Evaluation of PIC 181 and Mn:PIN-PMN-PT thickness extensional rings for use in power ultrasonic devices for minimally invasive surgery

High-Q PIC 181 hard piezoceramic and high-k Mn:PIN-PMN-PT piezocrystal thickness extensional rings have been compared for use in the actuation of an ultrasonic scalpel for robotic endo-surgery. Measured material properties have been verified with both finite element analysis and laser vibrometry, to assess the materials' suitability for high power devices. Measured material properties have been verified with both finite element analysis and laser vibrometry, to assess material's suitability for high power devices. Measurements have shown a $k_{t}=0.25$ and $Q_{m}=2200$ , and $k_{t}=0.62$ and $Q_{m}=1100$ , for PIC 181 and Mn:PIN-PMN-PT respectively. Conventional bolted Langevin-style transducers (BLTs) have been successfully designed and built to resonate at 20 kHz for both piezomaterials. Modal parameters and performance have been modelled in FEA and measured via laser doppler vibrometry. When devices were excited with $\mathbf{50\ V}_{rms}$ at L1 a displacement of: $\mathbf{8}\ \mu\mathbf{m}$ and $\mathbf{7}\ \mu \mathbf{m}$ was measured for PIC-181 and Mn:PIN-PMN-PT BLTs respectively. Results suggest that a similar resonant frequency can be achieved with a shorter and equally functional device excited by Mn:PIN-PMN-PT piezocrystals.