Whisker shape changes induced by touch
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We study why whiskers of land mammals are approximately conical by considering a tapered whisker under contact with an object. We convert the Euler-Bernoulli quasi-static equation into a boundary-value equation and analyze it using dynamical system theory. The equation has two solutions, one stable and one unstable, that coalesce in a saddle-node bifurcation. Beyond the bifurcation, the whisker slips-off. Slip-off does not occur for cylindrical hairs for realistic parameters. We suggest that slip-off events code radial distances of objects far from the whisker base. Experimental results show that conical whiskers can sweep pass textures in a series of stick-slip events, but cylindrical hairs are stuck.