A new chip-scale device can sensitively detect lead levels in drinking water, whose toxicity affects 240 million people worldwide. Engineers and collaborators at the Massachusetts Institute of Technology (MIT) have developed a compact, low-cost technology for detecting and measuring lead in water. This new system uses photonic chips and crown ethers to capture lead ions, providing near-instantaneous and accurate results with just a drop of water.
Artistic rendering of the surface of the chip, showing the optical interferometer on the chip used to detect the presence of lead. The illustration shows the binding process of lead to crown ether. Source: Jia Xu Brian Sia
Engineers at the Massachusetts Institute of Technology, Nanyang Technological University, and several companies have developed a small and inexpensive technology for detecting and measuring lead concentrations in water that has the potential to make significant progress in tackling this long-standing global health problem.
The World Health Organization estimates that 240 million people worldwide are exposed to drinking water that contains unsafe and toxic lead, which can affect children's brain development, cause birth defects, and produce a variety of neurological, cardiac, and other damaging effects. In the U.S. alone, an estimated 10 million households still have drinking water delivered through lead pipes.
Microfluidic chamber for the delivery of analytical solution and optical fibers on the side to measure the photon response of the chip Image source: Courtesy of the researchers
Jia Xu Brian Sia, a postdoctoral fellow at the Massachusetts Institute of Technology and senior author of the paper introducing the new technology, said: "This is an unresolved public health crisis that kills more than 1 million people a year. "
However, testing for lead in water requires expensive, cumbersome equipment and often takes days to get results. Or, using a simple test strip, you can only get the answer to whether lead exists, but you can't know the concentration of lead. Current regulations from the U.S. Environmental Protection Agency (EPA) require that drinking water contain no more than 15 parts per billion of lead, which is so low that it is difficult to detect.
The new system, which can be commercially available within two to three years, can detect lead concentrations as low as parts per billion with high accuracy using a simple chip-based detector mounted in a handheld device. The technology allows for quantitative measurements almost instantaneously and requires only a drop of water.
The findings were described in a paper published May 14 in the journal Nature Communications by Sia, MIT graduate student and lead author Luigi Ranno, Professor Hu Juejun, and 12 others from MIT and other academic and industrial institutions.
Jarsh Brian Sia (left) and Luigi Lanno (right) demonstrate the fully encapsulated sensor chip and microfluidic chamber. Image source: Courtesy of the researchers
The team set out to find a simple detection method based on a photonic chip that uses light to make measurements. The challenging part is finding a way to attach certain ring-shaped molecules to the surface of the photonic chip called crown ether, which can capture specific ions, such as lead. After years of hard work, they finally achieved this attachment through a chemical process called Fischer esterification. "This is one of the key breakthroughs we have made in this technology.
In tests of the new chip, the researchers found that it could detect lead in water as low as one part per billion. At higher concentrations, which may be associated with the detection of environmental contamination such as mine tailings, the accuracy is within 4%.
Versatility and practical application
"The unit works in water with varying levels of acidity, with a pH ranging from 6 to 8, covering most environmental samples," Sia says. They tested the unit with seawater and tap water and verified the accuracy of the measurements. "
To achieve such accuracy, current tests require a device called an inductively coupled plasma mass spectrometer. "These units can be big and expensive," Sia said. Sample processing can take several days and requires an experienced technician. "
While the new chip system they developed is a "core part of innovation," Lanno said, further work is needed to develop it into an integrated handheld device for practical use. "To make an actual product, it needs to be packaged into a usable form factor," he explains. This requires coupling a small chip-based laser on a photonic chip. It's a matter of mechanical design, optical design, chemistry, and supply chain. He said that while it will take time, the basic concept is simple and straightforward. "
The system can be used to detect other similar contaminants in water, including cadmium, copper, lithium, barium, cesium, and radium. The device can be used with simple cartridges that can be swapped out to detect different elements, each using a slightly different crown ether that binds to specific ions.
Implications for global health
"People aren't measuring enough water, especially in developing countries, and that's a problem," Lanno said. "It's because they need to collect water, prepare samples, and bring it to these big, expensive instruments. Conversely, "with this handheld device, even untrained personnel can be brought to the water source for on-site monitoring at a low cost," making regular, continuous, widespread testing feasible. "
Hu, a John F. Elliott professor in the Department of Materials Science and Engineering, said, "I hope that this technology will be applied as soon as possible for the benefit of human society." It's a great example of how technology from lab innovation can really have a very tangible impact on society, which is certainly very fulfilling. "
Wang Hou, an associate professor at the School of Environmental Science and Engineering at Hunan University in China, said: "If this research can be extended to detect multiple metallic elements at the same time, especially the radioactive elements currently involved, then its potential will be enormous." "
"This study has led to the design of a sensor that can detect lead concentrations in water instantly," Wang added. This can be used to monitor the concentration of lead pollution in industrial wastewater such as battery manufacturing and lead smelting in real time, thereby facilitating the establishment of industrial wastewater monitoring systems. I think the innovation and development potential of this research is quite commendable. "
Wang Qian, Principal Research Scientist at the Singapore Institute of Materials, commented: "The ability to universally, portably and quantitatively detect lead has proven challenging, mainly due to cost concerns. This work demonstrates the potential to achieve this in a highly integrated form that is compatible with large-scale, low-cost manufacturing. "
编译来源：ScitechDaily