When society collapses, accidents can happen. Whether taking a crossbow bolt in the shoulder after being mistaken for a zombie or enduring a nasty run-in with barbed wire while escaping invaders, stopping internal bleeding fast will be key. Since the aliens nuked all the hospitals, surgery is out of the question, so you'll need a backup in a pinch. DARPA's injectable polymer foam can do the trick. Shoot the expandable foam in your gut to stanch bleeding and buy yourself some time until you can find a non-zombified physician.