This work reports the actuation of droplets of nanofluid by the electrowetting on dielectric (EWOD) effect. The nanofluid is comprised of an aqueous (deionized water) suspension of 3 nm diameter bismuth telluride nanoparticles capped with thioglycolic acid (TGA). Microdroplets of nanofluid are cast on Si(001) wafers coated with 100 nm thick layers of silicon dioxide and AF Teflon. Applying an electric field between the substrate and an electrode immersed in the nanofluid droplet results in a strong change in the contact angle from 110 • to 84 • for a 0-60 V voltage range. The droplets of nanofluid exhibit enhanced stability and absence of contact angle saturation in the tested voltage range when compared with droplets of aqueous solutions of 0.01 M Na 2 SO 4 or thioglycolic acid in deionized water. We propose that ion generation due to capping-agent desorption is a key factor determining the EWOD effect in the bismuth telluride nanofluid along with the nanoparticle contribution to charge transport. Our results open up new vistas for using nanofluids for microscale actuator device applications.

Using molecular dynamics simulations we study the thermodynamic behavior of a singlecomponent covalent material described by the recently proposed Environment-Dependent Interatomic Potential (EDIP). The parameterization of EDIP for silicon exhibits a range of unusual properties typically found in more complex materials, such as the existence of two structurally distinct disordered phases, a density increase upon melting of the low-temperature amorphous phase, and negative thermal expansion coefficients for both the crystal (at high temperatures) and the amorphous phase (at all temperatures). Structural differences between the two disordered phases also lead to a first-order transition between them, which suggests the existence of a second critical point, as is believed to exist for amorphous forms of frozen water.For EDIP-Si, however, the unusual behavior is associated not only with the open nature of tetrahedral bonding but also with a competition between four-fold (covalent) and five-fold (metallic) coordination. The unusual behavior of the model and its unique ability to simulate the liquid/amorphous transition on molecular-dynamics time scales make it a suitable prototype for fundamental studies of anomalous thermodynamics in disordered systems.

We propose an extension to the technique of fluctuation electron microscopy that quantitatively measures a medium-range order correlation length in amorphous materials. In both simulated images from computer-generated paracrystalline amorphous silicon models and experimental images of amorphous silicon, we find that the spatial autocorrelation function of dark-field transmission electron micrographs of amorphous materials exhibits a simple exponential decay. The decay length measures a nanometre-scale structural correlation length in the sample, although it also depends on the microscope resolution. We also propose a new interpretation of the fluctuation microscopy image variance in terms of fluctuations in local atomic pair distribution functions.

Eisenbraun, E.T.; Upham, A.; Dash, R.; Zeng, W.; Hoefnagels, J.P.M.; Lane, S.; Anjum, D.; Dovidenko, K.; Kaloyeros, A.E.; Arkles, B.; Sullivan, J.J.

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