Droplets and optics

I thought I will mention something about perhaps, the less talked about aspect of droplets, which is its optical properties. Ever since the modern understanding of light and a sound explanation of  the rainbow from an optics point of view (both credited to Sir Isaac Newton in the sevententh century), droplet optics has been studied widely and is today exploited in modern applications. 

An interesting application of this is in lenses and microscopes. In what is called a droplet lens, the natural shape of the droplets is tuned to create a microscope lens. In one of the ways, apparently… the droplet is placed on a glass plate covered with Teflon, to keep the drop round and prevent spreading. An electric current is then applied to the plate to change the droplet shape and by changing the amount of current, one can focus an image through the drop. More recently, researchers at MIT have devised tiny micro-lenses from 'beads of oil mixed in water', which is comparable in size to the width of a human hair. They reconfigure the properties of each droplet to adjust the way they filter and scatter light, similar to adjusting the focus on a microscope. A combination of chemistry and light is used to precisely shape the curvature of the interface between the internal bead and the surrounding droplet. 

More info on this here ……