How dry are dried samples? Water adsorption measured by STM

Influence of random roughness on the adhesion between metal surfaces due to capillary condensation

“…Another explanation for the force deviation originates from scanning tunneling microscopy ͑STM͒ studies, which indicated that below 60% RH the water film on Au is not closed but droplet formation takes place ͑even for RH as low as 15%͒. 12 The average height of droplets ϳ5 -10 nm did not decrease much with lower RH, while the amount and size of droplets was decreased. 12 The total adhesion force can be divided into a capillary force and an interfacial tension force due to surface tension acting tangentially to the interface along the contact line with the solid body.…”

“…12 The average height of droplets ϳ5 -10 nm did not decrease much with lower RH, while the amount and size of droplets was decreased. 12 The total adhesion force can be divided into a capillary force and an interfacial tension force due to surface tension acting tangentially to the interface along the contact line with the solid body. 11 For the relatively smooth films, the theory prediction for flat surfaces gives an approximate upper limit for the force F up =4 ␥R s cos͑ ͒ Ref.…”

“…For the contact angle of water onto Au surfaces of 70 o Ref. 12 we obtain for R s =50 m, F up = 1.5ϫ 10 4 nN. With increasing roughness, surfaces can be more hydrophobic, 13 leading to reduced capillary force.…”

Evidence for capillarity contributions to gecko adhesion from single spatula nanomechanical measurements

“…Early studies of gecko adhesion invoked capillary forces (8,11) due to liquid bridges, whereas a recent investigation (12) rejected the contribution of capillarity and indicated that van der Waals forces alone can give rise to the high adhesion observed. Even a monolayer of water, always present on surfaces under normal atmospheric conditions (13,14), can significantly influence the attraction between two surfaces (15)(16)(17)(18)(19)(20). In view of the recent results obtained by Autumn et al (12), the controlling adhesion mechanism remains inconclusive.…”

Laser Response of a Quartz Crystal Microbalance: Frequency Changes Induced by Light Irradiation in the Air Phase

“…Quantitative analysis using STM has demonstrated that water molecules adsorbed on a gold film sputtered on a glass plate even at low relative humidity. 10 In situ observation of the water desorption process from the gold electrode has also been carried out with the QCM.…”