Adaptive Coupling of Resonators for Efficient Microwave Heating of Microfluidic Systems

An electronically adaptive coupling technique is presented for a microwave microstrip resonator to improve the efficiency of liquid heating in a microfluidic system. The concept is based on feeding the resonator with two synchronized inputs that have a variable phase shift between them. A Wilkinson power divider and phase shifter were designed and fabricated for this purpose. Both simulation and measurement (using chloroform as an exemplar liquid) demonstrated that the adaptive coupling can be used to optimize the heating efficiency of the liquid.