Ultrasonic heating and temperature measurement in microfluidic channels

► Developed microfluidic channels with integrated ultrasonic transducers. ► Used ultrasound for temperature measurement and heating in microfluidic channels. ► The accuracy of the temperature measurement was 0.1 °C. Microfluidic devices integrated with ultrasonic transducers were developed. Piezoelectric thin film based transducers and capacitive micromachined ultrasonic transducers (CMUTs) were integrated with microchannels. While piezoelectric transducers operated in the vicinity of 400 MHz, the operation frequency of the CMUTs was approximately 50 MHz. Ultrasound generated by the transducers was used for both heating the liquid and sensing the temperature of the liquid inside the channel. The temperature measurement method depends on the time of flight monitoring of the acoustic reflections inside the channel. The method was applied to channels with different heights from 200 μm to 500 μm. The accuracy of the method was found to be 0.1 °C. The measurement bandwidth could be as high as 1 MHz.