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Laser-Induced Spallation of Microsphere Monolayers

The detachment of a semi-ordered monolayer of polystyrene microspheres adhered to an aluminum-coated glass substrate is studied using a laser-induced spallation technique. The microsphere-substrate adhesion force is estimated from substrate surface displacement measurements obtained using optical interferometry, and a rigid-body model that accounts for the inertia of the microspheres. The estimated adhesion force is compared with estimates obtained from interferometric measurement of the out-of-plane microsphere contact resonance. Reasonable agreement is found between the two experiments. Scanning electron microscope images of detached monolayer regions reveal a unique morphology, namely, partially detached monolayer flakes composed of single hexagonal close packed crystalline domains. This work contributes to an improved understanding of microsphere adhesion and demonstrates a unique monolayer delamination morphology.