Portable platform for leukocyte extraction from blood using sheath-free microfluidic DLD.

Leukocyte count is routinely performed for diagnostic purposes and is rapidly emerging as a significant biomarker for a wide array of diseases. Additionally, leukocytes have demonstrated considerable promise in novel cell-based immunotherapies. However, the direct retrieval of leukocytes from whole blood is a significant challenge due to their low abundance compared to erythrocytes.

Microfluidic 3D hepatic cultures integrated with a droplet-based bioanalysis unit.

A common challenge in microfluidic cell cultures has to do with analysis of cell function without replacing a significant fraction of the culture volume and disturbing local concentration gradients of signals. To address this challenge, we developed a microfluidic cell culture device with an integrated bioanalysis unit to enable on-chip analysis of picoliter volumes of cell-conditioned media. The culture module consisted of an array of 140 microwells with a diameter of 300 m which were made low-binding to promote organization of cells into 3D spheroids.

Millifluidic valves and pumps made of tape and plastic.

There is growing interest in producing micro- and milli-fluidic technologies made of thermoplastic with integrated fluidic control elements that are easy to assemble and suitable for mass production. Here, we developed millifluidic valves and pumps made of acrylic layers bonded with double-sided tape that are simple and fast to assemble. We demonstrate that a layer of pressure-sensitive adhesive (PSA) is flexible enough to be deformed at relatively low pressures.

Secretion Function Analysis of Ex Vivo Immune Cells in an Integrated Microfluidic Device.

Immune cells play a major role in the development of cancer, from being able to inhibit it by secreting pro-inflammatory mediators, to assist in its development by secreting growth factors, immunosuppressive mediators, and ECM-modifying enzymes. Therefore, the ex vivo analysis of the secretion function of immune cells can be employed as a reliable prognostic biomarker in cancer. However, one limiting factor in current approaches to probe the ex vivo secretion function of cells is their low throughput and the consumption of large quantities of sample.

On-Chip Analysis of Protein Secretion from Single Cells Using Microbead Biosensors.

The profiling of the effector functions of single immune cells─including cytokine secretion─can lead to a deeper understanding of how the immune system operates and to potential diagnostics and therapeutical applications. Here, we report a microfluidic device that pairs single cells and antibody-functionalized microbeads in hydrodynamic traps to quantitate cytokine secretion. The device contains 1008 microchambers, each with a volume of ∼500 pL, divided into six different sections individually addressed to deliver an equal number of chemical stimuli.

Microfluidic systems for the analysis of blood-derived molecular biomarkers.

Biomarkers are relevant indicators of the physiological state of an individual. Although biomarkers can be found in diseased tissue and different biofluids, sampling from blood plasma is relatively easy and less invasive. Among the molecular biomarkers that can be found circulating in plasma are proteins, metabolites, nucleic acids, and exosomes.

A high-throughput multiplexed microfluidic device for COVID-19 serology assays.

The applications of serology tests to the virus SARS-CoV-2 are diverse, ranging from diagnosing COVID-19, understanding the humoral response to this disease, and estimating its prevalence in a population, to modeling the course of the pandemic. COVID-19 serology assays will significantly benefit from sensitive and reliable technologies that can process dozens of samples in parallel, thus reducing costs and time; however, they will also benefit from biosensors that can assess antibody reactivities to multiple SARS-CoV-2 antigens. Here, we report a high-throughput microfluidic device that can assess antibody reactivities against four SARS-CoV-2 antigens from up to 50 serum samples in parallel.

Birefringent optofluidic gratings.

A set of parallel microfluidic channels behaving as a diffraction grating operating in the Raman-Nath regime has been fabricated and studied. The diffraction efficiency of such structure can be tuned by selecting a liquid with a particular refractive index and/or optical anisotropy. Alternatively the optical properties of the liquid can be characterised by measuring the diffraction efficiency and the state of polarization of the diffracted beam.

An affordable 3D-printed positioner fixture improves the resolution of conventional milling for easy prototyping of acrylic microfluidic devices.

We present a simple and low-cost positioner fixture to improve the fabrication resolution of acrylic microchannels using conventional milling machines. The positioner fixture is a mechatronic platform that consists of three piezoelectric actuators assembled in a housing made of 3D printer parts. The upper part of the housing is raised by the simultaneous actuation of the piezoelectric elements and by the deformation of 3D-printed hinge-shaped supports.

A versatile microfluidic device for multiple ex vivo/in vitro tissue assays unrestrained from tissue topography.

Precision-cut tissue slices are an important in vitro system to study organ function because they preserve most of the native cellular microenvironments of organs, including complex intercellular connections. However, during sample manipulation or slicing, some of the natural surface topology and structure of these tissues is lost or damaged. Here, we introduce a microfluidic platform to perform multiple assays on the surface of a tissue section, unhindered by surface topography.

Integrated Microfluidic Device for Functional Secretory Immunophenotyping of Immune Cells.

Integrated platforms for automatic assessment of cellular functional secretory immunophenotyping could have a widespread use in the diagnosis, real-time monitoring, and therapy evaluation of several pathologies. We present a microfluidic platform with integrated biosensors and culture chambers to measure cytokine secretion from a consistent and uniform number of immune cells. The biosensor relies on a fluorescence sandwich immunoassay enabled by the mechanically induced trapping of molecular interactions method.

Microfluidic systems for cancer diagnostics.

Although not employed in the clinic as of yet, microfluidic systems are likely to become a key technology for cancer diagnostics and prognosis. Microfluidic devices have been developed for the analysis of various biomarkers including circulating tumor cells, cell-free DNA, exosomes, and proteins, primarily in liquid biopsies such as serum, plasma, and whole blood, avoiding the need for tumor tissue biopsies. Here, we summarize microfluidic technological advances that are used in cancer diagnosis, prognosis, and to monitor its progression and recurrence, that will likely lead to personalized therapies.

Liquid refractive index measured through a refractometer based on diffraction gratings.

We developed two versions of refractometers to measure the refractive index of liquids. One refractometer comprises a glass cell with a surface relief grating on the inner face of one of its walls, while the other one is a microfluidic channel in the form of serpentine that behaves as a grating. Measurements of the liquid refractive index were performed by sensing the first order intensity.

Facile assembly of an affordable miniature multicolor fluorescence microscope made of 3D-printed parts enables detection of single cells.

Fluorescence microscopy is one of the workhorses of biomedical research and laboratory diagnosis; however, their cost, size, maintenance, and fragility has prevented their adoption in developing countries or low-resource settings. Although significant advances have decreased their size, cost and accessibility, their designs and assembly remain rather complex. Here, inspired on the simple mechanism from a nut and a bolt, we report the construction of a portable fluorescence microscope that operates in bright-field mode and in three fluorescence channels: UV, green, and red.

Automated Droplet-Based Microfluidic Platform for Multiplexed Analysis of Biochemical Markers in Small Volumes.

The ability to detect multiple analytes in a small sample volume has significance for numerous areas of research, including organs-on-chip, small animal experiments, and neonatology. The objective of this study was to develop an automated microfluidics platform for multiplexed detection of analytes in microliter sample volumes. This platform employed computer-controlled microvalves to create laminar co-flows of sample and assay reagent solutions.

Dynamic Generation of Concentration- and Temporal-Dependent Chemical Signals in an Integrated Microfluidic Device for Single-Cell Analysis.

Intracellular signaling pathways are affected by the temporal nature of external chemical signaling molecules such as neurotransmitters or hormones. Developing high-throughput technologies to mimic these time-varying chemical signals and to analyze the response of single cells would deepen our understanding of signaling networks. In this work, we introduce a microfluidic platform to stimulate hundreds of single cells with chemical waveforms of tunable frequency and amplitude.

An Affordable and Portable Thermocycler for Real-Time PCR Made of 3D-Printed Parts and Off-the-Shelf Electronics.

The polymerase chain reaction (PCR) is a sought-after nucleic acid amplification technique used in the detection of several diseases. However, one of the main limitations of this and other nucleic acid amplification assays is the complexity, size, maintenance, and cost of their operational instrumentation. This limits the use of PCR applications in settings that cannot afford the instruments but that may have access to basic electrical, electronic, and optical components and the expertise to build them.

Pressure-actuated monolithic acrylic microfluidic valves and pumps.

In this article, we describe a microfluidic device with embedded valves and pumps made exclusively of layers of acrylic glass. Flat acrylic sheets are carved out with a micromilling machine and bonded together by solvent bonding. The working principle of the valves is based on a thin flexible membrane (≈100 μm) machined on one acrylic sheet and actuated with pneumatic pressure.

Simple scaling laws for the evaporation of droplets pinned on pillars: Transfer-rate- and diffusion-limited regimes.

The evaporation of droplets can give rise to a wide range of interesting phenomena in which the dynamics of the evaporation are crucial. In this work, we find simple scaling laws for the evaporation dynamics of axisymmetric droplets pinned on millimeter-sized pillars. Different laws are found depending on whether evaporation is limited by the diffusion of vapor molecules or by the transfer rate across the liquid-vapor interface.

Sessile droplets for chemical and biological assays.

Sessile droplets are non-movable droplets spanning volumes in the nL-to-μL range. The sessile-droplet-based platform provides a paradigm shift from the conventional, flow-based lab-on-a-chip philosophy, yet offering similar benefits: low reagent/sample consumption, high throughput, automation, and most importantly flexibility and versatility. Moreover, the platform relies less heavily on sophisticated fabrication techniques, often sufficient with a hydrophobic substrate, and no pump is required for operation.

Massive Parallel Analysis of Single Cells in an Integrated Microfluidic Platform.

New tools that facilitate the study of cell-to-cell variability could help uncover novel cellular regulation mechanisms. We present an integrated microfluidic platform to analyze a large number of single cells in parallel. To isolate and analyze thousands of individual cells in multiplexed conditions, our platform incorporates arrays of microwells (7 pL each) in a multilayered microfluidic device.

A low-cost 3-D printed stethoscope connected to a smartphone.

We demonstrate the fabrication of a digital stethoscope using a 3D printer and commercial off-the-shelf electronics. A chestpiece consists of an electret microphone embedded into the drum of a 3D printed chestpiece. An electronic dongle amplifies the signal from the microphone and reduces any external noise.

Evaporation-Driven Bioassays in Suspended Droplets.

The microtiter plate has been an essential tool for diagnostics, high-throughput screening, and biological assays. We present an alternative platform to perform bioassays in a microplate format that exploits evaporation to drive assay reactions. Our method consists of droplets suspended on plastic pillars; reactions occur in these droplets instead of the wells.

3D-printing of transparent bio-microfluidic devices in PEG-DA.

The vast majority of microfluidic systems are molded in poly(dimethylsiloxane) (PDMS) by soft lithography due to the favorable properties of PDMS: biocompatible, elastomeric, transparent, gas-permeable, inexpensive, and copyright-free. However, PDMS molding involves tedious manual labor, which makes PDMS devices prone to assembly failures and difficult to disseminate to research and clinical settings. Furthermore, the fabrication procedures limit the 3D complexity of the devices to layered designs.

Mechanically Induced Trapping of Molecular Interactions and Its Applications.

Measuring binding affinities and association/dissociation rates of molecular interactions is important for a quantitative understanding of cellular mechanisms. Many low-throughput methods have been developed throughout the years to obtain these parameters. Acquiring data with higher accuracy and throughput is, however, necessary to characterize complex biological networks.