Microfluidic cell sorter with integrated piezoelectric actuator

We demonstrate a low-power (<0.1 mW), low-voltage (<10 Vp-p) on-chip piezoelectrically actuated micro-sorter that can deflect single particles and cells at high-speed. With rhodamine in the stream, switching of flow between channels can be visualized at high actuation frequency (~1.7 kHz). The magnitude of the cell deflection can be precisely controlled by the magnitude and waveform of input voltage. Both simulation and experimental results indicate that the drag force imposed on the suspended particle/cell by the instantaneous fluid displacement can alter the trajectory of the particle/cell of any size, shape, and density of interest in a controlled manner. The open-loop E. Coli cell deflection experiment demonstrates that the sorting mechanism can produce a throughput of at least 330 cells/s, with a promise of a significantly higher throughput for an optimized design. To achieve close-loop sorting operation, fluorescence detection, real-time signal processing, and field-programmable-gate-array (FPGA) implementation of the control algorithms were developed to perform automated sorting of fluorescent beads. The preliminary results show error-free sorting at a sorting efficiency of ~70%. Since the piezoelectric actuator has an intrinsic response time of 0.1–1 ms and the sorting can be performed under high flowrate (particle speed of ~1–10 cm/s), the system can achieve a throughput of >1,000 particles/s with high purity

Dielectrophoretic assessment of microparticle dielectric properties employing a planar carbon electrode platform

Carbon-Electrode Dielectrophoresis (CarbonDEP) is a novel variation of the conventional electrode-based DEP. The use of carbon, instead of metal, offers advantages like a wider electrochemical stability window, excellent biocompatibility, and great mechanical properties. In order to optimize the performance of electrokinetic experiments, such as separation and concentration of microparticles, it is necessary to know the dielectric properties of the particle of interest a priori. For the extraction of dielectric properties using DEP, it is required that other electrokinetic phenomena, such as electroosmotic flow (EOF) and electrophoresis (EP), are not present on the experiment. Presented in this work is the implementation of a dielectric properties characterization platform based on CarbonDEP. A microdevice containing planar carbon electrodes was employed to manipulate carboxylated polystyrene particles with diameters of 1 ??m and 2.28 ??m. Particle responses were obtained by varying the magnitude and frequency of the applied AC potential. Velocity induced on the particles was measured experimentally and electric parameters of the microchannel were obtained through simulations in COMSOL Multiphysics. With this information, a system of non linear equations was built, from which the dielectric properties can be extracted. Potential applications of this work include, but are not limited to, environmental screening for water contamination, food safety, clinical analyses, and improvement of clean energy production methods. The results of this work have great potential to be used as guidelines for the further design and operation of CarbonDEP based systems

Rapid Concentration of Nanoparticles with DC Dielectrophoresis in Focused Electric Fields

<p>Abstract</p> <p>We report a microfluidic device for rapid and efficient concentration of micro/nanoparticles with direct current dielectrophoresis (DC DEP). The concentrator is composed of a series of microchannels constructed with PDMS-insulating microstructures for efficiently focusing the electric field in the flow direction to provide high field strength and gradient. The location of the trapped and concentrated particles depends on the strength of the electric field applied. Both &#8216;streaming DEP&#8217; and &#8216;trapping DEP&#8217; simultaneously take place within the concentrator at different regions. The former occurs upstream and is responsible for continuous transport of the particles, whereas the latter occurs downstream and rapidly traps the particles delivered from upstream. The performance of the device is demonstrated by successfully concentrating fluorescent nanoparticles. The described microfluidic concentrator can be implemented in applications where rapid concentration of targets is needed such as concentrating cells for sample preparation and concentrating molecular biomarkers for detection.</p