Design and Experimental Evaluation of Gripping Mechanisms for Automated Sewing of Biological Heart Valves

The production of biological heart valves requires the execution of a planar hand-made stitch (class-201) under strict quality and repeatability constraints. Although this process is still commonly performed manually, the growing shortage of skilled operators makes automation increasingly necessary. Existing automated solutions either operate in three dimensions or rely on conventional sewing technologies and therefore cannot reproduce the required planar stitch configuration. This work addresses this limitation by investigating the thread-management subsystem of an innovative planar sewing system designed for heart valve manufacturing. The subsys-tem performs key operations such as stitch pulling and the transfer of a thread skein through the material while using a non-standard thread source, as opposed to a conven-tional spool. Three alternative mechanisms, based on a common handling principle but employing different gripping strategies, were designed and implemented. The mecha-nisms were integrated into a prototype sewing platform and experimentally evaluated under representative operating conditions. Their performance was qualitatively compared in terms of thread gripping effectiveness, pulling capability, and operational repeatabil-ity. The results highlight the advantages and limitations of each design and identify the most effective solution for reliable skein handling within the automated planar sewing process.