Study of particle equilibrium based on the combination of light-actuated AC electroosmosis and light-actuated dielectrophoresis.

Optoelectronic tweezers (OETs) represent a flexible, high-throughput method for manipulating micro/nano particles or cells. This technique involves not only light-actuated dielectrophoresis (LDEP) but also light-actuated AC electroosmosis (LACE), which occurs concurrently in OETs devices. Despite this, the combination of negative LDEP and LACE has been relatively unexplored in previous research. To this end, particle equilibrium in OETs devices under the combined influence of negative LDEP and LACE was hereby proposed for what we believe is the first time. The findings revealed that particles experiencing negative dielectrophoresis encountered opposing forces from LDEP and LACE, reaching equilibrium near the light pattern. The location of the equilibrium point was frequency-dependent. The research further demonstrated the rapid differentiation between individual particles and adherent particles by leveraging the distinct equilibrium point positions. These phenomena were corroborated through numerical simulations, which showed a strong correlation between the theoretical analysis results and the experimental data. Overall, the particle equilibrium phenomenon in OET systems exhibits high stability and holds promising potential for future applications in particle or cell sorting and patterning two-dimensional structures.