Design and characterization of metallic microfasteners for mechanical adhesion to soft tissues.

Suturing by hand remains the gold standard for the manufacturing of bioprosthetic heart valves (BHVs), which is a time- and skill-intensive process to attach tissue valve grafts to stents. Suturing becomes even more challenging for the assembly of small devices, such as pediatric BHVs. Here, we report the development of a sutureless mechanical adhesion to tissue (MANTIS), a microstructured tissue fastening technology that mediates rapid attachment of rigid materials to compliant biological tissues. Following characterization of BHV tissue wall thickness, we designed 4 distinct MANTIS microfastener geometries that were fabricated in stainless steel foils via a photochemical machining process. Bioinspired microfastener designs mimicked flexure of the praying mantis claw to provide enhanced tissue entrapment upon insertion via controlled buckling. Tissue adhesion testing was performed on individual microfasteners and microfastener arrays, with all 4 MANTIS designs outperforming controls across normal, 0° shear, and 180° peel loading orientations. Overall, MANTIS shows promise as a sutureless adhesive technology for integrating mechanically disparate materials such as tissues and medical device surfaces. STATEMENT OF SIGNIFICANCE: Attaching rigid materials to soft biological tissues is a challenging problem. Current options such as sutures, staples, and chemical adhesives often fail to simultaneously achieve strong, permanent coupling in a rapidly deployable and compact form factor. Here, we designed and characterized a family of microfastener designs which can quickly puncture and interlock with connective tissue fibers to form strong adhesion that can resist multi-directional loads. This approach is reminiscent of VELCRO® and its hook-and-loop principle of operation, though our work also incorporates a "controllable deformation" functionality inspired by the praying mantis claw. We anticipate MANTIS will provide a valuable new solution for a wide range of applications that require reliable and strong attachment of device surfaces to biological tissues.