Material Uses Insect Technology to Stay Dry Under Water

Let's start with the basics, shall we?

In general water is bad for the long-term durability of most surfaces - especially metal surfaces.

Water molecules hold together pretty well. I've even seen (and highly endorse) magnets that show this.

Water molecules have some volume, especially when they hold to other water molecules.

(Now, the tougher step...)

If you can make bumps...pores...posts...something on the surface of a material that leaves spaces too small for water drops (clumps of water molecules) to go into, the surface of the material will stay dry.

Seriously...like forever dry...not from a coating that will eventually wear off...permanently dry (or at least for four months as the early research shows)...

Left column: (top) Polymer/HFS (NC1) composite coating on aluminum substrate, (bottom) silicon square microposts. Middle column: (top) zinc oxide nanorods on silicon substrate, (bottom) silicon nanowire forest. Right column: (top) silicon microgrooves, (bottom) silicon nanograss.

See those scanning electron micrographs (SEM) above? They're from an article on Nature's website. Each surface was tested to see how long it would resist being wetted when immersed in water (then in water that had been thoroughly degassed - to make sure it wasn't gas bubbles being trapped that resulted in the lack of wetting).

Left: Wetted surface with 25 μm pillar spacing. Middle: Wetted surface with 5 μm pillar spacing. Right: Dry surface with sub-micron pillar spacing. Abbreviations: Frozen water (H₂O), Silicon substrate (Si)

And there you can see their results. Make the pillars wide enough to leave 25 microns of space, get a wet surface...5 microns, still wet...less than one micron, dry...forever dry...perfectly dry.

There's a nice summary of the article on IFLScience's website, but you do, as always, run into the issue of that F in the web address...