A Portable Microfluidic Platform with Integrated Flexible Temperature Control and Real-Time Visualization

Many biochemical reactions performed in microfluidic systems, such as nucleic acid amplification and enzymatic assays, require precise, compact, portable, and programmable temperature control. However, existing platforms are often limited by high cost, bulkiness, and poor integration with real-time visualization. Here, we present a portable microfluidic platform that integrates a high-precision thermal regulation module with a smartphone-based imaging interface, enabling real-time sample monitoring under programmable temperature protocols. An STM32 microcontroller with a positional PID algorithm achieves a steady-state temperature accuracy of ±1.5 °C and adjustable heating and cooling rates of 0.1–5 °C/s, supporting both constant-temperature and thermal-cycling modes. As a representative application, we use this platform to evaluate the thermal stability of water-in-oil single-emulsion droplets under programmable heating. In this system, the oil phase was a mixture of silicone oil and RSN-749, and the mass ratio of the two components was varied to examine its effect on droplet stability. Our results suggest that, under the tested conditions, droplet coalescence tended to be more pronounced during temperature ramping than during isothermal holding. For this oil–surfactant formulation, the coalescence ratio remained below 4% across 20–95 °C. Therefore, this low-cost, user-friendly platform offers a practical analytical tool for temperature-controlled microfluidic reactions and thermal stability assessment, with potential for future point-of-care diagnostic workflows.