Microfluidics
[1] It has practical applications in the design of systems that process low volumes of fluids to achieve multiplexing, automation, and high-throughput screening.
Often, processes normally carried out in a lab are miniaturised on a single chip, which enhances efficiency and mobility, and reduces sample and reagent volumes.
One consequence is co-flowing fluids do not necessarily mix in the traditional sense, as flow becomes laminar rather than turbulent; molecular transport between them must often be through diffusion.
[15][16][17] Advantages of open microfluidics include accessibility to the flowing liquid for intervention, larger liquid-gas surface area, and minimized bubble formation.
Process monitoring capabilities in continuous-flow systems can be achieved with highly sensitive microfluidic flow sensors based on MEMS technology, which offers resolutions down to the nanoliter range.
Microdroplets allow for handling miniature volumes (μL to fL) of fluids conveniently, provide better mixing, encapsulation, sorting, and sensing, and suit high throughput experiments.
[40] Alternatives to the above closed-channel continuous-flow systems include novel open structures, where discrete, independently controllable droplets are manipulated on a substrate using electrowetting.
[45] To tune fluid penetration in porous substrates such as paper in two and three dimensions, the pore structure, wettability and geometry of the microfluidic devices can be controlled while the viscosity and evaporation rate of the liquid play a further significant role.
Many such devices feature hydrophobic barriers on hydrophilic paper that passively transport aqueous solutions to outlets where biological reactions take place.
[47] Current applications include portable glucose detection[48] and environmental testing,[49] with hopes of reaching areas that lack advanced medical diagnostic tools.
However, the RPS method does not work well for particles below 1 μm diameter, as the signal-to-noise ratio falls below the reliably detectable limit, set mostly by the size of the pore in which the analyte passes and the input noise of the first-stage amplifier.
This can be accomplished by identifying a transmembranal protein unique to the cell type of interest and subsequently functionalizing magnetic particles with the complementary antigen or antibody.
Microfluidic structures include micropneumatic systems, i.e. microsystems for the handling of off-chip fluids (liquid pumps, gas valves, etc.
[65] Additionally, microfluidic manufacturing advances mean that makers can produce the devices in low-cost plastics such as polymethymethacrylate (PMMA), polystyrene, cyclic olefin polymer (COP) and polyvinyl chloride (PVC) [66][67] and automatically verify part quality.
These microorganisms including bacteria[89] and the broad range of organisms that form the marine microbial loop,[90] responsible for regulating much of the oceans' biogeochemistry.
The PhLOC is based on the simultaneous application of Raman and UV-Vis-NIR spectroscopy,[101] which allows for the analysis of more complex mixtures which contain several actinides at different oxidation states.
[104] This approach has been found to have molar extinction coefficients (UV-Vis) in line with known literature values over a comparatively large concentration span for 150 μL[102] via elongation of the measurement channel, and obeys Beer's Law at the micro-scale for U(IV).
[102] Expansion of the PhLOC to miniaturize research of the full nuclear fuel cycle is currently being evaluated, with steps of the PUREX process successfully being demonstrated at the micro-scale.
This reduction in reagent volumes allows for new experiments like single-cell protein analysis, which due to size limitations of prior devices, previously came with great difficulty.
[112] The coupling of HPLC-chip devices with other spectrometry methods like mass-spectrometry allow for enhanced confidence in identification of desired species, like proteins.
[114] Some other practical applications of integrated HPLC chips include the determination of drug presence in a person through their hair[115] and the labeling of peptides through reverse phase liquid chromatography.
[116] Acoustic droplet ejection uses a pulse of ultrasound to move low volumes of fluids (typically nanoliters or picoliters) without any physical contact.
ADE technology is a very gentle process, and it can be used to transfer proteins, high molecular weight DNA and live cells without damage or loss of viability.
[136] Paper and droplet microfluidics allow for devices that can detect small amounts of unwanted bacteria or chemicals, making them useful in food safety and analysis.
[138] In addition to paper-based methods, research demonstrates droplet-based microfluidics shows promise in drastically shortening the time necessary to confirm viable bacterial contamination in agricultural waters in the domestic and international food industry.
[143] In addition, accurate prediction of postoperative disease progression in breast or prostate cancer patients is essential for determining post-surgery treatment.
[146][147] CTCs are isolated from blood by a microfluidic device, and are cultured on-chip, which can be a method to capture more biological information in a single analysis.
[152] Another advanced strategy is detecting growth rates of single-cell by using suspended microchannel resonators, which can predict drug sensitivities of rare CTCs.
[154] One strategy relevant to single-cell chromatin immunoprecipitation (ChiP)‐Sequencing is droplets, which operates by combining droplet‐based single cell RNA sequencing with DNA‐barcoded antibodies, possibly to explore the tumor heterogeneity by the genotype and phenotype to select the personalized anti-cancer drugs and prevent the cancer relapse.
[155] One significant advancement in the field is the development of integrated capillary electrophoresis (CE) systems on microchips, as demonstrated by Z. Hugh Fan and D. Jed.
