Optical tweezers are unique tools for manipulation and analysis of single cells. The development of miniaturised trapping systems is a key issue as they could reduce system complexity and improve usability. In addition miniaturised traps can be easily combined with microfluidic circuits and they could open the way to in-vivo applications. In Ref. [1], tweezers based on an optical fiber bundle were proposed, where the equivalent effect of a high NA focusing system was obtained by total-internal-reflection (TIR) at the interface between fibers and surrounding-medium. The optical beams' deflection obtained through TIR makes them converging in the same spatial point that corresponds to the trap. Such a fiber-based approach is in principle extremely powerful as it doesn't require any critical alignment and, besides miniaturization, it opens the way to the realization of a multipurpose tool including additional optical functions for analysis and actuation of the trapped cells.