Monitoring chemical reactions in real time usually involves external measuring devices with single functionalities, which add extra steps to the reaction setup and can cause contaminations. Wireless technologies such as Bluetooth and electronic systems-on-a-chip—which combine all necessary components on a single, small substrate—could simplify reaction monitoring and expand its possibilities.
Nikolay Cherkasov, Dmitry Isakov, and colleagues, University of Warwick, UK, have developed a smart magnetic stir bar (pictured) that can monitor the temperature, color, viscosity, and conductivity of a reaction mixture and transmit the data using Bluetooth. The team used a system-on-a-chip platform that includes a CPU and a Bluetooth transmitter and added a resistance thermometer, an ambient light sensor, an inertia sensor, and a conductivity sensor with two external copper-plated electrodes. The system is powered using either a coin cell battery or a small rechargeable Li-polymer battery.
The entire system has a length of about 5 cm and is enclosed either in a 3D-printed, translucent poly(methyl methacrylate) capsule (which can be opened to allow access to the electronics) or a sealed fluorinated ethylene propylene (FEP) pouch (which provides better chemical resistance). The collected data is transferred to a computer or smartphone with a Bluetooth receiver.
The team used the stirrer to monitor, for example, an acid–base titration, where it could determine the endpoint. They also tested it in an oscillation reaction and found that the stirrer system has a fast response time and can be used for real-time monitoring. Qualitative viscosity measurements using the inertia sensor were also possible with careful calibration. Overall, the system is affordable and can be customized due to its modular nature. However, its operation is limited to a fairly narrow temperature range (about −40 to 85 °C) due to the electronics involved.
- Monitoring Chemistry In Situ with a Smart Stirrer: A Magnetic Stirrer Bar with an Integrated Process Monitoring System,
Nikolay Cherkasov, Samuel Baldwin, Gregory J. Gibbons, Dmitry Isakov,
ACS Sens. 2020.