We demonstrate the feasibility of mechanical assembly of three-dimensional (3D) microstructures from fine particles by a micromanipulator under a scanning electron microscope. First, we experimentally show that micrometer-size particles can be picked up and placed with a needle-shaped handling tool. This is possible because adhesion forces due to electrostatic forces and van der Waals' forces dominate the dynamics of the micro-objects. To control the pick-and-place activity of the particles, the tool trajectory and the material combination are important. Second, we mechanically piled up 35 polymer spheres of 2 μm in diameter so as to form a 3D pyramid called a photonic crystal. A simple analysis shows that the magnitude of the adhesive force ranges from 10 pN to 10 μN and that the electrostatic force can be much larger than the van der Waals' force. However, we also found that we have difficulty explaining most experimental results. Clarification of the dynamics of the micro-objects and establishment of microrobotics based on these dynamics are necessary to meet the requirements for mechanical assembly of microstructures in various fields of science and technology.
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