Experimental Testing of Micro-Particles Collision

Abstract

We performed experiments on the collisions of micrometer scale (200–300 μm) stainless steel (316 and 440 C) particles and studied the interaction properties and the coefficient of restitution. We used a novel experimental apparatus to enable non-contact measurements based on laser excitations/detection and high-speed photography. The colliding particles were aligned in v-shaped grooves on a silicon wafer, fabricated using anisotropic etching techniques. We used high-power lasers to excite one of the particles (striker), and to control the impact velocity with high repeatability. The motion of the striker particle was triggered by partial laser ablation of its surface. The displacements of the particles involved in the collision were recorded with a high-speed camera mounted on an optical microscope. The particle velocities were obtained from the recorded images using digital image correlation. We calibrated the setup by tracking the dynamic excitation of single particles, and tested collisions between two particles. This study introduces a new experimental approach to understand the fundamental dynamic response of micro-particle collisions, and to test the limits of validity of the Hertzian interaction law.

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