Tunable adhesion of an elastic pillar by pressurizing inner cavity

This work studies the effect of a cavity with inner pressure on the adhesion of circular pillars with a flat tip in contact with a rigid smooth surface. The inner cavity of pillars is pressurized positively before the contact. The effect of the cavity on the adhesion is examined for different cavity diameters and different membrane thicknesses over the cavity. The shape of the tip of the pillars is changed in accordance with the cavity dimension and the positive cavity pressure, which allows the change of an adhesive contact type from a flat-punch adhesive contact to a spherical adhesive contact that results in tunable adhesion strength of circular pillars. The results demonstrate that having an inner cavity reduces the adhesion, where the cavity diameter is more effective than the membrane thickness over the cavity on the reduction of the adhesive force. Applying pressure to the inner cavity of the pillars changes the sphericity, which alters the adhesive force accordingly. The sphericity 0.1 almost has no effect on the tunable adhesion strength, where the higher sphericity results in the reduction of the adhesive force from high adhesive force to low adhesive force linearly with a tunable efficiency between 95% and 98%.