Manipulation of micro-components using vacuum grippers.

SUMMARY. During the past decades several microproducts have been fabricated for a great variety of applications in the traditional fields, including the medical and biomedical sectors, automotive, aeronautics and aerospace, Information Technology and telecommunication as well as in more innovative areas, such as household appliances, entertainment and sport equipment. Nevertheless, hybrid three dimensional micro products have still great difficulty in penetrating the market, mainly due to the limits of the fabrication processes that require manipulation and final assembly of microcomponents. These processes, being not yet automated, strongly affect the cost of products. Therefore, new market perspectives can be reached automating the assembly phase. The main challenge is due to the new physical scenario that appears when dealing with the assembly of millimetric and sub-millimetric parts. Indeed, at the microscale the high surface to volume ratio leads to the predominance of the superficial forces (e.g. electrostatic, van der Waals and surface tension forces) over the gravitational force; this results in an unpredictable behaviour of the traditional manipulating mechanisms, whereas an efficient and precise control of the grasp and release of thousands of microscopic and fragile parts is required. For this reason the downscaling of traditional handling strategies and the development of new handling techniques require further studies. Several solutions can be found in literature, with their advantages and limitations, i.e.: friction and jaw microgrippers, magnetic and electrical fields used to levitate objects, adhesive grippers exploiting capillary force. Also vacuum grippers can be miniaturized. Due to their intrinsic simplicity, vacuum grippers are very cheap and appear a promising solution for industrial applications, if some improvements are carried out. In this context, an experimental setup for the automatic manipulation of microcomponents through some vacuum grippers was developed. Moreover, an innovative design of a nozzle for a vacuum gripper was fabricated and tested, comparing its performance with traditional needles. The design was conceived in order to reduce the frequency of occlusions of the nozzle and handle a wide range of particles. The tests described in this paper concern mainly the success and the precision of the release of objects from the gripper. Indeed, this is one the crucial aspect of micromanipulation because microparts tend to stick to the gripper preventing the successful performance of manipulation tasks.