Adhesion Hysteresis from Interdependent Capillary and Electrostatic Forces

Abstract

Adhesion hysteresis commonly occurs at the nanoscale in humid atmospheres, yet mechanisms are not entirely understood. Here, the adhesion forces between silicon (111) oxide surfaces and tungsten oxide probes have been examined using interfacial force microscopy. The results show that the adhesion forces during surface approach and separation differ not only in magnitude but also in mechanism, arising mainly from capillary and electrostatic forces, respectively. Surface contact leads to a transient intersurface potential on dewetting. This mechanism of adhesion hysteresis differs in not relying singly on hysteretic wetting. Furthermore, by biasing the surfaces, nonadditivity is demonstrated between the capillary and electrostatic forces at the onset of condensation. These results hold important implications on the interpretation of force in nanoprobe geometries in humid atmospheres.

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“…Choi et al demonstrated that upon conventional pipetting, droplets pick up a spontaneous electrical charge [12]. At the nanoscale, charging by receding water menisci has been shown to be the cause of adhesion hysteresis [13]. Recently, several groups evaluated the potential of droplet surface charging for the purpose of energy harvesting from sliding or deforming rain drops, ocean waves and rotating partially filled containers [14][15][16][17].…”

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