Laser surface texturing of medical needles for friction control

Surface texturing has been used to create micro-dimples or micro-channels on medical needles to increase the visibility of ultrasound-guided percutaneous procedures. However, micro-features usually increase the friction between the needle and biological tissue. Higher insertion forces lead to patient discomfort and undesired needle placement errors. The present work investigates the friction between the textured needles and soft tissue. The purpose is to understand the friction behaviour between a textured hard surface and soft materials and to identify texture patterns that would minimise the friction of needle insertion without compromising its ultrasound visibility. Laser surface texturing was performed on medical needles to generate an array of micro-channels with a variety of channel widths, area densities, and channel orientations. A set of friction tests was carried out using an especially designed setup for needle insertion. The effects of channel width, area density, and channel orientation on friction force were experimentally investigated. It was found that the tribological characteristics between a textured hard surface and soft tissue greatly depend on the size, density, and orientation of the micro-features.