Ultrasonic waves are useful for arranging small particles in liquid, since the acoustic pressure exerts a sufficient trapping force on the particles. A composite material with layered structure can be fabricated by solidifying a particle suspension during the process of ultrasonic standing wave excitation. Fabrication of a 2D or 3D lattice structure is also possible by simultaneous excitation of two or three orthogonal ultrasonic standing waves. A polysiloxane resin is appropriate as a host material of such composite materials, since it is easily synthesized from a solution and its yields a small-periodicity structure due to its low sound velocity. Acrylic spheres, glass rods, and metal particles have been successfully arranged in polysiloxane resin forming layers or lattice structures. The spacing of particles was approximately 60 micrometers , which was half of the ultrasonic wavelength used. For heavy particles, a sample cell was continually rotated during the solidification process in order to prevent sedimentation.
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