In this topic, we aim to innovate the theory, design and fabrication of low-power consumption and high-performance micromachined ultrasonic transducers (MUTs), including capacitive micromachined micromachined ultrasonic transducers (CMUTs) and piezoelectric micromachined ultrasonic transducers (PMUTs). We are further exploring their applications in potable ultrasonic imaging, non-invasively monitoring of vital physiological signals, ultrasonic 3D biometrics and 3D ultrasonic gesture recognition.