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A small piece of paper loaded with biodegradable carbon electrodes could provide a cheap, sustainable and recyclable device for detecting toxic compounds in water.
Access to safe drinking water is one of the United Nations’ Sustainable Development Goals, since it is a basic human right and necessary in combatting equalities and reducing poverty. Yet in some of the world’s poorest countries, people are consuming dirty, disease-ridden water every day - and there is a lack of easily deployable and affordable water testing tools.
Inspired by the simplicity of litmus paper – used to test for acidity in water – a team of interdisciplinary researchers from the University of Bath’s Water Innovation & Research Centre (WRIC @ Bath) and Centre for Sustainable Chemical Technologies (CSCT), have developed an innovative microbial fuel cell (MFC), obtained by screen printing biodegradable carbon electrodes in a conductive ink onto a single piece of paper.
The MFC uses the natural biological processes of ‘electric’ bacteria attached to the carbon electrodes to generate an electric signal. When the bacteria are in the presence of polluted water, there is a change in the electric signal which can act as a warning that the water is unsafe to drink. The researchers put their MFC in a proof-of-concept test as a shock sensor for bioactive compounds - like formaldehyde - in water.
In their paper published in Biosensors and Bioelectronics, the researchers write: “It is membrane-less, as the paper substrate itself acts as the separator between the two electrodes. Moreover, there is no need for sample pumping, since capillary forces in the paper create autonomous microfluidics that can be manipulated by changing the paper structure, thus tuning the performance of the device.”
It is hoped the device could supply some of the world’s poorest countries with a low cost, simple and fast way to test the water supply. Each device is expected to cost no more than £1 and since the paper sensor is made from biodegradable components it is also environmentally friendly and will leave no metal residue. At less than 1g, the device is also easy-to-use and to transport.
The researchers are now investigating a means of connecting the sensor to and electronic device such as a mobile phone, via a wireless transmitter, for a quick and user-friendly way of identifying if a water supply is safe to use. The team have already found that they could enhance the sensor performance by folding back-to-back two MFCs electrically connected in parallel.
“This work could lead to a revolutionary way of testing water at the point of use, which is not only green, easy to operate and rapid, but also affordable to all,” states Dr Mirella Di Lorenzo, lead author of the study and Senior Lecturer in the Department of Engineering, WIRC @ Bath and CSCT
“This type of research will have a significant positive impact, especially benefitting those areas where access to even basic analytic tools is prohibitive. This device is a small step in helping the world realise the United Nations call to ensure access to safe drinking water and sanitation as a human right,” she adds
This is a great example of how scientists and engineers working closely together can develop useful technologies with the potential to impact positively on the lives of citizens globally - we were able to design the materials that facilitated the production of these devices and the engineering partners designed the devices.
Dr Janet Scott, Co-Author
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