title: Measurements of interface stress of silicon dioxide in contact with water-phenol mixtures by bending of microcantilevers.
abstract: We use the bending of silicon microcantilevers to measure changes in mechanical stress at interfaces between phenol-water mixtures and SiO(2). The curvature of the microcantilever is measured by an optical system that combines a rapidly scanning laser beam, a position-sensitive detector, and lock-in detection to achieve a long-time stability on the order of 6 mN m(-1) over 4 h and a short-time sensitivity of better than 1 mN m(-1). Thermally oxidized Si shows the smallest changes in interface stress as a function of phenol concentration in water. For hydrophilic SiO(2) prepared by chemical treatment, the change in interface stress at 5 wt % phenol in water is larger than that of thermally oxidized Si by -60 mN m(-1); for SiO(2) formed by exposure of the silicon microcantilever to ozone, the change in surface stress is larger than that of thermally oxidized Si by -330 mN m(-1).
authors.affiliation: Center of Advanced Materials for the Purification of Water with Systems, Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois 61801, USA. xzhang9@uiuc.edu
authors.forename: Xijing
authors.initials: X
authors.lastname: Zhang
authors.forename: David G
authors.initials: DG
authors.lastname: Cahill