Porous PDMS structures for the storage and release of aqueous solutions into fluidic environments

Reagent storage and delivery on integrated microfluidic chips for point-of-care diagnostics

Microfluidic-based point-of-care diagnostics offer several unique advantages over existing bioanalytical solutions, such as automation, miniaturisation, and integration of sensors to rapidly detect on-site specific biomarkers. It is important to highlight that a microfluidic POC system needs to perform a number of steps, including sample preparation, nucleic acid extraction, amplification, and detection. Each of these stages involves mixing and elution to go from sample to result. To address these complex sample preparation procedures, a vast number of different approaches have been developed to solve the problem of reagent storage and delivery. However, to date, no universal method has been proposed that can be applied as a working solution for all cases. Herein, both current self-contained (stored within the chip) and off-chip (stored in a separate device and brought together at the point of use) are reviewed, and their merits and limitations are discussed. This review focuses on reagent storage devices that could be integrated with microfluidic devices, discussing further issues or merits of these storage solutions in two different sections: direct on-chip storage and external storage with their application devices. Furthermore, the different microvalves and micropumps are considered to provide guidelines for designing appropriate integrated microfluidic point-of-care devices.

In vitro formation and extended culture of highly metabolically active and contractile tissues

3D cell culture models have gained popularity in recent years as an alternative to animal and 2D cell culture models for pharmaceutical testing and disease modeling. Polydimethylsiloxane (PDMS) is a cost-effective and accessible molding material for 3D cultures; however, routine PDMS molding may not be appropriate for extended culture of contractile and metabolically active tissues. Failures can include loss of culture adhesion to the PDMS mold and limited culture surfaces for nutrient and waste diffusion. In this study, we evaluated PDMS molding materials and surface treatments for highly contractile and metabolically active 3D cell cultures. PDMS functionalized with polydopamine allowed for extended culture duration (14.8 ± 3.97 days) when compared to polyethylamine/glutaraldehyde functionalization (6.94 ± 2.74 days); Additionally, porous PDMS extended culture duration (16.7 ± 3.51 days) compared to smooth PDMS (6.33 ± 2.05 days) after treatment with TGF-β2 to increase culture contraction. Porous PDMS additionally allowed for large (13 mm tall × 8 mm diameter) constructs to be fed by diffusion through the mold, resulting in increased cell density (0.0210 ± 0.0049 mean nuclear fraction) compared to controls (0.0045 ± 0.0016 mean nuclear fraction). As a practical demonstration of the flexibility of porous PDMS, we engineered a vascular bioartificial muscle model (VBAM) and demonstrated extended culture of VBAMs anchored with porous PDMS posts. Using this model, we assessed the effect of feeding frequency on VBAM cellularity. Feeding 3×/week significantly increased nuclear fraction at multiple tissue depths relative to 2×/day. VBAM maturation was similarly improved in 3×/week feeding as measured by nuclear alignment (23.49° ± 3.644) and nuclear aspect ratio (2.274 ± 0.0643) relative to 2x/day (35.93° ± 2.942) and (1.371 ± 0.1127), respectively. The described techniques are designed to be simple and easy to implement with minimal training or expense, improving access to dense and/or metabolically active 3D cell culture models.

Multiscale stiffness of human emphysematous precision cut lung slices

Emphysema is a debilitating disease that remodels the lung leading to reduced tissue stiffness. Thus, understanding emphysema progression requires assessing lung stiffness at both the tissue and alveolar scales. Here, we introduce an approach to determine multiscale tissue stiffness and apply it to precision-cut lung slices (PCLS). First, we established a framework for measuring stiffness of thin, disk-like samples. We then designed a device to verify this concept and validated its measuring capabilities using known samples. Next, we compared healthy and emphysematous human PCLS and found that the latter was 50% softer. Through computational network modeling, we discovered that this reduced macroscopic tissue stiffness was due to both microscopic septal wall remodeling and structural deterioration. Lastly, through protein expression profiling, we identified a wide spectrum of enzymes that can drive septal wall remodeling, which, together with mechanical forces, lead to rupture and structural deterioration of the emphysematous lung parenchyma.

Perspectives in translating microfluidic devices from laboratory prototyping into scale-up production

Transforming lab research into a sustainable business is becoming a trend in the microfluidic field. However, there are various challenges during the translation process due to the gaps between academia and industry, especially from laboratory prototyping to industrial scale-up production, which is critical for potential commercialization. In this Perspective, based on our experience in collaboration with stakeholders, e.g., biologists, microfluidic engineers, diagnostic specialists, and manufacturers, we aim to share our understanding of the manufacturing process chain of microfluidic cartridge from concept development and laboratory prototyping to scale-up production, where the scale-up production of commercial microfluidic cartridges is highlighted. Four suggestions from the aspect of cartridge design for manufacturing, professional involvement, material selection, and standardization are provided in order to help scientists from the laboratory to bring their innovations into pre-clinical, clinical, and mass production and improve the manufacturability of laboratory prototypes toward commercialization.

Thermally Responsive Alkane Partitions for Assay Automation

For point-of-care diagnostic tools to be impactful, they must be inexpensive, equipment-free, and sample-to-answer (i.e., require no user intervention). Here, we report a new approach to enable sample-to-answer diagnostics that utilizes thermally responsive alkane partitions (TRAPs) as automated pseudo-valves. When combined with the magnetic manipulation of microbeads, TRAPs enable the pumpless automation of all steps in complex assays. We demonstrate that in relatively narrow channel geometries, liquified alkane partitions continue to separate reagents on each side of the partition while enabling the transition of magnetic beads from one reagent to the next, replacing manual pipetting steps in conventional assays. In addition, we show that in relatively broader geometries, liquified partitions breach, enabling the addition/mixing of preloaded reagents. Through calculation and experimentation, we determine the geometric design rules for implementing the stationary and removable partitions in fluidic channels. In addition, we demonstrate that magnetic microbeads can be pulled through liquified stationary TRAPs without disrupting partition integrity and without disrupting bound protein complexes attached at the microbead surface. The TRAP technology introduced here can enable a new low-cost and equipment-free approach for fully automated sample-to-answer diagnostics.

The Influence of Self-Heating Iron on the Thermal, Mechanical, and Swelling Properties of PDMS Composites for Organic Solvents Removal

Volatile organic compounds pollute the environment and pose a serious threat to human health due to their toxicity, mutagenicity, and carcinogenicity. In this context, it is highly desirable to fabricate high-performance poly (dimethylsiloxane) (PDMS) composites to remove organic solvents from the environment using a simple technique. Therefore, in the present study, Fe-PDMS composites were fabricated using a technique based on magnetic induction heating with iron particles serving as a self-heating agent. Under an alternating magnetic field, the iron particles served as a thermal source that assisted in the progression of PDMS crosslinking. The influence of self-heating iron on the properties of the fabricated Fe-PDMS composites was also investigated. The hydrosilation reaction occurring during the crosslinking process was controlled using FT-IR. The heating efficiency of PDMS 1, PDMS 2, and PDMS 3 was studied as the function of induction time (0–5 min) and the function of iron content (0%, 1%, and 30% wt.%). The results revealed that the mechanical properties of the PDMS 2 composite were enhanced compared to those of the PDMS 1 and PDMS 3 composites. The mechanical properties of PDMS 3 were the least efficient due to cluster formation. PDMS 3 exhibited the highest thermal stability among all composites. Furthermore, the swelling behavior of different materials in various organic solvents was studied. PDMS was observed to swell to the greatest extent in chloroform, while swelling to a large extent was observed in toluene, pentane, and petroleum ether. PDMS swelling was the least in n-butanol. The elastomeric behavior of crosslinked PDMS, together with its magnetic character, produces stimuli-responsive magneto-rheological composites, which are quite efficient and suitable for applications involving the removal of organic solvents.

Extraction of Soil Solution into a Microfluidic Chip

Collecting real-time data on physical and chemical parameters of the soil is a prerequisite for resource-efficient and environmentally sustainable agriculture. For continuous in situ measurement of soil nutrients such as nitrate or phosphate, a lab-on-chip approach combined with wireless remote readout is promising. For this purpose, the soil solution, i.e., the water in the soil with nutrients, needs to be extracted into a microfluidic chip. Here, we present a soil-solution extraction unit based on combining a porous ceramic filter with a microfluidic channel with a 12 µL volume. The microfluidic chip was fabricated from polydimethylsiloxane, had a size of 1.7 cm × 1.7 cm × 0.6 cm, and was bonded to a glass substrate. A hydrophilic aluminum oxide ceramic with approximately 37 Vol.-% porosity and an average pore size of 1 µm was integrated at the inlet. Soil water was extracted successfully from three types of soil—silt, garden soil, and sand—by creating suction with a pump at the other end of the microfluidic channel. For garden soil, the extraction rate at approximately 15 Vol.-% soil moisture was 1.4 µL/min. The amount of extracted water was investigated for 30 min pump intervals for the three soil types at different moisture levels. For garden soil and sand, water extraction started at around 10 Vol.-% soil moisture. Silt showed the highest water-holding capacity, with water extraction starting at approximately 13 Vol.-%.

Fabrication of fine-pored polydimethylsiloxane using an isopropyl alcohol and water mixture for adjustable mechanical, optical, and thermal properties

A fabrication method for obtaining fine-pored PDMS is presented. Low-cost, volatile, and easily accessible IPA is used as a co-solvent in water and PDMS emulsions, allowing porous PDMS with adjustable mechanical, optical and thermal properties.

Wearable sensors: At the frontier of personalised health monitoring, smart prosthetics and assistive technologies

Wearable sensors have evolved from body-worn fitness tracking devices to multifunctional, highly integrated, compact, and versatile sensors, which can be mounted onto the desired locations of our clothes or body to continuously monitor our body signals, and better interact and communicate with our surrounding environment or equipment. Here, we discuss the latest advances in textile-based and skin-like wearable sensors with a focus on three areas, including (i) personalised health monitoring to facilitate recording physiological signals, body motions, and analysis of body fluids, (ii) smart gloves and prosthetics to realise the sensation of touch and pain, and (iii) assistive technologies to enable disabled people to operate the surrounding motorised equipment using their active organs. We also discuss areas for future research in this emerging field.

Flexible and porous microneedles of PDMS for continuous glucose monitoring

Microneedle (MN) is a key technology of the biomedical engineering field due to its capability of accessing the biological information in a minimally invasive manner. One of the huge demands for next-generation healthcare monitoring is continuous monitoring, especially of blood glucose concentration. For this, MN should be kept inserted into the human skin for a certain period of time, enduring stresses induced by daily human motion and at the same time measuring biomarkers in ISF. However, conventional MNs for biosensing are not suitable for a long term insertion due to the rigid structure and biological risks of MN breakage. In this study, a novel MN structure is proposed and investigated by combining flexible "sponge-like" porous PDMS matrix and coating by biodissolving hyaluronic acid (HA). The fabricated porous MNs coated with HA show ideal mechanical characteristics, by which the MNs are rigid enough to penetrate the skin and become flexible after insertion into the skin. It is also shown that the MN array successfully extracts ISF in vitro and in vivo not by capillary action but by repeated compressions. The results show the applicability of the flexible MNs to continuous blood glucose monitoring.

Hybrid 3D printed-paper microfluidics

3D printed and paper-based microfluidics are promising formats for applications that require portable miniaturized fluid handling such as point-of-care testing. These two formats deployed in isolation, however, have inherent limitations that hamper their capabilities and versatility. Here, we present the convergence of 3D printed and paper formats into hybrid devices that overcome many of these limitations, while capitalizing on their respective strengths. Hybrid channels were fabricated with no specialized equipment except a commercial 3D printer. Finger-operated reservoirs and valves capable of fully-reversible dispensation and actuation were designed for intuitive operation without equipment or training. Components were then integrated into a versatile multicomponent device capable of dynamic fluid pathing. These results are an early demonstration of how 3D printed and paper microfluidics can be hybridized into versatile lab-on-chip devices.

OOCHIP: Compartmentalized Microfluidic Perfusion System with Porous Barriers for Enhanced Cell-Cell Crosstalk in Organ-on-a-Chip

Improved in vitro models of human organs for predicting drug efficacy, interactions, and disease modelling are crucially needed to minimize the use of animal models, which inevitably display significant differences from the human disease state and metabolism. Inside the body, cells are organized either in direct contact or in close proximity to other cell types in a tightly controlled architecture that regulates tissue function. To emulate this cellular interface in vitro, an advanced cell culture system is required. In this paper, we describe a set of compartmentalized silicon-based microfluidic chips that enable co-culturing several types of cells in close proximity with enhanced cell–cell interaction. In vivo-like fluid flow into and/or from each compartment, as well as between adjacent compartments, is maintained by micro-engineered porous barriers. This porous structure provides a tool for mimicking the paracrine exchange between cells in the human body. As a demonstrating example, the microfluidic system was tested by culturing human adipose tissue that is infiltrated with immune cells to study the role if the interplay between the two cells in the context of type 2 diabetes. However, the system provides a platform technology for mimicking the structure and function of single- and multi-organ models, which could significantly narrow the gap between in vivo and in vitro conditions.

Particle-Based Porous Materials for the Rapid and Spontaneous Diffusion of Liquid Metals

Gallium-based room-temperature liquid metals have enormous potential for realizing various applications in electronic devices, heat flow management, and soft actuators. Filling narrow spaces with a liquid metal is of great importance in rapid prototyping and circuit printing. However, it is relatively difficult to stretch or spread liquid metals into desired patterns because of their large surface tension. Here, we propose a method to fabricate a particle-based porous material which can enable the rapid and spontaneous diffusion of liquid metals within the material under a capillary force. Remarkably, such a method can allow liquid metal to diffuse along complex structures and even overcome the effect of gravity despite their large densities. We further demonstrate that the developed method can be utilized for prototyping complex three-dimensional (3D) structures via direct casting and connecting individual parts or by 3D printing. As such, we believe that the presented technique holds great promise for the development of additive manufacturing, rapid prototyping, and soft electronics using liquid metals.

Precise generation of dynamic biochemical signals by controlling the programmable pump in a Y-shaped microfluidic chip with a "christmas tree" inlet

The generation of dynamic biochemical signals in a microfluidic control system is of importance for the study of the interaction between biological cells and their niches. However, most of microfluidic control systems are not able to provide dynamic biochemical signals with high precision and stability due to inherent mechanical vibrations caused by the actuators of the programmable pumps. In this paper, we propose a novel microfluidic feedback control system integrating an external feedback control system with a Y-shaped microfluidic chip with a "Christmas tree" inlet. The Proportional Integral Derivative (PID) controller is implemented to reduce the influence of vibrations. In order to regulate the control parameters efficiently, a mathematical model is built to describe the actuator of the programmable pump, in which a fractional-order model is utilized. Both simulation and experimental studies are carried out, confirming that the microfluidic feedback control system can precisely and stably generate desired dynamic biochemical signals.

On-Demand Droplet Merging with an AC Electric Field for Multiple-Volume Droplet Generation

We introduce a unique system to achieve on-demand droplet merging and splitting using a perpendicular AC electric field. The working mechanism involves a micropillar to split droplets, followed by electrocoalescence using an AC electric field. Adjusting the parameters of the AC signal and conductivity of the fluid result in different merging regimes. We observed a minimum threshold voltage and a strong influence of the surfactant. We hypothesize that the merging process is caused by dipole-dipole coalescence between the daughter droplets. At the same time, adjustment of the conductivity reveals a shift in the merging regimes and can be explained with an electric circuit diagram. Size-based sorting using this merging phenomenon is subsequently demonstrated, where alternate, single, double, and triple droplets sorting were achieved. The concept presented in this paper is potentially useful for drug dispensing or multivolume digital polymerase chain reaction, as droplets of multiple sizes can be generated simultaneously.

Reconfigurable, Self-Sufficient Convective Heat Exchanger for Temperature Control of Microfluidic Systems

Here, we demonstrate a modular, reconfigurable, and self-sufficient convective heat exchanger for regulation of temperature in microfluidic systems. The heat exchanger consists of polymer tubes wrapped around a plastic pole and fully embedded in an elastomer block, which can be easily mounted onto the microfluidic structure. It is compatible with various microfluidic geometries and materials. Miniaturized, battery-powered piezoelectric pumps are utilized to drive the heat carrying liquid through the heat exchanger at desired flow rates and temperatures. Customized temperature profiles can be generated by changing the configuration of the heat exchanger with respect to the microfluidic structure. Tailored dynamic temperature profiles can be generated by changing the temperature of the heat carrying liquid in successive cycles. This feature is used to study the calcium signaling of endothelial cells under successive temperature cycles of 24 to 37 °C. The versatility, simplicity, and self-sufficiency of the heat exchanger makes it suitable for various microfluidic based cellular assays.

Self-sufficient, low-cost microfluidic pumps utilising reinforced balloons

Here, we introduce a simple method for increasing the inflation pressure of self-sufficient pressure pumps made of latex balloons. Our method involves reinforcing the latex balloon with elastane fibres to restrict the expansion of the balloon and increase its inflation pressure. This allowed us to increase the operational inflation pressure of a latex balloon from 2.5 to 25 kPa. Proof-of-concept experiments show the suitability of the reinforced balloon for inducing lateral forces and recirculating flows, which are employed for hydrodynamic capturing of large human monocytes. We also demonstrate the ability for the rapid exchange of solutions in repeated cycles upon manual squeezing of the reinforced balloons. We also show the suitability of the reinforced balloon for studying the mechanobiology of human aortic endothelial cells under various shear stress levels. The simplicity, portability, affordability, hyper-elasticity and scalability of the reinforced balloon pumps make them suitable for a wide range of microfluidic applications.

Paraffin Oil Based Soft-Template Approach to Fabricate Reusable Porous PDMS Sponge for Effective Oil/Water Separation

Three-dimensional porous material holds enormous potential in the field of life science and environmental protection. In this work, we proposed a facile route for the large-scale synthesis of porous poly(dimethylsiloxane) (PDMS) sponge via paraffin oil based emulsion technique. A stable emulsion could be formed by emulsifying water in the PDMS solution with the aid of paraffin oil. Moreover, the amount of emulsified water in 5 g of PDMS solution is as high as 35 g, and the skeleton of the prepared PDMS sponge is still in intact. This method is cost-effective, rapid, and easily scaled up. The water contact angle of the obtained PDMS sponge is 141.9 ± 1°, and the absorption capacities of the sponges are 13.5-33.3 g g^-1 for various organic solvents. The PDMS sponge only needed 0.069 MPa force to realize the compression ratio of 90%, which it still maintained after over 50 cycles of compression. In addition, the porous PDMS sponge exhibited an excellent oil absorption and an outstanding reusability, which were potentially useful in water purification.

Asynchronous generation of oil droplets using a microfluidic flow focusing system

Here, we show that long-term exposure of PDMS based microfluidic droplet generation systems to water can reverse their characteristics such that they generate oil-in-water droplets instead of water-in-oil droplets. The competition between two oil columns entering via the two side channels leads to asynchronous generation of oil droplets. We identify various modes of droplet generation, and study the size, gap and generation rate of droplets under different combinations of oil and water pressures. Oil droplets can also be generated using syringe pumps, various oil viscosities, and different combinations of immiscible liquids. We also demonstrate the ability to dynamically change the gap between the oil droplets from a few hundred microns to just a few microns in successive cycles using a latex balloon pressure pump. This method requires no special equipment or chemical treatments, and importantly can be reversed by long-term exposure of the PDMS surfaces to the ambient air.

Multi-chamber petaloid root-growth chip for the non-destructive study of the development and physiology of the fibrous root system of Oryza sativa

The root system of plants is a major component of their bodies in terms of both function and bulk. The investigation of root system development is greatly assisted by microfluidic devices, which improve the spatial and temporal resolution of observations without destroying tissue. In the present study, a multi-chamber petaloid root-growth chip was developed for studying the development and physiology of root systems that have thin branching structures (i.e., fibrous root systems). The petaloid root-growth chip includes a central seed germination chamber and five root-growth chambers for observing the development of fibrous roots. The proposed device was applied for investigating the root system development of Oryza sativa. The phenotype and growth kinetics of O. sativa root systems grown in the proposed device were compared with those obtained during growth in a conventional conical flask with agar-based medium, and the results indicated that cultivation in the miniaturized device did not delay root system growth in the early stage (≤2 weeks). In addition, the transparent device enabled the non-destructive observation of the developmental and microstructural characteristics of the roots, such as the root caps, root border cells, and root hairs. Moreover, the ability to control the microenvironment in each of the five root-growth chambers individually facilitated the investigation of specific adaptations in the fibrous root growth of single O. sativa seedlings to different drought stresses. Accordingly, five polyethylene glycol (PEG)6000-induced drought stress conditions were established in the five root-growth chambers to investigate the root development of a single O. sativa seedling in the central germination chamber. In situ observations demonstrated that the different PEG6000-induced conditions affected the root growth responses and root microstructural adaptations of the single seedlings in each root-growth chamber. Therefore, the petaloid root-growth microfluidic chip can eliminate the effects of variations in different plant seeds to reveal the responses of plants to different environmental conditions more objectively while concurrently allowing for non-destructive observations at very high spatial and temporal resolution.

Liquid Metal-Elastomer Soft Composites with Independently Controllable and Highly Tunable Droplet Size and Volume Loading

Soft composites are critical for soft and flexible materials in energy harvesting, actuators, and multifunctional devices. One emerging approach to create multifunctional composites is through the incorporation of liquid metal (LM) droplets such as eutectic gallium indium (EGaIn) in highly deformable elastomers. The microstructure of such systems is critical to their performance; however, current materials lack control of particle size at diverse volume loadings. Here, we present a fabrication approach to create liquid metal-elastomer composites with independently controllable and highly tunable droplet size (100 nm ≤ D ≤ 80 μm) and volume loading (0 ≤ ϕ ≤ 80%). This is achieved through a combination of shear mixing and sonication of concentrated LM/elastomer emulsions to control droplet size and subsequent dilution and homogenization to tune LM volume loading. These materials are characterized utilizing dielectric spectroscopy supported by analytical modeling, which shows a high relative permittivity of 60 (16× the unfilled elastomer) in a composite with ϕ = 80%, a low tan δ of 0.02, and a significant dependence on ϕ and minor dependence on droplet size. Temperature response and stability are determined using dielectric spectroscopy through temperature and frequency sweeps with DSC. These results demonstrate a wide temperature stability of the liquid metal phase (crystallizing at <-85 °C for D < 20 μm). Additionally, all composites are electrically insulating across wide frequency (0.1 Hz-10 MHz) and temperature (-70 to 100 °C) ranges even up to ϕ = 80%. We highlight the benefit of LM microstructure control by creating all-soft-matter stretchable capacitive sensors with tunable sensitivity. These sensors are further integrated into a wearable sensing glove where we identify different objects during grasping motions. This work enables programmable LM composites for soft robotics and stretchable electronics where flexibility and tunable functional response are critical.

Microfluidic chip to interface porous microneedles for ISF collection

Porous microneedles (MNs) are expected to be applied for diagnostic microfluidic devices such as blood glucose monitoring as they enable a pain-free penetration of human skin and the extraction of interstitial fluids. However, conventional microfluidic systems require additional steps to separate the liquid from a porous structure used for fluid extraction. In this study, we developed a microfluidic system with a hydrodynamically designed interface between a porous MN array and microchannels to enable a direct analysis of liquids extracted by the porous MN array. The microfluidic chip with an interface for the MN array was successfully realized by standard MEMS processes, enabling a liquid flow through the whole microfluidic structure. The porous MN array was fabricated by the salt leaching and molding method, which was integrated with the chip and demonstrated the successful extraction of liquids from an agarose gel-based skin phantom.

Stable biphasic interfaces for open microfluidic platforms

We present an open microfluidic platform that enables stable flow of an organic solvent over an aqueous solution. The device features apertures connecting a lower aqueous channel to an upper solvent compartment that is open to air, enabling easy removal of the solvent for analysis. We have previously shown that related open biphasic systems enable steroid hormone extraction from human cells in microscale culture and secondary metabolite extraction from microbial culture; here we build on our prior work by determining conditions under which the system can be used with extraction solvents of ranging polarities, a critical feature for applying this extraction platform to diverse classes of metabolites. We developed an analytical model that predicts the limits of stable aqueous-organic interfaces based on analysis of Laplace pressure. With this analytical model and experimental testing, we developed generalized design rules for creating stable open microfluidic biphasic systems with solvents of varying densities, aqueous-organic interfacial tensions, and polarities. The stable biphasic interfaces afforded by this device will enable on-chip extraction of diverse metabolite structures and novel applications in microscale biphasic chemical reactions.

Preparation of carbon-containing, compressible, microporous, polymeric monoliths that regulate macroscopic conductivity

Compressible, microporous polymers have been prepared as a monolithic sponge and further regulated macroscopic conductivity when combined with carbon materials.

Spherical Shaped ( A g − F e 3 O 4 / H 2 O ) Hybrid Nanofluid Flow Squeezed between Two Riga Plates with Nonlinear Thermal Radiation and Chemical Reaction Effects

The main concern is to explore an electro-magneto hydrodynamic (EMHD) squeezing flow of ( A g − F e 3 O 4 / H 2 O ) hybrid nanofluid between stretchable parallel Riga plates. The benefits of the use of hybrid nanofluids, and the parameters associated to it, have been analyzed mathematically. This particular problem has a lot of importance in several branches of engineering and industry. Heat and mass transfer along with nonlinear thermal radiation and chemical reaction effects have also been incorporated while carrying out the study. An appropriate selection of dimensionless variables have enabled us to develop a mathematical model for the present flow situation. The resulting mathematical method have been solved by a numerical scheme named as the method of moment. The accuracy of the scheme has been ensured by comparing the present result to some already existing results of the same problem, but for a limited case. To back our results further we have also obtained the solution by anther recipe known as the Runge-Kutta-Fehlberg method combined with the shooting technique. The error analysis in a tabulated form have also been presented to validate the acquired results. Furthermore, with the graphical assistance, the variation in the behavior of the velocity, temperature and concentration profile have been inspected under the action of various ingrained parameters. The expressions for skin friction coefficient, local Nusselt number and local Sherwood number, in case of ( A g − F e 3 O 4 / H 2 O ) hybrid nanofluid, have been derived and the influence of various parameters have also been discussed.

"Do-it-in-classroom" fabrication of microfluidic systems by replica moulding of pasta structures

Here, we describe a novel method for fabrication of microfluidic structures in classroom environments. This method is based on replica moulding of pasta structures in polydimethylsiloxane. Placing pasta structures on a petroleum jelly base layer enables templating round-shaped structures with controllable cross-sectional profiles. The pasta structures can be easily deformed and combined to create more complex 3D microfluidic structures. Proof-of-concept experiments indicate the capability of this method for studying the mixing of neighbouring flows, generation of droplets, lateral migration of particles, as well as culturing, shear stress stimulation, and imaging of cells. Our "do-it-in-classroom" method bridges the gap between the classroom and the laboratory.

Egg Component-Composited Inverse Opal Particles for Synergistic Drug Delivery

Microparticles have a demonstrated value in drug delivery systems. The attempts to develop this technology focus on the generation of functional microparticles by using innovative but accessible materials. Here, we present egg component-composited microparticles with a hybrid inverse opal structure for synergistic drug delivery. The egg component inverse opal particles were produced by using egg yolk to negatively replicate colloid crystal bead templates. Because of their huge specific surface areas, abundant nanopores, and complex nanochannels of the inverse opal structure, the resultant egg yolk particles could be loaded with different kinds of drugs, such as hydrophobic camptothecin (CPT), by simply immersing them into the corresponding drug solutions. Attractively, additional drugs, such as the hydrophilic doxorubicin (DOX), could also be encapsulated into the particles through the secondary filling of the drug-doped egg white hydrogel into the egg yolk inverse opal scaffolds, which realized the synergistic drug delivery for the particles. It was demonstrated that the egg-derived inverse opal particles were with large quantity and lasting releasing for the CPT and DOX codelivery, and thus could significantly reduce cell viability, and enhance therapeutic efficacy in treating cancer cells. These features of the egg component-composited inverse opal microparticles indicated that they are ideal microcarriers for drug delivery.