Behind the natural beauty of a rosebud covered in dew drops lies a decades-old mystery: why don't the tiny droplets fall off, even when the flower is turned upside down?
The beading of water droplets on natural materials is not a rare thing.
But on many flowers and leaves the droplets slide off with the slightest tremble
because the surfaces are very rough and spiky at the microscopic scale, and the tips of the spikes are covered in wax.
The water molecules therefore come into contact with only a tiny fraction of the surface, and then only to water-repelling wax.
Lin Feng and her colleagues at Tsinghua University in Beijing found that although rose petals are coated with similar projections, they have wide, gentle-sloping troughs between the spikes, and no wax. The spikes keep the dew drops in a spherical shape, but the water 'leaks' into the troughs between spike-covered bumps, giving a bit of 'stick' and stopping a small droplet from rolling around (see
diagram).
clipped from: www.nature.com 