Incorporating planar folded front masses in bolted Langevin-style transducers for minimally invasive surgery

The Harmonic ACE (JJ Medical Devices, OH, USA) based on the conventional Bolted-Langevin Transducer (BLT) configuration of piezoelectric transducers is used in robotic surgery due to its fast cutting of soft tissues and improved cut quality. However, the manoeuvrability of the Harmonic Aceh which is the only ultrasonic scalpel compatible with the Da Vinci Surgical System (Intuitive Surgical Inc., CA, USA) is very limited for the surgeon, due to its long shaft and tool-robot configuration. Till now, there is no existing ultrasonic scalpel compatible with the Da Vinci Surgical System EndoWrist instruments. Therefore, the key objective of this work is to create miniaturised ultrasonic instruments to allow greater dexterity than conventional tools. To address this, an alternative approach can be adopted which utilises a planar folded front mass incorporated within BLT configurations with the aim to reduce the overall length of the tool whilst maintaining the amplification gain. The introduction of planar folded (PF) and twice planar folded (TPF) front masses within BLT configurations and after being optimised using design of experiments (DOE) techniques, demonstrate high amplification gains, GA = 90 @ 23 kHz and GA = 92 @ 21 kHz, respectively, and transducer lengths of 58 mm (87% length reduction) and 64 mm (86% length reduction) compared with a 450 mm Harmonic ACE.