Separation and Concentration without Clogging Using a High-Throughput Tunable Filter

We present a detailed experimental study of a hydrodynamic filtration microchip and show how chip performance can be tuned and clogging avoided by adjusting the flow rates. We demonstrate concentration and separation of microspheres at throughputs as high as 29  ml/min and with 96% pureness. Results of streakline visualizations show that the thickness of a tunable filtration layer dictates the cutoff size and that two different concentration mechanisms exist. Particles larger than pores are concentrated by low-velocity rolling over the filtration pillars, while particles smaller than pores are concentrated by lateral drift across the filtration layer. Results of microscopic particle image velocimetry and particle-tracking velocimetry show that the degree of lateral migration can be quantified by the slip velocity between the particle and the surrounding fluid. Finally, by utilizing differences in inertia and separation mode, we demonstrate size-based separation of particles in a mixtureacceptedVersio

Biocompatible bonding of a rigid off-stoichiometry thiol-ene-epoxy polymer microfluidic cartridge to a biofunctionalized silicon biosensor

Attachment of biorecognition molecules prior to microfluidic packaging is advantageous for many silicon biosensor-based lab-on-a-chip (LOC) devices. This necessitates biocompatible bonding of the microfluidic cartridge, which, due to thermal or chemical incompatibility, excludes standard microfabrication bonding techniques. Here, we demonstrate a novel processing approach for a commercially available, two-step curable polymer to obtain biocompatible ultraviolet initiated (UVA)-bonding of polymer microfluidics to silicon biosensors. Biocompatibility is assessed by UVA-bonding to antibody-functionalized ring resonator sensors and performing antigen capture assays while optically monitoring the sensor response. The assessments indicate normal biological function of the antibodies after UVA-bonding with selective binding to the target antigen. The bonding strength between polymer and silicon chips (non-biofunctionalized and biofunctionalized) is determined in terms of static liquid pressure. Polymer microfluidic cartridges are stored for more than 18 weeks between cartridge molding and cartridge-to-silicon bonding. All bonded devices withstand more than 2500 mbar pressure, far exceeding the typical requirements for LOC applications, while they may also be de-bonded after use. We suggest that these characteristics arise from bonding mainly through intermolecular forces, with a large extent of hydrogen bonds. Dimensional fidelity assessed by microscopy imaging shows less than 2% shrinkage through the molding process and the water contact angle is approximately 80°. As there is generally little absorption of UVA light (365 nm) in proteins and nucleic acids, this UVA-bonding procedure should be applicable for packaging a wide variety of biosensors into lab-on-a-chip systems.acceptedVersio

ACE Insertion/Deletion Polymorphism (rs4646994) Is Associated With the Increased Risk of Multiple Myeloma

Introduction: The insertion (I allele) deletion (D allele) polymorphism of ACE gene (rs4646994) may influence the etiopathogenesis of multiple myeloma (MM). ACE gene is expressed in bone marrow cells and encodes angiotensin converting enzyme (ACE). It converts angiotensin I to active peptide angiotensin II, which stimulates proliferation of hematopoietic stem cells. This suggests possible association of ACE I/D gene polymorphism with MM. The aim of our study was to check possible impact of this polymorphism on risk of development and outcome of MM, as well as, sensitivity to bortezomib in cell cultures derived from MM patients.Objects and Methods: Genomic DNA from 98 newly diagnosed MM patients and 100 healthy blood donors were analyzed by PCR method. Chromosomal aberrations were detected by use of cIg-FISH. In a subgroup of 40 MM patients nucleated bone marrow cells were treated with bortezomib in vitro.Results: The Hardy-Weinberg equilibrium test showed that genotypic frequencies diverged significantly from the equilibrium. The differences between I and D allele frequencies in control and study population were significant (p = 0.046). We observed the association between DD genotype and more than 2-fold risk of MM - OR = 2.69; p < 0.0001. We did not detect any significant differences among studied genotypes regarding clinical and laboratory parameters. Moreover, we did not observe the association between survival of MM patients and I/D genotypes. Bortezomib increased number of apoptotic and necrotic cells, but the only statistically significant differences were observed in the number of viable cells at 1 nM between ID and DD genotypes (p = 0.026).Conclusion: Presented results confirmed the significant relationship between ACE (I/D) polymorphism and risk of MM development. We did not observe the association of ACE I/D polymorphism with disease outcome and bortezomib in vitro sensitivity

Teflon-carbon black as new material for the hydrophobic patterning of polymer labs-on-a-chip

We provide a new method for the selective surface patterning of microfluidic chips with hydrophobic fluoropolymers which is demonstrated by the fabrication of hydrophobic valves. It enables efficient optical quality control for the surface patterning thus permitting the lowcost production of highly reproducible hydrophobic valves. Specifically, a fluoropolymer-solvent-dye solution based on carbon black (CB) is presented which creates superhydrophobic surfaces (contact angle = 157.9°) onchips made from cyclic olefin copolymer (COC). It further provides good visibility for the quality control (QC) in polymer labs-on-a-chip and increases the burst pressure of hydrophobic valves. Finally, an application which aims for the amplification of mRNA on-chip and relies on the defined flow control by hydrophobic valves is presented. Here, the QC in combination with the Teflon-CB coating improves the average standard deviation of the burst pressures from 14.5% down to 6.1 % compared to solely Teflon-coated valves.Teflon-carbon black as new material for the hydrophobic patterning of polymer labs-on-a-chi

A tunable, microfluidic filter for clog‑free concentration and separation of complex algal cells

Postprint version of published article. The final publication is available at Springer via http://dx.doi.org/10.1007/s10404-019-2209-yAn inherent problem with microfluidic filters is the tendency to clog, especially when applied to cells due to their geometrical complexity, deformability, and tendency to adhere to surfaces. In this work, we handle live algal cells of high complexity without signs of clogging, achieved by exploiting hydrodynamic interactions around trilobite-shaped filtration units. To characterize the influence of cell complexity on the separation and concentration mechanisms, we compare the hydrodynamic interactions to those of synthetic, rigid microparticles. We discover that simple rolling along the filter structures, which prevents clogging for particles, cannot be applied to cells. Instead, we find that inertial effects must be employed to minimize the filter interactions and that this modification leads to only a minor reduction in device performance.acceptedVersio

Simultaneous improvement of surface finish and bonding of centrifugal microfluidic devices in cyclo-olefin polymers

Two key issues in the manufacturing of microfluidic devices are to obtain low surface roughness, i.e. in the range of nanometers (to facilitate optical detection and controlled flow through microfluidic networks), and to achieve robust bonding. Here we report that a chemical polishing step, used for smoothening the surface of cyclo-olefin polymer (COP) components manufactured by micromilling, reduces the surface roughness (to Ra ∼ 150 nm) and facilitates a leak-tight COP-COP bond. We report new results on COP structuring and surface characterization by white light interferometry (WLI), infrared spectroscopy (FTIR-ATR), contact angle measurements and transmittance measurements, as well as demonstrations of a functional thermally bonded centrifugal microfluidic devicesSimultaneous improvement of surface finish and bonding of centrifugal microfluidic devices in cyclo-olefin polymersacceptedVersio

Curved passive mixing structures: a robust design to obtain efficient mixing and mass transfer in microfluidic channels

Analyte mixing and delivery to a functionalized sensor surface are important to realize several advantages associated with biosensors integrated with microfluidic channels. Here, we present a comparison between a herringbone structure (HBS) and a curved passive mixing structure of their efficiency at facilitating mixing and surface saturation using fluorescein included in one of the inlets of a Y-channel microfluidic device. We performed a large parametric study to assess the effects of varying the height of the microfluidic channel as well as the height, width, and spacing of the passive mixing structures. Scanning confocal microscopy combined with a custom-designed image-analysis procedure were utilized to visualize and quantify the observed changes in efficiency in inducing solute mixing by the different designs. The flow patterns within the channels were found to vary significantly with changes in the geometry of the passive mixing structures, which in turn affected the efficiency of the channel at mixing the fluid and saturating the surface opposite the mixing structures. The solute mixing as a function of the channel length was also determined; an initial slow mixing rate does not always coincide with a low mixing index (MI). We found that the range of MIs for the curved mixing structure 1 cm downstream from the inlet was 0.85–0.99 whilst for our HBS it was 0.74–0.98, depending on the design parameters of the passive mixing structures. Overall, this study shows that the curved passive mixing structure family is more robust in inducing efficient mixing than the HBSs

Curved passive mixing structures: a robust design to obtain efficient mixing and mass transfer in microfluidic channels

Analyte mixing and delivery to a functionalized sensor surface are important to realize several advantages associated with biosensors integrated with microfluidic channels. Here, we present a comparison between a herringbone structure (HBS) and a curved passive mixing structure of their efficiency at facilitating mixing and surface saturation using fluorescein included in one of the inlets of a Y-channel microfluidic device. We performed a large parametric study to assess the effects of varying the height of the microfluidic channel as well as the height, width, and spacing of the passive mixing structures. Scanning confocal microscopy combined with a custom-designed image-analysis procedure were utilized to visualize and quantify the observed changes in efficiency in inducing solute mixing by the different designs. The flow patterns within the channels were found to vary significantly with changes in the geometry of the passive mixing structures, which in turn affected the efficiency of the channel at mixing the fluid and saturating the surface opposite the mixing structures. The solute mixing as a function of the channel length was also determined; an initial slow mixing rate does not always coincide with a low mixing index (MI). We found that the range of MIs for the curved mixing structure 1 cm downstream from the inlet was 0.85–0.99 whilst for our HBS it was 0.74–0.98, depending on the design parameters of the passive mixing structures. Overall, this study shows that the curved passive mixing structure family is more robust in inducing efficient mixing than the HBSs

Simultaneous improvement of surface finish and bonding of centrifugal microfluidic devices in cyclo-olefin polymers

Two key issues in the manufacturing of microfluidic devices are to obtain low surface roughness, i.e. in the range of nanometers (to facilitate optical detection and controlled flow through microfluidic networks), and to achieve robust bonding. Here we report that a chemical polishing step, used for smoothening the surface of cyclo-olefin polymer (COP) components manufactured by micromilling, reduces the surface roughness (to Ra ∼ 150 nm) and facilitates a leak-tight COP-COP bond. We report new results on COP structuring and surface characterization by white light interferometry (WLI), infrared spectroscopy (FTIR-ATR), contact angle measurements and transmittance measurements, as well as demonstrations of a functional thermally bonded centrifugal microfluidic device

Simultaneous improvement of surface finish and bonding of centrifugal microfluidic devices in cyclo-olefin polymers

Two key issues in the manufacturing of microfluidic devices are to obtain low surface roughness, i.e. in the range of nanometers (to facilitate optical detection and controlled flow through microfluidic networks), and to achieve robust bonding. Here we report that a chemical polishing step, used for smoothening the surface of cyclo-olefin polymer (COP) components manufactured by micromilling, reduces the surface roughness (to Ra ∼ 150 nm) and facilitates a leak-tight COP-COP bond. We report new results on COP structuring and surface characterization by white light interferometry (WLI), infrared spectroscopy (FTIR-ATR), contact angle measurements and transmittance measurements, as well as demonstrations of a functional thermally bonded centrifugal microfluidic devicesSimultaneous improvement of surface finish and bonding of centrifugal microfluidic devices in cyclo-olefin polymersacceptedVersio