  Optical trapping can be used to manipulate the three-dimensional (3-D) motion
of spherical particles based on the simple prediction of optical forces and the
responding motion of samples. However, controlling the 3-D behaviour of
non-spherical particles with arbitrary orientations is extremely challenging,
due to experimental difficulties and the extensive computations. Here, we
achieved the real-time optical control of arbitrarily shaped particles by
combining the wavefront shaping of a trapping beam and measurements of the 3-D
refractive index (RI) distribution of samples. Engineering the 3-D light field
distribution of a trapping beam based on the measured 3-D RI map of samples
generates a light mould, which can be used to manipulate colloidal and
biological samples which have arbitrary orientations and/or shapes. The present
method provides stable control of the orientation and assembly of arbitrarily
shaped particles without knowing a priori information about the sample
geometry. The proposed method can be directly applied in biophotonics and soft
matter physics.
