Dielectrophoretic particle chromatographie (DPC) at preparative scale (SPP 2045)
Trapping of monodisperse PS particles of different size and at different flow rates in the PCB based setup. All data are obtained at 15 kHz and 75 Vpp. Voltage was applied after 30 s and turned off at 300 s. (A) Fluorescence signal of 3 μm and 6 μm PS particles at 6 ml/min volume flow. (B) Fluorescence signal for 1μm particles at 1 and 4 ml/min. (C) Monodisperse trapping efficiency as a function of particle size and flow rate.
Overview of the experimental setup based on PCB. The particles are suspended in water, stirred by a magnetic stirrer, and pumped by a piston pump (A) into the separation device (B). The separation chamber is formed by two PCBs on which the electrodes arrays are located. A silicone gasket (0.5 mm thickness) defines the flow path of the suspension as well as the height of the channel. Cover plates made of polypropylene and screws are used to press the components onto each other. The electrodes are connected to an amplifier which provides a sinusoidal voltage to operate the device (D). The suspension leaving the channel is flowing into a flow cell (C) that is coupled to a light source. The resulting fluorescence signal is recorded by a spectrometer (E) connected to a computer.
Workflow of dielectrophoretic particle chromatography (DPC). (A) Top view of the microfluidic device (sketch). (B) The microfluidic separation column (side view, height h = 80 μm and electrode width/spacing d1 = d2 = 100 μm ) is continuously flushed with a carrier fluid. Once per experiment a particle suspension is injected. The device is used for two different types of experiment. (I) The crossover frequency of particles is determined using field-flow fractionation (FFF) at a fixed frequency f by comparing the elution profiles with and without applied voltage (V0) (C). The obtained particle characteristics where used as input parameters for a full-scale simulation model realized in COMSOL Multiphysics to find suitable process parameters (D). (II) Eventually, the set of process parameters is used as starting point for experiments to achieve a chromatographic separation by using frequency-modulated ( f = f (t) ) DPC (E).
Image: Microfluidic device for dielectrophoretic particle chromatography. A constant fluid flow carries particles through a meandering channel. The bottom of the channel is given by an array of electrodes on top of a transparent substrate.