Pool-Boiling Heat-Transfer Enhancement on Cylindrical Surfaces with Hybrid Wettable Patterns.

In this study, pool-boiling heat-transfer experiments were performed to investigate the effect of the number of interlines and the orientation of the hybrid wettable pattern. Hybrid wettable patterns were produced by coating superhydrophilic SiO2 on a masked, hydrophobic, cylindrical copper surface. Using de-ionized (DI) water as the working fluid, pool-boiling heat-transfer studies were conducted on the different surface-treated copper cylinders of a 25-mm diameter and a 40-mm length. The experimental results showed that the number of interlines and the orientation of the hybrid wettable pattern influenced the wall superheat and the HTC. By increasing the number of interlines, the HTC was enhanced when compared to the plain surface. Images obtained from the charge-coupled device (CCD) camera indicated that more bubbles formed on the interlines as compared to other parts. The hybrid wettable pattern with the lowermost section being hydrophobic gave the best heat-transfer coefficient (HTC). The experimental results indicated that the bubble dynamics of the surface is an important factor that determines the nucleate boiling.

A Lego®-like swappable fluidic module for bio-chem applications.

A Lego®-like swappable fluidic module (SFM) is proposed in this research. We designed and fabricated selected modular fluidic components, including functional and auxiliary types that can be effortlessly swapped and integrated into a variety of modular devices to rapidly assemble a fully-portable, disposable fluidic system. In practice, an integrated SFM uses finger-operated, electricity-free pumps to deliver fluids. Using a swirling mechanism, the vortex mixer can rapidly mix two liquids in a one-shot mixing event. We demonstrate the successful application of this SFM in several microfluidic applications, such as the synthesis of gold nanoparticles (AuNPs) from chloroauric acid (HAuCl4), and nucleic acid amplification from the Hepatitis B virus (HBV) with a capillary convective polymerase chain reaction (ccPCR).

A real-time convective PCR machine in a capillary tube instrumented with a CCD-based fluorometer.

This research reports the design, analysis, integration, and test of a prototype of a real-time convective polymerase chain reaction (RT-cPCR) machine that uses a color charged coupled device (CCD) for detecting the emission of fluorescence intensity from an RT-cPCR mix in a microliter volume glass capillary. Because of its simple mechanism, DNA amplification involves employing the cPCR technique with no need for thermocycling control. The flow pattern and temperature distribution can greatly affect the cPCR process in the capillary tube, a computational fluid dynamics (CFD) simulation was conducted in this study for the first time to estimate the required period of an RT-cPCR cycle. This study also tested the PCR mix containing hepatitis B virus (HBV) plasmid samples by using SYBR Green I fluorescence labeling dye to assess the prototype performance. The measured results from the image-processing scheme indicate that the RT-cPCR prototype with a CCD-based fluorometer can achieve similar DNA quantification reproducibility compared to commercial machines, even when the initial DNA concentration in the test PCR mix is reduced to 10 copies/µL.

Pool boiling of nanoparticle-modified surface with interlaced wettability.

This study investigated the pool boiling heat transfer under heating surfaces with various interlaced wettability. Nano-silica particles were used as the coating element to vary the interlaced wettability of the surface. The experimental results revealed that when the wettability of a surface is uniform, the critical heat flux increases with the more wettable surface; however, when the wettability of a surface is modified interlacedly, regardless of whether the modified region becomes more hydrophilic or hydrophobic, the critical heat flux is consistently higher than that of the isotropic surface. In addition, this study observed that critical heat flux was higher when the contact angle difference between the plain surface and the modified region was smaller.

Development of a multilayered polymeric DNA biosensor using radio frequency technology with gold and magnetic nanoparticles.

This study utilized the radio frequency (RF) technology to develop a multilayered polymeric DNA sensor with the help of gold and magnetic nanoparticles. The flexible polymeric materials, poly (p-xylylene) (Parylene) and polyethylene naphtholate (PEN), were used as substrates to replace the conventional rigid substrates such as glass and silicon wafers. The multilayered polymeric RF biosensor, including the two polymer layers and two copper transmission structure layers, was developed to reduce the total sensor size and further enhance the sensitivity of the biochip in the RF DNA detection. Thioglycolic acid (TGA) was used on the surface of the proposed biochip to form a thiolate-modified sensing surface for DNA hybridization. Gold nanoparticles (AuNPs) and magnetic nanoparticles (MNPs) were used to immobilize on the surface of the biosensor to enhance overall detection sensitivity. In addition to gold nanoparticles, the magnetic nanoparticles has been demonstrated the applicability for RF DNA detection. The performance of the proposed biosensor was evaluated by the shift of the center frequency of the RF biosensor because the electromagnetic characteristic of the biosensors can be altered by the immobilized multilayer nanoparticles on the biosensor. The experimental results show that the detection limit of the DNA concentration can reach as low as 10 pM, and the largest shift of the center frequency with triple-layer AuNPs and MNPs can approach 0.9 and 0.7 GHz, respectively. Such the achievement implies that the developed biosensor can offer an alternative inexpensive, disposable, and highly sensitive option for application in biomedicine diagnostic systems because the price and size of each biochip can be effectively reduced by using fully polymeric materials and multilayer-detecting structures.

Real-time remote monitoring of temperature and humidity within a proton exchange membrane fuel cell using flexible sensors.

This study developed portable, non-invasive flexible humidity and temperature microsensors and an in situ wireless sensing system for a proton exchange membrane fuel cell (PEMFC). The system integrated three parts: a flexible capacitive humidity microsensor, a flexible resistive temperature microsensor, and a radio frequency (RF) module for signal transmission. The results show that the capacitive humidity microsensor has a high sensitivity of 0.83 pF%RH(-1) and the resistive temperature microsensor also exhibits a high sensitivity of 2.94 × 10(-3) °C(-1). The established RF module transmits the signals from the two microsensors. The transmission distance can reach 4 m and the response time is less than 0.25 s. The performance measurements demonstrate that the maximum power density of the fuel cell with and without these microsensors are 14.76 mW·cm(-2) and 15.90 mW·cm(-2), with only 7.17% power loss.

Improvement on thermal performance of a disk-shaped miniature heat pipe with nanofluid.

The present study aims to investigate the effect of suspended nanoparticles in base fluids, namely nanofluids, on the thermal resistance of a disk-shaped miniature heat pipe [DMHP]. In this study, two types of nanoparticles, gold and carbon, in aqueous solution are used respectively. An experimental system was set up to measure the thermal resistance of the DMHP with both nanofluids and deionized [DI] water as the working medium. The measured results show that the thermal resistance of DMHP varies with the charge volume and the type of working medium. At the same charge volume, a significant reduction in thermal resistance of DMHP can be found if nanofluid is used instead of DI water.

Investigation of electrical and magnetic properties of ferro-nanofluid on transformers.

This study investigated a simple model of transformers that have liquid magnetic cores with different concentrations of ferro-nanofluids. The simple model was built on a capillary by enamel-insulated wires and with ferro-nanofluid loaded in the capillary. The ferro-nanofluid was fabricated by a chemical co-precipitation method. The performances of the transformers with either air core or ferro-nanofluid at different concentrations of nanoparticles of 0.25, 0.5, 0.75, and 1 M were measured and simulated at frequencies ranging from 100 kHz to 100 MHz. The experimental results indicated that the inductance and coupling coefficient of coils grew with the increment of the ferro-nanofluid concentration. The presence of ferro-nanofluid increased resistance, yielding to the decrement of the quality factor, owing to the phase lag between the external magnetic field and the magnetization of the material.

DNA detection using commercial mobile phones.

This study investigates the feasibility of using mobile phones cameras for DNA detection. DNA amplification uses the convective polymerase chain reaction (cPCR) technique due to its simple mechanism, which requires no thermal cycling control. Fluorescence increment analysis and information entropy analysis are employed separately to determine whether the test samples contain target DNA (Positive) or not (Negative). The fluorescence increment method uses the brightness of the captured images before and after DNA amplification to calculate ΔF. ΔF values above a threshold level indicate that the test sample is positive. The information entropy method defines the probability, P(C/X), which indicates whether the fluorescence image tends towards a specific shape. If a DNA template is successfully amplified, the captured fluorescence image should be a perfect circle. P(C/X) provides a threshold of 0.5 to identify a circle and values above 0.5 indicate the test sample is positive. Experimental results show that P(C/X) is more effective than ΔF for determining DNA detection results. The information entropy analysis method is applied to ten mobile phones of three different brands equipped with camera sensors, which have pixel numbers ranging from 120 M to 800 M. The clinical evaluation study (n = 60) for screening hepatitis B virus (HBV) plasmid samples shows that the accuracy rate of all models of mobile phones ranges from 85% to 100%. This illustrates that successful DNA detection can be achieved using the most widely deployed electronic device.

Rapid DNA amplification in a capillary tube by natural convection with a single isothermal heater.

Herein we describe a simple platform for rapid DNA amplification using convection. Capillary convective PCR (CCPCR) heats the bottom of a capillary tube using a dry bath maintained at a fixed temperature of 95°C. The tube is then cooled by the surrounding air, creating a temperature gradient in which a sample can undergo PCR amplification by natural convection through reagent circulation. We demonstrate that altering the melting temperature of the primers relative to the lowest temperature in the tube affects amplification efficiency; adjusting the denaturation temperature of the amplicon relative to the highest temperature in the tube affects maximum amplicon size, with amplicon lengths of ≤500 bp possible. Based on these criteria, we successfully amplified DNA sequences from three different viral genomes in 30 min using CCPCR, with a sensitivity of ~30 copies per reaction.

Applications of ferro-nanofluid on a micro-transformer.

An on-chip transformer with a ferrofluid magnetic core has been developed and tested. The transformer consists of solenoid-type coil and a magnetic core of ferrofluid, with the former fabricated by MEMS technology and the latter by a chemical co-precipitation method. The performance of the MEMS transformer with a ferrofluid magnetic core was measured and simulated with frequencies ranging from 100 kHz to 100 MHz. Experimental results reveal that the presence of the ferrofluid increases the inductance of coils and the coupling coefficient of transformer; however, it also increases the resistance owing to the lag between the external magnetic field and the magnetization of the material.

A micro circulating PCR chip using a suction-type membrane for fluidic transport.

A new micromachined circulating polymerase chain reaction (PCR) chip is reported in this study. A novel liquid transportation mechanism utilizing a suction-type membrane and three microvalves were used to create a new microfluidic control module to rapidly transport the DNA samples and PCR reagents around three bio-reactors operating at three different temperatures. When operating at a membrane actuation frequency of 14.29 Hz and a pressure of 5 psi, the sample flow rate in the microfluidic control module can be as high as 18 microL/s. In addition, an array-type microheater was adopted to improve the temperature uniformity in the reaction chambers. Open-type reaction chambers were designed to facilitate temperature calibration. Experimental data from infrared images showed that the percentage of area inside the reaction chamber with a thermal variation of less than 1 degrees C was over 90% for a denaturing temperature of 94 degrees C. Three array-type heaters and temperature sensors were integrated into this new circulating PCR chip to modulate three specific operating temperatures for the denaturing, annealing, and extension steps of a PCR process. With this approach, the cycle numbers and reaction times of the three separate reaction steps can be individually adjusted. To verify the performance of this circulating PCR chip, a PCR process to amplify a detection gene (150 base pairs) associated with the hepatitis C virus was performed. Experimental results showed that DNA samples with concentrations ranging from 10(5) to 10(2)copies/microL can be successfully amplified. Therefore, this new circulating PCR chip may provide a useful platform for genetic identification and molecular diagnosis.

DNA detection using a radio frequency biosensor with gold nanoparticles.

This study presents a novel method for DNA detection with multi-layer AuNPs to enhance overall detection sensitivity. This essay achieves not only an innovative radio-frequency biosensor but also a critical signal amplification methodology. Results show that bandwidth change for multi-layer AuNP with hybridization of DNA exceeds that for the double-layer AuNP up to 0.5 GHz. Furthermore, the developed biosensor detection limit for the DNA set employed in this essay is currently 10 pM. A single base-pair mutation of the wild-type target DNA could be distinguished from the perfect match target DNA at the melting temperature of 47 degrees C with a temperature controlling system. Experimental results in this study indicate that the proposed biosensor and the developed amplification methodology are successful. As health care becomes much more essential in modern life, this biosensor has potential applications in a screening kit for recognizing, sensing, and quantifying biomolecules in real samples.

A flexible surface wetness sensor using a RFID technique.

This paper presents a flexible wetness sensor whose detection signal, converted to a binary code, is transmitted through radio-frequency (RF) waves from a radio-frequency identification integrated circuit (RFID IC) to a remote reader. The flexible sensor, with a fixed operating frequency of 13.56 MHz, contains a RFID IC and a sensor circuit that is fabricated on a flexible printed circuit board (FPCB) using a Micro-Electro-Mechanical-System (MEMS) process. The sensor circuit contains a comb-shaped sensing area surrounded by an octagonal antenna with a width of 2.7 cm. The binary code transmitted from the RFIC to the reader changes if the surface conditions of the detector surface changes from dry to wet. This variation in the binary code can be observed on a digital oscilloscope connected to the reader.

Ultrasensitive electrical detection of protein using nanogap electrodes and nanoparticle-based DNA amplification.

The present study describes an ultrasensitive protein biochip that employs nanogap electrodes and self-assembled nanoparticles to electrically detect protein. A bio-barcode DNA technique amplifies the concentration of target antigen at least 100-fold. This technique requires the establishment of conjugate magnetic nanoparticles (MNPs) and gold nanoparticles (AuNPs) through binding between monoclonal antibodies (2B2), the target antigen, and polyclonal antibodies (GP). Both GP and capture ssDNA (single-strand DNA) bonds to bio-barcode ssDNA are immobilized on the surface of AuNPs. A denature process releases the bio-barcode ssDNAs into the solution, and a hybridization process establishes multilayer AuNPs over the gap surface between electrodes. Electric current through double-layer self-assembled AuNPs is much greater than that through self-assembled monolayer AuNPs. This significant increase in electric current provides evidence that the solution contains the target antigen. Results show that the protein biochip attains a sensitivity of up to 1 pg/ microL.