NUS engineers invent smartphone device that detects harmful algae in 15 minutes

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.

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