Engineers at MIT, Nanyang Technological University, and several companies have developed a compact and inexpensive technology for detecting and measuring lead concentrations in water, potentially enabling significant progress in addressing this persistent global health problem.

The World Health Organization estimates that 240 million people worldwide are exposed to drinking water containing unsafe levels of toxic lead, which can affect brain development in children, cause birth defects, and produce various neurological, cardiac, and other harmful effects. In the United States alone, it is estimated that 10 million households still receive drinking water through lead pipes.

“This is an unresolved public health crisis leading to more than a million deaths annually,” says Jia Xu Brian Sia, a postdoctoral fellow at MIT and the lead author of the paper describing the new technology.

However, testing for lead in water requires expensive, bulky equipment and usually takes several days to get results. Or it uses simple test strips that only detect the presence of lead without information about its concentration. Current EPA regulations require that drinking water contain no more than 15 parts per billion of lead, a concentration so low that it is difficult to detect.

The new system, which could be ready for commercial application within two to three years, could detect lead concentrations as low as 1 part per billion, with high accuracy, using a simple detector chip housed in a handheld device. The technology provides near-instantaneous quantitative measurements and requires only a drop of water.

The findings are described in a paper published today in the journal Nature Communications, by Sia, MIT graduate student and lead author Luigi Ranno, Professor Juejun Hu, and 12 others at MIT and other institutions in academia and industry.

The team aimed to find a simple detection method based on the use of photonic chips, which use light to perform measurements. The challenge was to find a way to attach specific ring-shaped molecules known as crown ethers to the surface of the photonic chip, which can capture specific ions like lead. After years of effort, they achieved this using a chemical process known as Fischer esterification. “This is one of the key breakthroughs we have achieved in this technology,” says Sia.

When testing the new chip, researchers demonstrated that it could detect lead in water at concentrations as low as one part per billion. At much higher concentrations, which may be relevant for testing environmental contamination such as mining waste, the accuracy is within 4 percent.

The device operates in water with different acidity levels, ranging from pH values of 6 to 8, “which covers most environmental samples,” says Sia. They tested the device with seawater and tap water, confirming the accuracy of the measurements.

To achieve such a level of accuracy, current tests require a device called an inductively coupled plasma mass spectrometer. “These devices can be large and expensive,” says Sia. Sample processing can take days and requires experienced technical staff.

While the new chip system they developed is “the core of the innovation,” Ranno says, further work will be needed to develop it into an integrated, handheld device for practical use. “To create an actual product, you need to package it in a user-friendly form,” he explains. This would involve having a small chip laser connected to the photonic chip. “It’s about mechanical design, some optical design, chemistry, and finding the supply chain,” he says. Although it takes time, he says, the basic concepts are simple.

The system can be adapted to detect other similar contaminants in water, including cadmium, copper, lithium, barium, cesium, and radium, says Ranno. The device could be used with simple cartridges that can be replaced to detect different elements, each using slightly different crown ethers that can bind specific ions.

“The problem is that people do not measure their water often enough, especially in developing countries,” says Ranno. “And that’s because they need to collect the water, prepare a sample, and take it to these huge instruments that are extremely expensive.” Instead, “having this handheld device, something compact that even untrained personnel can bring to the source for field monitoring, at low cost,” could enable regular, ongoing widespread testing.

Hu, who is the John F. Elliott Professor of Materials Science and Engineering, says, “I hope this will be quickly implemented so we can benefit human society. This is a good example of technology coming from laboratory innovation where it can actually make a very tangible impact on society, which is of course very fulfilling.”

“If this research can be expanded to simultaneously detect more metallic elements, especially currently concerning radioactive elements, its potential would be huge,” says Hou Wang, an associate professor of environmental science and engineering at Hunan University in China, who was not involved in this work.

Wang adds, “This research has developed a sensor capable of instantly detecting lead concentration in water. This can be used in real-time to monitor lead pollution concentrations in wastewater discharged by industries such as battery manufacturing and lead smelting, facilitating the establishment of industrial wastewater monitoring systems. I think the innovative aspects and development potential of this research are highly commendable.”

The team included researchers at MIT, Nanyang Technological University and Temasek Laboratories in Singapore, the University of Southampton in the UK, and companies Fingate Technologies in Singapore and Vulcan Photonics, based in Malaysia. The work used facilities at MIT.nano, the Harvard University Center for Nanoscale Systems, NTU’s Center for Micro- and Nano-Electronics, and the Nanyang Nanofabrication Center.

The research team succeeded in integrating different disciplines in developing this technology, combining photonics, chemistry, and engineering to create a system that is affordable and easy to use. The key challenge was to create photonic chips that can reliably measure lead in real-world conditions, which required significant innovations in materials and processes.

The crown ethers used in the system are key to capturing lead ions. These molecules have a specific ring-shaped structure that allows efficient binding to lead, and the Fischer esterification process allows them to be stably attached to the chip surface. This approach enables the system’s high specificity and sensitivity, which is crucial for detecting low concentrations of lead in water.

Tests have shown that the device can operate under various conditions, including different acidity levels and the presence of other contaminants. This is important for application in diverse environments, from drinking water to industrial wastewater. Additionally, the system can be adapted to detect other toxic metals, making it extremely versatile.

One of the most important aspects of this technology is its affordability and ease of use. Traditional methods for detecting lead require expensive and complex equipment and trained personnel, which limits their application, especially in less developed areas. The new system, on the other hand, allows for rapid and accurate measurements with minimal cost and technical complexity.

Commercial application of this technology is expected to significantly improve the ability to monitor and manage water pollution. Integration into handheld devices will enable frequent and widespread testing, which is crucial for early detection and prevention of health risks associated with lead exposure.

The development of this technology also opens up opportunities for further research and innovation. There is potential to expand the device’s functionality to detect a wide range of contaminants, including radioactive elements, which would have a significant impact on industrial and environmental standards. The use of photonic chips for various analytical applications represents a significant step forward in sensor technology.

This research also demonstrates the value of an interdisciplinary approach in developing new technologies. Collaboration between different institutions and experts allowed for the resolution of complex problems and the development of innovative solutions that can have broad application. By linking theoretical insights and practical applications, the team was able to create a system that not only advances scientific understanding but also has real societal benefits.

The development of this technology represents an important step forward in the fight against lead pollution and other toxic metals in water. Its simplicity, affordability, and versatility make it an ideal solution for widespread application, from rural areas to industrial complexes. The team at MIT and their partners continue to work on refining and commercializing the system, with the goal of improving public health and environmental protection.

Source: Massachusetts Institute of Technology