Evaluation and diagnosis of blood alterations is a common request for clinical laboratories, requiring a complex technological approach and dedication of health resources. In this paper, we present a microfluidic device that owing to a novel combination of hydrodynamic and dielectrophoretic techniques can separate plasma from fresh blood in a microfluidic channel and for the first time allows optical real-time monitoring of the components of plasma without pre- or post-processing. The microchannel is based on a set of dead-end branches at each side and is initially filled using capillary forces with a 2-μL droplet of fresh blood. During this process, stagnation zones are generated at the dead-end branches and some red blood cells (RBCs) are trapped there. An electric field is then applied and dielectrophoretic trapping of RBCs is used to prevent more RBCs entering into the channel, which works like a sieve. Besides, an electroosmotic flow is generated to sweep the rest of the RBCs from the central part of the channel. Consequently, an RBC-free zone of plasma is formed in the middle of the channel, allowing real-time monitoring of the platelet behavior. To study the generation of stagnation zones and to ensure RBC trapping in the initial constrictions, two numerical models were solved. The proposed experimental design separates up to 0.1 μL blood plasma from a 2-μL fresh human blood droplet. In this study, a plasma purity of 99 % was achieved after 7 min, according to the measurements taken by image analysis. Graphical Abstract Schematics of a real-time plasma monitoring system based on a Hydrodynamic and direct-current insulator-based dielectrophoresis microfluidic channel.
Electrostatic parallel-plate actuators are a common way of actuating microelectromechanical systems, both statically and dynamically. In the static case, the stable actuation voltages are limited by the static pull-in condition, which indicates that the travel range is approximately limited to 1/3 of the initial actuation gap. Under dynamic actuation conditions, however, the stable voltages are reduced, whereas the travel range can be much extended. This is the case with the dynamic pull-in and the resonant pull-in conditions (RPCs). Using energy analysis, this paper extends the study of pull-in instability to the resonant case and derives the analytical RPC. This condition predicts snapping or pull-in of the structure for a given domain of dc and ac actuation voltages versus quality factor, taking into account the nonlinearities due to large amplitudes of oscillation. Experimental results are presented to validate the analytically derived RPC.
Abstract:Recently, there is a growing need for lab-on-a-chip devices in clinical analysis and diagnostics especially near the patient care. First step, in the most blood assays is plasma extraction from whole blood. This paper presents a novel high throughput blood plasma separation microfluidic chip, which with just a single droplet of undiluted human blood (~5µL) can separate (more than 0.1µL) plasma from whole blood without the need of external forces with high purity (more than 98%) and reasonable time (3 to 5 minutes). This would be the first step towards the realization of single use, self-blood test which does not require any external forces or connection to deliver and analyze a fresh whole blood sample in contrast to the conventional blood analysis which have variable waiting times. Polydimethylsiloxane (PDMS) is utilized as the base material to manufacture the microchip due to its biocompatibility and outstanding characteristics. PDMS has been modified with a strong nonionic surfactant (Silwet L-77) to achieve a hydrophilic behavior. The main advantage of this microfluidic chip design is the clogging delay on the filtration area, which results in an increased amount of extracted plasma (0.1 µL). Moreover, the plasma can be collected in one or more 10-µm-depth channels to facilitate the detection and readout of multiple blood assays. This high volume of extracted plasma is achieved; thanks to a novel design that combines the maximum pumping efficiency without disturbing the red blood cells (RBCs) trajectory by the use of different hydrodynamic principles such as constriction effect and symmetrical filtration mode. To demonstrate the microfluidic chip functionality, a novel hybrid microdevice, exhibiting the benefits of both microfluidics and lateral flow Immuno-chromatographic tests, is designed and fabricated. The performance of the presented hybrid microdevice is validated utilizing rapid detection of the thyroid stimulating hormone (TSH) within a single droplet of whole blood. ABSTRACTRecently, there is a growing need for lab-on-a-chip devices in clinical analysis and diagnostics especially near the patient care. First step, in the most blood assays is plasma extraction from whole blood. This paper presents a novel high throughput blood plasma separation microfluidic chip, which with just a single droplet of undiluted human blood (~5µL) can separate (more than 0.1µL) plasma from whole blood without the need of external forces with high purity (more than 98%) and reasonable time (3 to 5 minutes). This would be the first step towards the realization of single use, self-blood test which does not require any external forces or connection to deliver and analyze a fresh whole blood sample in contrast to the conventional blood analysis which have variable waiting times. Polydimethylsiloxane (PDMS) is utilized as the base material to manufacture the microchip due to its biocompatibility and outstanding characteristics. PDMS has been modified with a strong nonionic surfactant (Silwet L-77) to achieve a hydro...
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