Arduino-Compatible "Smart Stirrer" Monitors Chemical Reactions, Transmits Data to a Raspberry Pi

Scientists at the University of Warwick have developed a means for chemists to monitor a chemical reaction in situ — by putting sensors directly in the stir bar.

"Inspired by the miniaturization and efficiency of the sensors for telemetry, we have developed a device that provides the functionalities of laboratory magnetic stirring and integrated multi-sensor monitoring of various chemical reaction parameters," the team, led by senior author Nikolay Cherkasov, explains. "The device, called 'Smart Stirrer,' when immersed in a solution, can in situ monitor physical properties of the chemical reaction such as the temperature, conductivity, visible spectrum, opaqueness, stirring rate, and viscosity."

"This data is transmitted real-time over a wireless connection to an external system, such as a PC or smartphone. The flexible open-source software architecture allows effortless programming of the operation parameters of the Smart Stirrer in accordance with the end-user needs. The concept of the Smart Stirrer device with an integrated process monitoring system has been demonstrated in a series of experiments showing its capability for many hours of continuous telemetry with fine accuracy and a high data rate. Such a device can be used in conventional research laboratories, industrial production lines, flow reactors, and others where it can log the state of the process to ensure repeatability and operational consistency."

The team created two prototypes for the Smart Stirrer: The first combines a Microchip ATmega328P microcontroller with an RN4871 Bluetooth module; the second uses an all-in-one Nordic nRF52840 system-on-chip. "The first implementation benefits from an easy-to-program Arduino-compatible environment," the team notes, "the second provides an all-in-one system with an advanced Bluetooth 5 protocol, TX Power 8 dB, 64x faster 32-bit CPU, and 10-fold lower energy consumption."

As well as the microcontrollers, the Smart Stirrer includes a range of modular and stackable sensors including an "inertia module" with three-axis accelerometer, gyroscope, and magnetometer, an ambient light sensor, a thermistor, and a conductivity recorder — the latter using two external copper-plated electrodes. Power comes from a 36mAh coin-cell battery or a rechargeable lithium-polymer battery capable of transmitting 100 hours of data between charges. The data, meanwhile, are received on a Raspberry Pi 3 Model B+ single-board computer.

"In contrast to the commercial system such Gate Scientific that only operates in link with proprietary hotplate (with market price above $2,000), the presented device comprises affordable solution, and an open-source programming platform for a customizable functionality such as power mode, sensors used, sensors resolution, sampling rate, and data transfer rate," the team concludes. "The application of the Smart Stirrer was demonstrated in acid-base titration, and oscillating reaction."

"Additionally, it was shown that the Smart Stirrer can be used for a qualitative evaluation of the viscosity thus making this device a low-cost alternative to the existing solutions. The sensors demonstrated could form a platform for digitizing chemistry in research laboratories as well as industrial manufacturing. Connecting stirrers into the networks, Internet of Things, and wireless power will expand its application even further."

The team's work has been published under closed-access terms in the journal ACS Sensors, while the board designs and software are available under an unspecified open licence on the project's GitHub repository.