Lab On A Chip

Chain reactions are characterized by initiation, propagation and termination, are stochastic at microscopic scales and underlie vital chemical (e.g. combustion engines), nuclear and biotechnological (e.g. polymerase chain reaction) applications.1–5 At macroscopic scales, chain reactions are deterministic and limited to applications for entertainment and art such as falling domino and Rube Goldberg machines. Appositely, microfluidic lab-on-a-chip (also called a micro total analysis system),6,7 which were envisioned pursuant to microelectronic integrated circuits, are generally not integrated on a chip owing to an enduring dependency on cumbersome connections, peripherals, and on computers for automation.8–11 Capillary microfluidics integrate energy supply and flow control onto a single chip by using capillary phenomena, but programmability remains rudimentary with at most a handful (eight) operations possible.12–19 Here we introduce mesoscopic microfluidic chain reactions (MCRs) base...

The human gut is over a meter in length, liquid residence times span several hours. Recapitulating the human gut microbiome "on chip" holds promise to revolutionize therapeutic strategies for a variety of diseases, as well as for maintaining homeostasis in healthy individuals. A more refined understanding of bacterial-bacterial and bacterial-epithelial cell signalling is envisioned and such a device is a key enabler. Indeed, significant advances in the study of bacterial cell-cell signalling have been reported, including at length and time scales of the cells and their responses. Few reports exist, however, where signalling events that span physiologically relevant time scales are monitored and coordinated. Here, we employ principles of biofabrication to assemble, in situ, cell communities that are (i) spatially adjacent within partitioned microchannels for studying near communication and (ii) distally connected within longitudinal microfluidic networks so as to mimic long...

Microfluidics-based biochip applications have been increased abruptly in multiple fields because of the advantages in manifolds, which include decreased test sample utilization and reagent consumption with numerous purposes and highly listed benefits. In general, microfluidics involves two different techniques, namely active and passive methods, to enable the fluid flow within the channel that is mounted on the biochip. In this study, we focus on hydrostatic pressure-driven passive pumping methodology as it does not require any external actuators or power source to assist the flow. This technique solely depends on the gravitational pull to enhance fluid flow within the channel. The ultimate aim of this study is to design a microfluidic channel in which the geometrical parameters are optimized, and the respective velocity profile is obtained. The geometrical parameters such as the angle of contact between the channel and the ground (θ), channel dimension, and reservoir dimensions whi...

Circulating tumor cells (CTCs) play an essential role in the metastasis of tumors, and thus can serve as a valuable prognostic factor for malignant diseases. As a result, the ability to isolate and characterize CTCs is essential. This review underlines the potential of dielectrophoresis for CTCs enrichment. It begins by summarizing the key performance parameters and challenges of CTCs isolation using microfluidics. The two main categories of CTCs enrichment—affinity‐based and label‐free methods—are analysed, emphasising the advantages and disadvantages of each as well as their clinical potential. While the main argument in favour of affinity‐based methods is the strong specificity of CTCs isolation, the major advantage of the label‐free technologies is in preserving the integrity of the cellular membrane, an essential requirement for downstream characterization. Moving forward, we try to answer the main question: “What makes dielectrophoresis a method of choice in CTCs isolation?” T...

Fabrication conditions for high-aspect-ratio MNs by the photopolymerization of PEGDA were investigated. The influence of prepolymer molecular weight and the degree of UV absorption by the photoinitiator (PI) were studied to optimize the conditions.

This systematic review aimed to analyze the development and functionality of microfluidic concentration gradient generators (CGGs) for toxicological evaluation of different biological organisms. We searched articles using the keywords: concentration gradient generator, toxicity, and microfluidic device. Only 33 of the 352 articles found were included and examined regarding the fabrication of the microdevices, the characteristics of the CGG, the biological model, and the desired results. The main fabrication method was soft lithography, using polydimethylsiloxane (PDMS) material (91%) and SU-8 as the mold (58.3%). New technologies were applied to minimize shear and bubble problems, reduce costs, and accelerate prototyping. The Christmas tree CGG design and its variations were the most reported in the studies, as well as the convective method of generation (61%). Biological models included bacteria and nematodes for antibiotic screening, microalgae for pollutant toxicity, tumor and no...

The intricate microenvironment in which malignant cells reside is essential for the progression of tumor growth. Both the physical and biochemical features of the tumor microenvironment (TME) play a critical role in promoting the differentiation, proliferation, invasion, and metastasis of cancer cells. It is therefore essential to understand how malignant cells interact and communicate with an assortment of supportive tumor-associated cells including macrophages, fibroblasts, endothelial cells, and other immune cells. To study the complex mechanisms behind cancer progression, 3D spheroid and organoid models are widely in favor because they replicate the stromal environment and multicellular structure present within an in vivo tumor. It provides more precise data about the cell–cell interactions, tumor characteristics, drug discovery, and metabolic profile of cancer cells compared to oversimplified 2D systems and unrepresentative animal models. This review provides a description of t...

Detection of conformational changes in biomolecular assemblies provides critical information into biological and self-assembly processes. State-of-the-art in situ biomolecular conformation detection techniques rely on fluorescent labels or protein-specific binding agents to signal conformational changes. Here, we present an on-chip, label-free technique to detect conformational changes in a DNA nanomechanical tweezer structure with microwave microfluidics. We measure the electromagnetic properties of suspended DNA tweezer solutions from 50 kHz to 110 GHz and directly detect two distinct conformations of the structures. We develop a physical model to describe the electrical properties of the tweezers, and correlate model parameters to conformational changes. The strongest indicator for conformational changes in DNA tweezers are the ionic conductivity, while shifts in the magnitude of the cooperative water relaxation indicate the addition of fuel strands used to open the tweezer. Micr...

Although fused deposition modeling (FDM) is of great interest for the cost-effective manufacture of polymer parts with complex customized geometries, it currently provides insufficient mechanical integrity for the production of high performance functional structures, and is restricted to too limited a range of materials. The present work is aimed at investigating the suitability of new combinations of hard and soft thermoplastics for FDM. To this end, nonisothermal fusion bonding of polypropylene (iPP) and a thermoplastic elastomer (TPE) with a continuous plasticized iPP matrix was investigated by overinjecting the TPE onto a solid iPP insert. The influence of temperature and pressure was evaluated by tensile testing of butt joint specimens, and optical and electron microscopy. Interface temperatures approaching the iPP melting point gave high bond strengths for hold pressures above 200 bars, resulting in cohesive failure in the TPE as well as adhesive failure at the interface. The ...