A multi-modal miniature surface forces apparatus (µSFA) for interfacial science measurements
Article [Author's Original]
Is part ofLangmuir ; vol. 35, no. 48, pp. 15433-16070.
Publisher(s)American Chemical Society
Advances in the research of intermolecular and surface interactions result from the development of new and improved measurement techniques and combinations of existing techniques. Here, we present a new miniature version of the Surface Force Apparatus – the micro-SFA (µSFA) – that has been designed for ease of use and multi-modal capabilities with retention of the capabilities of other SFA models including accurate measurement of surface separation distance and physical characterization of dynamic and static physical forces (i.e., normal, shear, and friction) and interactions (e.g., van der Waals, electrostatic, hydrophobic, steric, bio-specific). The small physical size of the µSFA makes it portable and suitable for integration into commercially available optical and fluorescence light microscopes, as demonstrated here. The large white-light optical path entry and exit ports make it ideal for concurrent force measurements and spectroscopy studies. Examples of the use of the µSFA in combination with surface plasmon resonance (SPR) and Raman spectroscopy measurements are presented. Due to the short working distance constraints associated with Raman spectroscopy, a new interferometric technique was developed and applied for calculating the inter-surface separation distance based on Newton’s Rings. The introduction of the µSFA will mark a transition in SFA usage from primarily physical characterization to physical characterization with combined and concurrent in situ chemical and biological characterization, including (but not limited to) adsorption of selected molecules, determination of surface species and morphology, and (bio-)molecular binding kinetics.