delay lines, antennas, and, finally, frequency-selective surfaces and metamaterials.Pouria Yaghmaee, Onur Hamza Karabey, Bevan Bates, Christophe Fumeaux and Rolf Jakob

Practical private database queries based on a quantum key distribution protocol

Private queries allow a user Alice to learn an element of a database held by a provider Bob without revealing which element she was interested in, while limiting her information about the other elements. We propose to implement private queries based on a quantum key distribution protocol, with changes only in the classical post-processing of the key. This approach makes our scheme both easy to implement and loss-tolerant. While unconditionally secure private queries are known to be impossible, we argue that an interesting degree of security can be achieved, relying on fundamental physical principles instead of unverifiable security assumptions in order to protect both user and database. We think that there is scope for such practical private queries to become another remarkable application of quantum information in the footsteps of quantum key distribution.Comment: 7 pages, 2 figures, new and improved version, clarified claims, expanded security discussio