Attachment/detachment hysteresis of fiber-based magnetic grabbers

Abstract

We developed an experimental protocol to analyze the behaviour of a model fiber-based magnetic grabber. A fiber is vertically suspended and fixed to the substrate by its upper end. A magnetic droplet is attached to the free end of the fiber and when a permanent magnet approaches the droplet, the fiber is forced to bow and finally jumps to the magnet. It appears that one can flex the micro-fibers by very small micro or even nano-Newton forces. Using this setup, we discovered a hysteresis of fiber attachment/detachment: the pathway of the fiber jumping to and off the magnet depends on the distance between the magnet and the clamped end. This phenomenon was successfully explained by the Euler–Benoulli model of an elastic beam. The observed hysteresis of fiber attachment/detachment was attributed to the multiple equilibrium configurations of the fiber tip placed in a dipole-type magnetic field.