A micromachine high frequency ultrasound scanner using photolithographic fabrication

In this paper we describe two new types of transducer assemblies fabricated from polyimide films with photolithography that use a polyimide micromachine (MEMS) actuator to mechanically scan an ultrasound beam. Forward viewing transducers pivoting on cantilever hinges and side scanning transducers tilting on torsion hinges were fabricated on polyimide substrates with tables 1.125 mm and 2.25 mm wide. PZT transducers fabricated on these tables operating at 20 MHz and 30 MHz yielded insertion losses of 20-26 dB and fractional bandwidths of 34-49%. The transducer assemblies driven by MEMS actuators produced sector scans of 45-60 degrees in air at resonant frequencies of 32 to 90 Hz and sector scans in fluid of 6-8 degrees. Real time images of wire phantoms were obtained using a single channel imaging system based on a personal computer platform with LabVIEW (National Instruments Corp., Austin, TX) software.