High area nickel and cobalt surfaces were assembled using modified Tobacco mosaic virus (TMV) templates. Rod-shaped TMV templates (300 x 18 nm) engineered to encode unique cysteine residues were self-assembled onto gold patterned surfaces in a vertically oriented fashion, producing a >10-fold increase in surface area. Electroless deposition of ionic metals onto surface-assembled virus templates produced uniform metal coatings up to 40 nm in thickness. Within a nickel-zinc battery system, the incorporation of virus-assembled electrode surfaces more than doubled the total electrode capacity. When combined, these findings demonstrate that surface-assembled virus templates provide a robust platform for the fabrication of oriented high surface area materials.

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Breakup of viscoelastic filaments is pervasive in both nature and technology. If a filament is formed by placing a drop of saliva between a thumb and forefinger and is stretched, the filament's morphology close to breakup corresponds to beads of several sizes interconnected by slender threads. Although there is general agreement that formation of such beads-on-a-string (BOAS) structures only occurs for viscoelastic fluids, the underlying physics remains unclear and controversial. The physics leading to the formation of BOAS structures is probed by numerical simulation. Computations reveal that viscoelasticity alone does not give rise to a small, satellite bead between two much larger main beads but that inertia is required for its formation. Viscoelasticity, however, enhances the growth of the bead and delays pinch-off, which leads to a relatively long-lived beaded structure. We also show for the first time theoretically that yet smaller, sub-satellite beads can also form as seen in experiments.Take a drop of saliva from the top of your tongue or between your cheek and gums, place it between your thumb and forefinger, and then pull your fingers slowly apart to a distance of about a centimeter. With a little practice, you will see a complex, poorly understood, and practically relevant non-Newtonian fluid dynamical process evolve before your eyes. The small thread of fluid saliva first starts to thin and drain under the action of capillarity but rather than rapidly breaking-as a thread of a Newtonian fluid like water would-it persists and evolves into a periodic pattern of beads strung together as a fluid necklace as shown in By contrast, the drop of saliva shown in Figure 1(a) has no rigid cylindrical core; yet, in our digital rheometer, it displays a BOAS morphology. Therefore, the formation of the bead necklace must have a different origin in such fluids. One key requirement for the formation of beads in whole saliva is the presence of long chains of highly extensible polymer molecules such as mucopolysaccharides 9 that impart viscoelasticity to the fluid. It is widely accepted that the large viscoelastic stresses resulting from the elongation of these macromolecules resist thinning and play the same role as the rigid core. Here we show that, though necessary, viscoelasticity alone is not sufficient for the formation of beaded structures. Moreover, weshow that the BOAS phenomenon relies on the delicate interplay of four forces: capillary, viscous, elastic, and inertial. Indeed, when any of these forces dominates the others, it can overwhelm the dynamics of bead formation.The material properties of saliva vary across the population but typical values of saliva's density ρ, zero-shear-rate viscosity η 0 , and surface tension γ (ρ ∼ 1000 kg/m 3 , η 0 ∼ 1 mPa·s, and γ ∼ 60 mN/m) 9,10 are not markedly different from those of water-a low-viscosity or nearly inviscid fluid. However, the lifetime of the thread of saliva (with an initial radius R 2 of, say, 1 mm) is markedly longer than the simple estimate obtained by ...