Barbs make porcupine quills into nasty needles : Nature News & Comment

Microstructured barbs on the North American porcupine quill enable easy tissue penetration and difficult removal

Why Porcupine Quills Slide in with Ease But Come Out with Difficulty

Adirondack Wildlife: The Porcupine Gives Birth - - The Adirondack Almanack

Quill You Be Mine?

Porcupine Facts - Animal Facts Encyclopedia

Quill You Be Mine?

Microstructured barbs on the North American porcupine quill enable easy tissue penetration and difficult removal

Porcupines Writing for Nature

What Porcupines Can Teach Engineers

How porcupine quills work : r/Damnthatsinteresting

Medical marvels borrowed from nature itself including porcupine quills for stitches

Why A Snoot-full Of Porcupine Quills Can Be A Serious Matter – Feathered Photography