Gradient light field for directional capturing and positioning microparticle in optoelectronic tweezers

This study presents a gradient-light field in optoelectronic tweezers to achieve locating microparticles at a stable equilibrium position. By designing a light pattern with intensity gradients, a spatially varying dielectrophoretic force is generated, enabling microparticle manipulation. First, the electric field and force characters induced by gradient light are simulated. Subsequently, experimental results demonstrate that microparticles are moved along the direction of increasing light intensity and reach a stable position due to the change in force. Moreover, when an additional microparticle is introduced into the gradient light pattern, particle interactions lead to the other equilibrium state. The results verify that gradient light can be applied to directional positioning microparticles. The proposed method offers a label-free approach for studying bioparticles or cells with potential applications in positioning classification.