Just four dollars' worth of materials should be enough for a device that can provide a family's daily drinking water.Fouling is one of the main problems in desalination systems. As salt and other impurities are being filtered out of water, that material tends to build up on membranes or other surfaces in the device, requiring parts to be regularly cleaned, or worse, replaced. Wicking materials are among the most commonly fouled parts, so for the new project, scientists from MIT and Shanghai Jiao Tong University set out to design a wick-free solar desalination device.