A laminated, flex structure for electronic transport and hybridization of DNA.

We have developed the first prototypes of a three-dimensional, electrophoretically driven microlaboratory for the analysis of proteins and DNA. By selecting the appropriate spacing and geometrical configuration, oligonucleotides were transported, in a controlled, rapid fashion, by electrophoresis in free-space. Transport efficiencies over 2 mm distances exceeded 70%. Electrodes of similar design were combined with an electronically addressed DNA hybridization chip to form a fully electrophoretic microlaboratory. In this instance, gold-plated copper electrodes were patterned on a 2 mil thick polyimide substrate. This polyimide layer was stiffened with 20 mil of polyimide to provide support for flip-chip bonding of our standard 100-site Nanochip. This composite structure illustrated three-dimensional transport of target oligonucleotides, through a via in the polyimide, along a series of electrodes and onto the diagnostic chip. Upon reaching the diagnostic chip, electronic hybridization was performed for a competitive reverse dot blot assay. The electronic assay showed a specific to nonspecific ratio in excess of 20:1. These results suggested that this type of structure might be of practical consequence with the development of a microlaboratory for biowarfare applications.

Active microeletronic chip devices which utilize controlled electrophoretic fields for multiplex DNA hybridization and other genomic applications.

Microelectronic DNA chip devices that contain planar arrays of microelectrodes have been developed for multiplex DNA hybridization and a variety of genomic research and DNA diagnostic applications. These devices are able to produce almost any desired electric field configuration on their surface. This ability to produce well-defined electric fields allows charged molecules (DNA, RNA, proteins, enzymes, antibodies, nanobeads, and even micron scale semiconductor devices) to be electrophoretically transported to or from any microlocation on the planar surface of the device. Of key importance to the device function is the permeation layer which overcoats the microelectrodes. The permeation layer is generally a porous hydrogel material that allows water molecules and small ions (Na+, CI-, etc.) to freely contact the microelectrode surface, but impedes the transport of the larger analytes (oligonucleotides, DNA, RNA, proteins, etc.). The permeation layer prevents the destruction of DNA at the active microelectrode surface, ameliorates the adverse effects of electrolysis products on the sensitive hybridization reactions, and serves as a porous support structure for attaching DNA probes and other molecules to the array. In order to maintain rapid transport of DNA molecules, facilitate hybridization, and work within constrained current and voltage ranges, low conductance buffers and various electronic pulsing scenarios have also been developed. These active microelectronic array devices allow electrophoretic fields to be used to carry out accelerated DNA hybridization reactions and to improve selectivity for single nucleotide polymorphism (SNP), short tandem repeat (STR), and point mutation analysis.

Rheology of two commercially available cosmetic oil in water emulsions.

Rheological experiments were performed on two cosmetic O/W creams, CG Clarifying and CG Clean, before and after treatment (temperature, tumbling, centrifugation). Viscometry experiments were conducted in a shear range of 0.48-58 s ;-1. Strain sweeps were carried out at 0.1, 1, 5 and 10 Hz. Finally, frequency sweeps were performed in the linear viscoelastic region between 0.1 and 5 Hz. The characteristics of a ;good' O/W cream were found to be shear thinning behaviour, low yield stress, and predominately elastic behaviour.

Rheology of siloxane-stabilized water in silicone emulsions.

Using silicone copolymers in personal care products can improve the aesthetic performance of formulations. During their manufacture, distribution and topical application they are subject to various mechanical stresses. In this study rheology was used to measure their effects. A number of water in silicone (w/Si) emulsions were prepared in which the oil phase consisted of cyclomethicone. The surfactant used was a branched type silicone copolymer. Both viscoelastic and viscometry measurement were performed on model systems and on commercial products. Experimental data were obtained using a Bohlin rheometer. The measurements were taken applying shear rates in the range of 0.46-58 l s-1 and for the strain sweep frequencies of 0.1 Hz, 1 Hz and 10 Hz were applied. Oscillation tests were performed in the 0.1 Hz to 10 Hz range. All measurements were taken at 35deg;C, representing the approximate temperature encountered during topical application. The effect of surfactant concentration on viscoelastic properties was examined. It was shown that with increasing surfactant concentration the elastic moduli G' and the viscous moduli G" increased. Furthermore, the emulsions showed a transition from a predominantly elastic to a predominantly viscous response as the surfactant concentration increased. The effect of varying the water phase volume fraction on viscometry and viscoelastic measurements was also examined. With increasing water phase volume fraction the viscosity of the emulsions, as well as the yield stress, increased. The Cross and Sisko models were applied. From the Dougherty and Krieger equation phieff was calculated. It was found the the data derived from the Sisko model gave more reliable results. Results obtained from commercial samples showed a high proportion of elasticity; oscillation tests and viscometry experiments suggested that tumbling had the biggest impact on the theological profiles; viscosity, eta, shear stress, sigma, elastic module, G', and dynamic viscosity, eta', dropped to a minimum in these samples. Results from the two commercial samples were compared and it was observed that, although both were w/o emulsions, different rheological behaviour could be observed.