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.

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SummaryA modified blended elemental powder metallurgy (MBEPM) method has been developed for the production of low-cost Ti alloys and in situ Ti/TiB MMCs for automobile components such as connecting rods and inlet and exhaust valves. The MBEPM method uses Ti sponge fines as raw material, which contain a substantial amount of Cl. The Cl refines the microstructure of the as-sintered Ti-6Al-4V alloys, with a reduced prior b-grain size and a reduced alath size and aspect ratio. However, the grain refining effect of Cl is much less pronounced in as-sintered Ti-6Al-4V-10%TiB MMCs. The Cl is present in the as-sintered microstructure in three forms: (1) shells consisting of fine NaCl particles in macropores; (2) cuboidal NaCl precipitates in the alloy matrix; and (3) Cl and Na segregated to prior bgrain boundaries. Increasing the Cl content increases the tensile ductility of both Ti-6Al-4V alloys and Ti-6Al-4V-10%TiB MMCs, but has little effect on strength.

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A capillary-gripping method that enables micro-objects to be picked up flexibly and reliably is described. By controlling the dropwise condensation on a probe tip, the volume of the water droplet on the hydrophobic tip surface can be dynamically varied, which helps to establish appropriate capillary lifting forces during micromanipulation tasks. Droplet formation and the capillary lifting forces generated during the manipulation process were experimentally characterized. Micromanipulation experiments using a customized motion platform equipped with viewing microscopes were conducted to verify the performance potential of this method. A 100% success rate in 200 trials was achieved in picking up and manipulating polystyrene microspheres with radii of 20–50 μm.