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New Sensor Provides Accurate Lead Concentration Readings

Engineers from the Massachusetts Institute of Technology, Nanyang Technological University, along with several companies, have created a small and low-cost method for identifying and measuring lead levels in water. This development may significantly advance the ongoing efforts to address this persistent worldwide health concern. The research was published in Nature Communications.

New Sensor Provides Accurate Lead Concentration Readings
Artist’s impression of the chip surface, showing the on-chip light interferometer used to sense the presence of lead. The lead binding process to the crown ether is shown in the inset. Image Credit: Jia Xu Brian Sia

According to the World Health Organization, approximately 240 million people worldwide are exposed to unsafe levels of toxic lead in drinking water. Toxic lead can cause congenital disabilities, alter a child's brain development, and create various neurological, cardiac, and other damaging effects. An estimated 10 million households in the United States currently receive their drinking water through lead pipes.

It is an unaddressed public health crisis that leads to over 1 million deaths annually.

Jia Xu Brian Sia, Postdoc and Study Senior Author, Massachusetts Institute of Technology

However, testing for lead in water necessitates requires costly, heavy equipment, and results usually take days to obtain. Alternatively, it uses straightforward test strips that provide a positive or negative result but offer no details regarding the concentration of lead.

According to current EPA standards, lead concentrations in drinking water cannot exceed 15 parts per billion, a level so low that it is nearly impossible to detect.

The new system, which may be prepared for commercial deployment in two or three years, uses a straightforward chip-based detector contained within a portable device. It could detect lead concentrations as low as 1 part per billion with great accuracy. The technique provides quantitative measurements instantly with just a droplet of water.

The study was conducted by Sia, lead author Luigi Ranno, Professor Juejun Hu, and twelve other researchers from MIT and various academic and industrial institutions.

The group aimed to develop a straightforward detection technique based on photonic devices, which measure light. The difficulty was figuring out how to affix certain ring-shaped molecules, called crown ethers, which can absorb particular ions, like lead, to the photonic chip surface. After years of work, they achieved that connection through a chemical process called Fischer esterification.

Sia said, “That is one of the essential breakthroughs we have made in this technology.”

According to tests conducted by the researchers, the new device can detect lead in water in quantities as low as one part per billion. At significantly greater concentrations, the accuracy is within 4 %, which may be crucial for assessing environmental contaminants such as mine tailings.

According to Sia, the device can function in water with pH values between 6 and 8, “which covers most environmental samples.” They confirmed the measurement accuracy by testing the device with both tap water and seawater.

Current testing requires an apparatus known as an inductively coupled plasma mass spectrometer to reach such levels of accuracy. According to Sia, “These setups can be big and expensive.” It can take days to process the sample, and skilled technical staff are needed. 

Ranno says their newly created chip technology is “the core part of the innovation.” Despite this, more work will be required to incorporate it into a portable, useful gadget.

Sia adds, “For making an actual product, you would need to package it into a usable form factor.

This would entail integrating a compact chip-based laser with the photonic chip.

 It’s a matter of mechanical design, some optical design, some chemistry, and figuring out the supply chain.

Jia Xu Brian Sia, MIT Postdoc and Study Senior Author, Massachusetts Institute of Technology

According to Ranno, the technique can be modified to identify more comparable pollutants in water, such as radium, barium, cesium, copper, lithium, cadmium, and barium. Simple interchangeable cartridges that each utilize a slightly different crown ether that can bind to a certain ion might be used with the gadget to detect various elements. 

Ranno said, “There is this problem that people do not measure their water enough, especially in the developing countries, and that is because they need to collect the water, prepare the sample, and bring it to these huge instruments that are extremely expensive. Instead, having this handheld device, something compact that even untrained personnel can just bring to the source for on-site monitoring, at low costs, could make regular, ongoing widespread testing feasible.” 

I am hoping this will be quickly implemented, so we can benefit human society. This is a good example of a technology coming from a lab innovation where it may actually make a very tangible impact on society, which is, of course, very fulfilling.

Juejun Hu, John F. Elliott Professor, Department of Materials Science and Engineering, Massachusetts Institute of Technology

Hou Wang, Associate Professor of Environmental Science and Engineering at Hunan University in China, who was not associated with this work, said, “If this study can be extended to simultaneous detection of multiple metal elements, especially the presently concerning radioactive elements, its potential would be immense.”

Wang added, “This research has engineered a sensor capable of instantaneously detecting lead concentration in water. This can be utilized in real-time to monitor the lead pollution concentration in wastewater discharged from industries such as battery manufacturing and lead smelting, facilitating the establishment of industrial wastewater monitoring systems. I think the innovative aspects and developmental potential of this research are quite commendable.”

Wang Qian, a Principal Research Scientist at the Institute of Materials Research in Singapore, who also was not affiliated with this work, said, “The ability for the pervasive, portable, and quantitative detection of lead has proved to be challenging primarily due to cost concerns. This work demonstrates the potential to do so in a highly integrated form factor and is compatible with large-scale, low-cost manufacturing.”

The team has co-researchers from MIT, Nanyang Technological University, Temasek Laboratories in Singapore, the University of Southampton in the U.K., Fingate Technologies in Singapore, and Vulcan Photonics, headquartered 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. 

Journal Reference:

Ranno, L., et al. (2024) Crown ether decorated silicon photonics for safeguarding against lead poisoning. Nature Communications.


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