Improved continuous magnetic separation assisted with advection flows in microfluidic channels

Department of Biomedical EngineeringMagnetophoretic separation efficiency is determined by a ratio of magnetic particles isolated by magnetic flux density gradients. Because the magnetic flux density gradients rapidly decrease as the distance from the magnetic source increases, the magetic particles which are placed far from the magnetic source are not separated. This is one of the key challenges to achieve high throughput magnetic separation device. Here, we report a magnetic separation device inducing specific fluid flow by patterning the obstacle arrays on the channel. We achieve highly augmented magnetic separation efficiency using chaotic convection flows induced by the slanted ridges in the channels. The asymmetric pressure gradients across the cross-section of the channel are induced by the slanted ridge arrays pattern in the channel, and then it occurs the spiral flows inside the microchannel. The spiral flows transfer the magnetic particles or biological cells integrated with magnetic particles toward the area with high magnetic flux density gradient where is close to the ferromagnetic nickel structure with magnet. With this suggested approach, over 91.68% of E. coli bound with magnetic nanoparticles (200 nm) in whole blood are successfully isolated at a flow rate up to 1.6 mL/h, in a single microfluidic channel, whereas conventional devices without advective rotational flows only isolated under 27.72%.ope

Random Access Game in Fading Channels with Capture: Equilibria and Braess-like Paradoxes

The Nash equilibrium point of the transmission probabilities in a slotted ALOHA system with selfish nodes is analyzed. The system consists of a finite number of heterogeneous nodes, each trying to minimize its average transmission probability (or power investment) selfishly while meeting its average throughput demand over the shared wireless channel to a common base station (BS). We use a game-theoretic approach to analyze the network under two reception models: one is called power capture, the other is called signal to interference plus noise ratio (SINR) capture. It is shown that, in some situations, Braess-like paradoxes may occur. That is, the performance of the system may become worse instead of better when channel state information (CSI) is available at the selfish nodes. In particular, for homogeneous nodes, we analytically present that Braess-like paradoxes occur in the power capture model, and in the SINR capture model with the capture ratio larger than one and the noise to signal ratio sufficiently small.Comment: 30 pages, 5 figure