Microfluidic Technology and Application in Urinal Analysis

Microfluidic technology offers numerous advantages in minimizing and integrating the traditional assays. However, the lack of efficient control components of the microfluidic systems has been hindering the widely commercialization of the technology. The research work in this dissertation focused on the development of effective control components for microfluidic applications. A linear peristaltic pump was firstly designed, fabricated, and tested for conventional microfluidics by synchronously compressing the microfluidic channel with a miniature cam-follower system in Chapter 2. The miniature cam-follower system and microfluidic chip was prototyped using three-dimensional (3D) printing technology and soft lithography technology. Results from experimental test showed that the pump is self-priming and tolerant of bubbles. The pumping flowrate and back pressure could be controlled by changing the driving speed of the motor. Then a novel pinch-type valving system that can be used to realize both normally closed and normally open valves for centrifugal microfluidics was demonstrated in Chapter 3. A sliding wedge was actuated by centrifugal force to drive the valves. Experimental test and theoretical predication showed that the burst frequency of the valves could be tuned by changing the physical parameters of the valving system. In Chapter 4, the pinch type valving system was then further improved for better integration of multiple valves in limited space to realize sequential control of microfluidics. A valve chip with grooves on the surface was used to drive multiple valves. A flow switch which is capable of working at low rotation frequency and constant rotation direction is realized. Finally, the microfluidic platform was utilized for automatic urinalysis for the application at point of care (POC) to eliminate the difficulties in control of sample distribution and read-out time in manually conducted colorimetric urinalysis. 3D printed prototype of the microfluidic chip was used to test the proposed system. Commercial urinalysis strips was integrated with the microfluidic system for detecting glucose, specific gravity, PH, and protein from simulated urine sample. The color change of the pads was recorded using smartphone camera and analyzed to quantify the interested parameters

A Rapid Micromixer for Centrifugal Microfluidic Platforms

This paper presents an innovative mixing technology for centrifugal microfluidic platforms actuated using a specially designed flyball governor. The multilayer microfluidic disc was fabricated using a polydimethylsiloxane (PDMS) replica molding process with a soft lithography technique. The operational principle is based on the interaction between the elastic covering membrane and an actuator pin installed on the flyball governor system. The flyball governor was used as the transducer to convert the rotary motion into a reciprocating linear motion of the pin pressing against the covering membrane of the mixer chamber. When the rotation speed of the microfluidic disc was periodically altered, the mixing chamber was compressed and released accordingly. In this way, enhanced active mixing can be achieved with much better efficiency in comparison with diffusive mixing

First-Principles Study on the Stability, Site Preference, Electronic Structure and Magnetism of Alloyed Fe3B with Ni3P-Type Structure

First-principles calculations were performed to investigate the site preference of alloying elements, and the effect of alloying elements on stability, electronic structure and magnetism of Ni3P-type Fe3B. The calculated energies suggested that all studied compounds are thermodynamically stable while it is relatively difficult to synthesize the (Fe2.875,Cu0.125)B, (Fe2.875,W0.125)B and (Fe2.875,Nb0.125)B. The (Fe2.875,W0.125)B is the most stable compound from the view of cohesive energy. Mn element prefers to occupy the Fe2 site, whereas the others are more likely to reside in the Fe1 site. It can be found from the electronic structures that the DOSs of both Fe3B and alloyed Fe3B are dominated by Fe-d states, and all the compounds mainly contain Fe-B covalent bond, Fe-Fe covalent bond and Fe-Fe metallic bond. Based on the magnetic moments (Ms) results, it can be known that the Fe3B, (Fe2.875,Mn0.125)B, (Fe2.875,Co0.125)B, (Fe2.875,Ni0.125)B and (Fe2.875,Cu0.125)B are ferromagnetic compounds, whereas the others are ferrimagnetic compounds. Only Mn and Co are able to enhance the magnetism of Fe3B. Moreover, Mn is the most favorable candidate for improving the magnetic properties of Fe3B among the alloying elements. These results can be used to guide the composition design and performance optimization of magnetic materials containing Fe3B with Ni3P-type structure

Determination of Permeability and Inertial Coefficients of Sintered Metal Porous Media Using an Isothermal Chamber

Sintered metal porous media are widely used in a broad range of industrial equipment. Generally, the flow properties in porous media are represented by an incompressible Darcy‒Forchheimer regime. This study uses a modified Forchheimer equation to represent the flow rate characteristics, which are then experimentally and theoretically investigated using a few samples of sintered metal porous media. The traditional steady-state method has a long testing time and considerable air consumption. With this in mind, a discharge method based on an isothermal chamber filled with copper wires is proposed to simultaneously determine the permeability and inertial coefficient. The flow rate discharged from the isothermal chamber is calculated by differentiating the measured pressure, and a paired dataset of pressure difference and flow rate is available. The theoretical representations of pressure difference versus flow rate show good agreement with the steady-state results. Finally, the volume limit of the isothermal chamber is addressed to ensure sufficient accuracy

Ultralow lattice thermal conductivity and promising thermoelectric properties of a new 2D MoW3Te8 membrane

Assembling new van der Waals (vdW) materials is challenging for the development of two-dimensional (2D) function devices. The MoW3X8 membrane (X = Se, Te) is a new 2D TMDs membrane molecule composed of one WX2 monolayer and one WX2-MoX2-WX2 sandwich trilayer. The presence of Mo/W atoms endows the new structure with the bridges between X atoms that connect pairs of MoX2/WX2 monolayers and the terminal sites that produce the van der Waals gap in these layers. The mirror symmetry is broken and the phonon dispersion is suppressed by reducing the dimensionality of the MoW3X8 membrane. In this work, the phonon transport and thermoelectric properties of the MoW3X8 membrane are investigated using first-principles method combined with the semi-classical Boltzmann transport and relaxation time approximation (RTA) theories. It is found that the larger gap between low-frequency and high-frequency optical branches in the membrane prevents atomic vibrations and drastically reduces the phonon velocity in a mid-frequency range below the gap. The low-lying optical and acoustic phonon modes are closely linked in MoW3Te8 membranes, enhancing the phonon–phonon scattering and thereby shortening the phonon relaxation time. These characteristics allow the MoW3Te8 membrane to achieve an extremely low lattice thermal conductivity of 0.49 Wm-1K−1 relative to that of the MoW3Se8 membrane (3.25 Wm-1K−1), which also leads to the improvement in thermoelectric performance of the former one. Besides, the maximum ZT values of 4 (4.5) at 900 K and the carrier concentration of 4 × 1011 cm−2 in the n-type (p-type) MoW3Te8 membrane could be enriched because of the low lattice thermal conductivity

siRNA suppression of hTERT using activatable cell-penetrating peptides in hepatoma cells

Activatable cell-penetrating peptides (aCPPs) allow non-viral, low cytotoxic and selective delivery of compounds into target cells for cancer therapy. In tumour cells, up-regulation of human telomerase reverse transcriptase (hTERT) frequently occurs and is being considered as a target in cancer diagnosis and treatment. siRNA sequence that target hTERT mRNA can silence the gene and reduce hTERT protein expression to reduce cell proliferation and inhibit cell growth. In our study, we tested a matrix metalloproteinase-2 (MPP2) aCPP in delivering hTERT siRNA into hepatocellular carcinoma cells (SMMC-7721) to silence the hTERT gene. Cultured SMMC-7721 cells were transfected with a complex of aCPPs and hTERT-specific siRNA-encoding or control plasmids. Compared with cells treated with the complex of control plasmid–CPPs, cells treated with the hTERT-specific siRNA-encoding plasmid–CPP complex had a prolonged G1-phase, but a shorter G2/S-phase, indicating a G1-arrest. Treatment with the hTERT-specific siRNA resulted in a significant decrease (by 26%; P<0.05) in hTERT mRNA levels. The aCPPs tested in this study provides a non-viral delivery of siRNA into cancer cells to silence target genes in cancer therapy

Analysis of mRNA expression of genes related to fatty acids synthesis in goose fatty liver

The aim of our study was to evaluate the effect of overfeeding on mRNA expression levels of genes involved in lipogenesis, in order to understand the mechanism of hepatic stea - tosis in the goose. Using Landes geese (Anser anser) and Sichuan White geese (Anser cygnoides) as experimental animals, we quantified the mRNA expression of lipogenic genes, acetyl-CoA carboxylase-&alpha; (ACC&alpha;) and fatty acid synthase (FAS), and of two transcription factors, sterol regulatory element-binding proteins- 1 (SREBP-1) and carbohydrate responsive element-binding protein (ChREBP) by real-time polymerase chain reaction (RTPCR), and measured the lipid and triglyceride (TG) content in the liver and the plasma level of glucose, insulin and TG. Our results indicated that compared to the control group, the overfeeding induced an increase of the lipid and TG content in the liver and also of the plasma insulin and TG concentration in both breeds. However, the plasma glucose level decreased after overfeeding in the Sichuan White goose, and there was no evident change in the Landes goose. Lastly, the mRNA expression of ACC&alpha;, FAS, SREBP-1 and ChREBP in the overfed group was lower than in the control group in both breeds. We concluded that the lipogenesis pathway plays a role in overfeeding- induced hepatic steatosis and that the decreased mRNA level of related genes may be the indicator of hepatic steatosis

Lower thermal conductivity of body centered cubic carbon (C14): a comparative study with diamond

In recent years, the material preparation technology has ushered into a stage of rapid development, increasingly more carbon materials are found to display superior properties, making them suitable for designing nano-scale devices. Within the applications of electronic devices, a considerable amount of consumed energy has to be converted into heat; thus the efficiency of heat transport inside these devices can largely determine their overall performance. Decent elucidations of the heat transport mechanisms within low-dimensional materials will be helpful to achieve thermal management control of the related devices and furthermore, to improve their conversion efficiency. It is well understood that the heat transport within these kinds of materials is largely associated with their structural features. In this study, we focused on a novel material, body centered cubic carbon (C14), which is composed of sp3 hybridized carbon atoms. Such a novel material displays superior electronic properties; however, its thermal properties remain to be investigated. In order to systematically evaluate the practical applicability of this novel material, first-principles calculations were employed to systematically solve its structure; furthermore, its thermal conductivity, phonon dispersion spectrum, phonon properties, Grüneisen parameters, scattering phase space and mechanical properties were all described in detail. We found that C14 performs well in heat transport; and via systematical comparison with another allotrope, diamond, its transport mechanism was further summarized. We hope the physical insights provided by this study could serve as theoretical support for nano-scale device design