Highly modular PDMS microwave-microfluidic chip reactor for MAOS applications

In this work, we introduce a microfluidic chip reactor based on a Complementary Split Ring Resonator (CSRR) for conducting microscale microwave-assisted organic synthesis (MAOS). This microwave-microfluidic chip reactor (µw-µf-CR) is easy to assemble and highly customizable, featuring interchangeable flow cells fabricated on inexpensive PDMS, providing high levels of versatility in terms of manufacturing and design. Various flow cells were designed and explored, offering internal volumes ranging from 2.82 to 6.48 μL and accommodating flow rates between 5 to 8 μL/min. This allows the reaction to be irradiated within a timeframe spanning from seconds to minutes. Remarkably, our setup design bears the potential to operate across a broad range of frequencies (around 2 or 6-12 GHz). Moreover, it provides controllable and efficient heating, reaching temperatures up to 120°C within seconds with a maximum low input power of 4.4 W. Simulations showed an excellent homogeneous heat distribution throughout the flow cell. The applicability of the µw-µf-CR was demonstrated in several organic reactions, where good yields and short reaction times were observed.