Lack of access to clean water causes the deaths of millions of people worldwide and in regions such as sub-Saharan Africa, clean water can be several days walk away. Producing a simple and cheap method of purifying water which doesn’t rely on first-world amenities such as a steady electricity supply, or batteries, has proven a significant challenge thus far, but a new prototype device created by Ryan Lynch and Marcus Triest offers hope of doing just this, for an estimated cost of around US$5.