The water drops shown here, which are attached to a specially manufactured wire, appear like a festive necklace with colorful Christmas tree balls.
Not only do the drops look beautiful, they are part of a study led by Kyoo-Chul Kenneth Park of Northwestern University in Illinois. The research deals with the formation and transport of droplets on extremely hydrophilic wires.
Park and his team studied droplets of different sizes and viscosities on wires of different diameters to find the optimal combination of speed and energy. When the water-attracting wire is tilted, the droplets move and whiz down the string. The researchers were surprised by the high speed that occurs when two water droplets slide into one another and merge. The merger increases the speed of the droplets by up to 270 percent.
By understanding droplet transport down a wire, Park explains, his team is closer to optimizing the ability to harvest fog from the atmosphere. As water scarcity becomes an increasing problem around the world, fog catchers have proven to be an inexpensive and easily accessible way to collect potable water. However, they are inefficient as the water droplets often escape through the mesh of the collector sheets. "This work could provide the theoretical basis for a new way to develop 3D fog catchers that are better than traditional 2D meshes," said Park.
The new study results can also help with other practical applications such as oil-water separation and the control of pollutant emissions from industrial plants. The biomedical application area for masks and filters that protect people from microplastics and virus-containing droplets from the air is also interesting.