Detecting water leaks with ‘smart paper’

A SMART paper laced with conductive nanomaterials could be used to easily locate water leaks in a complex network of pipes, according to researchers.

The paper can act as a switch in the presence of water, and could be wrapped around pipes alongside an inexpensive alarm system to aid repair work.

Water leaks are a common issue faced by large-scale manufacturing plants and water utilities. Locating them can require a lot of time and effort, often involving the disassembly of several pieces. There are many types of sensor on the market to help with this, which employ acoustic, thermal, electromagnetic, and chemical detection techniques, but each has its own weaknesses and cost.

“Water sensing is very challenging to do due to the polar nature of water, and what is used now is very expensive and not practical to implement,” said Anthony Dichiara, an engineer at the school of environment and forest sciences at University of Washington, US.

His team’s solution to this, published in the Journal of Materials Chemistry A, involves incorporating conductive carbon nanomaterials into the traditional papermaking process.

First, Kraft softwood pulp is added to water, and its fibres split in a mill to facilitate binding. Layer-by-layer nanoassembly follows, by gradually adding cationic polyacrylamide and commercially available hydroxyl-functionalised carbon nanotubes, which are pre-adsorbed with alkali lignin surfactant. The nanomaterials bind to the pulp, and the solids are pressed and rolled into paper.

In tests, when water hit the paper, its fibres swelled up to three times their original size. The researchers found that the expansion displaced conductivity inside the paper, which could work as a switch to attached electronic devices. Upon drying, the paper became conductive again, and could be reused several times.

The team says that the paper can detect trace amounts of water in mixtures of liquids, which could be valuable in industries where water is an impurity, such as for petroleum and biofuel.

Dichiara hopes to scale up production of the smart paper to commercial scale. “I believe that for large-scale applications, this is definitely doable,” he said. “The price for nanomaterials is going to drop, and we’re already using an established papermaking process. You just add what we developed in the right place and time in the process.”

Journal of Materials Chemistry A: http://doi.org/cf7v