Micro-gripping methods for micro-spheres sorting

The current innovation of the mechatronic products has led to the use of miniaturized devices that combine components with different material, shape, reduced mass, and extremely small size, in order to increase the functionalities and the efficiency of the products. This trend involves new issues related to the manufacturing and automated assembly of these products. Even in constantly developing non-industrial sectors such as biomedicine, the need for automated equipment for preparing and manipulating biological samples represents a current challenge. In particular, the sorting and feeding systems cover an essential role since they can affect the task strategy, the operation scheduling, and the overall system performance. Moreover, they should cope with the adhesion issues related to micro-scale manipulation, as all the devices that handle sub-millimetric components. In this context, this paper presents two methods and the related tools for the automated sorting and manipulation of micro-spheres: the former exploits a micro-gripping tool and implements a pick-and-place (P&P) approach, while the latter is based on newly conceived devices implementing a "store-and-place" (S&P) strategy. The two methods were studied considering two application examples. They were firstly exploited to perform the automated reballing of a BGA (Ball Grid Array) package to be mounted on a Printed Circuit Board; the implemented tasks will be described and discussed to underline their characteristics and applicability. Furthermore, a second application of the methods to the sorting and placement of fertilized Zebrafish eggs is envisaged.