Optical trapping can be used to manipulate the three-dimensional (3-D) motionof spherical particles based on the simple prediction of optical forces and theresponding motion of samples. However, controlling the 3-D behaviour ofnon-spherical particles with arbitrary orientations is extremely challenging,due to experimental difficulties and the extensive computations. Here, weachieved the real-time optical control of arbitrarily shaped particles bycombining the wavefront shaping of a trapping beam and measurements of the 3-Drefractive index (RI) distribution of samples. Engineering the 3-D light fielddistribution of a trapping beam based on the measured 3-D RI map of samplesgenerates a light mould, which can be used to manipulate colloidal andbiological samples which have arbitrary orientations and/or shapes. The presentmethod provides stable control of the orientation and assembly of arbitrarilyshaped particles without knowing a priori information about the samplegeometry. The proposed method can be directly applied in biophotonics and softmatter physics.
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