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. 2012 Dec 10;109(52):21289–21294. doi: 10.1073/pnas.1216441109

Fig. 3.

Fig. 3.

The reduced penetration force of the natural porcupine quill can be replicated in synthetic polyurethane quills. (A and B) FE-SEM images show the barbless and barbed synthetic PU quills. (Scale bar: 100 μm.) (C) The forces required to penetrate the PU quills into muscle tissue to 4 mm-depth (see Fig. S3B for experimental details). The mean values are shown with SD (n = 5, Student t test at the level of 95% significance). The box plot whiskers are set to ±1.2 SD. (D) Representative force versus extension plots from the penetration–retraction tests of the natural quill and replica molded PU quills performed in muscle tissue. (E) Fabricated quill-mimetic needle. (F) The forces required to penetrate the fabricated barbed/barbless needles into a model of human skin. The data shows the mean penetration force with SD (n = 3, each needle was used at least four times, Student t test at the level of 95% significance). The two “X”s in box plots of C and F indicate first and 99th percentiles.