Application of asymmetric surface fabricated by femtosecond laser process for microparts feeding

Femtosecond laser technology has the ability to form stable minute grating structures on various materials, including silicon wafers and stainless steel. By forming a periodic structure on a surface of sliding parts, the tribology characteristics can be improved, because the effect of adhesion decreases. Application of a double-pulsed femtosecond laser irradiation technique can generate periodic structures with asymmetric profiles. We previously showed that microparts, such as ceramic chip capacitors and resistors, can be fed along asymmetric surfaces using simple planar symmetric vibrations. Microparts move in one direction because they adhere to these surfaces asymmetrically. In this study, we tested the ability of an asymmetric surface microfabricated by a double-pulsed femtosecond laser irradiation technique to feed 0402-type capacitors (size, 0.4 x 0.2 x 0.2 mm; weight, 0.1 mg). Among the characteristics evaluated were the differences in profiles of the two inclined surfaces, the effect of decreased adhesion, the coefficient of friction in both the forward and the backward directions, and the friction angle of the 0402-type capacitors in both directions. Using the results of feeding experiments of these capacitors, we assessed the relationship between driving frequency and feeding velocity.