title: Operation of astigmatic-detection atomic force microscopy in liquid environments.
abstract: The astigmatic detection system (ADS) based on commercial optical pickup head was demonstrated to achieve a sub-nanometer sensitivity in detecting the vertical movement of an object surface in air. The detection laser spot of the ADS was sub-μm and the detection bandwidth was over 80 MHz. These advantages allow detection of high-frequency mechanical resonance of very small objects, which would have many important applications in nanotechnology. In this work, we optimized the operation conditions of ADS to achieve good sensitivity in aqueous solutions. We demonstrated good contrast and good spatial resolution of cancer cells in water with the optical profilometry mode. We also built an ADS-AFM (atomic force microscopy) for imaging in water. A novel cantilever holder was designed, and the spurious peaks were suppressed down to 26.0% of the real resonance peak. Most importantly, we demonstrated that the ADS-AFM could resolve single atomic steps on a graphite substrate and image soft DNA molecules on mica in water.
authors.affiliation: Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan.
authors.forename: H-S
authors.initials: HS
authors.lastname: Liao
authors.forename: K-Y
authors.initials: KY
authors.lastname: Huang
authors.forename: I-S
authors.initials: IS
authors.lastname: Hwang
authors.forename: T-J
authors.initials: TJ
authors.lastname: Chang
authors.forename: Wesley W
authors.initials: WW
authors.lastname: Hsiao
authors.forename: H-H
authors.initials: HH
authors.lastname: Lin
authors.forename: E-T
authors.initials: ET
authors.lastname: Hwu
authors.forename: C-S
authors.initials: CS
authors.lastname: Chang
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D006108:Graphite / Q000737:chemistry; D018625:Microscopy, Atomic Force / Q000379:methods*; D055620:Optical Phenomena; D013499:Surface Properties; D014867:Water
chemical_list: D000538:Aluminum Silicates; D014867:Water; D006108:Graphite; D004247:DNA; C011934:mica