Yi Cui and co-workers, Stanford University, USA, have developed a cloth-based device that allows water purification at high flow rates – 80,000 times faster than existing filters – thanks to its large pores, but still small enough to restrain pathogens.

Ordinary cotton is dipped into a solution of carbon nanotubes and silver nanowires for up to 20 min and allowed to dry. Water is passed through the cloth under gravity, and an electric field applied. Over 98 % of Escherichia coli bacteria that were exposed to 20 V for several seconds were killed. Multiple layers of fabric were used to make the filter several cm thick.

The large pores also mean that biofouling is less of a problem for this type of filter.

• High Speed Water Sterilization Using One-Dimensional Nanostructures
  D. T. Schoen, A. P. Schoen, L. Hu, H. S. Kim, S. C. Heilshorn, Y. Cui,
  Nano Lett. 2010, 10.
  DOI: 10.1021/nl101944e