Engineering Measurements and Instrumentation: First Edition

This electronic book (e-book) is created with partial financial support from a grant generously provided by the Miller Open Education Mini-Grant Program. This e-book is created as an open educational resource (OER) and it is meant to be used by students and educators for solely educational and non-commercial purposes. This e-book is intended to be used as a complementary resource for engineering measurements and instrumentation course, at junior engineering level. If you have any comments or suggestions, please reach out to the author via email: [email protected]://lib.dr.iastate.edu/opentextbooks/1001/thumbnail.jp

Ionic electroactive polymer actuators as active microfluidic mixers

On-chip sample processing is integral to the continued development of lab-on-a-chip devices for various applications. An active microfluidic mixer prototype is proposed using ionic electroactive polymer actuators (IEAPAs) as artificial cilia. A proof-of-concept experiment was performed in which the actuators were shown to produce localized flow pattern disruptions in the laminar flow regime. Suggestions for further engineering and optimization of a scaled-down, complete device are provided. While the device in its current state of development necessitates further engineering, the use of IEAPAs addresses issues currently associated with the use of electromechanical actuators as active microfluidic mixers and may prove to be a useful alternative to other similar materials

A novel method for fabricating conductive microfibers for microbial fuel cells

The increasing demand for energy resources has urged scientists to focus on improving the renewable energy sources. Microbial fuel cells (MFCs) have received an increasing attention. Both energy conversion mechanism and electrode type have attributed to affect the efficiency of the microbial fuel cells. Electrodes as one of the most important components of the microbial fuel cells have been widely investigated. While most of the electrode materials are carbon based, there is very little effort on introducing novel materials for this purpose. This paper intends to shed an insight on the effect of using a new cathode material on the performance of microbial fuel cells. We employ hydrodynamic forces to control both molecular organization and microstructure size and shape in order to create highly structured microfibers. A microfluidic sheath flow device is used for the fabrication processes. The core flow is acrylate solution and UV light cures the photoinitiator to start the polymerization process. The exiting stream goes inside a water bath, where the sheath flow dissolves in the DI water and the core flow forms the microfibers. Controlled self-assembly can be used to deposit a thin layer of functionalized metal nanoparticles on the polymeric structure made from microfibers to enhance their electric conductivity. A conductive and porous network formed by the microfibers can be used as an efficient cathode material in microbial fuel cells. Furthermore, using this fabrication technique we can make microfibers with different shapes and sizes

Using Shewanella Oneidensis MR1 as a Biocatalyst in a Microscale Microbial Fuel Cell

Microbial fuel cell (MFC) technology is a promising area in the field of renewable energy because of their capability to use the energy contained in wastewater, which has been previously an untapped source of power. Microscale MFCs are desirable for their small footprints, relatively high power density, fast start-up, and environmentally-friendly process. Microbial fuel cells employ microorganisms as the biocatalysts instead of metal catalysts, which are widely applied in conventional fuel cells. MFCs are capable of generating electricity as long as nutrition is provided. Miniature MFCs have faster power generation recovery than macroscale MFCs. Additionally, since power generation density is affected by the surface-to-volume ratio, miniature MFCs can facilitate higher power density. We have designed and fabricated a microscale microbial fuel cell with a volume of 4 μL in a polydimethylsiloxane (PDMS) chamber. The anode and cathode chambers were separated by a proton exchange membrane. Carbon cloth was used for both the anode and the cathode. Shewanella Oneidensis MR-1 was chosen to be the electrogenic bacteria and was inoculated into the anode chamber. We employed Ferricyanide as the catholyte and introduced it into the cathode chamber with a constant flow rate of approximately 50 μL/hr. We used trypticase soy broth as the bacterial nutrition and added it into the anode chamber approximately every 15 hours once current dropped to base current. Using our miniature MFC, we were able to generate a maximum current of 4.62 μA

Mechanical and physical properties of poly(vinyl alcohol) microfibers fabricated by a microfluidic approach

A microfluidic platform was used to fabricate continuous and non-rounded polyvinyl alcohol (PVA) microfibers. We showed that the size and cross-section of the PVA fibers can be controlled by changing the PVA concentration in dimethyl sulfoxide (DMSO) and flow rate ratio between the core and sheath fluids. The PVA concentration was varied from 6% to 12%, and the sheath-to-core flow rate ratio used for this study was in the range of 500:5 to 500:20. The aspect ratio of the fibers became larger when the PVA concentration increased and the flow rate ratio decreased. Additionally, we simulated the microfluidic fiber fabrication process and the results were consistent with the experimental results. The dissolution of the PVA fibers fabricated with different characteristics was also studied. It was shown that increasing the PVA concentration and decreasing the flow rate ratio increased the dissolution time of the fibers in DI water. A tensile test was conducted to obtain the stress–strain curves for different types of fibers. The results showed that a wide range of mechanical properties can be achieved by changing the PVA concentration and the flow rate ratio. The increase of PVA concentration from 6% to 12% enhanced the tensile stress at break and Young\u27s modulus by a factor of 4.9 and 2.02, respectively. The mechanical strength of the fibers was shown to drop when the flow rate ratio decreased

Fluid‐Induced Alignment of Carbon Nanofibers in Polymer Fibers

Carbon nanofiber/polycaprolactone (CNF/PCL) composite fibers are fabricated using a microfluidic approach. The fibers are made with different content levels of CNFs and flow rate ratios between the core and sheath fluids. The electrical conductivity and tensile properties of these fibers are then investigated. It is found that at a CNF concentration of 3 wt%, the electrical conductivity of the composite fiber significantly increases to 1.11 S m−1. The yield strength, Young\u27s modulus, and ultimate strength of the 3 wt% CNF increase relative to the pure PCL by factors of 1.72, 2.88, and 1.23, respectively. Additionally, the results show that a microfluidic approach can be considered as an effective method to align CNFs along the fibers in the longitudinal direction

On-chip development of hydrogel microfibers from round to square/ribbon shape

We use a microfluidic approach to fabricate gelatin fibers with controlled sizes and cross-sections. Uniform gelatin microfibers with various morphologies and cross-sections (round and square) are fabricated by increasing the gelatin concentration of the core solution from 8% to 12%. Moreover, the increase of gelatin concentration greatly improves the mechanical properties of gelatin fibers; the Young\u27s modulus and tensile stress at break of gelatin (12%) fibers are raised about 2.2 and 1.9 times as those of gelatin (8%) fibers. The COMSOL simulations indicate that the sizes and cross-sections of the gelatin fibers can be tuned by using a microfluidic device with four-chevron grooves. The experimental results demonstrate that the decrease of the sheath-to-core flow-rate ratio from 150 : 1 to 30 : 1 can increase the aspect ratio and size of ribbon-shaped fibers from 35 μm × 60 μm to 47 μm × 282 μm, which is consistent with the simulation results. The increased size and shape evolution of the cross-section can not only strengthen the Young\u27s modulus and tensile stress at break, but also significantly enhance the tensile strain at break

Development of Polymeric Porous Membrane for Mediator-Less Microbial Fuel Cells: An Electrochemical Study

In this work, gold nanoparticles (AuNPs) are embedded on the proton exchange membrane in a straightforward manner and are made highly stable. Nanoparticles provide high surface-to-volume ratio with excellent biocompatibility, using appropriate ligands, which allows for a biocompatible environment for bacterial functions. High conductivity, high surface area and catalytic properties of AuNPs make them excellent materials for MFCs. We employed layer-by-layer (LbL) self-assembly technique to prepare multilayered thin-films of polycation poly(allylamine hydrochloride) (PAH) and negatively functionalized AuNPs. The (PAH/AuNP) thin-films act as the catalyst layers and are to provide means for high porosity and high electrical conductive in the LbL thin-films when the polycation serve to assist LbL thin-film formation through ionic bonds. Scanning electron microscopy was used to investigate the morphology and nano/microstructure of the porous membrane catalyst. Samples consisting of different thickness thin-films were tested for their performance over five-day periods. Bioelectricity was generated using Shewanella oneidensis MR-1 cultivated on organic substrate with trypticase soy broth medium. Trypticase soy broth and ferricyanide were injected into the anode and cathode chambers as anolyte and catholyte respectively. Generated voltage and current were monitored and recorded using LabView though NI-DMM, over five-day periods

A Microfluidic Reactor for Energy Applications

Miniature microbial fuel cells have recently drawn lots of attention as portable power generation devices due to their short startup time and environmentally-friendly process which could be used for powering small integrated biosensors. We designed and fabricated a microbial fuel cell in a microfluidic platform. The device was made in polydimethylsiloxane with a volume of 4 μL and consisted of two carbon cloth electrodes and proton exchange membrane. Shewanella Oneidensis MR-1 was chosen to be the electrogenic bacterial strain and inoculated into the anode chamber. Ferricyanide was used as the catholyte and pumped into the cathode chamber at a constant flow rate during the experiment. The mi- niature microbial fuel cell generated a maximum current of 2.59 μA and had a significantly short startup time