Development of Wet Tweezers Based on Capillary Force for Complex-Shaped and Heterogeneous Micro-Assembly

In this paper, we have described newly developed wet tweezers based on capillary force for micro-assembly of complex-shaped objects. The tweezers are composed of two movable rods driven by a piezoelectric linear motor and two thin tubes. The two rods penetrate the liquids in the thin tubes. If we simply stamp the rods on a base, we can apply a drop of even high viscosity liquids. If we contact them to an object, we can pick it up by capillary force. Because we use the pair of the rods for picking up, posture of objects are fixed. That is important for accurate micro-assembly. To investigate generative force of the wet tweezers, we study relationship among viscosity, surface tension, and shape of meniscus of the liquid. We also formulate the capillary force as a function of gap distance between the rod and the object with three different liquids. In several experiments, we have confirmed the wet tweezers have good assembling accuracy and possibility to realize heterogeneous and complex-shaped micro-assembly.