Synergistic adhesion mechanisms of spider capture silk.

It is well known that capture silk, the main sticky component of the orb web of a spider, plays an important role in the spider's ability to capture prey via adhesion. However, the detailed mechanism with which the spider achieves its unparalleled high-adhesion performance remains elusive. In this work, we combine experiments and theoretical analysis to investigate the adhesion mechanisms of spider silk.

Revisiting the Critical Condition for the Cassie-Wenzel Transition on Micropillar-Structured Surfaces.

Biological and engineering applications of superhydrophobic surfaces are limited by the stability of the wetting state determined by the transition from the Cassie-Baxter state to the Wenzel state (C-W transition). In this paper, we performed water droplet squeeze tests to investigate the critical conditions for the C-W transition for solid surfaces with periodic micropillar arrays. The experimental results indicate that the critical transition pressures for the samples with varying micropillar dimensions are all significantly higher than the theoretical predictions.

Line tension effects on the wetting of nanostructures: an energy method.

The superhydrophobicity and self-cleaning property of micro/nano-structured solid surfaces require a stable Cassie-Baxter (CB) wetting state at the liquid-solid interface. We present an energy method to investigate how the three-phase line tension affects the CB wetting state on nanostructured materials. For some nanostructures, the line tension may engender a distinct energy barrier, which restricts the position of the three-phase contact line and affects the stability of the CB wetting state.

Frogs use a viscoelastic tongue and non-Newtonian saliva to catch prey.

Frogs can capture insects, mice and even birds using only their tongue, with a speed and versatility unmatched in the world of synthetic materials. How can the frog tongue be so sticky? In this combined experimental and theoretical study, we perform a series of high-speed films, material tests on the tongue, and rheological tests of the frog saliva. We show that the tongue's unique stickiness results from a combination of a soft, viscoelastic tongue coupled with non-Newtonian saliva.

Stability of Cassie-Baxter wetting states on microstructured surfaces.

A stable Cassie-Baxter (CB) wetting state is indispensable for the superhydrophobicity of solid surfaces. In this paper, we analyze the equilibrium and stability of CB wetting states. Using an energy approach, the stability criteria of CB wetting states are established for solid surfaces with either two- or three-dimensional symmetric microstructures.

Efficient Self-Propelling of Small-Scale Condensed Microdrops by Closely Packed ZnO Nanoneedles.

Realizing the efficient self-propelling of small-scale condensed microdrops is very challenging but extremely important to design and develop advanced condensation heat transfer nanomaterials and devices, for example, for power generation and thermal management. Here, we present the efficient self-propelling of small-scale condensed microdrops on the surface of closely packed ZnO nanoneedles, as-synthesized by facile, rapid, and inexpensive wet chemical crystal growth followed by hydrophobic modification. Compared with flat surfaces, the nanostructured surfaces with the same low-surface-energy chemistry possess far higher time-averaged density of condensed droplets at the microscale, among which those with diameters below 10 μm occupy more than 80% of the total drop number of residual condensates.