Persistent Rocking Motion of Microparticles Under Acoustic Tone-Burst Base Excitation

Abstract

In this work the rocking vibrational response of individual micro-spherical toner particles under a noncontact tone-burst (gated-harmonic) excitation was studied. An unexpected ringing motion which persisted for long periods of time with minimal damping was observed and reported. It was observed that a weak bond, as a result of suspected pure intermolecular (van der Waals) interactions, led to detectable natural frequencies and persistent rocking motion (ringing) observed while the response of a particle with a stronger bond followed closely the substrate surface motion without a relative vibrating motion. For toner particles with a mean diameter of 8.9 μm, a beat phenomenon vibrational behavior was also observed and reported at the tone-burst central frequency of 500 kHz, which was very close to the most dominant observed natural frequency of the particle’s rocking motion of 501.5 kHz. Strong natural frequencies of the rocking motion were observed in three groups lying in the range of 450–525 kHz. The associated work of adhesion for these three observed natural frequency groups was calculated and found to lie in the range between 65 and 82 mJ/m2. The ringing mechanism observed and reported here could lead to the development of a very accurate adhesion characterization technique for individual micro-particles. The approach involves no particle detachment and thus allows the studying of the effects of environmental changes on the same bond without bond breakage.