The effect of operating conditions on the optically induced electrokinetic (OEK)-based manipulation of magnetic microbeads in a microfluidic system

Abstract

Magnetic microbeads are widely utilized in microfluidic systems for various applications. For these tasks, the effective and efficient manipulation of magnetic microbeads is important. Among the techniques for microparticle manipulation, the optically induced electrokinetic (OEK) [e.g., optically induced dielectrophoresis (ODEP) or light-actuated AC electroosmosis (LACE)]-based technique is promising. However, its utilization for magnetic microbead manipulation in a microfluidic system has not yet been fundamentally studied. To address this issue, the effect of operating conditions on the OEK-based magnetic microbead manipulation investigated. The results showed that the maximum terminal velocity (Vterminal) of a light image that can manipulate microbeads decreased significantly with increasing AC frequency. In addition, the results revealed that the Vterminal increased with increasing intrinsic a-Si:H layer thickness (Ta-Si) when the AC frequency was higher than 30 kHz, whereas the results completely reversed when the frequency was lower than 30 kHz. Additionally, the Vterminal of larger magnetic microbeads was higher than that of smaller microbeads when the AC frequency was higher than 50 kHz; conversely, the results significantly reversed when the frequency was lower than 30 kHz. Moreover, microbead manipulation under high conductivity conditions could significantly affect the magnitude of the Vterminal. Based on the fast manipulation velocity in LACE-based microbead manipulation, its application for basic unit operations in a microfluidic system was demonstrated. Overall, this study has provided some fundamental information for the selection of optimum operating conditions for OEK-based magnetic microbead manipulation in a microfluidic system.