Mechanical Probing of Icelike Water Monolayers

Direct measurements of the normal force interactions between a mica-tungsten contact pair at various humidity levels reveal the presence of repulsive forces at about 0.5 nm before intimate contact. Such repulsive interactions begin to appear above 20% RH and are fully developed in the range of 38-45% RH. Using the DMT model of contact, a reduced elastic modulus of approximately 6.7 GPa is extracted from these repulsive interactions and attributed to the presence of icelike water on mica at room temperature. The collapse of such structures was also inferred from the measurements.