A THEORETICAL-MODEL FOR LASER CLEANING OF MICROPARTICLES IN A THIN LIQUID LAYER

A theoretical model for removal of tiny particles from solid surface b y laser cleaning with a thin liquid layer is established by taking adh esion force and cleaning force into account. When pulsed laser irradia tes on the solid surface coated with a thin liquid film, a sheet of li quid near the liquid/substrate interface can be superheated through th ermal diffusion. The rapid growth of vapor bubbles inside the superhea ted liquid can generate transient stress wave with high pressure, larg e enough to expel micron and sub-micron particles from the contaminate d surface. Through calculating adhesion force and cleaning force, the cleaning threshold of laser fluence can be predicted from this theoret ical model and the difference between cleaning force and adhesion forc e increases with increasing of laser fluence, leading to higher cleani ng efficiency.