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Microassembly deals with micron or millimeter scale objects where the tolerance requirements are in the micron range. Typical applications include electronics components (silicon fabricated circuits), optoelectronics components (photo detectors, emitters, amplifiers, optical fibers, microlenses, etc.), and MEMS (Micro-Electro-Mechanical-System) dies. The assembly processes generally require not only high precision but also high throughput at low manufacturing cost. While conventional macroscale assembly methods have been utilized in scaled down versions for microassembly applications, they exhibit limitations on throughput and cost due to the inherently serialized process. Since the assembly process depends heavily on the manipulation performance, an efficient manipulation method for small parts will have a significant impact on the manufacturing of miniaturized products. The objective of this study on 'parallel micromanipulation' is to achieve these three requirements through the handling of multiple small parts simultaneously (in parallel) with high precision (micromanipulation). As a step toward this objective, a new manipulation method is introduced. The method uses a distributed actuation array for gripper free and parallel manipulation, and a centralized, shared actuator for simplified controls. The method has been implemented on a testbed 'Piezo Active Surface (PAS)' in which an actively generated friction force field is the driving force for part manipulation. Basic motion primitives, such as translation and rotation of objects, are made possible with the proposed method. This study discusses the design of the proposed manipulation method PAS, and the corresponding manipulation mechanism. The PAS consists of two piezoelectric actuators for X and Y motion, two linear motion guides, two sets of nozzle arrays, and solenoid valves to switch the pneumatic suction force on and off in individual nozzles. One array of nozzles is fixed relative to the surface on which the objects are placed, while the other set is actuated by the actuator relative to this surface. The combination of piezoactuation and pneumatic force generates a friction force that can manipulate multiple objects simultaneously, without grippers. We model the manipulation as the quasistatic motion with an approximation of limit surface. Also an experiment was carried to validate the proposed idea and the design of the prototype. The object manipulated in the experiments was a small piece of silicon wafer (1 mm X 4 mm) with 10 Hz of 10 micrometers stroke of the piezoelectric actuation system. The method is being extended to the parallel manipulation of small objects such as v-groove fiber assemblies and MEMS dies. The combined precision of piezoelectric actuation and speed of parallel manipulation is expected to yield a low cost microassembly method.
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