Tape underlayment rotary-node (TURN) valves for simple on-chip microfluidic flow control

A microfluidic finger-actuated blood lysate preparation device enabled by rapid acoustofluidic mixing

For many blood-based diagnostic tests, including prophylactic drug analysis and malaria assays, red blood cells must be lysed effectively prior to their use in an analytical workflow. We report on a finger-actuated blood lysate preparation device, which utilises a previously reported acoustofluidic micromixer module. The integrated device includes a range of innovations from a sample interface, to the integration of blisters on a laser engraved surface and a large volume (130 μL) one-stroke manual pump which could be useful in other low-cost microfluidic-based point-of-care devices. The adaptability of the acoustic mixer is demonstrated on highly viscous fluids, including whole blood, with up to 65% percent volume fraction of red blood cells. Used in conjunction with a lysis buffer, the micromixer unit is also shown to lyse a finger-prick (approximately 20 μL) blood sample in 30 seconds and benchmarked across ten donor samples. Finally, we demonstrate the ease of use of the fully integrated device. Cheap, modular, but reliable, finger-actuated microfluidic functions could open up opportunities for the development of diagnostics with minimal resources.

Towards practical sample preparation in point-of-care testing: user-friendly microfluidic devices

Microfluidic technologies offer a number of advantages for sample preparation in point-of-care testing (POCT), but the requirement for complicated external pumping systems limits their wide use. To facilitate sample preparation in POCT, various methods have been developed to operate microfluidic devices without complicated external pumping systems. In this review, we introduce an overview of user-friendly microfluidic devices for practical sample preparation in POCT, including self- and hand-operated microfluidic devices. Self-operated microfluidic devices exploit capillary force, vacuum-driven pressure, or gas-generating chemical reactions to apply pressure into microchannels, and hand-operated microfluidic devices utilize human power sources using simple equipment, including a syringe, pipette, or simply by using finger actuation. Furthermore, this review provides future perspectives to realize user-friendly integrated microfluidic circuits for wider applications with the integration of simple microfluidic valves.

Management and potentialities of primary cancer cultures in preclinical and translational studies

The use of patient-derived primary cell cultures in cancer preclinical assays has increased in recent years. The management of resected tumor tissue remains complex and a number of parameters must be respected to obtain complete sample digestion and optimal vitality yield. We provide an overview of the benefits of correct primary cell culture management using different preclinical methodologies, and describe the pros and cons of this model with respect to other kinds of samples. One important advantage is that the heterogeneity of the cell populations composing a primary culture partially reproduces the tumor microenvironment and crosstalk between malignant and healthy cells, neither of which is possible with cell lines. Moreover, the use of patient-derived specimens in innovative preclinical technologies, such as 3D systems or bioreactors, represents an important opportunity to improve the translational value of the results obtained. In vivo models could further our understanding of the crosstalk between tumor and other tissues as they enable us to observe the systemic and biological interactions of a complete organism. Although engineered mice are the most common model used in this setting, the zebrafish (Danio rerio) species has recently been recognized as an innovative experimental system. In fact, the transparent body and incomplete immune system of zebrafish embryos are especially useful for evaluating patient-derived tumor tissue interactions in healthy hosts. In conclusion, ex vivo systems represent an important tool for cancer research, but samples require correct manipulation to maximize their translational value.

A lab-on-a-disc with reversible and thermally stable diaphragm valves

A lab-on-a-disc is a unique microfluidic platform that utilizes centrifugal force to pump liquids. This offers many benefits for point-of-care devices because it eliminates the need for connections to multiple pumps and complex tubing connections. A wide range of applications including clinical chemistry, immunoassay, cell analysis, and nucleic acid tests could be demonstrated on a spinning disc. To enable the performance of assays in a fully integrated and automated manner, the robust actuation of integrated valves is a prerequisite. However, conventional passive-type valves incur a critical drawback in that their operation is dependent on the rotational frequency, which is easily influenced by the channel geometry and chemistry, in addition to the physical properties of the liquids to be transferred. Even though a few active-type valving techniques permit the individual actuation of valves, independent of the rotational frequency, complex procedures for the fabrication as well as actuation mechanisms have prevented their broader acceptance in general applications. Here, we report on a lab-on-a-disc incorporating individually addressable diaphragm valves (ID valves) that enable the reversible and thermally stable actuation of multiple valves with unprecedented ease and robustness. These ID valves are configured from an elastic epoxy diaphragm embedded on a 3D printed push-and-twist valve, which can be easily actuated by a simple automatic driver unit. As a proof of concept experiment, an enzyme-linked immunosorbent assay (ELISA) and a polymerase chain reaction (PCR) were performed on a disc in a fully automated manner to demonstrate the robust, reversible, leak-free, and thermally stable actuation of the valves.

Screw-actuated displacement micropumps for thermoplastic microfluidics

The fabrication of on-chip displacement pumps integrated into thermoplastic chips is explored as a simple and low cost method for achieving precise and programmable flow control for disposable microfluidic systems. The displacement pumps consist of stainless steel screws inserted into threaded ports machined into a thermoplastic substrate which also serve as on-chip reagent storage reservoirs. Three different methods for pump sealing are investigated to enable high pressure flows without leakage, and software-defined control of multiple pumps is demonstrated in a self-contained platform using a compact and self-contained microcontroller for operation. Using this system, flow rates ranging from 0.5-40 μl min^-1 are demonstrated. The pumps are combined with on-chip burst valves to fully seal multiple reagents into fabricated chips while providing on-demand fluid distribution in a downstream microfluidic network, and demonstrated for the generation of size-tunable water-in-oil emulsions.

Effect of temperature on biofilm formation by Antarctic marine bacteria in a microfluidic device

Polar biofilms have become an increasingly popular biological issue because new materials and phenotypes have been discovered in microorganisms in the polar region. Various environmental factors affect the functionality and adaptation of microorganisms. Because the polar region represents an extremely cold environment, polar microorganisms have a functionality different from that of normal microorganisms. Thus, determining the effective temperature for the development of polar biofilms is crucial. Here, we present a simple, novel one-pot assay for analysis of the effect of temperature on formation of Antarctic bacterial biofilm using a microfluidic system where continuous temperature gradients are generated. We find that a specific range of temperature is required for the growth of biofilms. Thus, this microfluidic approach provides precise information regarding the effective temperature for polar biofilm development with a new high-throughput screening format.

Thick-tissue bioreactor as a platform for long-term organotypic culture and drug delivery

We have developed a novel, portable, gravity-fed, microfluidics-based platform suitable for optical interrogation of long-term organotypic cell culture. This system is designed to provide convenient control of cell maintenance, nutrients, and experimental reagent delivery to tissue-like cell densities housed in a transparent, low-volume microenvironment. To demonstrate the ability of our Thick-Tissue Bioreactor (TTB) to provide stable, long-term maintenance of high-density cellular arrays, we observed the morphogenic growth of human mammary epithelial cell lines, MCF-10A and their invasive variants, cultured under three-dimensional (3D) conditions inside our system. Over the course of 21 days, these cells typically develop into hollow "mammospheres" if cultured in standard 3D Matrigel. This complex morphogenic process requires alterations in a variety of cellular functions, including degradation of extracellular matrix that is regulated by cell-produced matrix proteinases. For our "drug" delivery testing and validation experiments we have introduced proteinase inhibitors into the fluid supply system, and we observed both reduced proteinase activity and inhibited cellular morphogenesis. The size inhibition results correlated well with the overall proteinase activities of the tested cells.

Controlling flow in microfluidic channels with a manually actuated pin valve

There is a need for a simple method to control fluid flow within microfluidic channels. To meet this need, a simple push pin with a polydimethylsiloxane (PDMS) tip has been integrated into microfluidic networks to be placed within the microchannel to obstruct flow. This new valve design can attain on/off control of fluid flow without an external power source using readily-available, low-cost materials. The valve consists of a 14 gauge (1.6 mm) one inch piece of metal tubing with a PDMS pad at the tip to achieve a fluidic seal when pressed against a microfluidic channel's substrate. The metal tubing or pin is then either manually pushed down to block or pulled up to allow fluid flow. The valve was validated using a pressure transducer and fluorescent dye to determine the breakthrough pressure the valve can withstand over multiple cycles. In the first cycle, the median value for pressure withstood by the valve was 8.8 psi with a range of 17.5-2.7 psi. The pressure the valves were able to withstand during each successive trial was lower suggesting they may be most valuable as a method to control the initial introduction of fluids into a microfluidic device. These valves can achieve flow regulation within microfluidic devices, have a small dead volume, and are simple to fabricate and use, making this technique widely suitable for a range of applications.