Micromachined Arrayed Capacitive Ultrasonic Sensor/Transmitter with Parylene Diaphragms

Abstract

Following our previous report in which a capacitive ultrasonic sensor featuring a polymer Parylene diaphragm was developed by the micromachining technique, in the present study, an arrayed device comprising 5×5 sensors/transmitters was fabricated and characterized. In addition to the durability and high sensitivity due to polymer nonbrittleness and flexibility, merits attributable to Parylene, such as biocompatibility, chemical resistivity, complementary metal oxide semiconductor (CMOS) compatibility, and conformal deposition, are expected to be achieved in the future. The dispersion of sensitivity and resonant frequency of the individual sensors in the developed arrayed device was experimentally investigated. The electrical scanning of receiving directivity was performed using the arrayed device based on the delay-and-summation principle. A wide scanning angle of at least 50° was achieved. Each developed sensor was activated as a transmitter by applying an impulsive high voltage. The transmitted waveform was detectable as far as 1,000 mm away. The ultrasound was transmitted over a wide direction ranging from θ=-80 to 80°. The possibility of the electrical scanning of transmitting directivity was preliminarily confirmed using the arrayed device.