Lab On a Chip System for Size-Based Gold and Polymer Nanoparticle Separation

Despite the increasing demand for nanoscale biomolecule analysis for point-of-care (POC) application, nanoparticle separation remains a challenge in many applications due to huge sample loss during separation, low throughput, large scale input materials requirement, and sophisticated technologies. As the separation efficiency may affect the subsequent sample processing and analysis, a robust and reliable size-based separation technique is necessary. This study presents a lab on a chip system to enhance the separation performance by using rapid and straightforward polymer prototyping. In particular, the system consists of a microfluidic network with embedded membrane filters with different pore size cut-offs and an ultrasonic transmitter for acoustic agitation. Using the novel system, we successfully demonstrate the fractionation of 15 nm Au NP from polydisperse nanoparticle solution in the presence of ultrasonic wave (28-40 kHz) generated by the transducer incorporated with the microfluidic system during the separation. Ultrasonic irradiation helps in preventing cake formation and reversing the fouling process by acoustic agitation. The suggested system significantly increases the flow rate during the separation process and improves the recovery of target size nanoparticles. This microfluidic platform is expected to serve as a powerful tool for sample preparation and analytical methodology in POC applications.

Th-MOF showing six-fold imide-sealed pockets for middle-size-separation of propane from nature gas

Separation of propane from nature gas is of great importance to industry. However, in light of size-based separation, there still lacks effective method to directly separate propane from nature gas, due to the comparable physical properties for these light alkanes (C1-C4) and the middle size of propane. In this work, we found that a new Th-MOF could be an ideal solution for this issue. The Th-MOF takes UiO-66-type structure, but with the pocket sealed by six-fold imide groups; this not only precisely reduces the size of pocket to exactly match propane, but also enhances the host-guest interactions through multiple supramolecular interactions. As a result, highly selective adsorption of propane over methane, ethane, and butane was observed, implying unique middle-size separation. The actual separation was confirmed by breakthrough experiments, and it is found that both relatively smaller molecules (methane and ethane) and relatively bigger molecules (butane) break through the Th-MOF column within 10 min/g, whereas propane with middle size can maintain very long retention time up to 80 min/g, strongly suggesting middle-size separation and its superior application in direct separation of propane from nature gas. The separation mechanism, as unveiled by both theoretical calculation and comparative experiments, is due to the six-fold imide-sealed pockets that could effectively distinguish propane from other light alkanes through both size effect and host-guest interactions.

Molecular Detection and Quantification of the Striga Seedbank in Ethiopian Sorghum Field Soils

Aims Striga hermonthica is a devastating parasitic weed in Sub-Saharan Africa (SSA) and its persistent soil seedbank is the major contributing factor for its prevalence and persistence. So far, there is little to no information on the Striga seedbank density in agricultural fields in SSA due to the lack of reliable detection and quantification methods. Methods We developed a high-throughput method that combines density- and size-based separation techniques with quantitative polymerase chain reaction (qPCR)-based detection of Striga seeds in soil. The method was optimized and validated on two physicochemically different Striga-free Dutch agricultural soils by introducing increasing numbers of Striga seeds (0, 1, 3, 9, 27, 81 and 243 seeds). Results The results showed that as little as one seed of S. hermonthica per 150 g of soil can be detected. This technique was subsequently tested on soil samples of 48 sorghum fields from different agro-ecological zones in Ethiopia to map the geospatial distribution of the Striga seedbank along a trajectory of more than 1500 km. Considerable variation in Striga seed densities was observed for these soils: in 75% of the field soils, Striga seeds were detectable up to 86 seeds per 150 g of soil. Correlation analyses further revealed a significant non-linear relationship between the seed density and Striga incidence assessed in the same sorghum field soils at the time of soil sampling. Conclusions The method developed allows for high-through-put and accurate mapping of the Striga seedbank in physicochemically diverse field soils and can be used to predict Striga incidence and to assess the impact of management strategies on Striga seedbank dynamics.

Modeling of Deformable Cell Separation in a Microchannel with Sequenced Pillars

Embedded pillar microstructures are an efficient approach for controlling and sculpting shear flow in a microchannel but have not yet demonstrated to be effective for deformability-based cell separation and sorting. Although simple pillar configurations (lattice, line sequence) worked well for size-based separation of rigid particles, they had a low separation efficiency for circulating cells. The objective of this study was to optimize sequenced microstructures for separation of deformable cells. This was achieved by numerical analysis of pairwise cell migration in a microchannel with multiple pillars, which size, longitudinal spacing, and lateral location as well as the cell elasticity and size varied. This study revealed two basic pillar configurations optimized for deformability-based separation: 1) “duplet” that consists of two closely spaced pillars positioned far below the centerline and above the centerline halfway to the wall; and 2) “triplet” composed of three widely-spaced pillars located below, above and at the centerline, respectively. The duplet configuration is well suited for deformable cell separation in short channels, while the triplet or a combination of duplets and triplets provides even better separation in long channels. These optimized pillar microstructures can dramatically improve microfluidic methods for sorting and isolation of blood and rare circulating tumor cells.

Inertial Microfluidics-Based Separation of Microalgae Using a Contraction–Expansion Array Microchannel

Microalgae separation technology is essential for both executing laboratory-based fundamental studies and ensuring the quality of the final algal products. However, the conventional microalgae separation technology of micropipetting requires highly skilled operators and several months of repeated separation to obtain a microalgal single strain. This study therefore aimed at utilizing microfluidic cell sorting technology for the simple and effective separation of microalgae. Microalgae are characterized by their various morphologies with a wide range of sizes. In this study, a contraction–expansion array microchannel, which utilizes these unique properties of microalgae, was specifically employed for the size-based separation of microalgae. At Reynolds number of 9, two model algal cells, Chlorella vulgaris (C. vulgaris) and Haematococcus pluvialis (H. pluvialis), were successfully separated without showing any sign of cell damage, yielding a purity of 97.9% for C. vulgaris and 94.9% for H. pluvialis. The result supported that the inertia-based separation technology could be a powerful alternative to the labor-intensive and time-consuming conventional microalgae separation technologies.

Adsorption-based membranes for air separation using transition metal oxides

In this work, we use computational modeling to examine the viability of adsorption-based pore-flow membranes for separating gases when a purely size-based separation strategy is ineffective. Using molecular dynamics simulations...

Acoustofluidic centrifuge for nanoparticle enrichment and separation

Liquid droplets have been studied for decades and have recently experienced renewed attention as a simplified model for numerous fascinating physical phenomena occurring on size scales from the cell nucleus to stellar black holes. Here, we present an acoustofluidic centrifugation technique that leverages an entanglement of acoustic wave actuation and the spin of a fluidic droplet to enable nanoparticle enrichment and separation. By combining acoustic streaming and droplet spinning, rapid (<1 min) nanoparticle concentration and size-based separation are achieved with a resolution sufficient to identify and isolate exosome subpopulations. The underlying physical mechanisms have been characterized both numerically and experimentally, and the ability to process biological samples (including DNA segments and exosome subpopulations) has been successfully demonstrated. Together, this acoustofluidic centrifuge overcomes existing limitations in the manipulation of nanoscale (<100 nm) bioparticles and can be valuable for various applications in the fields of biology, chemistry, engineering, material science, and medicine.