Compliant Needle Vibration Cutting of Soft Tissue

This work investigates the performance of a novel compliant needle for cutting tissue. The novel cutting geometry transfers axial vibration to transverse motion at the tip. The cutting edge of the geometry is defined in terms of the time-dependent inclination and rake angle. Finite element analysis was performed to determine the compliant geometry effect on the axial vibration modes of the needles. An ultrasonic transducer is used to apply the axial vibration. An ultrasonic horn was developed to increase the amplitude of vibration. Experiments were performed to determine the effectiveness of the compliant needle geometry. The motion of the compliant needle is measured with a stereomicroscope. The two compliant geometries developed transverse motion of 4.5 mu m and 16.0 mu m. The control needle with fixed geometry developed no measured transverse motion. The insertion force was recorded for two different compliant geometries and a control geometry inserted into a polyurethane sheet. The puncture force of the control needle with applied vibration and the two compliant needles was up to 29.5% lower than the control insertion without applied vibration. The compliant needles reduced the friction force up to 71.0%. The significant reduction of the friction force is explained by the compliant needles' ability to create a larger crack in the material because of their transverse motion.