Interaction between positive and negative dielectric microparticles/microorganism in optoelectronic tweezers.

Optoelectronic tweezers (OET) is a noncontact micromanipulation technology for controlling microparticles and cells. In the OET, it is necessary to configure a medium with different electrical properties to manipulate different particles and to avoid the interaction between two particles. Here, a new method exploiting the interaction between different dielectric properties of micro-objects to achieve the trapping, transport, and release of particles in the OET system was proposed. Besides, the effect of interaction between the micro-objects with positive and negative dielectric properties was simulated by the arbitrary Lagrangian-Eulerian (ALE) method. In addition, compared with conventional OET systems relying on fabrication processes involving the assembly of photoelectric materials, a contactless OET platform with an iPad-based wireless-control interface was established to achieve convenient control. Finally, this platform was used in the interaction of swimming microorganisms (positive-dielectric properties) with microparticles (negative-dielectric properties) at different scales. It showed that one particle could interact with 5 particles simultaneously, indicating that the interaction can be applied to enhance the high-throughput transportation capacities of the OET system and assemble some special microstructures. Owing to the low power, microorganisms were free from adverse influence during the experiment. In the future, the interaction of particles in a simple OET platform is a promising alternative in micro-nano manipulation for controlling drug release from uncontaminated cells in targeted therapy research.