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•Microfluidics is transforming traditional techniques in biotechnology.•Multi-step experiments are automated on single device in parallel reactors.•Millions of parallel reactions can ...be conducted and analyzed in a single assay.•Cells and biomolecules are precisely positioned for high-throughput analysis.
Academic microfluidics has decisively shifted in recent years from the research on phenomenology and proof-of-concept fluidic functionalities to the developments oriented at applications with biology, medicine and biotechnology in prime focus. Significant efforts are made to demonstrate that microfluidics can be used in unspecialized laboratories to perform previously mundane tasks faster and easier, or to venture into new research areas that were unavailable or unattractive when only classical means of microbiology or biotechnology were employed. Here we review a variety of biological experiments recently performed in microfluidic assays. We categorize the microfluidic systems by the key role they play in the biological experiments as: (i) controlled reaction chambers, (ii) high-throughput arrays, or (iii) micro-positioning systems. We also discuss the outlook for further development and applications of microfluidics in biological sciences.
While shear emulsification is a well understood industrial process, geometrical confinement in microfluidic systems introduces fascinating complexity, so far prohibiting complete understanding of ...droplet formation. The size of confined droplets is controlled by the ratio between shear and capillary forces when both are of the same order, in a regime known as jetting, while being surprisingly insensitive to this ratio when shear is orders of magnitude smaller than capillary forces, in a regime known as squeezing. Here, we reveal that further reduction of-already negligibly small-shear unexpectedly re-introduces the dependence of droplet size on shear/capillary-force ratio. For the first time we formally account for the flow around forming droplets, to predict and discover experimentally an additional regime-leaking. Our model predicts droplet size and characterizes the transitions from leaking into squeezing and from squeezing into jetting, unifying the description for confined droplet generation, and offering a practical guide for applications.
Since antibiotic resistance is a major threat to global health, recent observations that the traditional test of minimum inhibitory concentration (MIC) is not informative enough to guide effective ...antibiotic treatment are alarming. Bacterial heteroresistance, in which seemingly susceptible isogenic bacterial populations contain resistant sub-populations, underlies much of this challenge. To close this gap, here we developed a droplet-based digital MIC screen that constitutes a practical analytical platform for quantifying the single-cell distribution of phenotypic responses to antibiotics, as well as for measuring inoculum effect with high accuracy. We found that antibiotic efficacy is determined by the amount of antibiotic used per bacterial colony forming unit (CFU), not by the absolute antibiotic concentration, as shown by the treatment of beta-lactamase-carrying Escherichia coli with cefotaxime. We also noted that cells exhibited a pronounced clustering phenotype when exposed to near-inhibitory amounts of cefotaxime. Overall, our method facilitates research into the interplay between heteroresistance and antibiotic efficacy, as well as research into the origin and stimulation of heterogeneity by exposure to antibiotics. Due to the absolute bacteria quantification in this digital assay, our method provides a platform for developing reference MIC assays that are robust against inoculum-density variations.
Abstract We present a new strategy for the fabrication of artificial skeletal muscle tissue with functional morphologies based on an innovative 3D bioprinting approach. The methodology is based on a ...microfluidic printing head coupled to a co-axial needle extruder for high-resolution 3D bioprinting of hydrogel fibers laden with muscle precursor cells (C2C12). To promote myogenic differentiation, we formulated a tailored bioink with a photocurable semi-synthetic biopolymer (PEG-Fibrinogen) encapsulating cells into 3D constructs composed of aligned hydrogel fibers. After 3–5 days of culture, the encapsulated myoblasts started migrating and fusing, forming multinucleated myotubes within the 3D bioprinted fibers. The obtained myotubes showed high degree of alignment along the direction of hydrogel fiber deposition, further revealing maturation, sarcomerogenesis, and functionality. Following subcutaneous implantation in the back of immunocompromised mice, bioprinted constructs generated organized artificial muscle tissue in vivo . Finally, we demonstrate that our microfluidic printing head allows to design three dimensional multi-cellular assemblies with an exquisite compartmentalization of the encapsulated cells. Our results demonstrate an enhanced myogenic differentiation with the formation of parallel aligned long-range myotubes. The approach that we report here represents a robust and valid candidate for the fabrication of macroscopic artificial muscle to scale up skeletal muscle tissue engineering for human clinical application.
Tailoring the morphology of macroporous structures remains one of the biggest challenges in material synthesis. Herein, we present an innovative approach for the fabrication of custom macroporous ...materials in which pore size varies throughout the structure by up to an order of magnitude. We employed a valve‐based flow‐focusing junction (vFF) in which the size of the orifice can be adjusted in real‐time (within tens of milliseconds) to generate foams with on‐line controlled bubble size. We used the junction to fabricate layered and smoothly graded porous structures with pore size varying in the range of 80–800 μm. Additionally, we mounted the vFF on top of an extrusion printer and 3D‐printed constructs characterized by a predefined 3D geometry and a controlled, spatially varying internal porous architecture, such as a model of a bone. The presented technology opens new possibilities in macroporous material synthesis with potential applications ranging from tissue engineering to aerospace industry and construction.
Functionally graded materials: By using on‐demand reconfigurable microfluidics, foams with on‐line controlled bubble size can be easily produced. Such foams serve as templates for the synthesis of advanced materials with spatially varying internal porous architectures, which may find applications in a variety of fields.
Getting your bugs in a row: A microfluidic device for manipulating and monitoring the continuous growth of populations of bacteria within microdroplets was developed (see scheme). This device allows ...for monitoring hundreds of populations of bacteria to study changes in growth rates and the effects of antibiotics, including the evolution of antibiotic resistance in real time.
One-dimensional conductive particle assembly holds promise for a variety of practical applications, in particular for a new generation of electronic devices. However, synthesis of such chains with ...programmable shapes outside a liquid environment has proven difficult. Here we report a route to simply 'pull' flexible granular and colloidal chains out of a dispersion by combining field-directed assembly and capillary effects. These chains are automatically stabilized by liquid bridges formed between adjacent particles, without the need for continuous energy input or special particle functionalization. They can further be deposited onto any surface and form desired conductive patterns, potentially applicable to the manufacturing of simple electronic circuits. Various aspects of our route, including the role of particle size and the voltages needed, are studied in detail. Looking towards practical applications, we also present the possibility of two-dimensional writing, rapid solidification of chains and methods to scale up chain production.
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