3.3. Interferometry measurement of the adsorption film
To estimate adsorption film thickness, off-line measurement was carried out using a two-medium approach, as schematically shown in Fig. 10. After a test, the specimen slider was unloaded and thoroughly rinsed with water to remove unbound protein. After fully dried, the slider was then mounted against the disc with a specified wedge gap. The optical path lengths were measured in two different media, 1 and 2, which filled the gap. For the same gap thickness hf, optical path lengths were determined as,