Heat transfer time determination based on DNA melting curve analysis

The determination of the physical properties of fluids—such as the thermal characteristics, which include heat transfer time (Δt)—is becoming more challenging as system sizes shrink to micro- and nanometer scales. Hence, knowledge of these properties is crucial for the operation of devices requiring precise temperature (T) control, such as polymerase chain reactions, melting curve analysis (MCA), and differential scanning fluorimetry. In this paper, we introduced a flow-through microfluidic system to analyze thermal properties such as Δt among samples and the sidewall of a silicon chip using microscopic image analysis. We performed a spatial MCA with double-stranded deoxyribonucleic acid (dsDNA) and EvaGreen intercalator, using a flow-through microfluidic chip, and achieved a T gradient of ≈ 2.23 K mm⁻¹. We calculated the mean value of Δt as ≈ 33.9 ms from a melting temperature (T_M) location shift along the microchannel for a variable flow rate. Our system had a T resolution of ≈ 1.2 mK pixel⁻¹ to distinguish different dsDNA molecules—based on the T_M location within the chip—providing an option to use it as a high-throughput device for rapid DNA or protein analysis.