A vacuum microgripping tool with integrated vibration releasing capability

Abstract

Pick-and-place of micro-objects is a basic task in various micromanipulation demands. Reliable releasing of micro-objects is usually disturbed due to strong scale effects. This paper focuses on a vacuum micro-gripper with vibration releasing functionality, which was designed and assembled for reliable micromanipulation tasks. Accordingly, a vibration releasing strategy of implementing a piezoelectric actuator on the vacuum microgripping tool is presented to address the releasing problem. The releasing mechanism was illustrated using a dynamic micro contact model. This model was developed via theoretical analysis, simulations and pull-off force measurement using atomic force microscopy. Micromanipulation experiments were conducted to verify the performance of the vacuum micro-gripper. The results show that, with the assistance of the vibration releasing, the vacuum microgripping tool can achieve reliable release of micro-objects. A releasing location accuracy of 4.5±0.5 μm and a successful releasing rate of around 100% (which is based on 110 trials) were achieved for manipulating polystyrene microspheres with radius of 35-100 μm.

High-Speed Active Release End-Effector Motions for Precise Positioning of Adhered Micro-Objects

“…These methods reduce the adhesion force by using pressure changes (vacuum tools) [6], voltage control [7], and dynamic effects (vibration) [8]- [13]. Among existing methods for active release, dynamic effects, i.e., the release of microobjects from an end-effector by vibrating the end-effector to generate inertial force, has drawn much attention recently owing to its high success rate.…”

“…For this experiment, On the other hand, for the 10-μm microbeads, a 40× objective lens was applied, providing a visual space of 128 μm × 128 μm. To release an object for precise positioning, the release height was a vital factor because it determined location accuracy after release [6] [9]. In this experiment, the release height was fixed to 20 μm by changing the Z-positions of both end-effectors (Figure 8(d)).…”

“…However, they applied a special mechanism with two arms controlled by an electrostatic actuator and a piezoelectric (PZT) actuator to apply these methods. Rong et al separated 35 -100 μm microbeads from an end-effector with 4.5 ± 0.5 μm position accuracy by using vibration release with a vacuum tool [6].…”

Analysis of rotational flow generated by circular motion of an end effector for 3D micromanipulation

“…For example, Kim et al [9] utilized high speed motions of an end effector to release object on the desired position. Rong et al and Takahashi et al presented a vacuum tool and voltage control method for precise releasing [10,11]. Moreover, it is difficult to deal with fragile objects, and contamination of the end effector is a weakness [12].…”

“…However, the main difficulty of contact manipulation is releasing micro-objects adhering to the manipulator because of large adhesion forces. Thus, to release microobjects at the desired position, special releasing strategies are necessary [9][10][11]. For example, Kim et al [9] utilized high speed motions of an end effector to release object on the desired position.…”