We show the fractionation of whole blood components and isolation of blood plasma with no dilution by using a continuousflow deterministic array that separates blood components by their hydrodynamic size, independent of their mass. We use the technology we developed of deterministic arrays which separate white blood cells, red blood cells, and platelets from blood plasma at flow velocities of 1,000 m͞sec and volume rates up to 1 l͞min. We verified by flow cytometry that an array using focused injection removed 100% of the lymphocytes and monocytes from the main red blood cell and platelet stream. Using a second design, we demonstrated the separation of blood plasma from the blood cells (white, red, and platelets) with virtually no dilution of the plasma and no cellular contamination of the plasma.

The fractionation of small particles in a liquid based on their size in a micropost array by deterministic lateral displacement was recently demonstrated with unprecedented resolution (L. R. Huang, E. C. Cox, R. H. Austin and J. C. Sturm, Science, 2004, 304, 987-990, ). In this paper, we present a model of how the critical particle size for fractionation depends on the micropost geometry, depending specifically on the gap between posts, the offset of posts in one row with respect to another, and whether the fluid is driven by hydrodynamics or by electroosmosis. In general the critical particle diameter is much smaller than the gap, which prevents clogging. The model is supported by data with particles from 2.3 to 22 microm.

We present a continuous-flow microfluidic device that enables cell by cell separation of cells selectively tagged with magnetic nanoparticles. The cells flow over an array of microfabricated magnetic stripes, which create a series of high magnetic field gradients that trap the magnetically labeled cells and alter their flow direction. The process was observed in real time using a low power microscope. The device has been demonstrated by the separation of leukocytes from whole human blood.

Various types of luminescent color centers made in diamond by substitution of carbon with nitrogen, [1] nickel, [2] silicon, [3] and/or a vacancy have been of interest for applications in many fields. One of the most widely used ways for making diamond luminescent involves substitution of one carbon atom with nitrogen and creation of a vacancy at a location adjacent to the nitrogen atom, thus forming a nitrogen-vacancy (NV) color center. [1] NV-photoluminescent diamonds are extremely photostable, [4] biocompatible, [5] exhibit amiable surface chemistry, [6] and show optically detectable sensitivity to magnetic fields. [1] Although the production of 25-nm luminescent diamond based on high-temperature high-pressure (HTHP) synthesis [7,8] has already brought exciting results in quantum physics [1,9] and the life sciences, [4,7,10] crystals no larger than a few nanometers will break ground in these applications [3,6,11] and other fields. [12,13] Functionalized single-digit nanodiamonds (SNDs) may be used to track biomolecules with minimal steric and biochemical perturbations, are small enough to show detectable quantum interactions between NV centers located in different crystals, [14] and will facilitate the realization of high-resolution magnetic [12,15] and near-field optical microscopes. [13] SNDs have recently been produced by breaking detonation-synthesized nanodiamonds [16] into 5-nm primary crystals [17] but no progress has yet been reported towards embedding NV centers into SNDs. Furthermore, there is growing concern that NV centers in SNDs cannot form due to physical barriers, such as the proximity to surface traps and reduced stability of defects. [3,18,19] A study of NV centers in similar-scale diamond grains created with chemical vapor deposition found no NV centers in crystals smaller than 20 nm. [18] Furthermore, theoretical work suggests that nitrogen becomes less energetically stable in the core of nanodiamonds as they become smaller. [20] It has also been suggested that luminescence may be quenched by nearby surface defects, [18] and that high levels of oxygen and other impurities in detonation-synthesized diamond may affect the formation of NV centers. Intrinsic short-lived luminescence from surface defects in SNDs further confounds the issue. [21] Herein, we examine the properties of weakly bound clusters of SNDs by using spectrally and temporally resolved luminescence detection, electron paramagnetic resonance (EPR) spectroscopy, and transmission electron microscopy (TEM), and present the first report of the successful detection of NV centers in 5-nm diamond. Furthermore, we provide a simple physical argument on why the probability of creating a color center in a small crystal scales as the fifth power of the crystal size.NV centers in diamonds were created by high-energy proton irradiation followed by thermal annealing (see Experimental Section). For luminescence measurements, samples containing equal weights of 55-nm HTHP diamonds and SNDs were uniformly distributed on quartz substrates. Prist...

The advent of microfluidics in the 1990s promised a revolution in multiple industries, from healthcare to chemical processing. Deterministic Lateral Displacement (DLD) is a continuous-flow microfluidic particle separation method discovered in 2004 that has been applied successfully and widely to the separation of blood cells, yeast, spores, bacteria, viruses, DNA, droplets, and more. DLD is conceptually simple and can deliver consistent performance over a wide range of flow rates and particle concentrations.Despite wide use and in-depth study, DLD has not yet been fully understood or fully optimised, with different approaches to the same problem yielding varying results. We endeavour here to provide an up-to-date expert opinion on the state-of-art and current fundamental, practical, and commercial challenges as well as experimental and modelling opportunities. Since these challenges and opportunities arise from constraints on hydrodynamics, fabrication and operation at the micro-and nano-scale, we expect this article to serve as a guide for the broader micro-and nanofluidic community to identify and address open questions in the field.