An inexpensive, versatile, compact, programmable temperature controller and thermocycler for simultaneous analysis and visualization within a microscope

Microfluidic Lab on a Chip (LOC) devices are key enabling technologies for research and industry due to their compact size, which increases the number of integrated operations while decreasing reagent use. Common operations within these devices such as chemical and biological reactions, cell growth, or kinetic measurements often require temperature control. Commercial temperature controllers are constrained by cost, complexity, size, and especially versatility for use in a broad range of applications. Small companies and research groups need temperature control systems that are more accessible, which have a wide applicability. This work describes the fabrication and validation of an inexpensive, modular, compact, and user-friendly temperature control system that functions within a microscope. This system provides precise temperature acquisition and control during imaging of any arbitrary sample which complies with the size of a microscope slide. The system includes two parts. The first part is a compact and washable Device Holder that is fabricated from high-temperature resistant material and can fit securely inside a microscope stage. The second part is a robust Control Device that incorporates all the necessary components to program the temperature settings on the device and to output temperature data. The system can achieve heating and cooling times between 50 °C and 100 °C of 32 s and 101 s, respectively. A Bluetooth enabled smartphone application has been developed for real-time data visualization. The utility of the temperature control system was shown by monitoring rhodamine B fluorescence in a microfluidic device over a range of temperatures, and by performing a polymerase chain reaction (PCR) within a microscope. This temperature control system could potentially impact a broad scope of applications that require simultaneous imaging and temperature control.