Focalseal is a polyethylene glycol based synthetic hydrogel. It is FDA approved as a sealant to limit airleak following pulmonary resection. In preclinical use, this type of sealant has also been shown to be effective as a hemostatic adjunct to prevent anastomotic bleeding and to seal other types of closure such as the dura, pancreatic stump, or open wounds. The sealant has two components, a primer and a sealant, and is applied in two steps and then polymerized by the application of a blue-green light (Fig. 1) (Genzyme Biosurgery, Inc. Cambridge, MA). The sealant does not bond covalently to tissue and is degraded by hydrolysis. This kind of sealant is flexible and nontoxic and has many intriguing possible applications as well as some mechanical properties that are essential to understand for safe use.