Nov 8 2019
A highly sensitive system developed by a team of engineers at the National University of Singapore (NUS) utilizes a smartphone to quickly identify the presence of toxin-creating algae in water in just 15 minutes.
The NUS research team behind the novel algae detection device is led by Assistant Professor Bae Sung Woo (center) who is holding the smartphone platform. With him are two team members: Mr Thio Si Kuan (left) who is holding the microfluidic chip, and Miss Chiang Li Ching Elaine (right). Image Credit: National University of Singapore.
This latest technological innovation can produce test results on-site, and by using the wireless communications capabilities of the smartphone, findings can be reported in real time.
This revolutionary technology can considerably help in preventing the spread of dangerous pathogens in aquatic settings, which could cause environmental problems and threaten global public health.
The NUS researchers, headed by Assistant Professor Bae Sung Woo from NUS Civil and Environmental Engineering, initially reported the study results online in Harmful Algae scientific journal on 25th July, 2019.
Current Challenges of Water Quality Monitoring
A sudden increase in the growth of the algae population and their related toxins in coastal waters, rivers, ponds, and lakes can have an adverse impact on the quality of water. This could consequently have unfavorable impacts on aquatic ecosystems, human health, and water supply. For example, an algae bloom destroyed over 500 tons of fish in Singapore in 2015, causing a few fish farmers to lose millions of dollars.
Traditional techniques used for the detection and analysis of algae are time-intensive and need expensive and dedicated instruments equipment, as well as experienced operators, to sample and test the water. One method is to use complex equipment to test the presence of chlorophyll, but such instruments cost over S$3,000 (US$2,200).
Another standard technique is to perform cytometric analysis and image analysis to identify algal cells, but even this approach requires equipment that cost over S$100,000 (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.
Sungwoo Bae, Assistant Professor, Department of Civil and Environmental Engineering, National University of Singapore
In order to deal with the present problems in water quality monitoring, Assistant Professor Bae and his research team came up with a new device, which took one year to develop. This device tracks microbial water quality quickly and with excellent reliability.
New “Lab-On-a-Chip” Technology: Cheaper, Smaller, and Highly Sensitive
The latest invention by the NUS team contains three portions—a smartphone, a microfluidic chip, and a modifiable 3D-printed platform that is integrated with electrical and optical components like an LED light and portable power source.
Initially, the chip is coated with a type of photoconductive polymer-based material called titanium oxide phthalocyanine. During the analysis process, the photoconductive layer guides the water droplets to move along the chip, thereby playing a key role.
Next, the coated chip is positioned on top of a smartphone screen, which projects a pattern of dark and light areas onto the chip. When the water droplets are deposited on the chip’s surface, a voltage drop variation, produced by the dark and light regions illuminated on the photoconductive layer, alters the surface tension of the water droplets. As a result, the water droplets move toward the dark illuminated regions.
Simultaneously, this movement causes the water droplets to combine with a chemical that stains the algae cells existing in the water sample. The light patterns guide the mixture toward the smartphone’s camera.
Following this, a green filter and an LED light source integrated into the 3D-printed platform, close to the smartphone’s camera, create appropriate conditions for the camera to take the fluorescent images of the stained algae cells. The images that are captured can be sent to the smartphone’s app to quantify the number of algae cells existing in the sample.
In addition, the images can be transferred wirelessly to another site through the smartphone to count the number of algae cells. It takes less than 15 minutes to complete the whole analysis process.
This user-friendly and portable device weighs less than 600 g and costs less than S$300 (US$220), excluding the smartphone. Furthermore, the test kit is extremely sensitive, which means a small quantity of water sample is enough to create consistent results.
High Detection Accuracy of 90%
The NUS researchers used water samples obtained from the reservoirs and sea to test their system. They subsequently filtered and spiked the water samples with certain amounts of four different types of toxin-producing algae—two types of marine water algae called C. closterium and Amphiprora sp. and two types of freshwater algae called M. aeruginosa and C. reinhardtii.
To test the presence of algae, the researchers performed experiments using the novel device as well as a hemocytometer, a typical cell-counting technique often utilized for monitoring the water quality.
The latest smartphone system successfully detected the four types of algae with 90% accuracy, similar to the results produced by the hemocytometer.
The combination of on-chip sample preparation, data capture and analysis makes our system unique. 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.
Sungwoo Bae, Assistant Professor, Department of Civil and Environmental Engineering, National University of Singapore
The study was supported by the National Research Foundation Singapore through its Marine Science Research and Development Programme, and the Ministry of Education.
Commercialization and Further Studies
At present, the researchers are in discussion with industry partners to commercialize their new technology. In addition, the NUS team is creating an innovative microfluidic chip that can be incorporated with a customized version of the present 3D-printed smartphone platform to identify the presence of foodborne pathogens like salmonella and other infectious microorganisms.