Enrichment and Selection of Particles through Parallel Induced-Charge Electro-osmotic Streaming for Detection of Low-Abundance Nanoparticles and Targeted Microalgae.

Manipulation of micro- and nanoscale objects is an essential procedure in many detection and sensing applications, including disease diagnosis and environmental monitoring. Induced-charge electro-osmotic (ICEO) vortices present excellent advantages in the enrichment and selection of micro/nanoscale particles for downstream detection due to gentle conditions and contactless operation, but the application of this method is currently constrained by the throughput. Double-layer charging at the ends of bipolar electrodes can maintain a continuous flow of electric current in the fluidically isolated channels, which provides a feasible method to manipulate particles using parallel ICEO vortices, promoting throughput of particle manipulation without compromising efficiency and overcoming the complicated ohmic contact of electrodes. Encouraged by these, we put forward a novel method with parallel ICEO vortices to manipulate micro/nanoscale samples for downstream detection. First, we study the extension regulation of the low-frequency electric field and mediating effect of the open BPEs on the extended electric field and characterize electric equilibrium states of microparticles and their voltage dependence. Afterward, we leverage this method to enrich nanoparticles for detection of low-abundance nanoparticles with about 20- and 40-fold fluorescence intensities by integrating with a simple fiber-optic sensor. Furthermore, this technique is engineered for the selection of targeted microalgae to continuously detect their proliferation behaviors by combining with a homemade electrical impedance spectroscopy device. This method can reinforce the throughput of ICEO vortices and enables it to integrate with simple and economical sensors to accomplish disease diagnosis and environmental monitoring.