High-performance planar ultrasonic tool based on d₃₁-mode piezocrystal

Ultrasonic scalpels based on the conventional mass-spring configuration of piezoelectric transducers are widely used in procedures such as oral, hepatic, and pancreatic surgery. However, the weight and self-heating of this configuration are weaknesses. To address these, an alternative approach can be adopted which utilizes a planar configuration of a cutting blade to which piezoelectric drive components are bonded directly. This paper details the design and characterization of three such planar scalpels, made of surgical-grade stainless steel and silicon. These tools operate in the d31 mode configuration, utilizing relaxor-PT single-crystal binary (PMN-PT) and manganese-doped ternary (Mn:PIN-PMN-PT) composition piezoelectric materials. The scalpels, with shapes resembling a dagger, are able to produce longitudinal displacements >5 μm when driven with 20 V(p-p) at their respective resonant frequencies, 73 and 106 kHz. It is observed that both blade and piezoelectric materials significantly affect the performance of the planar tool. The mechanical quality factor, Q(M), of PMNPT based silicon tool is ~1500 in air compared with ~350 for its stainless steel counterpart, and the use of Mn:PIN-PMNPT further increases the Q(M) to ~2400. Furthermore, the study on the effect of various tissue-loading conditions suggest that skin is the most difficult tissue to penetrate, consequently leading to significant reduction in the tool's efficiency and therefore demanding high-Q(M) tools.