Device developed by NUS engineers uses smartphone to detect harmful algae in minutes

Postgraduate student Elaine Chiang, Assistant Professor Bae Sung-woo and postgraduate student Thio Si Kuan at the NUS Faculty of Engineering on Nov 6, 2019.
Postgraduate student Elaine Chiang, Assistant Professor Bae Sung-woo and postgraduate student Thio Si Kuan at the NUS Faculty of Engineering on Nov 6, 2019.PHOTO: SINGAPORE PRESS HOLDING LTD

SINGAPORE - Conventional tests for the presence of algae in water involve bulky and expensive equipment and can take up to a week to get results as researchers have to take the sample back to their labs for analysis.

But a team of engineers from the National University of Singapore (NUS) has developed an easy-to-use, portable system that makes use of a smartphone to detect the presence of toxin-producing algae in water within 15 minutes.

It costs less than S$300, far cheaper than conventional methods which can range from $3,000 to $100,000.

Shortening the interval between collecting water samples and analysis will enable preventive action to be taken earlier to nip potential algae blooms in the bud, said Assistant Professor Bae Sung-woo, who is from the NUS engineering faculty's Civil and Environmental Engineering department.

"By the time you get the results of the analysis a week later, the fact is the water in the sea is no longer the water you collected. It might be too late," said Prof Bae during a media demonstration of the new portable system at NUS on Wednesday (Nov 6).

"Our device can be used to detect algae in water bodies any time and anywhere, and before the algae are visible to the naked eye. It will be particularly useful in helping fish farmers to take early action."

Prof Bae developed the device alongside doctoral student Thio Si Kuan and master's student Elaine Chiang, who are both also from the Faculty of Engineering.

The device weighs less than 600g and has three components: a chip coated with a layer of photoconductive material which becomes more electrically conductive when exposed to light, a custom 3D-printed box that houses a battery and an LED light, and a smartphone of any model.

Droplets from a water sample are deposited onto the chip, which lies above the smartphone in the box.


The droplets are mixed with a dye to stain any viable algae cells present, and are made to move with the aid of an electrical field generated by the smartphone and the box's battery towards a small hole lying above the smartphone's camera.

The smartphone camera then captures images of the stained algae cells illuminated by the LED light.

Depending on the staining dye used, different kinds of algae cells will show up in different colours, which can then be analysed by an app to calculate the level of algae present in the sample.

Prof Bae said the smartphone system has an accuracy rate of 90 per cent, comparable to a standard cell-counting technique using an instrument called a hemocytometer.

The research team is currently in discussion with industry partners to commercialise the technology.

They are also working on developing their own app that can automatically analyse images and generate reports on the types of algae detected.

In 2015, fish farmers from 77 farms in Singapore were hit by an algae bloom that wiped out more than 500 tonnes of fish, costing them millions of dollars.

Most fish farmers in Singapore do not have their own devices for monitoring algae levels, relying on their observations of fish behaviour to determine if something is amiss, said Mr Simon Ho, who has been a fish farmer for about 10 years.

Asked about the NUS device, Mr Ho reserved judgment, saying it was hard to come to a conclusion without more information and trying it out himself.

"There are many different types of algae and how accurate a device is in telling them apart is very important because some algae are poisonous and some are not," he added.