No abstract

No abstract

The exploration and application of electrokinetic techniques in micro total analysis systems have become ubiquitous in recent years, and scientists are expanding the use of such techniques in areas where comparable active or passive methods are not as successful. In this work, for the first time, we utilize the concept of AC electroosmosis to design a phase-controlled field-effect micromixer that benefits from a three-finger sinusoidally shaped electrodes. Analogous to field-effect transistor devices, the principle of operation for the proposed micromixer is governed by the source-gate and source-drain voltage potentials that are modulated by introducing a phase lag between the driving electrodes. At an optimized flow rate and biasing scheme, we demonstrate that the source, gate, and drain voltage phase relations can be configured such that the micromixer switches from an unmixed state (phase shift of 0°) to a mixed state (phase shift of 180°). High mixing efficiencies beyond 90% was achieved at a volumetric flow rate of 4 µL/min corresponding to ~13.9 mm/s at optimized voltage excitation conditions. Finally, we employed the proposed micromixer for the synthesis of nanoscale lipid-based drug delivery vesicles through the process of electrohydrodynamic-mediated nanoprecipitation. The phase-controlled electrohydrodynamic mixing utilized for the nanoprecipitation technique proved that nanoparticles of improved monodispersity and concentration can be produced when mixing efficiency is enhanced by tuning the phase shifts between electrodes.

With the aim of improving the reproducibility of capacitive immunosensors, we performed a comparative study of four different insulating/immobilization chemistries.

Microfluidic-based chemical synthesis is uniquely suited for the fabrication of reproducible and monodisperse nanoparticle batches due to the highly controlled reaction environments in microscale dimensions. With many passive and active micromixers emerging for the on-chip chemical synthesis needs, electrically driven fluid actuation is yet an unexplored technique with much-unrealized potentials. Accordingly, in this study, we propose a micromixer based on electrohydrodynamic-driven fluid instabilities for the synthesis of liposomes using the nanoprecipitation principle. The mixing channel embeds microelectrodes to impose a transverse electric field upon coflowing reagent-containing solvent and antisolvent streams. The sharp discontinuity in electrical parameters of solvent and antisolvent solutions at their interfaces is the source of fluid motion when low AC voltages are applied to the electrodes. The fluid instabilities at the interfaces lead to efficient mixing and nanoprecipitation of nanoparticles producing highly monodisperse liposomes for the unprecedented flow rates up to 400 μL/min and small voltages up to 10 V pp compared to its counterpart active micromixers. The liposome characteristics were studied by systematically evaluating the flow parameters, initial lipid concentrations, and surface charge. The obtained results and the working mechanism of the proposed micromixer can readily be extended to the production of nanoparticles of different chemistries relying on mixing of biphasic liquids.