Blood has been the most reliable body fluid commonly used for the diagnosis of diseases. Although there have been promising investigations for the development of novel lab-on-a-chip devices to utilize other body fluids such as urine and sweat samples in diagnosis, their stability remains a problem that limits the reliability and accuracy of readouts. Hence, accurate and quantitative separation and characterization of blood cells are still crucial. The first step in achieving high-resolution characteristics for specific cell subpopulations from the whole blood is the isolation of pure cell populations from a mixture of cell suspensions. Second, live cells need to be purified from dead cells; otherwise, dead cells might introduce biases in the measurements. In addition, the separation and characterization methods being used must preserve the genetic and phenotypic properties of the cells. Among the characterization and separation approaches, dielectrophoresis (DEP) is one of the oldest and most efficient label-free quantification methods, which directly purifies and characterizes cells using their intrinsic, physical properties. In this study, we present the dielectrophoretic separation and characterization of live and dead monocytes using 3D carbon-electrodes. Our approach successfully removed the dead monocytes while preserving the viability of the live monocytes. Therefore, when blood analyses and disease diagnosis are performed with enriched, live monocyte populations, this approach will reduce the dead-cell contamination risk and achieve more reliable and accurate test results.

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a low cost, flexible and quick process to fabricate microchannels keeps increasing.Historically, the majority of the initial microfluidics work was done using glass-or silicon-made microfluidic devices (Harrison et al. 1992;Wilding et al. 1994;Woolley and Mathies 1994;Jiang et al. 1995) using techniques like wet and dry etching. In the mid-1990s, a revolution in the fabrication of microfluidics took place with the advent of soft lithography, where a master mold is used to make poly-dimethylsiloxane (PDMS) replicas by casting (Dong et al. 1996;Xia and Whitesides 1998;Duffy et al. 1998). Soft lithography is now a standard for microfluidic prototyping, in part because it enables a relatively inexpensive and rapid fabrication. As long as a master mold is available, experimental microfluidics devices can be made in few hours without the need for a cleanroom. However, the master molds are still mostly fabricated in a cleanroom following a number of processes including dry etching of silicon, and especially SU-8 photolithography (Martinez-Duarte and Madou 2011). As expected, the resolution and achievable complexity of the master mold depend highly on the choice of fabrication technique. For example, microchannels with features of even 100 nm are possible to fabricate using electron beam lithography (Rogers and Nuzzo 2005; Alom Ruiz and Chen 2007). However, most microfluidic devices would feature dimensions from the tens of micrometers to several hundreds, achievable with conventional SU-8 photolithography.Other relatively inexpensive fabrication techniques are printer based, such as that presented by Carrilho et al. (2009) who selectively deposited hydrophobic wax on regular paper to create channel walls. In this particular case, the cross section of the channel is not empty, but contains fibers that facilitate the wicking of the sample throughout the fluidic network. Bruzewicz et al. (2008) also demonstrated a Abstract In this paper, we focus on characterizing the limits of xurography, or patterning with a razor blade, of a pressure-sensitive double-sided adhesive. This is a rapid, inexpensive technique to fabricate robust microfluidics devices. Straight, curved and square serpentine as well as zigzag channels of different dimensions are studied. General guidelines are provided to assess feasibility of a particular geometry a priori. The mechanics of the cut are explored with the aim at identifying the bottlenecks that limit the maximum resolution achieved in xurography of adhesive films. A number of advantages and disadvantages of this technique compared to other common fabrication techniques are also provided.

Monocyte heterogeneity and its prevalence are revealed as indicator of several human diseases ranking from cardiovascular diseases to rheumatoid arthritis, chronic kidney diseases, autoimmune multiple sclerosis, and stroke injuries. When monocytes and macrophages are characterized and isolated with preserved genetic, phenotypic and functional properties, they can be used as label‐free biomarkers for precise diagnostics and treatment of various diseases. Here, the dielectrophoretic responses of the monocytes and macrophages were examined. We present 3D carbon‐electrode dielectrophoresis (carbon‐DEP) as a separation tool for U937 monocytes and U937 monocyte‐differentiated macrophages. The carbon‐electrodes advanced the usability and throughput of DEP separation, presented wider electrochemical stability. Using the 3D carbon‐DEP chip, we first identified the selective positive and negative DEP responses and specific crossover frequencies of monocytes and macrophages as their signatures for separation. The crossover frequency of monocytes and macrophages was 17 and 30 kHz, respectively. Next, we separated monocyte and macrophage subpopulations using their specific dielectrophoretic responses. Afterward, we used a fluorescence‐activated cell sorter to confirm our results. Finally, we enriched 70% of monocyte cells from the mixed cell population, in other words, concentration of monocyte cells to macrophage cells was five times increased, using the 30‐kHz, 10‐Vpp electric field and 1 μL/min flow rate.

Here, we report on an enrichment protocol using carbon electrode dielectrophoresis to isolate and purify a targeted cell population from sample volumes up to 4 ml. We aim at trapping, washing, and recovering an enriched cell fraction that will facilitate downstream analysis. We used an increasingly diluted sample of yeast, 10 6 -10 2 cells/ml, to demonstrate the isolation and enrichment of few cells at increasing flow rates. A maximum average enrichment of 154.2 6 23.7 times was achieved when the sample flow rate was 10 ll/min and yeast cells were suspended in low electrically conductive media that maximizes dielectrophoresis trapping. A COMSOL Multiphysics model allowed for the comparison between experimental and simulation results. Discussion is conducted on the discrepancies between such results and how the model can be further improved. Published by AIP Publishing.