Vibration study of novel compliant needle used for vibration-assisted needle insertion

Needles are among the most widely used medical devices, and their placement accuracy significantly affects the effectiveness of a treatment and the success or precision of a diagnosis. Vibration-assisted needle insertion is a dynamic insertion technique which can improve needle insertion accuracy by reducing the insertion force. This paper presents the vibration analysis of a novel compliant needle design for vibration-assisted insertion in medical applications. The needle design is featured by its 4-bevel needle tip and micro-slots on the needle shaft. Harmonic analysis was applied to reveal the relationship between slot location and transverse vibration amplitude, and an empirical method was developed to determine the slot locations which lead to maximum and minimum transverse amplitudes. The results were evaluated and validated by actual amplitude measurement of selected needle prototypes. Insertion experiment into tissue phantom was then conducted using these prototypes to investigate how transverse vibration amplitude affect insertion force. It was found that adding transverses vibration of small amplitude to axial vibration had the best outcome. This paper provides useful practical guidelines for design and optimization of needles for vibration-assisted insertion in medical applications and for improvement of insertion accuracy.