Ordinarily, levels of potentially-harmful algae are monitored by collecting water samples from bodies of water, then transporting those samples to a laboratory. The problem is, by the time those samples reach the lab and get tested, algae populations may have increased substantially – even to the point that local people should be warned to boil their water before drinking it.

With that in mind, scientists at the National University of Singapore have developed a system consisting of three parts: a 3D-printed platform containing electronics, a smartphone that sits in that platform, and a reusable microfluidic chip.

The chip is coated in a polymer known as titanium oxide phthalocyanine, which produces an electrical current when exposed to light. It gets placed on the smartphone's screen, after which droplets of water are deposited onto it. The phone then projects a light pattern consisting of light and dark areas onto the chip, producing a variation in voltage across its surface. This alters the surface tension of the droplets, causing them to flow into the dark areas.

There, tiny microfluidic channels in the chip's surface guide the water to a transparent area of the device, over top of the smartphone's camera. Additionally, as the water moves through the channels, in mixes with a chemical that stains any algae cells that are present.

With some help from an LED light source and a green filter that are built into the platform, the phone is subsequently able to take photos of the water sample, in which all the algae cells fluoresce. They can then easily be counted by an accompanying app, allowing users to determine if algae levels in the lake are getting dangerously high.

The whole process can be carried out on-location within 15 minutes, and the whole rig (excluding the phone) costs only about US$220 to make.

When tested alongside a traditionally-used hemocytometer, the smartphone system was found to be 90 percent as accurate at monitoring levels of four different types of toxin-producing algae. Further development should boost that figure even higher.

"The combination of on-chip sample preparation, data capture and analysis makes our system unique," says the lead scientist, Asst. Prof. Bae Sung Woo. "With this tool, water quality tests can be conducted anytime and anywhere."

A paper on the research was recently published in the journal Harmful Algae. And for another take on a smartphone-based algae-detection system, check out the setup that's being developed at North Carolina State University.

According to newatlas