ADHESION FORCE MEASUREMENTS USING AN ATOMIC-FORCE MICROSCOPE UPGRADEDWITH A LINEAR POSITION-SENSITIVE DETECTOR

The atomic force microscope (AFM), in addition to providing images on an atomic scale, can be used to measure the forces between surfaces an d the AFM probe. The potential uses of mapping the adhesive forces on the surface include a spatial determination of surface energy and a di rect identification of surface proteins through specific protein-ligan d binding interactions. The capabilities of the AFM to measure adhesiv e forces can be extended by replacing the four-quadrant photodiode det ection sensor with an external linear position sensitive detector and by utilizing a dedicated user-programmable signal generator and acquis ition system. Such an upgrade enables the microscope to measure in the larger dynamic range of adhesion forces, improves the sensitivity and linearity of the measurement, and eliminates the problems inherent to the multiple repetitious contacts between the AFM probe and the speci men surface.