The diagnosis of infectious diseases is entering a new and interesting phase. Technologies based on paper microfluidics, coupled to developments in isothermal amplification of Nucleic Acids (NAs) raise opportunities for bringing the methods of molecular biology in the field, in a low setting environment. A lot of work has been performed in the domain over the last few years and the landscape of contributions is rich and diverse. Most often, the level of sample preparation differs, along with the sample nature, the amplification and detection methods, and the design of the device, among other features. In this review, we attempt to offer a structured description of the state of the art. The domain is not mature and there exist bottlenecks that hamper the realization of Nucleic Acid Amplification Tests (NAATs) complying with the constraints of the field in low and middle income countries. In this domain however, the pace of progress is impressively fast. This review is written for a broad Lab on a Chip audience.

Inferring the directionality of interactions between cellular processes is a major challenge in systems biology. Time-lagged correlations allow to discriminate between alternative models, but they still rely on assumed underlying interactions. Here, we use the transfer entropy (TE), an information-theoretic quantity that quantifies the directional influence between fluctuating variables in a model-free way. We present a theoretical approach to compute the transfer entropy, even when the noise has an extrinsic component or in the presence of feedback. We re-analyze the experimental data from Kiviet et al. (2014) where fluctuations in gene expression of metabolic enzymes and growth rate have been measured in single cells of E. coli. We confirm the formerly detected modes between growth and gene expression, while prescribing more stringent conditions on the structure of noise sources. We furthermore point out practical requirements in terms of length of time series and sampling time which must be satisfied in order to infer optimally transfer entropy from times series of fluctuations.

An RNA-directed recombination reaction can result in a network of interacting RNA species. It is now becoming increasingly apparent that such networks could have been an important feature of the RNA world during the nascent evolution of life on the Earth. However, the means by which such small RNA networks assimilate other available genotypes in the environment to grow and evolve into the more complex networks that are thought to have existed in the prebiotic milieu are not known. Here, we used the ability of fragments of the Azoarcus group I intron ribozyme to covalently self-assemble via genotype-selfish and genotype-cooperative interactions into full-length ribozymes to investigate the dynamics of small (three- and four-membered) networks. We focused on the influence of a three-membered core network on the incorporation of additional nodes, and on the degree and direction of connectivity as single new nodes are added to this core. We confirmed experimentally the predictions that additional links to a core should enhance overall network growth rates, but that the directionality of the link (a "giver" or a "receiver") impacts the growth of the core itself. Additionally, we used a simple mathematical model based on the first-order effects of lower-level interactions to predict the growth of more complex networks, and find that such a model can, to a first approximation, predict the ordinal rankings of nodes once a steady-state distribution has been reached.

Polymers among new classes of materials such as polydimethylsiloxane (PDMS), cyclic olefin copolymer (COC), Norland optical adhesive (NOA), and THV (fluoropolymer) were evaluated as surface‐modified microfluidic materials, including investigating the incorporation of silica‐like functional groups onto these surfaces. The functionalization of these materials was performed using a hybrid reactor equipped with magnetron sputtering using a silica target and with a PECVD apparatus starting from hexamethyldisiloxane as a chemical precursor. Coated microfluidic materials were then evaluated in terms of wettability, stability, composition, and structure. The deposited coatings were proved to be stable up to 2 month in air and water storage for these materials, with COC providing the most stable substrate.

A plasma microreactor dedicated to chemical synthesis has been conceived and developed using soft-lithography techniques. In this study, we propose to use highly reactive species created by the plasma discharge to replace traditionally used chemical initiators. A dielectric barrier discharge plasma was generated under atmospheric pressure and then dispersed into a continuous liquid phase with a T-junction geometry. Injected metal electrodes made it possible for in situ optical observations with an intensified charge-coupled device camera. No signal was detected when analyzing the exhaust liquid by electron spin resonance (ESR) spectroscopy. Numerical simulations confirmed that only low quantities of hydroxyl radicals could diffuse into the liquid phase, giving a concentration of DMPO-OH of 10

In a recent work, Lefranc and Bouchaud (LB) showed that the Mode I crack opening displacement in a thin sheet of Agar gel deviates significantly from the square root profile predicted by linear elastic fracture mechanics. In this letter we re-examine this problem and show that the experimentally measured crack opening displacement is consistent with the prediction based on finite elastostatics and a hyperelastic strain hardening model.

The travel of droplets, bubbles, vesicles, capsules, living cells or small organisms in microchannels is a hallmark in microfluidics applications. A full description of the dynamics of such objects requires a quantitative understanding of the complex hydrodynamic and interfacial interactions between objects and channel walls. In this paper, we present an interferometric method that allows absolute topographic reconstruction of the interspace between an object and channel walls for objects confined in microfluidic channels. Wide field microscopic imaging in reflection interference contrast mode (RICM) is directly performed at the bottom wall of microfluidic chips. Importantly, we show that the reflections at both the lower and upper surface of the microchannel have to be considered in the quantitative analysis of the optical signal. More precisely, the contribution of the reflection at the upper surface is weighted depending on the light coherence length and channel height. Using several wavelengths and illumination apertures, our method allows reconstructing the topography of thin films on channel walls in a range of 0–500 nm, with a precision as accurate as 2 nm for the thinnest films. A complete description of the protocol is exemplified for oil in water droplets travelling in channels of height 10–400 μm at a speed up to 5 mm s−1.