Abstract
By peeling of nano-particle (PNP) process, the magnetic nano-particles in an aqueous solution are employed to be locally magnetically controlled for adhering to a substrate surface and removing the material. In order to remove the material on the surface, the touching phenomenon of particle on surface needs to be confirmed. In this study, the touching phenomenon of nano-particle on the substrate surface was experimentally observed in situ the PNP process by our developed optical system applying multi-wavelength evanescent fields. The action forces, such as DLVO force and magnetic force, on the particle were measured by the height Z of the particle from the substrate surface. Fe3O4 particles with the sized range 50-100nm dispersed in the KOH solution (pH value of 10) were employed to be magnetically pulled to approach a silica glass surface by the controllable magnetic field generated by a solenoid coil. During the magnetic field generating, the height Z of nano-particle were measured at the closest approximately 10 nm, in which the DLVO force at measured height Z approximately 0.5-0.9 pN by calculation. To pull the particle touch on the glass surface, the pulling magnetic force on the particle size in range 50-100 nm should be higher than 1 pN approximately.
