Measuring shear strength of soft-tissue adhesives

A method for evaluating strength of adhesives for hydrogels and soft tissues is presented. Quantitative measurements of shear strength for applications in tissue engineering and biomedicine are performed in torsion using a rheometer. Small, disk shaped specimens of soft biological tissues and/or hydrogels (8 mm diameter, 1-2 mm thick) are mounted onto rheometer tools and then bonded together using the adhesive to be tested. The torsional loading geometry imposes simple shear without deforming the planar adhesive bond, in contrast to the lap-shear test. It retains the advantages of the napkin ring test while reducing artifacts due to cutting and handling soft specimens. The method is demonstrated by measuring the shear strength of two types of biomedical adhesives (cyanoacrylate and polyethylene glycol-based) between model hydrogels (gelatin) and tissues (corneal stroma and skin).