  Dynamic control of compact chip-scale contactless manipulation of particles
for bioscience applications remains a challenging endeavor, which is restrained
by the balance between trapping efficiency and scalable apparatus. Metasurfaces
offer the implementation of feasible optical tweezers on a planar platform for
shaping the exerted optical force by a microscale-integrated device. Here, we
design and experimentally demonstrate a highly efficient silicon-based metalens
for two-dimensional optical trapping in the near-infrared. Our metalens concept
is based on the Pancharatnam-Berry phase, which enables the device for
polarization-sensitive particle manipulation. Our optical trapping setup is
capable of adjusting the position of both the metasurface lens and the particle
chamber freely in three directions, which offers great freedom for optical trap
adjustment and alignment. Two-dimensional (2D) particle manipulation is done
with a relatively low numerical aperture metalens ($NA_{ML}=0.6$). We
experimentally demonstrate both 2D polarization sensitive drag and drop
manipulation of polystyrene particles suspended in water and transfer of
angular orbital momentum to these particles with a single tailored beam. Our
work may open new possibilities for lab-on-a-chip optical trapping for
bioscience applications and micro to nanoscale optical tweezers.
