Separation of blood plasma by inertial focusing using microfluidic chips

Blood plasma is widely used in clinical and biochemical tests, and techniques for plasma separation are essential for biomedical research. The technique of inertial microfluidics provides the capability to focus microparticles or cells in microchannels without the need for active device components. Based on the theory of inertial focusing, we designed and fabricated microfluidic chips with asymmetrically curved channels. Focusing performance was evaluated using homemade fluorescent microspheres as models. We found that the flow velocities required for maintenance of stable inertial focusing varied significantly among microspheres of different sizes. The microdevice was further employed for the separation of plasma from diluted blood samples. We achieved a 90% separation efficiency when the sample was separated twice in the device. These data suggest that microdevices can separate plasma efficiently without damaging blood cells, and can be readily integrated with other analytical devices.