Microwave-Microfluidic Sensor in Hybrid 3-D Printing and Laminate Technology for Chemicals Monitoring from Differential Reflection

A novel microwave-microfluidic sensor for liquid chemicals monitoring is proposed featuring low liquid volume, high sensitivity, and low port count. The sensor is constructed as an open-ended broadside-coupled-line section with a liquid channel between the strips. Applying differential excitation to the sensor leads to most of the associated electric field being enclosed within the channel, and thus high sensitivity on the measured samples electrical properties is obtained. Therefore, the information about the tested liquid can be extracted solely from the one-port-differential reflection coefficient over a broad frequency range after calibration. A hybrid 3-D printing and laminate technology is employed for the realization of an exemplary sensor to ensure good electrical and mechanical performance. The concept is verified by measurements of a set of alcohols for which the reference-normalized absolute percent error is below 10% to 15 % in the 0.2 GHz to 15 GHz range.