With pollution levels rising, the need to quickly check water quality has become more urgent than ever. Traditional monitoring systems often rely on expensive bulky equipment with operational difficulty, making them impractical in remote areas or in places with limited resources.
In a significant advancement, researchers at Institute of Science Tokyo (Science Tokyo), Japan, have built a self-powered device that detects toxic amines in water using electrochemiluminescence (ECL). The technology works by producing light during a chemical reaction. The brightness of the light indicates whether pollutants are present, allowing for the detection of contamination on the spot.
The ECL process relies on two key molecules: a chromophore, which serves as the light emitter; and a coreactant, which is a sacrificial species. These molecules undergo redox reactions that push the chromophore into an excited state. As the chromophore relaxes back to its ground state, it emits light, indicating the presence of the target compound. Traditionally, ECL required an external power supply to drive these reactions. The new device, however, needs no power source at all. Instead, it taps into the voltage generated when liquid flows through the system.
The research team was led by Professor Shinsuke Inagi from the Department of Chemical Science and Engineering at Science Tokyo, along with Dr. Elena Villani (then a specially appointed Assistant Professor) and Mr. Rintaro Suzuki (then a graduate student). The features and working of the device have been published in the journal Nature Communications.
“Since this ECL technique does not require a power supply, it opens new possibilities for applications such as pollutant detection in rivers or pipelines using natural flow energy. This concept can be extended for the ECL detection of a large pool of analytes, beyond environmental monitoring, such as for food and water testing, and biowarfare agents,” said Inagi.
The team designed a microfluidic device with two chambers containing platinum wire electrodes, connected by a channel filled with porous material. The electrodes are connected by an ammeter, forming a split bipolar electrode system. When liquid is pushed through the channel, even with a simple hand-operated syringe, it generates a streaming potential of up to 2–3 volts, enough to trigger redox reactions at the electrodes.
For the chromophore, the researchers deposited benzothiadiazole-triphenylamine (BTD-TPA) on the anode, while tri-n-propylamine (TPrA) was used as the coreactant. The researchers chose to detect amines as they are widely used in industrial processes and are known to be toxic, carcinogenic, and cause genetic mutations.
Here is an exclusive Tech Briefs interview, edited for length and clarity, with Inagi.
Tech Briefs: What was the biggest technical challenge you faced while developing this pollution sensor?
Inagi: The biggest challenge was that, despite being an electrochemiluminescence analysis method, it essentially does not use a power supply device. To achieve this, we utilize the voltage generated by liquid flow (streaming potential), but since this is typically a weak voltage (several mV), we needed to devise a way to generate the voltage required for electrochemical reactions (1 V or more). We resolved this by using a porous resin monolith material in the flow channel, which allowed us to generate voltage while keeping the liquid delivery pressure low.
Tech Briefs: Can you explain in simple terms how it works please?
Inagi: Related to the above, when a dilute electrolyte solution is delivered through a microchannel, a phenomenon called streaming potential causes a voltage between upstream and downstream. By placing electrodes upstream and downstream and connecting them with a conductive wire, the generated voltage can be used for electrochemical reactions. In other words, it becomes an electrochemical reaction device that does not require an external power supply. We applied this device to electrochemiluminescence analysis. Light is emitted by simultaneously inducing the electrochemical oxidation of a luminophore and the electrochemical oxidation of amines as a coreactant. Using this mechanism, amines can be detected based on the luminescence behavior.
Tech Briefs: Do you have any set plans for further research/work/etc.? If not, what are your next steps?
Inagi: Currently, samples need to be delivered using a plunger pump or syringe pump, so it would be ideal if this could be achieved with lower-pressure flows. In other words, we are looking toward naturally occurring flows such as rivers. To accomplish this, we need to develop devices that can generate high enough voltage at lower pressures, and we are working toward realizing this goal.
Tech Briefs: Is there anything else you’d like to add that I didn’t touch upon?
Inagi: Related to question 3, various surplus pressures exist in our daily lives and different industries. Pressure is applied in water supply pipes and chemical plant piping. One of our goals is to effectively utilize these pressures for electrochemical reactions (including not only analytical applications but also substance production).
Tech Briefs: Do you have any advice for researchers aiming to bring their ideas to fruition?
Inagi: What feels truly new and interesting is at times, considered unconventional. You may even face criticism. Without being discouraged by this, I hope you will challenge yourself from multiple angles and make it into a valuable step forward. Research and study in different fields will provide helpful hints.
