Comparison of performance of ultrasonic surgical cutting devices incorporating PZT piezoceramic and Mn:PIN-PMN-PT piezocrystal

Bolted Langevin-style Transducers (BLT) are widely adopted in ultrasonic surgical devices. A BLT is normally comprised of a stack of piezoelectric Pb(Zr
x
Ti
1-x
)O
3
(PZT) rings. Recently, piezoelectric single crystal material Mn-doped Pb(In
1/2
Nb
1/2
)O
3
-Pb(Mg
1/3
Nb
2/3
)O
3
- PbTiO
3
(Mn:PIN-PMN-PT) has emerged as a potential alternative. Differently from PZT, where a trade-off in material properties is necessary, Mn:PIN-PMN-PT crystal simultaneously exhibits high piezoelectric coefficient, d
ij
, electromechanical coupling coefficient, k
ij
, and mechanical quality factor, Q
m
. As a result of the higher efficiency, lower electromechanical losses and higher energy density of the piezocrystal material, there is potential for designing smaller ultrasonic devices incorporating Mn:PIN-PMN-PT in BLTs. A stepped shape horn with a thin and rounded blade, forming a surgical tip, was tuned to its 1
^st
longitudinal mode (L1) at around 20 kHz. Equivalent tips were then attached to the two BLTs, one incorporating the piezoceramic and one employing the piezocrystal material. The full devices were therefore tuned to L2 at 20kHz. The two devices were also excited in the L6 mode at around 60 kHz to investigate the frequency effect on the achievable displacement amplitude at the blade tip. Experimental results show that the Mn:PIN-PMN-PT driven surgical device achieved higher displacement amplitude for the same applied voltage, as a result of the higher power density of the piezocrystal material.