Thin-slots Machining of Compliant Needles for Vibration-assisted Medical Insertion

This paper presents a geometric analysis modeling and control of micro-slots manufacturing for compliant needles fabrication and biomedical applications. In medical applications, the insertion accuracy of medical needles is closely related with the insertion forces encountered during the relative motion between needle and tissue. This paper presents a new design of compliant needle featured by 4-bevel tip and shaft slots for vibratory needle insertion, whose capability in reducing insertion force has been demonstrated in our earlier works. The effects of the design variables of the slots on needle tip vibration pattern are studied using harmonic analysis with a focus on slot width and slot depth. This paper presents a method of using harmonic analysis to identify the effects of the design variables of the slots on needle tip vibration pattern with a focus on slot width and slot depth. Based on the analysis results, an analytical model is presented and validated for accurate calculation of slot depth in the EDM-based (electrical discharge machining) fabrication process. To use slot width to fine tune the tip vibration, a methodology involving additional electrode motions after initial slot cutting is proposed to increase slot width. This paper provides practical design and manufacturing guidance for vibration-assisted medical insertion devices. Examples and experimental results are presented in the paper for demonstration and validation. The presented geometric analysis model and manufacturing techniques can be used for micro-slots fabrication and biomedical applications.