A Recent Approach towards Fluidic Microstrip Devices and Gas Sensors: A Review

This paper aims to review some of the available tunable devices with emphasis on the techniques employed, fabrications, merits, and demerits of each technique. In the era of fluidic microstrip communication devices, versatility and stability have become key features of microfluidic devices. These fluidic devices allow advanced fabrication techniques such as 3D printing, spraying, or injecting the conductive fluid on the flexible/rigid substrate. Fluidic techniques are used either in the form of loading components, switching, or as the radiating/conducting path of a microwave component such as liquid metals. The major benefits and drawbacks of each technology are also emphasized. In this review, there is a brief discussion of the most widely used microfluidic materials, their novel fabrication/patterning methods.

User-friendly, magnetically sealed plug-and-play sensor module for online electrochemical sensing for fluidic devices

The growth in fluidic devices, such as organ-on-chip (OOC) technology, comes with a need for growth in sensing capabilities of key biomolecules to help elucidate changes during the time course of experiments. We developed an on-line, easy-to-assemble, 3D-printed electrochemical sensor module that is magnetically sealed for ease of assembly. The sensor module includes a plug-and-play format for electrochemical sensors made in finger-tight fittings to allow for a wide selection of experimental set-ups and target molecules. Here, we report the feasibility of the sensor module as well as demonstrate its use for electrochemical sensing with integrated thermoplastic electrodes (TPEs). The sensor module withstood over 300 kPa of backpressure and demonstrated reliable performance with TPEs when using cyclic voltammetry (CV) and amperometry under flow conditions. CVs using the ferri/ferrocyanide (K3/4[Fe(CN)6]) redox system demonstrate that the sensor module does not hinder the expected linear response with respect to analyte concentration. Further CVs and amperometry demonstrated the use of the sensor module under flow conditions. Such success in device design and usability is promising for future work using the on-line sensor module with a variety of applications.

The ejection of large non-oscillating droplets from a hydrophobic wedge in microgravity

When confined within containers or conduits, drops and bubbles migrate to regions of minimum energy by the combined effects of surface tension, surface wetting, system geometry, and initial conditions. Such capillary phenomena are exploited for passive phase separation operations in micro-fluidic devices on earth and macro-fluidic devices aboard spacecraft. Our study focuses on the migration and ejection of large inertial-capillary drops confined between tilted planar hydrophobic substrates (a.k.a., wedges). In our experiments, the brief nearly weightless environment of a 2.1 s drop tower allows for the study of such capillary dominated behavior for up to 10 mL water drops with migration velocities up to 12 cm/s. We control ejection velocities as a function of drop volume, substrate tilt angle, initial confinement, and fluid properties. We then demonstrate how such geometries may be employed as passive no-moving-parts droplet generators for very large drop dynamics investigations. The method is ideal for hand-held non-oscillatory ‘droplet’ generation in low-gravity environments.

Directional manipulation of diffusio-osmosis flow by design of solute-wall and solvent-wall interactions

Understanding of the diffusio-osmosis, the flow induced by a solute gradient acting in narrow interfacial layers at nanoscale solid-liquid interface, is of great value in view of the increasing importance of micro- and nano-fluidic devices and self-propelling particle. Here, using molecular dynamics simulations, we develop a numerical method for direct simulation of diffusio-osmosis flows mimicking the realistic experiment without any assumed external forces. It allows us to obtain reliable flow details which is however hard to get in experiments. We found that the solvent-wall interaction, previously overlooked in classical paradigm, plays a critical role in diffusio-osmosis process. In particular, diffusio-osmosis is controlled by the interaction difference between solute-wall and solvent-wall. When solute-than solvent-wall, a surface excess (depletion) of solute particles on solid-liquid interface is formed which induces diffusio-osmosis flow towards low (high) concentration. We modified the classical Derjaguin expression to include the effect of nanoscale hydrodynamics boundary conditions for the accurate prediction of diffusio-osmosis characteristics. Overall, our results provide the clear guidance for controlling fluids flow and manipulating motion of colloids under tunable solute concentrations.

3D printing of metallic micro-gears for micro-fluidic applications

Micro-fluidic devices are essential to handle fluids on the micro-meter scale (micro-scale), making them crucial to biomedical applications, where micro-gear is the key component for active fluid mixing. Rapid and direct fabrication of micro-gears is preferred because they are usually custom-made to specific applications and iterative design is needed. However, conventional manufacturing (CM) techniques for micro-fluidic devices are labor-intensive and time-consuming as multiple steps are required. Three-dimensional (3D) printing, or formally known as additive manufacturing (AM) offers a promising alternative over CM techniques in producing near-net shape complex geometries, given the micro-scale fabrication process. In this work, two types of powder-bed fusion (PBF) AM techniques, namely laser-PBF (L-PBF) and electron beam-PBF (EB-PBF) are used to benchmark 3D-printed micro-gears from stainless steel 316L micro-granular powders. Results showcase the preeminence of L-PBF over EB-PBF in generating distinguishable micro-scale features on gear profiles and superior micro-hardness in mechanical property. Overall, PBF metal AM shows significant promise in advancing the otherwise tedious state of CM for micro-gears.

IMPROVEMENT OF THE MICROFLUIDIC DEVICE FOR THE GENERATION OF MONODISPERSE MICROBUBBLES AS DRUG TRANSPORT SYSTEMS

INTRODUCTION: The localized delivery of drugs has been established since the early eighties of the 20th century as a promising alternative for the localized treatment of tumours, based on the mitigation of side effects produced by traditional methods, notably the administration of chemotherapy by systemic route. Countless scientific works have been dealing with this theme in an attempt to make this therapeutic technique viable and accessible. One of the ways to take the drug to the chosen site is through the use of microbubbles as drug carrier units activated through an ultrasonic field with adequate wavelength and frequency. Therefore, these units must have very peculiar characteristics, such as dimensions, homogeneity, echogenicity and structural characteristics, in addition to the ability to take the therapeutic vector intact to the desired location. In the generation of microbubbles, microfluidic devices of different geometries and different configurations are used, according to the state of the art related to this theme. DEVELOPMENT: In this work the technique used is the fabrication of micro fluidic devices using 3D printing. With this technique, it is possible to manufacture the devices in a single step, eliminating time-consuming and more complex intermediate procedures. The devices were manufactured using an Object Eden 250 printer, using the transparent resin VeroClear®. With these devices it was possible to produce microbubbles with diameters of the order of 16-73 µm with degrees of poly dispersion less than 1%. However, there are difficulties to be overcome, notably with regard to the final composition of the devices. Due to the physical characteristics of the microbubble, notably in relation to its lipid coating layer, the search for drug transport systems is an important strategy. CONCLUSION: In this work, an account of these difficulties will be made, in addition to the proposition of alternatives to overcome them. Additionally, compatible drugs will be suggested to be attached to microbubbles according to their structural composition.

An Exploratory Approach to Study Electro-Osmotic of Non-Newtonian Bio-Bi-Phase Flow Due to Peristaltic Transport of Particulate Fluid

The present article aims to probe the impacts of electro-magneto-hydrodynamics (EMHD) peristaltic flow of in-compressible, dusty, non-Newtonian fluid in a hose of predetermined dimension together with homogeneously scattered analogous rigid particles. In the presence of transversal static magnetic field, Navier-Stokes’s equations are employed to design a flow problem for the particulate phase. Governing flow problem is simplified by approximation of long wavelength and zero Reynolds number. The analytical solution for both velocities (solid-liquid) and pressure rise is computed by using well known computational software Mathematica. Perturbation method is employed to extract analytical solution of the resulting ordinary differential equations. Impacts of different physical parameters, expansion in trapped bolus for fluid and particulate velocity profile by increasing Hartmann number are displayed and explained through graphs. Furthermore, a rise in skin friction is noticed with the rise in particle effect and electro-osmotic parameter. This study may have greater significance and viable applications to improve the quality of micro-fluidic devices.