A team of engineers from the National University of Singapore (NUS) has developed a highly
sensitive system that uses a smartphone to rapidly detect the presence of toxin-producing
algae in water within 15 minutes.
This invention can generate test results on-site, and findings can be reported in real-time
using the smartphone's wireless communications capabilities.
This technological breakthrough could play a big role in preventing the spread of harmful
microorganisms in aquatic environments, which could threaten global public health and cause
environmental problems.
A sudden surge in the volume of algae and their associated toxins in lakes, ponds, rivers,
and coastal waters can adversely affect water quality, and in turn, may have unfavourable
effects on human health, aquatic ecosystems, and water supply.
For instance, in 2015, an algae bloom wiped out more than 500 tonnes of fish in Singapore,
and caused some fish farmers to lose millions of dollars.
Conventional methods of algae detection and analysis are time consuming, and require specialised
and costly equipment, as well as skilled operators to conduct water sampling and testing.
One approach is to test for the presence of chlorophyll using complex instruments that
cost more than US$2,200.
Another common method is to carry out cytometric and image analysis to detect algal cells - this
method involves equipment that cost more than US$73,000 .
Currently, it can take a day or more to collect water samples from a site, bring them back
to the laboratory for testing, and analyse the results.
This long lead time is impractical for monitoring of algae blooms, as the management of contamination
sources and affected waters could be slowed down.
To address the current challenges in water quality monitoring, research team took a year
to develop the novel device that monitors microbial water quality rapidly and with high
reliability.
The new NUS invention comprises three sections - a microfluidic chip, a smartphone, and a
customisable 3D-printed platform that houses optical and electrical components such as
a portable power source and an LED light.
The chip is first coated with titanium oxide phthalocyanine, a type of photoconductive
polymer-based material.
The photoconductive layer plays the important role of guiding water droplets to move along
the chip during the analysis process.
The coated chip is then placed on top of the screen of a smartphone, which projects a pattern
of light and dark regions onto the chip.
When droplets of the water sample are deposited on the surface of the chip, a voltage drop
difference, created by the light and dark areas illuminated on the photoconductive layer,
modifies the surface tension of the water droplets.
This causes the water droplets to move towards the dark illuminated areas.
At the same time, this movement induces the water droplets to mix with a chemical that
stains algae cells present in the water sample.
The mixture is guided by the light patterns towards the camera of the smartphone.
Next, an LED light source and a green filter embedded in the 3D-printed platform, near
the camera of the smartphone, create the conditions suitable for the camera to capture fluorescent
images of the stained algae cells.
The images can be sent to an app on the smartphone to count the number of algae cells present
in the sample.
The images can also be sent wirelessly to another location via the smartphone to quantify
the number of algae cells.
The entire analysis process can be completed within 15 minutes.
This portable and easy-to-use device costs less than US$220 - excluding the smartphone
- and weighs less than 600 grams.
The test kit is also highly sensitive, hence only a small amount of water sample is needed
to generate reliable results.
The NUS research team tested their system using water samples collected from the sea
and reservoirs.
The new smartphone system was able to detect the four types of algae with an accuracy of
90 per cent, comparable with the results generated by the hemocytometer.
With this tool, water quality tests can be conducted anytime and anywhere.
This new method is also very cost efficient as the microfluidic chip can be washed and
re-used.
This device will be particularly useful for fish farmers who need to monitor the water
quality of their fish ponds on a daily basis.