Man-made membrane mimics nature

Mangrove plants and human kidneys have inspired NUS scientists to develop a biomimetic membrane that could shave 30 per cent off the cost of purifying water. Taking their cue from these natural systems, the team from the NUS Environmental Research Institute is the first in the world to make a successful membrane that incorporates aquaporins — proteins which channel water molecules while blocking out ions and other solutes.

Unlike existing commercial membrane systems, these biomimetic membranes do not require high hydraulic or osmotic pressures to purify water, explained NUS Chemical and Biomolecular Engineering Associate Professor Tong Yen Wah, who led the research team. High energy costs are a challenge for industry players who recover water from saline sources using existing membrane systems.

Another reason why these biomimetic membranes could lead to cheaper drinking water in the future is because they are more durable than conventional biomimetic membranes. Their higher mechanical strength and stability during the water filtration process makes them more suitable for industrial applications in water treatment and desalination.

The team has employed aquaporins from Eschericia coli bacteria, as aquaporins from this bacteria are more affordable to produce than those from other sources. Membranes embedded with these proteins have the ability to allow a high volume of water molecules to pass through a pore or channel in the membrane, leaving behind impurities like salt. Aquaporins have enabled mangrove plants to filter between 90 and 95 per cent of salt at their roots, and the human kidney to purify up to 150 litres of water daily.

Assoc Prof Tong holding a crossflow membrane testing system, where purified water crosses through the biomimetic membrane into a dilution of blackcurrant syrup, which becomes lighter in colour

The NUS researchers’ main challenge now is to reduce the cost of producing the aquaporins, which makes this innovation two to three times more expensive than conventional membranes. They aim to price this invention so that it is only 10 to 20 per cent higher than existing membranes.

Even though these membranes might cost more initially, their efficiency and hardiness will lower overall operational costs in the long run, Assoc Prof Tong noted.

These membranes have other applications too, besides water purification. The team is currently in discussions with medical technology company AWAK Technologies to incorporate the membranes into wearable kidney dialysis devices. It could reduce the size of the device, which is as big as a hardcover book right now, to one that is about the size of a mobile phone, Assoc Prof Tong said.

Starting January 2016, the scientists will start a two-year project to test the feasibility of the patent-pending technology at Singapore national water agency PUB’s new desalination facility in Tuas.

See press release and media coverage.