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Freestanding, flexible and open through-hole polymeric micro- and nanostructured membranes were successfully fabricated over large areas (>16 cm2) via solvent removal of sacrificial scaffolds filled with polymer resin by spontaneous capillary flow. Most of the polymeric membranes were obtained through a rapid UV curing processes via cationic or free radical UV polymerisation. Free standing microstructured membranes were fabricated across a range of curable polymer materials, including: EBECRYL3708 (radical UV polymerisation), CUVR1534 (cationic UV polymerisation) UV lacquer, fluorinated perfluoropolyether urethane methacrylate UV resin (MD700), optical adhesive UV resin with high refractive index (NOA84) and medical adhesive UV resin (1161-M). The present method was also extended to make a thermal set polydimethylsiloxane (PDMS) membranes. The pore sizes for the as-fabricated membranes ranged from 100 µm down to 200 nm and membrane thickness could be varied from 100 µm down to 10 µm. Aspect ratios as high as 16.7 were achieved for the 100 µm thick membranes for pore diameters of approximately 6 µm. Wide-area and uniform, open through-hole 30 µm thick membranes with 15 µm pore size were fabricated over 44 × 44 mm2 areas. As an application example, arrays of Au nanodots and Pd nanodots, as small as 130 nm, were deposited on Si substrates using a nanoaperture polymer through-hole membrane as a stencil.

Fractionating whole blood and separating its constituent components one from another is an essential step in many clinical applications. Currently blood sample handling and fractionation processes remain a predominantly manual task that require well-trained operators to produce reliable and reproducible results. Herein, we demonstrate an advanced on-chip whole human blood fractionation and cell isolation process combining (i) an aqueous two-phase system (ATPS) to create complex separation layers with (ii) a centrifugal microfluidic platform (PowerBlade) with active pneumatic pumping to control and automate the assay. We use a polyethylene glycol (PEG) and dextran (DEX) mixture as the two-phase density gradient media and our automated centrifugal microfluidic platform to fractionate blood samples. Different densities of precisely tuned PEG–DEX solutions were tested to match each of the cell types typically targeted during blood fractionation applications. By employing specially designed microfluidic devices, we demonstrate the automation of the following steps: loading of a whole blood sample on-chip, layering of the blood on the ATPS solution, blood fractionation, precise radial repositioning of the fractionated layers, and finally extraction of multiple, selected fractionated components. Fractionation of up to six distinct layers is shown: platelet-rich plasma, buffy coat, PEG, DEX with neutrophils, red blood cells (RBCs) and high density gradient media (HDGM). Furthermore, through controlled dispensing of HDGM to the fractionation chamber, we show that each of the fractionated layers can be repositioned radially, on-the-fly, without disturbing the interfaces, allowing precise transfer of target fractions and cell types into external vials via a chip-to-world interface. Cell counting analysis and cell viability studies showed equivalence to traditional, manual methods. An overall cell viability greater than 90% of extracted cells demonstrates that the proposed approach is suitable for cell isolation applications. This proof-of-principle demonstration highlights the utility of the proposed system for automated whole blood fractionation and isolation for blood cell applications. We anticipate that the proposed approach will be a useful tool for many clinical applications such as standard cell isolation procedures and other bioanalytical assays (e.g., circulating tumor cells, and cell and gene therapy).

In this paper, we present a simple, versatile method that creates patterns for cell migration studies using thermoplastic elastomer (TPE). The TPE material used here can be robustly, but reversibly, bonded to a variety of plastic substrates, allowing patterning of cultured cells in a microenvironment. We first examine the bonding strength of TPE to glass and polystyrene substrates and com-pare it to thermoset silicone-based PDMS under various conditions and demonstrate that the TPE can be strongly and reversibly bonded on commercially available polystyrene culture plates. In cell migration studies, cell patterns are templated around TPE features cored from a thin TPE film. We show that the significance of fibroblast cell growth with fetal bovine serum (FBS)-cell culture media compared to the cells cultured without FBS, analyzed over two days of cell culture. This simple approach allows us to generate cell patterns without harsh manipulations like scratch assays and to avoid damaging the cells. We also confirm that the TPE material is non-toxic to cell growth and supports a high viability of fibroblasts and breast cancer cells. We anticipate this TPE-based patterning approach can be further utilized for many other cell patterning applications such as in cell-to-cell communication studies.

The development of technology for the rapid, automated identification of bacterial culture isolates can help regulatory agencies to shorten response times in food safety surveillance, compliance, and enforcement as well as outbreak investigations. While molecular methods such as polymerase chain reaction (PCR) enable the identification of microbial organisms with high sensitivity and specificity, they generally rely on sophisticated instrumentation and elaborate workflows for sample preparation with an undesirably high level of hands-on engagement. Herein, we describe the design, operation and performance of a lab-on-a-chip system integrating thermal lysis, PCR amplification and microarray hybridization on the same cartridge. The assay is performed on a centrifugal microfluidic platform that allows for pneumatic actuation of liquids during rotation, making it possible to perform all fluidic operations in a fully-automated fashion without the need for integrating active control elements on the microfluidic cartridge. The cartridge, which is fabricated from hard and soft thermoplastic polymers, is compatible with high-volume manufacturing (e.g., injection molding). Chip design and thermal interface were both optimized to ensure efficient heat transfer and allow for fast thermal cycling during the PCR process. The integrated workflow comprises 14 steps and takes less than 2 h to complete. The only manual steps are related to loading of the sample and reagents on the cartridge as well as fluorescence imaging of the microarray. On-chip lysis and PCR amplification both provided results comparable to those obtained by bench-top instrumentation. The microarray, incorporating a panel of oligonucleotide probes for multiplexed detection of seven enterohemorrhagic E. coli priority serotypes, was implemented on a cyclic olefin copolymer substrate using a novel activation scheme that involves the conversion of hydroxyl groups (derived from oxygen plasma treatment) into reactive cyanate ester using cyanogen bromide. On-chip hybridization was demonstrated in a non-quantitative fashion using fluorescently-labelled gene markers for E. coli O157:H7 (rfbO157, eae, vt1, and vt2) obtained through a multiplexed PCR amplification step.

A versatile method for fabricating both plasmonic and conductive metal structures in situ in polymer materials is presented. The process relies on UV induced radical polymerization of acrylic resin and gold nanoparticle formation by the reduction of a gold precursor in the presence of a photoinitiator. The room temperature fabrication process provides control over nanoparticle size, growth and distribution within the polymer matrix., 2020 IEEE 20th International Conference on Nanotechnology (IEEE-NANO), July 29-31, 2020, Montreal, QC, Canada

Hierarchical micro-nanostructures comprising nanopillars superimposed onto micropillars were successfully fabricated over larger areas on thermoplastic cyclic olefin polymer (COP) substrates. Both the nanostructures (100 nm to 500 nm diameter) and microstructures (14-20 μm diameter) were hot-embossed monolithically using an intermediate fluorinated polymer mold replicated from a Si master. The as-fabricated thermoplastic hierarchical micro-nanopillar surfaces are superhydrophobic with advancing contact angles greater than 150°. Superhydrophobic surfaces with static contact angle as large as 167° were achieved on COP substrates using nanopillars as small as 150 nm and following post-fabrication fluorocarbon coating. The sliding angle of a water drop on the superhydrophobic surface is 2.5°., 2020 IEEE 20th International Conference on Nanotechnology (IEEE-NANO), July 29-31, 2020, Montreal, QC, Canada

A multiplexed droplet PCR (mdPCR) workflow and detailed protocol for determining epigenetic-based white blood cell (WBC) differential count is described, along with a thermoplastic elastomer (TPE) microfluidic droplet generation device. Epigenetic markers are used for WBC subtyping which is of important prognostic value in different diseases. This is achieved through the quantification of DNA methylation patterns of specific CG-rich regions in the genome (CpG loci). In this paper, bisulfite-treated DNA from peripheral blood mononuclear cells (PBMCs) is encapsulated in droplets with mdPCR reagents including primers and hydrolysis fluorescent probes specific for CpG loci that correlate with WBC sub-populations. The multiplex approach allows for the interrogation of many CpG loci without the need for separate mdPCR reactions, enabling more accurate parametric determination of WBC sub-populations using epigenetic analysis of methylation sites. This precise quantification can be extended to different applications and highlights the benefits for clinical diagnosis and subsequent prognosis.

This paper describes the development of an on-chip nucleic acid (NA) extraction assay from whole blood using a centrifugal microfluidic platform that allows for pneumatic actuation of liquids during rotation. The combination of pneumatic and centrifugal forces makes it possible to perform fluidic operations without the need for integrating active control elements on the microfluidic cartridge. The cartridge is fabricated from thermoplastic polymers (e.g., Zeonor 1060R) and features a simple design that is compatible with injection molding. In addition, the cartridge is interfaced with two external vials for off-chip storage of the blood sample and retrieval of the eluted NA solution, respectively. On-chip capture of NAs is performed using an embedded solid-phase extraction matrix composed of commercial glass microfiber filters (Whatman GF/D and GF/F). The yield of the automated, on-chip extraction protocol, determined by measuring absorbance at 260 nm, is comparable to some of the best manually operated kits (e.g., Qiagen QIAamp DNA Mini Kit) while providing low assay-to-assay variability due to the high level of control provided by the platform for each processing step. The A260/A280 and A260/A230 ratios of the absorbance spectra also reveal that protein contamination of the sample is negligible. The capability of the pneumatic platform to circulate air flux through the microfluidic conduit was used to dry leftover ethanol residues retained in the capture matrix during washing. This method, applied in combination with localized heating, proved effective for reducing ethanol contamination in eluted samples from ∼12% to 1% (v/v).

Transformative advances in metagenomics are providing an unprecedented ability to characterize the enormous diversity of microorganisms and invertebrates sustaining soil health and water quality. These advances are enabling a better recognition of the ecological linkages between soil and water, and the biodiversity exchanges between these two reservoirs. They are also providing new perspectives for understanding microorganisms and invertebrates as part of interacting communities (i.e. microbiomes and zoobiomes), and considering plants, animals, and humans as holobionts comprised of their own cells as well as diverse microorganisms and invertebrates often acquired from soil and water. The Government of Canada's Genomics Research and Development Initiative (GRDI) launched the Ecobiomics Project to coordinate metagenomics capacity building across federal departments, and to apply metagenomics to better characterize microbial and invertebrate biodiversity for advancing environmental assessment, monitoring, and remediation activities. The Project has adopted standard methods for soil, water, and invertebrate sampling, collection and provenance of metadata, and nucleic acid extraction. High-throughput sequencing is located at a centralized sequencing facility. A centralized Bioinformatics Platform was established to enable a novel government-wide approach to harmonize metagenomics data collection, storage and bioinformatics analyses. Sixteen research projects were initiated under Soil Microbiome, Aquatic Microbiome, and Invertebrate Zoobiome Themes. Genomic observatories were established at long-term environmental monitoring sites for providing more comprehensive biodiversity reference points to assess environmental change.

Health maintenance and disease prevention in astronauts are of high priority during space missions. To achieve this aim, basic science of molecular biology has to be joined with modern noninvasive tools allowing high-fidelity research on diagnosing and monitoring of the astronauts’ health status. Experts from biology, medicine, and engineering should merge their expertise to enable additive effects for development and improvement of stress and immune-monitoring tools under extreme environmental conditions. This will hereby ensure not only the success of space missions, especially when leaving the Earth orbit in the future, but also will provide important impetus for many other applications on Earth as well.

SummaryCirculating tumor cells (CTCs) are rare (few cells per milliliter of blood) and mostly isolated as single cell CTCs (scCTCs). CTC clusters (cCTCs), even rarer, are of growing interest, notably because of their higher metastatic potential, but very difficult to isolate. Here, we introduce gravity-based microfiltration (GµF) for facile isolation of cCTCs. We identify cluster break-up as a confounding cause, and achieve ∼85% capture efficiency. GµF from orthotopic ovarian cancer mouse models and from 10 epithelial ovarian cancer (EOC) patients uncovered cCTCs in every case, with between 2-100+ cells. cCTCs represented between 5-30% of all CTC events, and 10-80% of captured CTCs were clustered; remarkably, in two patients, more CTCs were circulating as cCTCs than scCTCs. GµF uncovered the unexpected prevalence, frequency and sometimes large size of cCTCs in EOC patients with either metastatic and localized disease, and motivates additional studies to uncover their properties and role in disease progression.

Pathogenic bacteria can be a major cause of illness from environmental sources as well as the consumption of contaminated products, giving rise to public health concerns globally. The surveillance of such living organisms in food and water supplies remains an important challenge in mitigating their deleterious societal effects. Here, we have developed an optimized bioorthogonal non-canonical amino acid tagging approach to the imaging, capture, and interrogation of shigatoxigenic/verotoxigenic Escherichia coli (VTEC) and Listeria that enables the distinction between living wild-type pathogenic bacteria. The approaches utilize homopropargylglycine (HPG), as well as optimized growth media, that restricts endogenous methionine biosynthesis in a variety of species of public health concern. Endogenous methionine residues are then replaced with HPG, which can then be modified using a myriad of compatible bioorthogonal reactions for tagging of exclusively live bacteria. The methods reported allow for the very rapid screening and identification of living pathogenic organisms.

We present an integrated microfluidic system for performing isolation and concentration of Phytophthora ramorum pathogens using a chip whose working principle is based on inertial lateral migration in curving flows. The chip was fabricated from multiple layers of thermoplastic polymers and features an embedded spiral separation channel along with peristaltic microvalves for fluidic operation and process control. A pumping system paired with a fully programmable pressure manifold is used to boost concentration levels by recirculating the sample liquid multiple times through the separation chip, making it possible to reduce sample volumes from 10 to 1 mL or less. The system was calibrated using fluorescent polymer particles with a nominal diameter of 30 µm which is comparable to that of P. ramorum sporangia. The separation process has been shown to be highly effective and more than 99% of the beads can be recovered in the concentrated batch. Experiments conducted with P. ramorum sporangia have shown that a 5.3-fold increase in pathogen content with 95% recovery can be achieved using three subsequent concentration cycles. The utility of the method has been validated by processing a sample derived from infested Rhododendron leaves where a 6.1-fold increase in the concentration of P. ramorum has been obtained after four concentration cycles. Although specifically designed and demonstrated for sporangia of P. ramorum, the method and related design rules can easily be extended to other microbial organisms, effectively supporting bioanalytical applications where efficient, high-throughput separation of target species is of primary concern.

Colloidal suspensions of buoyancy neutral particles flowing in circular pipes focus into narrow distributions near the wall due to lateral migration effects associated with fluid inertia. In curving flows, these distributions are altered by Dean currents and the interplay between Reynolds and Dean numbers is used to predict equilibrium positions. Here, we propose a new description of inertial lateral migration in curving flows that expands current understanding of both focusing dynamics and equilibrium distributions. We find that at low Reynolds numbers, the ratio δ between lateral inertial migration and Dean forces scales simply with the particle radius, coil curvature and pipe radius as "Equation missing". A critical value δc = 0.148 of this parameter is identified along with two related inertial focusing mechanisms. In the regime below δc, coined subcritical, Dean forces generate permanently circulating, twinned annuli, each with intricate equilibrium particle distributions including eyes and trailing arms. At δ > δc (supercritical regime) inertial lateral migration forces are dominant and particles focus to a single stable equilibrium position.

Growing needs for highly efficient energy storage devices have prompted increasing research efforts in energy-efficient and sustainable materials. In this context, nanoporous noble metals have been studied extensively because of their extraordinary properties. However, existing electrochemical/chemical dealloying approaches for their synthesis largely lack the ability to optimize their structure/function relationships. To overcome this limitation, we developed a thermal-decomposition strategy for the synthesis of component-controllable nanoporous PtPd alloys composed of ∼2 nm sawtooth-like ligaments induced by a high density of twinning boundaries (boundary spacing ∼ 1 nm). Such twinned and ultrathin ligaments exhibit large curvatures between concave and convex regions, associated with abundant low-coordination surface atomic steps and kinks. These low-coordination atoms are sites of high catalytic activity, as confirmed by theoretical simulations. The optimized Pt25Pd75 sample exhibits the best catalytic performance among all the currently reported catalysts, and has a mass activity of 1110 mA mg−1Pt−1 and high stability for the electro-oxidation of methanol.

We present an all-thermoplastic integrated sample-to-answer centrifugal microfluidic Lab-on-Disc system (LoD) for nucleic acid analysis. The proposed CD system and engineered platform were employed for analysis of Bacillus atrophaeus subsp. globigii spores. The complete assay comprised cellular lysis, polymerase chain reaction (PCR) amplification, amplicon digestion, and microarray hybridization on a plastic support. The fluidic robustness and operating efficiency of the assay were ensured through analytical optimization of microfluidic tools enabling beneficial implementation of capillary valves and accurate control of all flow timing procedures. The assay reliability was further improved through the development of two novel microfluidic strategies for reagents mixing and flow delay on the CD platform. In order to bridge the gap between the proof-of-concept LoD and production prototype demonstration, low-cost thermoplastic elastomer (TPE) was selected as the material for CD fabrication and assembly, allowing the use of both, high quality hot-embossing and injection molding processes. Additionally, the low-temperature and pressure-free assembly and bonding properties of TPE material offer a pertinent solution for simple and efficient loading and storage of reagents and other on-board components. This feature was demonstrated through integration and conditioning of microbeads, magnetic discs, dried DNA buffer reagents and spotted DNA array inserts. Furthermore, all microfluidic functions and plastic parts were designed according to the current injection mold-making knowledge for industrialization purposes. Therefore, the current work highlights a seamless strategy that promotes a feasible path for the transfer from prototype toward realistic industrialization. This work aims to establish the full potential for TPE-based centrifugal system as a mainstream microfluidic diagnostic platform for clinical diagnosis, water and food safety, and other molecular diagnostic applications.

This paper describes the design, functioning and use of a portable detection platform for multiplex nucleic acid testing. The system features a bead-supported DNA hybridization assay performed inside a microfluidic cartridge. Polystyrene particles modified with DNA capture probes are confined in the detection area and exposed to a solution of fluorescently labeled target DNA strands. The cartridge, fabricated from inexpensive thermoplastic polymers, allows for conducting up to eight assays in parallel. The detection instrument is equipped with a pneumatic module and a manifold lid serving as an interface to mediate fluid displacement on the cartridge. The fluorescence signal deriving from each assay is recorded by a semi-confocal fluorescence reader embedded in the detection platform. The compact design of the instrument and its level of integration make it possible to obtain an analytical result in less than 15 min, while only few manual steps need to be performed in between. A proof-of-concept demonstration involving Cy3-labeled, PCR-amplified genomic DNA confirms the ability to detect Bacillus anthracis in a multiplexed single-assay format using lef and capC genes. Limits of quantification are on the order of 1 × 109 copies/μL for lef targets. © 2013 Springer-Verlag Berlin Heidelberg.

Despite the advances made in the field of regenerative medicine , the progress in cutting-edge technologies for separating target therapeutic cells are still at early stage of development. These cells are often rare, such as stem cells or progenitor cells that their overall properties should be maintained during the separation process for their subsequent application in regenerative medicine. This work, presents separation of oligodendrocyte progenitor cells (OPCs) from rat brain primary cultures using an integrated thermoplastic elastomeric (TPE)- based multilayer microfluidic device fabricated using hot-embossing technology. OPCs are frequently used in recovery, repair and regeneration of central nervous system after injuries. Indeed, their ability to differentiate in vitro into myelinating oligodendrocytes , are extremely important for myelin repair. OPCs form 5–10% of the glial cells population. The traditional macroscale techniques for OPCs separation require pre-processing of cells and/or multiple time consuming steps with low efficiency leading very often to alteration of their properties. The proposed methodology implies to separate OPCs based on their smaller size compared to other cells from the brain tissue mixture. Using aforementioned microfluidic chip embedded with a 5 μm membrane pore size and micropumping system, a separation efficiency more than 99% was achieved. This microchip was able to operate at flow rates up to 100 μl/min, capable of separating OPCs from a confluent 75 cm 2 cell culture flask in less than 10 min, which provides us with a high-throughput and highly efficient separation expected from any cell sorting techniques.

We report the synthesis of Fe(3)O(4)/silica core/shell nanoparticles and their functionalization with S-nitrosothiols. These nanoparticles are of immense interest because of their nitric oxide (NO) release capabilities in human alveolar epithelial cells. Moreover, they act as large storage reservoirs of NO that can be targeted magnetically to the specific site with a sustainable release of NO for up to 50 h. Such nanoparticles provide an enhancement of the biocompatibility with released NO while allowing intracellular accumulation ascribed to their small size.

We demonstrate a one-step procedure for the synthesis of Fe3O4–silica core–shell nanoparticles with hierarchically ultra-large pores independent of any post-treatment such as annealing and template-molecule removal. The nanoporous silica shells with available amine groups were functionalized by clickable linkers to produce pH-sensitive amides for regulating the release of an anti-cancer drug, doxorubicin (DOX). The loading amount of DOX reached up to 13.2 mg per 100 mg nanoparticles, 74.2% of which can be effectively released after 63 h at body temperature and pH 5 with decreased side effects. Such excellent features of these nanoparticles appear to arise from the integrated hierarchically ultra-large open-porosities and a homogeneous dispersibility in aqueous solution that has a great potential for their use as drug delivery systems.

BACKGROUND: Insulin-like growth factor-binding protein 7 (IGFBP7) is an abundant, selective and accessible biomarker of glioblastoma multiforme (GBM) tumour vessels. In this study, an anti-IGFBP7 single-domain antibody (sdAb) was developed to target GBM vessels for molecular imaging applications. METHODS: Human GBM was modelled in mice by intracranial implantation of U87MG.EGFRvIII cells. An anti-IGFBP7 sdAb, isolated from an immune llama library by panning, was assessed in vitro for its binding affinity using surface plasmon resonance and by ex vivo immunobinding on mouse and human GBM tissue. Tumour targeting by Cy5.5-labelled anti-IGFBP7 sdAb as well as by anti-IGFBP7 sdAb conjugated to PEGylated Fe3O4 nanoparticles (NPs)-Cy5.5 were assessed in U87MG.EGFRvIII tumour-bearing mice in vivo using optical imaging and in brain sections using fluorescent microscopy. RESULTS: Surface plasmon resonance analyses revealed a medium affinity (KD�40�50 nM) binding of the anti-IGFBP7 sdAb to the purified antigen. The anti-IGFBP7 sdAb also selectively bound to both mouse and human GBM vessels, but not normal brain vessels in tissue sections. In vivo, intravenously injected anti-IGFBP7 sdAb-Cy5.5 bound to GBM vessels creating high imaging signal in the intracranial tumour. Similarly, the anti-IGFBP7 sdAb-functionalised PEGylated Fe3O4 NP-Cy5.5 demonstrated enhanced tumour signal compared with non-targeted NPs. Fluorescent microscopy confirmed the presence of anti-IGFBP7 sdAb and anti-IGFBP7 sdAb- PEGylated Fe3O4 NPs selectively in GBM vessels. CONCLUSIONS: Anti-IGFBP7 sdAbs are novel GBM vessel-targeting moieties suitable for molecular imaging.

This paper describes an experimentally simple and efficient way of integrating bead-based mechanical cell lysis on a plastic chip. The chip is fabricated from machined slides of poly(methylmethacrylate) and accommodates a metal disk along with solid microbeads in a designated lysis chamber. Magnetic actuation of the metal disk induces collisions and frictional forces within the lysis matrix causing cell disruption. The efficiency of nucleic acid extraction was investigated using spores of Bacillus atrophaeus subsp. globigii and the amount of genomic DNA in the lysates has been quantified by real-time PCR. Compared to a standardized DNA extraction method based on BD GeneOhm™ Lysis Kit, the yield was dependent on the composition of the lysis matrix, including size and relative amount of microbeads, along with instrumental parameters, such as duration and frequency of agitation. The interplay of these parameters should allow for optimizing lysis protocols to faithfully disrupt any particular type of cell without affecting the genetic material to be extracted.

This paper presents a low-cost technique for the fabrication of complex electrowetting-on-dielectric (EWOD) digital microfluidic devices. Using this original technology, we have developed devices in which 560 electrodes are used to mix and split nl-size liquid droplets and transport them to 100 analysis spots patterned on a disposable plastic top plate. We demonstrate the multiplexing capability of the developed devices by creating on-chip arrays of droplets with various concentration gradients. Finally, automated biomolecular immobilization and hybridization assays are performed in nl-size droplets under numerous conditions simultaneously with only a limited number of stock solutions., 24th IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2011), Jan. 23-27, 2011, Cancun, Mexico

This article describes the fabrication of microfluidic networks (μFNs) from a commercially available (styrene)-(ethylene/butylene)-(styrene) (SEBS) block copolymer (BCP). The unique combination of hard and elastomeric properties provided by this material promotes high-throughput replication of fluidic structures using thermoforming technologies, while retaining the advantage of quick and easy assembly via conformal contact, as commonly achieved for devices fabricated from poly(dimethylsiloxane (PDMS). We employ Versaflex CL30, which is optically transparent, available at low cost (e.g., $2.50/Lbs), and likely to be compatible with a broad range of biological species. We demonstrate excellent fidelity in replication of fluidic structures using hot embossing lithography in conjunction with a photolithographically prepared Si/SU-8 master mold. Moreover, we introduce rapid prototyping of high-quality structures using an approach that we call soft thermoplastic lithography (STPL). Thanks to the rheological characteristics of the SEBS copolymer, STPL enables thermoforming on a heated master at temperatures around 170°C. Using this approach, replication can be completed within a very short period of time (e.g., less than 3 min) without the need of resorting to pressure- or vacuum-assisted instrumentation. Serving as a proof-of-concept, we devise a μFN that is suitable for the formation of miniaturized arrays comprising fluorescently labeled oligonucleotides and proteins on hard plastic substrates. Resultant spots are characterized by high fluorescent contrast, excellent edge definition, and uniform distribution of probes within the modified areas. © Springer-Verlag 2011.

Electrical actuation and control of liquid droplets in Hele-Shaw cells have significant importance for microfluidics and lab-on-chip devices. Numerical modeling of complex physical phenomena like contact line dynam- ics, dynamic contact angles or contact angle hysteresis involved in these processes do challenge in a significant manner classical numerical approaches based on macro- scopic Navier-Stokes partial differential equations. In this paper, we analyze the efficiency of a numerical lattice Boltzmann model to simulate basic transport operations of sub-millimeter liquid droplets in electrowetting actuated Hele-Shaw cells. We use a two-phase three-dimensional D3Q19 lattice Boltzmann scheme driven by a Shan-Chen- type mesoscopic potential in order to simulate the gas- liquid equilibrium state of a liquid droplet confined between two solid plates. The contact angles at the liquid- solid-gas interface are simulated by taking into consider- ation the interaction between fluid particles and solid nodes. The electrodes are designed as regions of tunable wettability on the bottom plate and the contact angles adjusted by changing the interaction strength of the liquid with these regions. The transport velocities obtained with this approach are compared to predictions from analytical models and very good agreement is obtained.

Miniaturized DNA arrays are obtained by using elastic deformation in conjunction with conventional pin spotting. The process takes advantage of elastomers that offer high mechanical flexibility, which makes it possible to achieve substantial miniaturization in a single step.

This paper describes two enhanced resist reflow methods for the fabrication of microlens arrays and demonstrates their use for integrated biomolecular fluorescence detection on printed microarrays. A PDMS (polydimethylsiloxane) microlens array was fabricated by a double soft lithography approach using a photoresist microlens array as master mold. Additionally, by using both a careful control of the surface wettability and thermal treatments, we demonstrate the possibility to extend the resist reflow process in order to tune the diameters of microlens array over a large range by using a unique photomask pattern. We introduce an enhanced reflow on hydrophobic surfaces obtained by fluorosilane treatment and identify a threshold shrinkage temperature (T"s"h"r"i"n"k"a"g"e) of 140^oC, above which the diameter of microlenses can be then reduced down to 40% compared with the initial pattern on the photomask. Furthermore, on hydrophilic substrates, achieved by an accurate incomplete development of the photoresist, we demonstrate a nearly perfect linear dependency ([email protected]/^oC) of microlens diameter spreading up to 70% the initial diameter inside a temperature reflow window of 110-140^oC. For both approaches, above a freezing temperature (T"f"r"e"e"z"i"n"g) of 170^oC, the microlens profile characteristics are temperature independent. By using high numerical aperture microlens array, we provide a proof of concept for the integration and enhanced light collection of the fluorescent signals collected form a microarray of fluorescent spots thus showing the potential of the concept for biophotonic integration.

The organization of cells and extracellular matrix (ECM) in native tissues plays a crucial role in their functionality. However, in tissue engineering, cells and ECM are randomly distributed within a scaffold. Thus, the production of engineered-tissue with complex 3D organization remains a challenge. In the present study, we used contact guidance to control the interactions between the material topography, the cells and the ECM for three different tissues, namely vascular media, corneal stroma and dermal tissue. Using a specific surface topography on an elastomeric material, we observed the orientation of a first cell layer along the patterns in the material. Orientation of the first cell layer translates into a physical cue that induces the second cell layer to follow a physiologically consistent orientation mimicking the structure of the native tissue. Furthermore, secreted ECM followed cell orientation in every layer, resulting in an oriented self-assembled tissue sheet. These self-assembled tissue sheets were then used to create 3 different structured engineered-tissue: cornea, vascular media and dermis. We showed that functionality of such structured engineered-tissue was increased when compared to the same qnon-structured tissue. Dermal tissues were used as a negative control in response to surface topography since native dermal fibroblasts are not preferentially oriented in vivo. Non-structured surfaces were also used to produce randomly oriented tissue sheets to evaluate the impact of tissue orientation on functional output. This novel approach for the production of more complex 3D tissues would be useful for clinical purposes and for in vitro physiological tissue model to better understand long standing questions in biology.

Arrays of Au nanowells (NWs) were fabricated by electron-beam lithography (EBL) and characterized by surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS). It is revealed that these Au NW arrays exhibit multiple SP resonances that can be tuned by adjusting the geometrical characteristics of the NWs. SERS activity of Au NWs was confirmed for a range of excitation wavelengths and a number of model compounds including rhodamine 6G (R6G), phthalazine, and single-stranded oligonucleotides. According to numerical simulations based on the discrete dipole approximation (DDA), SERS enhancement originates from high electromagnetic fields (hot spots) localized both inside and outside individual NWs. In addition, far-field intercoupling effects between NWs have been observed experimentally in arrays with subwavelength pitch sizes. We show that the SERS enhancement factors can also be tuned and optimized by adjusting the geometry of NWs.

We explore periodic gold nanoposts as substrates for the enhanced surface plasmon resonance imaging (SPRi) detection of DNA hybridization. Rigorous coupled-wave analysis was used to model and design the nanopost-based SPRi biosensor. Arrayed gold nanoposts on gold-coated glass substrate, with various widths and periodicity, were fabricated using electron-beam lithography and characterized with scanning electron and atomic force microscopy. A scanning-angle SPRi apparatus was used to conduct the kinetic analysis of DNA hybridization on nanopost-based sensor surface and assess the corresponding SPR signal amplification. Experimental results showed that both the nanostructure size and period influenced the SPR signal enhancement; the optimized 30 nm height, 50 nm size, and 110 nm period nanoposts provided a fivefold SPR signal amplification compared with the plain 50 nm thick gold film used as control.

A nonparametric approach to the identification of magnetic anisotropies in ferromagnetic nanostructures is applied in order to study the influence of the bath acidity on the induced magnetic anisotropies in electrodeposited ferromagnetic nanowires. By using partial first order reversal curves (pFORC), we find a two-peak probability density function whose topology changes with the acidity of the electrodeposition bath. Numerical micromagnetic simulations suggest that this particular distribution originates in two populations of nonidentical nanowires with different magneto-crystalline anisotropies. Bath acidity values influence the balance between these two populations rather than the intrinsic properties of individual nanowires.

We present a numerical study on the dynamics of magnetic micro- and nano-objects subjected to magnetic field gradients in conventional continuous-flow microfluidic devices. By a mixed finite-element/discrete-element approach we solve the equations of the field driven motion for magnetic nano-objects floating in liquids at very low Reynolds numbers and compare the magnetic trapping efficiency of commercially available superparamagnetic microbeads to that of ferromagnetic nanowires. The drag force and the remanent magnetization of ferromagnetic nanowires are found to be responsible for the huge increase of their magnetic trappability whereas the slip-length associated with the Navier boundary condition at the transition to the nanoscale regime is found to be a much less important parameter.

We report a new technique for fabricating metal nanoring array. In the process, a Cr nanodisk array was first formed by evaporating Cr onto the bottom of a 200 nm period hole array having large undercut. The hole array was produced by NIL and RIE pattern transfer in a polymer sandwiched between a thin SiO₂ and Si layer, which were stacked on a second polymer layer; and the undercut was formed by excessive polymer RIE. The thin Si surrounding the Cr disk was subsequently etched through by SF₆ RIE, resulting in a ring-shaped hole structure in Si. After removing SiO₂ and the first polymer layer and etching through the second polymer layer, a metal ring array was created by standard evaporation and liftoff. As examples, we fabricated Cr nanoring array with height 15 nm, inner diameter 70–120 nm and ring-width down to 22 nm. We have found that, for a fixed hole diameter, the ring-diameter is strongly dependent on the hole depth. The ring symmetry and the wafer edge effect are discussed. The process can certainly be extended to metals other than Cr. Compared to previous methods, the current one is simpler, less costly and more suitable for narrow ring fabrication, though it suffers from reduced ring symmetry. However, asymmetric (nonconcentric) nanoring could be desirable for magnetic data storage and plasmonic devices.

The authors present a laser-assisted nanotransfer printing technique for transferring metal nanopatterns onto prepatterned substrates. A fused quartz mold covered with an array of chromium nanodots is pressed against the surface of a photolithographically patterned substrate, while a single laser pulse from a quadrupled-frequency solid state Nd:YAG laser is used to melt the thin metal structures. By controlling the laser fluence, selective metal pattern transfer can be realized only on the protruded area of the substrate upon separation of the quartz support. The transferred chromium nanodots are then used as an etch mask to pattern three-dimensional structures.

Polyimides have attractive thermal, mechanical and electrical properties, and have found applications in fields ranging from spacecraft to microelectronics and optoelectronics. Patterning polyimide at nanoscale would open the window for many new applications. In this work, we developed three approaches to pattern polyimide using nanoimprint lithography (NIL): imprint at its uncured soft state and cure it afterwards; imprint another low Tg polymer, then transfer the pattern into polyimide by RIE; and direct imprint into polyimide at temperature higher than its Tg. Polyimide gratings with 200nm period and 110nm line-width were successfully fabricated by all the three approaches. Each approach has its advantages and disadvantages. The first method is relatively simple and fast, but some residual solvent and water may cause outgassing when subjected to temperature well above 200^oC for prolonged time. The second approach is more complicated, while the third approach needs very high temperature. Two applications of the nanostructured polyimide are demonstrated: as a flexible mould to structure PMMA by NIL and as a template for chemical sensor based on surface enhanced Raman spectroscopy (SERS). Both applications have taken advantage of polyimide's high temperature stability and excellent mechanical properties, and cannot be realized by other common thermoplastic polymers. We believe that NIL is an efficient technique to pattern polyimide with high throughput and low cost.

The Enzyme-Linked Immuno-Sorbent Assay, or ELISA, is commonly utilized to quantify small concentrations of specific proteins for a large variety of purposes, ranging from medical diagnosis to environmental analysis and food safety. However, this technique requires large volumes of costly reagents and long incubation periods. The use of microfluidics permits one to specifically address these drawbacks by decreasing both the volume and the distance of diffusion inside the micro-channels. Existing microfluidic systems are limited by the necessary control of extremely low flow rates to provide sufficient time for the molecules to interact with each other by diffusion only. In this paper, we describe a new microfluidic design for the realization of parallel ELISA in stop-flow conditions. Magnetic beads were used both as a solid phase to support the formation of the reactive immune complex and to achieve a magnetic mixing inside the channels. In order to test the detection procedure, the formation of the immune complex was performed off-chip before the reactive beads were injected into the reaction chamber. Anti-streptavidin antibodies were quantified with low picomolar sensitivity (0.1-6.7 pM), a linear range of 2 orders of magnitude and good reproducibility. This work represents the first step toward a new platform for simple, highly effective and parallel microfluidic ELISA.

Today, the focus in microfluidic platforms for diagnostics is on the integration of several analysis steps toward sample-to-answer systems. One of the main challenges to integration is the requirement for serial valving to allow the sequential release of fluids in a temporally and spatially controlled manner. The advantages offered by centrifugal microfluidic platforms make them excellent candidates for integration of biological analysis steps, yet they are limited by the lack of robust serial valving technologies. This is especially true for the majority of centrifugal microfluidic devices that rely on hydrophilic surfaces, where few passive serial valving techniques function reliably. Building on the useful functionality of centrifugal microfluidic siphoning previously shown, a novel serial siphon valve is introduced that relies on multiple, inline siphons to provide for a better controlled, sequential release of fluids. The introduction of this novel concept is followed by an analytical analysis of the device. Proof-of-concept is also demonstrated, and examples are provided to illustrate the range of functionality of the serial siphon valve. The serial siphon is shown to be robust and reproducible, with variability caused by the dependence on contact angle, rotation velocity, and fluidic properties (viz., surface tension) significantly reduced compared to current microfluidic, centrifugal serial valving technologies.