Self-driven filter-based blood plasma separator microfluidic chip for point-of-care testing

There is currently a growing need for lab-on-a-chip devices for use in clinical analysis and diagnostics, especially in the area of patient care. The first step in most blood assays is plasma extraction from whole blood. This paper presents a novel, self-driven blood plasma separation microfluidic chip, which can extract more than 0.1 mu l plasma from a single droplet of undiluted fresh human blood (similar to 5 mu l). This volume of blood plasma is extracted from whole blood with high purity (more than 98%) in a reasonable time frame (3 to 5 min), and without the need for any external force. This would be the first step towards the realization of a single-use, self-blood test that does not require any external force or power source to deliver and analyze a fresh whole-blood sample, in contrast to the existing time-consuming conventional blood analysis. The prototypes are manufactured in polydimethylsiloxane that has been modified with a strong nonionic surfactant (Silwet L-77) to achieve hydrophilic behavior. The main advantage of this microfluidic chip design is the clogging delay in the filtration area, which results in an increased amount of extracted plasma (0.1 mu l). Moreover, the plasma can be collected in one or more 10 mu m-deep 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 maximum pumping efficiency without disturbing the red blood cells' trajectory through the use of different hydrodynamic principles, such as a constriction effect and a symmetrical filtration mode. To demonstrate the microfluidic chip's functionality, we designed and fabricated a novel hybrid microdevice that exhibits the benefits of both microfluidics and lateral flow immunochromatographic tests. The performance of the presented hybrid microdevice is validated using rapid detection of thyroid stimulating hormone within a single droplet of whole blood.