Micromilling of microbarbs for medical implants

Successful application of many implantable medical devices often depends on the technique used for attaching the devices to living tissue. Although mechanical attachment techniques that use micro-scale piercing elements are very promising, the fabrication of the micro-scale piercing elements poses considerable challenges. In this paper, the use of the mechanical micromilling process for fabrication of micro-scale piercing elements (microbarbs) from biocompatible materials is investigated. Two micro-scale milling tools with custom geometries are used during the fabrication. To gain an understanding of the process conditions on the performance metrics of micromilling forces, surface roughness, and burr formation, a design of experiments study is performed on polymethyl methacrylate (PMMA). The geometric capability of the process is demonstrated by fabricating PMMA microbarbs with different sizes (widths from 68 to 174 mu m), edge sharpnesses (60 degrees and 90 degrees included angles), and heights (from 84 to 460 mu m). The capability to micromill a variety of biocompatible materials is demonstrated by creating microbarbs from non-biodegradable 304 stainless steel and PMMA, from bioresorbable polylactic acid (PLA), and from a fibrin based plastic. It is concluded that the micromilling process can be used for effectively fabricating arrays of microbarbs. (c) 2007 Elsevier Ltd. All rights reserved.