Basic research of ultra-miniature medical ultrasound transducer by hydrothermal method

点击翻译按钮获取中文摘要

Material properties of hydrothermally synthesized PZT poly-crystalline films were measured and relationships between number of deposition and crystal sizes, thickness of films, composition rates were investigated. Crystal size and film thickness grew up proportionally with number of deposition. PZT crystals grew up about 2 μm per one deposition and grew up about 30 μm with 15 times of deposition and film thickness increased to 50 μm. Array type ultrasound probes including 8 elements with 35 μm width, 4mm length, element pitch of 70 μm were fabricated by using hydrothermally synthesized PZT films. It could be confirmed that the probes had high distance resolution without any acoustic matching layer. It was found by measured directivity that element factor was +1-65°, group factor was about +/-10° by driving 8 elements simultaneously. The ultrasound beam could be sector scanned with phased array technique. Needle type miniature hydrophones were fabricated by deposition of PZT film on titanium wires with diameter from 0.2 to 1.0 mm and it was proved that fabricated hydrophone could be used from 1 to 20 MHz. However, peaks and dips could be observed in the frequency characteristics. The frequency of peaks and dips depend on diameter of titanium wire. The hydrophone was fabricated by using tapered titanium wire to suppress the peaks and dips in the frequency characteristics and back echo from the end of titanium wire. Furthermore, we tried to fabricate catheter type ultrasound transducer with thin titanium wire as acoustic wave guide by hydrothermal method.