New solar-powered water filter could solve the problem of providing off-grid clean water Apr 1 2021 A new invention that uses sunlight to drive water purification could help solve the problem of providing clean water off the grid. The device resembles a large sponge that soaks up water but leaves contaminants - like lead, oil and pathogens - behind. To collect the purified water from the sponge, one simply places it in sunlight. The researchers described the device in a paper published this week in the journal Advanced Materials. The inspiration for the device came from the pufferfish, a species that takes in water to swell its body when threatened, and then releases water when danger passes, said the device's co-inventor Rodney Priestley, the Pomeroy and Betty Perry Smith Professor of Chemical and Biological Engineering, and Princeton's vice dean for innovation.