A microfluidic platform for electrical detection of DNA hybridization

Current methods used for detection of DNA hybridization involve the use of DNA microarrays which require overnight incubation times along with bulky and expensive fluorescent scanners. Here, we demonstrate electrical detection of DNA hybridization in an oligonucleotide functionalized microfluidic channel. We use microchannels functionalized with DNA probes integrated with electrodes for measuring conductance across the channel. As beads conjugated with the target DNA passing through the channel are captured on the surface, we are able to electrically detect changes in resistance due to bead capture. Our assay can be completed in less than an hour using less than a microliter of reagent, and has the potential for extensive multiplexing. Such a device can be useful as a handheld platform in a clinical setting where one would need to rapidly genotype a small number of genes rapidly.     

A novel integrated microfluidic platform based on micro-magnetic sensor for magnetic bead manipulation and detection

We present a novel integrated microfluidic platform based on micro-magnetic sensor for manipulating and detecting magnetic beads (MB). A micro-spiral planar coil in MB manipulating system microfabricated by micro-electro-mechanical system technology is implemented to manipulate MB, and a giant magnetoimpedance (GMI) based micro-magnetic sensor is employed to detect the trapped MB. In our work, MB can be efficiently trapped by trapping force generated from micro-coil in microchannel. Next, trapped MB are detected by the changing ratio of impedance, as well as the variation of resistance and reactance in GMI sensor for trapped MB induce weak stray magnetic field under the magnetization by external magnetic field. The maximum difference of GMI ratio between with beads condition and without beads condition is 4.0% at the optimum driving frequency of 20 MHz under the external magnetic field of 15 Oe, and resistance ratio varies more significantly than reactance ratio. In comparison with traditional MB detecting methods by GMI sensor, the integrated microfluidic platform based on GMI sensor can not only manipulate and detect MB signal sensitively, but also enhance detection efficiency and decrease the experiment errors. Furthermore, this platform avoids contamination from the solutions in chemically reactive layers and reduces assay time in future biomarker detection. In our work, the microfluidic platform based on GMI sensor has potential applications in biomarker detection via MB manipulation and detection.     

A novel filtration method integrated on centrifugal microfluidic devices

A method has been developed that integrates filters directly into centrifugal microfluidic devices. This technique is suitable for both rapid prototyping and commercial applications. Commercially available filter paper was sealed into the centrifugal microfluidic device with a simple manual fabrication procedure. The method was validated using soil slurry in water and a variety of filter papers with pore sizes ranging from 0.7 to 11 μm. Filtration times of 4 s to several minutes were obtained for 100 μL samples depending on the type of filter paper and rotation rate utilized. The validity of the method was demonstrated by assessing the amount of light lost due to the scatter or absorption caused by particles in the filtered sample while the device was in motion. Filtration and sedimentation were compared and after 30 min of centrifugation, sedimentation had not removed particles as well as filtration. This technique opens up centrifugal microfluidic devices to a wide range of samples.     

A microfluidic platform with integrated flow sensing for focal chemical stimulation of cells and tissue

A microfluidic platform for precise biochemical control of the extracellular microenvironment was developed. A chemical interface was established with cells or tissues through the precise and focal delivery of soluble chemical agents through a pore addressed by a polymer microchannel. Thermal flow sensors were integrated along the length of the microchannel and monitored internal flow rate. Sensor performance was characterized in anticipation of future studies with real-time feedback control of focal delivery. The microfluidic system was characterized by determining the fluid delivery rates through the pores and concentration profiles of agents delivered. Finally, focal delivery to rat retinal tissue was demonstrated.     

A novel three-dimensional microfluidic platform for on chip multicellular tumor spheroid formation and culture

The formation of three-dimensional (3D) multicellular cell spheroids such as microspheres and embryoid bodies has recently gained much attention as a useful cell culture technique, but few studies have investigated the suitability of glass for spheroids formation and culture. In this work, we present a novel three-dimensional microfluidic device made of poly(dimethylsiloxane) (PDMS) and glass for the easy and rapid synthesis and culture of tumor spheroid. The cell culture unit is composed of an array of microwells on the bottom of a glass plate, bigger microwells and elastomeric microchannels on the top of a PDMS plate. Cell suspension can be easily introduced into the cell culture unit and exchange with the external liquid environment by the microfluidic channels. A single tumor spheroid can be formed and cultured in each glass cell culture chamber, the surface of which was modified with poly(vinyl alcohol) to render it to be resistant to cell adhesion. As the cell culture medium could be replaced, spheroids of the human breast cancer (MCF-7) cells were cultured on the chip for 3 days, reaching the diameters of about 150 μm. Furthermore, the MCF-7 cells were successfully cultured on the chip in 2D and 3D culture modes. Results have shown that glass is well suitable for multicellular tumor spheroids culture. The established platform provides a convenient and rapid method for tumor spheroid culture, which is also adaptable for anticancer drug screening and fundamental biomedical research in cell biology.     

A microfluidic platform for formation of double-emulsion droplets

A new method for actively controlling the number of internal droplets of water-in-oil-in-water (W/O/W) double-emulsion droplets was demonstrated. A new microfluidic platform for double-emulsion applications has been developed, which integrates T-junction channels, moving-wall structures, and a flow-focusing structure. Inner water-in-oil (W/O) single-emulsion droplets were first formed at a major T-junction. Then the droplets were sub-divided into smaller uniform droplets by passing through a series of secondary T-junctions (branches). The moving-wall structures beside the secondary T-junctions were used to control the number of the sub-divided droplets by selectively blocking the branches. Finally, double-emulsion droplets were formed by using a flow-focusing structure downstream. Experimental data demonstrate that the inner and outer droplets have narrow size distributions with coefficient of variation (CV) of less than 3.5% and 5.7%, respectively. Double-emulsion droplets with 1, 2, 3, and up to 10 inner droplets have been successfully formed using this approach. The size of the inner droplets and outer droplets could be also fine-tuned with this device. The development of this new platform was promising for drug delivery applications involving double emulsions.     

New production method of convex microlens arrays for integrated fluorescence microfluidic detection systems

A new method for producing microlens array with large sag heights is proposed for integrated fluorescence microfluidic detection systems. Three steps in this production technique are included for concave microlens array formations to be integrated into microfluidic systems. First, using the photoresist SU-8 to produce hexagonal microchannel array is required. Second, UV curable glue is injected into the hexagonal microchannel array. Third, the surplus glue is rotated by a spinner at high velocity and exposed to a UV lamp to harden the glue. The micro concave lens molds are then finished and ready to produce convex microlens in poly methsiloxane (PDMS) material. This convex microlens in PDMS can be used for detecting fluorescence in microfluidic channels because a convex microlens plays the light convergence role for optical fiber detection.     

A novel microfluidic high-throughput resistive pulse sensing device for cells analysis

Microfluidic impedance-based devices offer a simple method for counting and sizing particles and cells in fields of biomedical research and clinical diagnosis. In this work, we present design, fabrication and operational characteristics of a novel high throughput original MEMS-based Coulter counter. This microfluidic device possesses two sub channels including two pairs of coplanar Au/Cr electrodes in each channels which allows double detection of the particles simultaneously and increases the throughput. The present design provides minimizing the cross talk and obviating the need for hydrodynamic focusing of the sample particles by adjusting Y shape insulation obstacle in direction of flow. Moreover, reducing coincidence events and removing electrode polarization effect were purposed by applying optimum sizes for electrodes considering the ease of fabrication and low costs. The reliability of the novel device was evaluated for polystyrene particles and cancer cells in conductive solutions. Results, which were recorded as relative resistance pulses across four sensing zones, illustrate the capability of the double-channel proposed device in detecting, counting and sizing 10 and 20 µm polystyrene particles. The superiority of present design was proved by relative counting error of below 3 and 11% for the 10 µm and 20 µm particles, respectively and a throughput of hundreds particles per second. Aiming at demonstrating the functionality of the proposed device in the biomedical area, counting of SP2/0 cells was performed. The measured counting outputs for cells in the size range of 5.63–17.6 µm were validated with results of hemocytometer cell counter, with relative error less than 7%.

     

A microfluidic platform with permeable walls for the analysis of vascular and extravascular mass transport

The interface between the blood pool and the extravascular matrix is fundamental in regulating the transport of molecules, nanoparticles and cells under physiological and pathological conditions. In this work, a microfluidic chip is presented comprising two parallel microchannels connected laterally via an array of high aspect ratio micropillars, constituting the permeable vascular membrane. A double-step lithographic process combined with a replica molding approach is employed to realize 80 different arrays of micropillars exhibiting three cross-sectional geometries (rectangular, elliptical and curved); two orientations (normal and parallel) with respect to the flow; and a variety of width and gap sizes, respectively, ranging from 10 to 20 μm and 2 to 5 μm. As compared to conventional rectangular structures, the curved pillars provide higher bending stiffness, lower adhesive interactions, and smaller intra-channel separation distances. Specifically, 10-μm-wide curved pillars, laying parallel to the flow, offered the highest mechanical stability. To assess vascular permeability, the extravascular channel was filled with a hyaluronic acid hydrogel, while fluorescent Dextran molecules and calibrated polystyrene beads were injected in the vascular channel. Membrane permeability was observed to reduce with the molecular weight of Dextran and diameter of the beads, ranging from about 6 × 10^?5 to 2 × 10^?5 cm/s for 40 and 250 kDa Dextran and up to zero for 1.5 μm beads. The presented data demonstrate the potential of the proposed microfluidic chip for analyzing the vascular and extravascular mass transport, over multiple spatial and temporal scales, in a variety of diseases involving differential permeation across vascular walls.     

Dielectrophoresis-based microfluidic platform to sort micro-particles in continuous flow

Non-invasive separation of particles with different sizes and sensitivities has been a challenge and interest for point-of-care diagnostics and personalized treatment. Dielectrophoresis is widely known as a powerful technique to sort the particles and (most importantly to) distinguish cells and monitor their state without the need for biochemical tags. In this paper, a dielectrophoresis-based microchannel design is proposed which allows for continuous particle sorting and separation under the applied AC field. It is also practical to implement the platform for monitoring cell behavior irregularities caused by certain diseases toward diagnosis and treatment. In this regard, the device employs dielectrophoretic (DEP) force exerted on the particles by only two electrodes with oblique arrangement in the channel. The electrodes are arranged with a bevel angle to the fluid flow direction but they are not parallel and therefore a gradually decreasing electric field is achieved along the channel’s width. As a result, the dielectrophoretic force, acting on the particles of different sizes, would also gradually decrease along channels width which renders the necessary distinguishing lateral displacements of particles for separation. Therefore, the particles with different sizes can be sorted in a continuous-flow regime and be received at multiple outlet reservoirs with no need to turn the electric field on/off. The presented device is fabricated and evaluated in the experiment to prove its feasibility. Afterward, using numerical simulations, we investigate the optimum design parameters in the presented device to enhance device efficiency for separating particles with different size ranges.

     

A 3D printed centrifugal microfluidic platform for automated colorimetric urinalysis

Colorimetric urinalysis is a commonly performed test for rapid and low-cost diagnosis. Conventional colorimetric urinalysis is manually conducted using dipsticks and suffers from difficulties in control of sample distribution and color interpretation. This paper reports a microfluidic platform for conducting automated colorimetric urinalysis. Centrifugal microfluidic technology was used for regulating the distribution of urine sample in designed volume and time sequence. The prototype of the microfluidic chip was fabricated using 3D printing technology. To test the feasibility of the prototype system, commercial urinalysis strips were integrated with the microfluidic system for detecting glucose, specific gravity, PH, and protein from simulated urine sample. The color change of the strips was recorded using a smartphone and analyzed to quantify the interested parameters. The H (hue), S (saturation) and V (value) coordinates of the HSV color space were extracted and related to the change of the four parameters. The intensity change of V channel showed good representation of the change of glucose concentration and specific gravity. The intensity change of S channel decreased as the increase of PH and protein concentration. The proposed Lab-on-CD platform has potential for automating colorimetric urinalysis to reduce the user errors, thus to made the testing results conducted by non-professionals more reliable.

     

Mesh convergence test system in integrated platform environment for finite element analysis

The Journal of Supercomputing - We designed integrated computer-aided engineering (CAE) middleware with a CAE solution for modeling and simulation work to reduce the cost and time of product...     

A post-bonding-free fabrication of integrated microfluidic devices for mass spectrometry applications

This paper presents a novel process for fabricating integrated microfluidic devices with embedded electrodes which utilizes low-cost UV curable resins. Commercial UV glue is sandwiched between two substrates and is used for both the structural material and the bonding adhesive. During the exposure procedure, the pattern of micro-fluidic channels is defined using a standard lithography process while the two substrates are bonded. The un-cured UV glue is then removed by vacuum suction to form the sealed microfluidic channel. With this simple approach, conventional high-temperature bonding processes can be excluded in the fabrication of sealed microfluidic structures such that the developed method is highly advantageous for fabricating microchip devices with embedded electrodes. The overall time required to fabricate the sealed microchip device is less than 10 min since no time-consuming etching and bonding process is necessary. An innovative micro-reactor integrated with an in-channel micro-plasma generator for real-time chemical reaction analysis is fabricated using the developed process. On-line mass-spectrum (MS) detection of an esterification reaction is successfully demonstrated, which results in a fast, label-free, preparation-free analysis of chemical samples. The developed process can thus show its potential for rapid and low-cost microdevice manufacturing.     

A novel and secure IoT based cloud centric architecture to perform predictive analysis of users activities in sustainable health centres

Diabetes, blood pressure, heart, and kidney, some of the diseases common across the world, are termed ’silent killers’. More than 50 % of the world’s population are affected by these diseases. If suitable steps are not taken during the early stages then severe complications occur from these diseases. In the work proposed, we have discussed the manner in which the Internet-of-Things based Cloud centric architecture is used for predictive analysis of physical activities of the users in sustainable health centers. The architecture proposed is based on the embedded sensors of the equipment rather than using wearable sensors or Smartphone sensors to store the value of the basic health-related parameters. Cloud centric architecture is composed of a Cloud data center, Public cloud, Private cloud, and uses the XML Web services for secure and fast communication of information. The architecture proposed here is evaluated for its adoption, prediction analysis of physical activities, efficiency, and security. From the results obtained it can be seen that the overall response between the local database server and Cloud data center remains almost constant with the rise in the number of users. For prediction analysis, If the results collected in real time for the analysis of physical activities exceed any of the parameter limits of the defined threshold value then an alert is sent to the health care personnel. Security analysis also shows the effective encryption and decryption of information. The architecture presented is effective and reduces the proliferation of information. It is also suggested, that a person suffering from any of the diseases mentioned above can defer the onset of complications by doing regular physical activities.     

A novel intelligent verification platform based on a structured analysis model

An intelligent verification platform based on a structured analysis model is presented.Using an abstract model mechanism with specific signal interfaces for user callback,the unified structured analysis data,shared by the electronic system level design,functional verification,and performance evaluation,enables efficient management review,auto-generation of code,and modeling in the transaction level.We introduce the class tree,flow parameter diagram,structured flow chart,and event-driven finite state machine as structured analysis models.As a sand table to carry maps from different perspectives and levels via an engine,this highly reusable platform provides the mapping topology to search for unintended consequences and the graph theory for comprehensive coverage and smart test cases.Experimental results show that the engine generates efficient test sequences,with a sharp increase in coverage for the same vector count compared with a random test.     

A novel microfluidic switch for pH control using Chitosan based hydrogels

We report a novel pH-sensitive hydrogel based micro-valve for metered flow that has applications in a laboratory made “Intelligent valving system”. The hydrogel solution was prepared through Chitosan and poly vinyl alcohol in acetic acid and crystallized using gluteraldehyde as the crosslinking agent in the form of thin wafers and it was found to be very sensitive to pH changes. The pore structure of hydrogel was investigated through Field Emission Scanning Electron Microscopy and thin wafers of the gel were physically placed inside PDMS microchannels. Flow metering in these channels was observed by controlled expansion of the hydrogel plug till complete valving was realized. This valving device was further precisely characterized with micro Particle Image Velocimetry using a solution containing fluorescent polymeric micro beads. The principle advantage of this hydrogel device is the smaller range of pH (varying between pH 3 and 7) over which the valving response is observed.