Optimizing light pattern curvature to improve the performance of optoelectronic tweezers in micromanipulation

Optoelectronic tweezers (OET) offer a versatile, programmable, and contactless method for manipulating microscale objects. While factors like AC voltage and light intensity have been extensively studied, the role of light pattern curvature in the performance of OET manipulation remains underexplored. This study investigates how the curvature of light patterns affects the movement of polystyrene microparticles under negative dielectrophoretic (DEP) forces in an OET system. Experimental results show that as the curvature decreases, the maximum velocity of microparticles first increases to a peak and then gradually decreases. Numerical simulations reveal that light pattern curvature significantly influences the horizontal and vertical DEP forces, altering equilibrium positions and maximum velocities. By defining the optimal curvature (χ, the ratio of microparticle diameter to the inner diameter of the light pattern), we found that microparticles achieve maximum velocity and stability at this optimal ratio regardless of the sizes. These findings offer key insights into optimizing OET for improved manipulation performance, facilitating more precise and efficient applications in micromanipulation, micro-assembly, microfabrication, and beyond.