In spite of large amount of research in fabricating surfaces of varying wettability by biomimicking the naturally occurring surfaces, the work on fundamentally and industrially important air bubble adhesion on solid surfaces and its applications are still in the burgeoning stage. The present progress report provides a discussion and a critical evaluation of the recent literature available on the fabrication of superaerophilic/superaerophobic surfaces via synergic modification of surface topography and surface chemistry. An abridge on the physics behind bubble wetting on a solid in a liquid medium is deciphered here, considering the interfacial surface tension balance at the three‐phase contact line, Laplace pressure, hydrostatic pressure, and surface forces, respectively. Emphasis is made on the advancement in micro/nanofabrication technologies to fabricate surfaces that break the conventional wisdom of complementary behavior of water and air bubble contact angles. The progress report presented here also shines light on the mechanism of air bubble dynamics on solid surfaces and the latest developments in achieving surfaces of varied air bubble adhesion and its applications. Finally, the prospects of the superaerophobic and superaerophilic surfaces in the near future together with the challenges faced in accomplishing them are also insinuated.

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We report a two-layer microfluidic device to study the combined effect of confinement and chemical gradient on the motility of wild-type E. coli. We track individual E. coli in 50...

A femtosecond oscillator is employed to create periodic grid patterns in a commonly used polymer, poly (methyl methacrylate), PMMA. The wettability measured in terms of static water contact angle shows that the laser patterning causes an enhancement in water contact angle and the magnitude of change depends on the irradiation fluence during writing. A water droplet placed on a laser-patterned surface spreads anisotropically and exhibits different static water contact angle along different directions. Micro-Raman and Scanning Electron Microscope studies carried out on laser patterned and nonpatterned regions clearly confirm that the observed wettability change is due to physical (morphological) changes rather than chemical changes. More interestingly, the replica of the periodic laser patterned structures created on a soft polymer, polydimethylsiloxane (PDMS), via soft lithography technique exhibits superhydrophobic behaviour with a rolling-off nature for the water droplet. This is likely to find variety of applications in diverse fields ranging from passive defogging of windscreen to waterproof clothing to non-stick cookware.

We report a two-layer microfluidic device to study the combined effect of confinement and chemical gradient on the motility of wild type E. coli. We track individual E. coli in 50 μm and 10 μm wide channels, with a channel height of 2.5 μm, to generate quasi-2D conditions. We find that contrary to expectations, bacterial trajectories are super-diffusive even in absence of a chemical (glucose) gradient. The superdiffusive behaviour becomes more pronounced on introduction of a chemical gradient or on strengthening the lateral confinement. Runlength distributions for weak confinement in absence of chemical gradients follow an exponential distribution. Both confinement and chemoattraction induce deviations from this behaviour, with the runlength distributions approaching a power-law form under these conditions. Both confinement and chemoattraction suppress large angle tumbles as well. Our results suggest that wild-type E. coli modulates both its runs and tumbles in a similar manner under physical confinement and chemical gradient.

Drops impacting on thin powder layers can form fascinating patterns of powder particles by the interplay of processes such as micro-bubble generation and large air-disc entrapment.