A study on the deliberate use of thermal energy for microfluidic diodicity

In this work consideration is given to the deliberate use of thermal energy for micro one-way valves without moving parts which are one of the most important components in manipulating fluid states within a microfluidic or nanofluidic system allowing the fluid to flow in one direction while blocking it in the opposite direction. However, suitable technologies (e.g., Tesla or diffuser valves) are difficult to integrate and, in addition, featuring very low diodicities ( Di ≤ 2 ). Here it is demonstrated that by using a rather simple design encompassing a narrow central adiabatic section and a steady thermal input very high diodicities may result which for the case of water as working fluid attains a maximum theoretical value Di ≃ 7 which is difficult to overcome for a single phase liquid. The analytical model predicts a Reynolds number which maximizes de diodicity for a given length-to-diameter ratio aspect resulting from the competition between thermal advection and diffusion transport. Computational fluid dynamic simulations were carried out confirming the analytical model.