Abstract
This research investigates the chip flow angle in tissue oblique cutting. In needle insertion, the chip flow angle determines the contact length of tissue on the needle tip surface and is critical for the force model and cutting efficiency in needle biopsy. Needle biopsy is a common medical procedure where tissue is cut and removed from the body using the sharp edge of the needle tip. Experiments are performed on bovine liver and phantom gel to determine the chip flow direction. The results show that the tissue flow direction differs from the Stabler's rule. Three mathematical models for contact length are derived to explain contact length under varying conditions.