Effect of geometry on dielectrophoretic trap stiffness in microparticle trapping

Tutorial on Lateral Dielectrophoretic Manipulations in Microfluidic Systems

Microfluidic lab-on-a-chip systems can offer cost- and time-efficient biological assays by providing high-throughput analysis at very small volume scale. Among these extremely broad ranges of assays, accurate and specific cell and reagent control is considered one of the most important functions. Dielectrophoretic (DEP)-based manipulation technologies have been extensively developed for these purposes due to their label-free and high selectivity natures as well as due to their simple microstructures. Here, we provide a tutorial on how to develop DEP-based microfluidic systems, including a detailed walkthrough of dielectrophoresis theory, instruction on how to conduct simulation and calculation of electric field and generated DEP force, followed with guidance on microfabricating two forms of DEP microfluidic systems, namely lateral DEP and droplet DEP, and how best to conduct experiments in such systems. Finally, we summarize most recent DEP-based microfluidic technologies and applications, including systems for blood diagnoses, pathogenicity studies, in-droplet content manipulations, droplet manipulations and merging, to name a few. We conclude by suggesting possible future directions on how DEP-based technologies can be utilized to overcome current challenges and improve the current status in microfluidic lab-on-a-chip systems.

DC corral trapping of single nanoparticles and macromolecules in solution

Progress in sorting, separating, and characterizing ever smaller amounts of chemical and biological material depends on the availability of methods for the controlled interaction with nanoscale and molecular-size objects. Here, we report on the reversible, tunable trapping of single DNA molecules and other charged micro- and nanoparticles in aqueous solution using a direct-current (DC) corral trap setup. The trap consists of a circular, non-conductive void in a metal-coated surface that, when charged, generates an electrostatic potential well in the proximate solution. Our results demonstrate that stable, nanoscale confinement of charged objects is achievable over extended periods of time, that trap stiffness is controlled by the applied voltage, and that simultaneous trapping of multiple objects is feasible. The approach shows great promise for lab-on-a-chip systems and biomedical applications due to its simplicity, scalability, selectivity, and the capability to manipulate single DNA molecules in standard buffer solutions.