Researchers create smartphone system to test for lead in water

September 26, 2018 by Jeannie Kever, University of Houston
Researchers built a self-contained smartphone microscope that can operate in both fluorescence and dark-field imaging modes and paired it with an inexpensive Lumina 640 smartphone with an 8-megapixel camera. Credit: University of Houston

The discovery of lead in Flint, Michigan's drinking water drew renewed attention to the health risks posed by the metal. Now researchers at the University of Houston have created an inexpensive system using a smartphone and a lens made with an inkjet printer that can detect lead in tap water at levels commonly accepted as dangerous.

The system builds upon earlier work by Wei-Chuan Shih, associate professor of electrical & computer engineering, and members of his lab, including the discovery of an inexpensive elastomer lens that can convert a basic into a microscope.

The latest discovery, described in the journal Analytical Chemistry, combines nano-colorimetry with dark-field microscopy, integrated into the smartphone microscope platform to detect levels of lead below the safety threshold set by the Environmental Protection Agency.

"Smartphone nano-colorimetry is rapid, low-cost, and has the potential to enable individual citizens to examine (lead) content in on-demand in virtually any environmental setting," the researchers wrote.

Even small amounts of lead can cause serious health problems, with young children especially vulnerable to neurological damage. EPA standards require lead levels in drinking to be below 15 parts per billion, and Shih said currently available consumer test kits aren't sensitive enough to accurately detect lead at that level.

By using an inexpensive smartphone equipped with an inkjet-printed lens and using the dark-field imaging mode, researchers were able to produce a system that was both portable and easy to operate, as well as able to detect lead concentrations at 5 parts per billion in . The sensitivity reached 1.37 parts per billion in deionized water.

Shih and his students last year published an open-source dataset in Biomedical Optics Express, explaining how to convert a smartphone equipped with the elastomer lens into a microscope capable of fluorescence microscopy. That paper has been the journal's most frequently downloaded paper since its publication.

The latest application incorporates color analysis to detect nanoscale lead particles. In addition to Shih, researchers on the project include first author Hoang Nguyen and Yulung Sung, Kelly O'Shaughnessy and Xiaonan Shan, all with the UH Department of Electrical & Computer Engineering. (O'Shaughnessy was a summer intern from the University of Cincinnati under the National Science Foundation's Research Experiences for Undergraduates program.)

Applying the dataset published in 2017, the researchers built a self-contained smartphone microscope that can operate in both fluorescence and dark-field imaging modes and paired it with an inexpensive Lumina 640 smartphone with an 8-megapixel camera. They spiked tap water with varying amounts of lead, ranging from 1.37 parts per billion to 175 parts per billion. They then added chromate ions, which react with the lead to form lead chromate nanoparticles; the nanoparticles can be detected by combining colorimetric analysis and microscopy.

The analysis measured both the intensity detected from the nanoparticles, correlating that to the lead concentration, and verified that the reaction was spurred by the presence of lead.

The mixture was transferred to a polydimethylsiloxane slab attached to a glass slide; after it dried, deionized water was used to rinse off the chromate compound and the remaining sediment was imaged for analysis.

The microscopy imaging capability proved essential, Shih said, because the quantity of sediment was too small to be imaged with an unassisted smartphone camera, making it impossible to detect relatively low levels of lead.

Building upon the smartphone microscope platform to create a useful consumer product was key, Shih said. "We wanted to be sure we could do something that would be useful from the standpoint of detecting lead at the EPA standard," he said.

Explore further: DIY: Scientists release a how-to for building a smartphone microscope

More information: Hoang Nguyen et al. Smartphone Nanocolorimetry for On-Demand Lead Detection and Quantitation in Drinking Water, Analytical Chemistry (2018). DOI: 10.1021/acs.analchem.8b02808

Yu-Lung Sung et al. Fabricating optical lenses by inkjet printing and heat-assistedin situcuring of polydimethylsiloxane for smartphone microscopy, Journal of Biomedical Optics (2015). DOI: 10.1117/1.JBO.20.4.047005

Related Stories

New device for quick and accurate detection of lead

May 16, 2018

A research team from the Department of Chemistry of Hong Kong Baptist University (HKBU) has invented a portable device for one-stop detection of lead concentration in drinking water. The DNA-based device, which works together ...

Recommended for you

New targets in the battle against antibiotic resistance

November 16, 2018

Bacteria are increasingly resistant to available antibiotics. A team of chemists from the Technical University of Munich (TUM) have now identified important enzymes in the metabolism of staphylococci. Blocking these enzymes ...

AI heralds new frontiers for predicting enzyme activity

November 16, 2018

Researchers from the Departments of Chemistry and Engineering Science at the University of Oxford have found a general way of predicting enzyme activity. Enzymes are the protein catalysts that perform most of the key functions ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.