AFM-study of sticking effects for microparts handling

The purpose of this study was to find a coating for a silicon microgripper, reducing sticking effects for handling microparts under ambient or vacuum conditions. We used an AFM-tip and different surfaces as a model system to study the interactions between workpiece and gripper. The main problem under ambient conditions, and to a reduced extent even under vacuum conditions, are capillary forces, which always occur if the surface is an oxide. Hydrophobic coatings can solve this problem. However, an increased contact area due to the softness of these coatings can lead to even higher adhesion as well as workpiece contamination. Our measurement method allows to find out whether the coatings are suitable or not. In order to reduce sticking effects further, the van der Waals force must be decreased. First measurements support the theoretical calculations that surface structuring could be an effective way.

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