Micro-Fluidic Channels with Integrated Ultrasonic Transducers

This paper describes the work done in an attempt to integrate ultrasonic sensors in micro-fluidic channels. We have developed a system with fluidic channels having embedded zinc oxide transducers. A zinc oxide film is deposited on a glass substrate and is sandwiched between two electrodes. The transducers made are found to resonate at 400 MHz in thickness mode. The channels are made both from PDMS using a silicon master and from glass. These channels are aligned on top of the transducer forming a narrow path for fluid flow. The fluid of interest is pumped in the microchannels by means of a syringe pump and pulse echo measurements are done with the necessary circuitry. This paper will also show the results of the first experiments on mixing induced by the transducer and the measurement of physical dimensions, temperature of fluid in the channel using broad band pulse echo techniques. Index Terms micro-fluidics, cMUT, ultrasonic transducer, temperature sensing, mixing.