Scientists of the Technical University of Denmark have developed a new membrane filter to obtain ultra pure water with a main focus to get ultra pure water in the fabrication of semiconductors. All minerals, carbon compounds or gas molecules are filtered out by this special membrane. The filter could also be used to recycle sewage water.

The technology is based on a discovery of Prof Peter Agre who is a Nobel Prize winner and a molecular biologist from the Johns Hopkins University in Baltimore, USA. During his studies he discovered a special protein which is responsible for rapid permeation of water in cells. Peter Agre and his team named these proteins ‘aquaporins’, as they function as water pores on the nano scale. In plants they work like the plumbing system of cells and ensure a highly efficient but selective transport of water: only H2O molecules can pass through these channels. For plants this filter is a life-saver, as they make sure that the cell will not lose any minerals.
Ultra pure water

Ultra pure water is used in the semiconductor fabrication to clean silicon wafers residue-free. Even the smallest particles could affect the conductivity of the computer chips that will be fabricated from these silicon wafers. Big manufacturers therefore use millions of litres per day. Production of ultra pure water is complex, uses a lot of energy and is quite expensive.
Construction

Proteins are taken out of their natural environment and put into an artificial membrane mimicking the membrane of cells to construct a durable filter membrane, thereby creating a matrix in which these proteins sit in large quantities so that they can collectively work as a water filter.
The scientists have therefore constructed a net made from a perforated Teflon film that holds them together. The net holes are only 300 microns in diameter and are literally burned into the Teflon with a special kind of laser using CO2. The net is further supported with a second layer underneath the net made from porous hydrogel. It is flexible and resembles tissue, similar to soft contact lenses.
So far the researchers are testing their filters in lab experiments only and expect that it will soon become a practical device.