Sample-to-answer centrifugal microfluidic droplet PCR platform for quantitation of viral load.

Droplet digital polymerase chain reaction (ddPCR) stands out as a highly sensitive diagnostic technique that is gaining traction in infectious disease diagnostics due to its ability to quantitate very low numbers of viral gene copies. By partitioning the sample into thousands of droplets, ddPCR enables precise and absolute quantification without relying on a standard curve. However, current ddPCR systems often exhibit relatively low levels of integration, and the analytical process remains dependent on elaborate workflows for up-front sample preparation.

Reversible bonding in thermoplastic elastomer microfluidic platforms for harvestable 3D microvessel networks.

Transplantable ready-made microvessels have therapeutic potential for tissue regeneration and cell replacement therapy. Inspired by the natural rapid angiogenic sprouting of microvessels , engineered injectable 3D microvessel networks are created using thermoplastic elastomer (TPE) microfluidic devices. The TPE material used here is flexible, optically transparent, and can be robustly yet reversibly bonded to a variety of plastic substrates, making it a versatile choice for microfluidic device fabrication because it overcomes the weak self-adhesion properties and limited manufacturing options of poly(dimethylsiloxane) (PDMS).

Perspectives on Using Fast-Dissolving Paracetamol for Mild-to-Moderate Pain Management in Elderly or Diabetic Patients with Delayed Gastric Emptying Rates: An Exploratory Study.

Purpose: Pain is considered a major clinical and socioeconomic problem worldwide. Delayed gastric emptying rates allegedly influence the suitability of pain-relief medications in patient populations such as the elderly and individuals with diabetes. Faster pain relief was reportedly achieved by using a fast-dissolving paracetamol (FD-APAP) formulation.

Facile Fabrication of Flexible Polymeric Membranes with Micro and Nano Apertures over Large Areas.

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).

Automated sample-to-answer centrifugal microfluidic system for rapid molecular diagnostics of SARS-CoV-2.

Testing for SARS-CoV-2 is one of the most important assets in COVID-19 management and mitigation. At the onset of the pandemic, SARS-CoV-2 testing was uniquely performed in central laboratories using RT-qPCR. RT-qPCR relies on trained personnel operating complex instrumentation, while time-to-result can be lengthy (, 24 to 72 h).

Use of Polymer Micropillar Arrays as Templates for Solid-Phase Immunoassays.

We investigate the use of periodic micropillar arrays produced by high-fidelity microfabrication with cyclic olefin polymers for solid-phase immunoassays. These three-dimensional (3D) templates offer higher surface-to-volume ratios than two-dimensional substrates, making it possible to attach more antibodies and so increase the signal obtained by the assay. Micropillar arrays also provide the capacity to induce wicking, which is used to distribute and confine antibodies on the surface with spatial control.

Multifunctional magnetic nanoparticle cloud assemblies for capture of bacteria and isolation of microbial DNA.

We investigate the formation of suspended magnetic nanoparticle (MNP) assemblies (M-clouds) and their use for bacterial capture and DNA extraction. M-clouds are obtained as a result of magnetic field density variations when magnetizing an array of micropillars coated with a soft ferromagnetic NiP layer. Numerical simulations suggest that the gradient in the magnetic field created by the pillars is four orders of magnitude higher than the gradient generated by the external magnets.

An automated centrifugal microfluidic assay for whole blood fractionation and isolation of multiple cell populations using an aqueous two-phase system.

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.

Evaporation-Driven Water-in-Water Droplet Formation.

We present new observations of aqueous two-phase system (ATPS) thermodynamic and interfacial phenomena that occur inside sessile droplets due to water evaporation. Sessile droplets that contain polymeric solutions, which are initially in equilibrium in a single phase, are observed at their three-phase liquid-solid-air contact line. As evaporation of a sessile droplet proceeds, we find that submicron secondary water-in-water (W/W) droplets emerge spontaneously at the edges of the mother sessile droplet due to the resulting phase separation from water evaporation.

Polymer Micropillar Arrays for Colorimetric DNA Detection.

We describe the use of periodic micropillar arrays, produced from cyclic olefin copolymer using high-fidelity microfabrication, as templates for colorimetric DNA detection. The assay involves PCR-amplified gene markers for O157:H7 (, , , and ) incorporating a detectable digoxigenin label, which is revealed through an immunoenzymatic process following hybridization with target-specific oligonucleotide capture probes. The capacity of micropillar arrays to induce wicking is used to distribute and confine capture probes with spatial control, making it possible to achieve a uniform signal while allowing multiple, independent probes to be arranged in close proximity on the same substrate.

Anisotropic permeability in deterministic lateral displacement arrays.

We uncover anisotropic permeability in microfluidic deterministic lateral displacement (DLD) arrays. A DLD array can achieve high-resolution bimodal size-based separation of microparticles, including bioparticles, such as cells. For an application with a given separation size, correct device operation requires that the flow remains at a fixed angle to the obstacle array.

Microfluidic Integration of a Cloth-Based Hybridization Array System (CHAS) for Rapid, Colorimetric Detection of Enterohemorrhagic Escherichia coli (EHEC) Using an Articulated, Centrifugal Platform.

We describe the translation of a cloth-based hybridization array system (CHAS), a colorimetric DNA detection method that is used by food inspection laboratories for colony screening of pathogenic agents, onto a microfluidic chip format. We also introduce an articulated centrifugal platform with a novel fluid manipulation concept based on changes in the orientation of the chip with respect to the centrifugal force field to time the passage of multiple components required for the process. The platform features two movable and motorized carriers that can be reoriented on demand between 0 and 360° during stage rotation.

Twin tubular pinch effect in curving confined flows.

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.

Microfluidic filtration and extraction of pathogens from food samples by hydrodynamic focusing and inertial lateral migration.

Detecting pathogenic bacteria in food or other biological samples with lab-on-a-chip (LOC) devices requires several sample preparation steps prior to analysis which commonly involves cleaning complex sample matrices of large debris. This often underestimated step is important to prevent these larger particles from clogging devices and to preserve initial concentrations when LOC techniques are used to concentrate or isolate smaller target microorganisms for downstream analysis. In this context, we developed a novel microfluidic system for membrane-free cleaning of biological samples from debris particles by combining hydrodynamic focusing and inertial lateral migration effects.

All-thermoplastic nanoplasmonic microfluidic device for transmission SPR biosensing.

Early and accurate disease diagnosis still remains a major challenge in clinical settings. Biomarkers could potentially provide useful tools for the detection and monitoring of disease progression, treatment safety and efficacy. Recent years have witnessed prodigious advancement in biosensor development with research directed towards rapid, real-time, label-free and sensitive biomarker detection.

Printing of sub-20 nm wide graphene ribbon arrays using nanoimprinted graphite stamps and electrostatic force assisted bonding.

Nano-graphene ribbons are promising in many electronic applications, as their bandgaps can be opened by reducing the widths, e.g. below 20 nm.

Fabrication of a 60-nm-diameter perfectly round metal-dot array over a large area on a plastic substrate using nanoimprint lithography and self-perfection by liquefaction.

Typically, nanopatterning on plastic substrates has poor fidelity, poor adhesion, and low yield. Here the proposal of and the first experiment using a new fabrication method that overcomes the above obstacles and has achieved arrays of 60-nm-diameter, perfectly round metal dots over a large area on a polyethylene terephthalate (PET) substrate with high fidelity and high yield is reported. This new method is based on the use of a thin hydrogen silsesquioxane (HSQ) layer on top of PET, nanoimprint lithography, and self-perfection by liquefaction (SPEL).

Sub-10 nm self-enclosed self-limited nanofluidic channel arrays.

We report a new method to fabricate self-enclosed optically transparent nanofluidic channel arrays with sub-10 nm channel width over large areas. Our method involves patterning nanoscale Si trenches using nanoimprint lithography (NIL), sealing the trenches into enclosed channels by ultrafast laser pulse melting and shrinking the channel sizes by self-limiting thermal oxidation. We demonstrate that 100 nm wide Si trenches can be sealed and shrunk to 9 nm wide and that lambda-phage DNA molecules can be effectively stretched by the channels.

Crossing microfluidic streamlines to lyse, label and wash cells.

We present a versatile method for continuous-flow, on-chip biological processing of cells, large bio-particles, and functional beads. Using an asymmetric post array in pressure-driven microfluidic flow, we can move particles of interest across multiple, independent chemical streams, enabling sequential chemical operations. With this method, we demonstrate on-chip cell treatments such as labeling and washing, and bacterial lysis and chromosomal extraction.

Wafer-scale patterning of sub-40 nm diameter and high aspect ratio (>50:1) silicon pillar arrays by nanoimprint and etching.

We demonstrate wide-area fabrication of sub-40 nm diameter, 1.5 µm tall, high aspect ratio silicon pillar arrays with straight sidewalls by combining nanoimprint lithography (NIL) and deep reactive ion etching (DRIE). Imprint molds were used to pre-pattern nanopillar positions precisely on a 200 nm square lattice with long range order.

Microfluidic device for label-free measurement of platelet activation.

In this work we demonstrate a new microfluidic method for the rapid assessment of platelet size and morphology in whole blood. The device continuously fractionates particles according to size by displacing them perpendicularly to the fluid flow direction in a micro-fabricated post array. Whole blood, labeled with the fluorescent, platelet specific, antibody PE-anti-CD41, was run through the device and the positions of fluorescent objects noted as they exited the array.

Hydrodynamic metamaterials: microfabricated arrays to steer, refract, and focus streams of biomaterials.

We show that it is possible to direct particles entrained in a fluid along trajectories much like rays of light in classical optics. A microstructured, asymmetric post array forms the core hydrodynamic element and is used as a building block to construct microfluidic metamaterials and to demonstrate refractive, focusing, and dispersive pathways for flowing beads and cells. The core element is based on the concept of deterministic lateral displacement where particles choose different paths through the asymmetric array based on their size: Particles larger than a critical size are displaced laterally at each row by a post and move along the asymmetric axis at an angle to the flow, while smaller particles move along streamline paths.

Single sub-20 nm wide, centimeter-long nanofluidic channel fabricated by novel nanoimprint mold fabrication and direct imprinting.

We report and demonstrate a new method to fabricate single fluidic-channels of uniform channel width (11-50 nm) and over 1.5 cm in length, which are essential to developing innovative bio/chemical sensors but have not been fabricated previously. The method uses unconventional nanofabrication (a combination of crystallographic anisotropic etching, conformal coating, and edge patterning, etc.

Air cushion press for excellent uniformity, high yield, and fast nanoimprint across a 100 mm field.

Imprint pressure uniformity is crucial to the pattern uniformity and yield of nanoimprint lithography (NIL) and, hence, its applications. We studied a novel imprint method, air cushion press (ACP), in which the mold and substrate are pressed against each other by gas pressure rather than solid plates, and compared it with a common method, solid parallel-plate press (SPP). We found that (a) under normal imprinting conditions the measured pressure distribution across a 100-mm-diameter single imprint field in ACP is nearly an order of magnitude more uniform; (b) ACP is immune to any dust and topology variations on the backside of the mold or substrate; (c) when a dust particle is between the mold and substrate, ACP reduces the damage area by orders of magnitude; (d) ACP causes much less mold damage because of significantly less lateral shift between the mold and substrate; and (e) ACP has much smaller thermal mass and therefore significantly faster speed for thermal imprinting.

Deterministic hydrodynamics: taking blood apart.

We show the fractionation of whole blood components and isolation of blood plasma with no dilution by using a continuous-flow 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 microm/sec and volume rates up to 1 microl/min. 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.