Microparticle manipulation has been widely used in clinical
diagnosis,
cell separation, and biochemical analysis via optics, electronics,
magnetics, or acoustic wave driving. Among them, the bulk acoustic
wave (BAW) driving method has been increasingly adopted because of
non-contact, easy control, and precise manipulation. However, its
low manipulation efficiency limits the usage of the BAW driving in
high viscosity solutions. Therefore, in order to obtain larger driving
force and more flexible manipulation of microparticles, both two-dimensional
(2D) and three-dimensional (3D) platforms based on the BAW and liquid
crystal backflow effect (LCBE) driving in liquid crystal (LC) solutions
are proposed. The driving forces applied on the microparticles allow
for the change of microparticle moving direction, which is also ascertained
through theory analysis combined with various driving methods. Specifically,
the maximum moving speed (68.78 μm/s) of the polystyrene particles
is obtained by the BAW (13 Vpp) combined with LCBE (30 V) at a low
frequency of 7.2 kHz in the 2D platform. Precise position manipulation
in 3D is also fulfilled through a programmable logic control model
using polystyrene particles as a demonstration. In addition, red blood
cells mixed with LC solutions are arranged in a line or gathered in
the pressure nodes of the BAW forces along with sinusoid signals generated
by various transducer combinations. Therefore, it is approved that
the LC solution that induces the LCBE force could increase the microparticle
manipulation efficiency in both 2D and 3D platforms. The proposed
method will open up new avenues in particle manipulation and benefit
a variety of applications in cell separation, drug synthesis, analytical
chemistry, and others.
