The element Mercury is useful, but nasty stuff indeed, particularly when it finds its way into drinking water.

A liquid metal found in natural deposits such as ores containing other elements, Mercury is often used for making electrical products like dry-cell batteries, fluorescent light bulbs, electrical switches and a variety of control equipment. Those uses account for some 50 percent of the mercury used worldwide.

People who drink water contaminated with mercury in excess of the maximum contaminant levels over a period of years are likely to suffer kidney damage and a host of other ills. Elemental mercury is released from industrial processes, agricultural processes, household sources, commercial and medical products, sewage discharge and sediment. Mercury vapor is known to cause nervous system damage when ingested at high concentration levels. Organic mercury, on the other hand, is produced by bacterial organisms in surface water that convert inorganic mercury into organic mercury. That version is the form of mercury which poses a significant threat to human health. Typically ingested by fish, it accumulates in the tissues of fish – and the humans that eat those fish.

A large, predatory fish can contain as much as 100,000 times more methyl mercury than the water which surrounds it.

Both inorganic and organic mercury are considered to have a serious detrimental effect on children, That's due in part to the fact that both forms of mercury are more easily absorbed into a child's system.

But have no fear, researchers at UCLA have now designed a 3D printed attachment for smartphones (and an app to drive it) which can detect the presence of mercury in water. Inexpensive, lightweight and relatively simple to use, the researchers say the "lab on a phone" will reduce both the time – and the cost – of detecting mercury in water supplies.

The app also allows users to plot concentration levels to create a "crowdsourced" map of affected areas, and perhaps the best feature of the system is that tests for mercury contamination can be performed by nearly anyone after some minimal training.

So how does it work?

According to Aydogan Ozcan, the principal investigator for the research project,  a sample of suspect water is collected in a disposable test tube and then exposed to the smartphone equipped with an optical attachment. By using the attachment's LEDs set at two specific frequencies, the device detects minute changes in how light is transmitted to the phone's built-in camera. The system can detect mercury-laden nanoparticle clustering in contaminated water.

"Our new platform for mercury testing is essentially a lab on a phone." Ozcan said. "It's portable, lightweight and inexpensive to manufacture. Because of the global proliferation of mobile devices, it could make testing for mercury widely available. Having this kind of test available in resource-limited areas and in the field was an important motivation for our work."

Previous methods of testing water for mercury contamination in laboratories used expensive instruments and require complex preparation by professionally trained personnel. This latest testing technology uses an attachment produced at UCLA using a 3D printer.

Ozcan says the UCLA device uses nanoscale gold particles and short fragments of synthetic DNA to detect the presence of mercury ions, and it can detect mercury concentrations down to 3 to 4 parts per billion, that's about the maximum safe concentration level for drinking water set by the U.S. Environmental Protection Agency and the World Health Organization.

The process takes about 20 minutes per test, and that time frame includes 10 minutes of "incubation time."

The research team says their device will drive down the cost per test to somewhere around five cents, and the phone attachments weigh less than 40 grams and cost around $37 each to produce.

Team members on the project include Qingshan Wei, a UCLA postdoctoral scholar and lead author on the research, UCLA undergraduates Richie Nagi, Kayvon Sadeghi, Eddie Yan and So Jung Ki, and UCLA researchers Steve Feng, Romain Caire and Derek Tseng.

Ozcan has also created a 3D printed microscope.