title: Microstructured barbs on the North American porcupine quill enable easy tissue penetration and difficult removal.
abstract: North American porcupines are well known for their specialized hairs, or quills that feature microscopic backward-facing deployable barbs that are used in self-defense. Herein we show that the natural quill's geometry enables easy penetration and high tissue adhesion where the barbs specifically contribute to adhesion and unexpectedly, dramatically reduce the force required to penetrate tissue. Reduced penetration force is achieved by topography that appears to create stress concentrations along regions of the quill where the cross sectional diameter grows rapidly, facilitating cutting of the tissue. Barbs located near the first geometrical transition zone exhibit the most substantial impact on minimizing the force required for penetration. Barbs at the tip of the quill independently exhibit the greatest impact on tissue adhesion force and the cooperation between barbs in the 0-2 mm and 2-4 mm regions appears critical to enhance tissue adhesion force. The dual functions of barbs were reproduced with replica molded synthetic polyurethane quills. These findings should serve as the basis for the development of bio-inspired devices such as tissue adhesives or needles, trocars, and vascular tunnelers where minimizing the penetration force is important to prevent collateral damage.
authors.affiliation: Division of Biomedical Engineering, Department of Medicine, Center for Regenerative Therapeutics, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Woo Kyung
authors.initials: WK
authors.lastname: Cho
authors.forename: James A
authors.initials: JA
authors.lastname: Ankrum
authors.forename: Dagang
authors.initials: D
authors.lastname: Guo
authors.forename: Shawn A
authors.initials: SA
authors.lastname: Chester
authors.forename: Seung Yun
authors.initials: SY
authors.lastname: Yang
authors.forename: Anurag
authors.initials: A
authors.lastname: Kashyap
authors.forename: Georgina A
authors.initials: GA
authors.lastname: Campbell
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Wood
authors.forename: Ram K
authors.initials: RK
authors.lastname: Rijal
authors.forename: Rohit
authors.initials: R
authors.lastname: Karnik
authors.forename: Robert
authors.initials: R
authors.lastname: Langer
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Karp
mesh_terms: D000268:Adhesiveness; D000825:Animal Structures / Q000033:anatomy & histology* / Q000502:physiology*; D000818:Animals; D001696:Biomechanical Phenomena; D006801:Humans; D009132:Muscles / Q000502:physiology*; D009656:North America; D010539:Permeability; D046328:Porcupines / Q000033:anatomy & histology*; D011200:Poultry; D012879:Skin Physiological Phenomena; D034421:Sus scrofa