An observational study of engineering online education during the COVID-19 pandemic.

The COVID-19 pandemic compelled the global and abrupt conversion of conventional face-to-face instruction to the online format in many educational institutions. Urgent and careful planning is needed to mitigate negative effects of pandemic on engineering education that has been traditionally content-centered, hands-on and design-oriented. To enhance engineering online education during the pandemic, we conducted an observational study at California State University, Long Beach (one of the largest and most diverse four-year university in the U.S.). A total of 110 faculty members and 627 students from six engineering departments participated in surveys and answered quantitative and qualitative questions to highlight the challenges they experienced during the online instruction in Spring 2020. Our results identified various issues that negatively influenced the online engineering education including logistical/technical problems, learning/teaching challenges, privacy and security concerns and lack of sufficient hands-on training. For example, more than half of the students indicated lack of engagement in class, difficulty in maintaining their focus and Zoom fatigue after attending multiple online sessions. A correlation analysis showed that while semi-online asynchronous exams were associated with an increase in the perceived cheating by the instructors, a fully online or open-book/open-note exams had an association with a decrease in instructor's perception of cheating. To address various identified challenges, we recommended strategies for educational stakeholders (students, faculty and administration) to fill the tools and technology gap and improve online engineering education. These recommendations are practical approaches for many similar institutions around the world and would help improve the learning outcomes of online educations in various engineering subfields. As the pandemic continues, sharing the results of this study with other educators can help with more effective planning and choice of best practices to enhance the efficacy of online engineering education during COVID-19 and post-pandemic.

Fabrication of patterned graphitized carbon wires using low voltage near-field electrospinning, pyrolysis, electrodeposition, and chemical vapor deposition.

We herein report a high-resolution nanopatterning method using low voltage electromechanical spinning with a rotating collector to obtain aligned graphitized micro and nanowires for carbon nanomanufacturing. A small wire diameter and a small inter-wire spacing were obtained by controlling the electric field, the spinneret-to-collector distance, the pyrolysis parameters, the linear speed of the spinneret, the rotational speed of the collector. Using a simple scaling analysis, we show how the straightness and the diameter of the wires can be controlled by the electric field and the distance of the spinneret to the collector. A small inter-wire spacing, as predicted by a simple model, was achieved by simultaneously controlling the linear speed of the spinneret and the rotational speed of the collector. Rapid drying of the polymer nanowires enabled the facile fabrication of suspended wires over various structures. Patterned polyacrylonitrile wires were carbonized using standard stabilization and pyrolysis to obtain carbon nanowires. Suspended carbon nanowires with a diameter of <50 nm were obtained. We also established a method for making patterned, highly graphitized structures by using the aforementioned carbon wire structures as a template for chemical vapor deposition of graphite. This patterning technique offers high throughput for nano writing, which outperforms other existing nanopatterning techniques, making it a potential candidate for large-scale carbon nanomanufacturing.

Fabrication of polymer and carbon polyhedra through controlled cross-linking and capillary deformations.

Fabrication of polymer polyhedral structures is achieved by first producing origami sheets with dissimilar stiffness levels at their folds and faces via multi-step photolithography. Subsequent capillary folding of the sheets towards permanently folded target shapes is realized by thermally controlling, simultaneously, the compliance of the sheets and the volume of the deposited droplets. This fabrication method allows us to create millimeter and sub-millimeter polyhedral structures with arbitrary levels of folding, to manufacture permanently folded polymer polyhedra using single-material monolayer sheets, and to produce carbon shapes from these carbon-rich polymer polyhedra through pyrolysis.

Influence of DNA-dye complex stability on separation resolution in microchip electrophoresis.

BACKGROUND: Different markers have been used to label DNA for sample detection in gel electrophoresis. Intercalating dyes, (e.g., YOYO) have been widely used to label DNA for sample detection, because they do not require the use of radioisotopes, covalent attachment or enzyme reactions. The labeling of DNA fragments can be achieved by simply mixing solutions of the intercalating dye and DNA sample. However, the separation quality of DNA labeled with intercalating dyes is greatly influenced by the buffer used, which affects the DNA-dye complex stability. RESULTS: In this study, we investigated the effects of DNA-dye complex stability on separation resolution of dsDNA migrating in a photopolymerized polyacrylamide gel by measuring mobility and dispersion coefficients on a microfluidic chip and comparing predicted separation resolution under different dye and buffer conditions. CONCLUSION: We found that a buffer containing tetrapentylammonium (NPe(4)(+)) yielded better separation resolution than the frequently used TBE buffer on our microchip electrophoresis system.

Fabrication of a microfluidic enzyme reactor utilizing magnetic beads.

An enzyme-catalyzed microfluidic assay using magnetic micro-beads is described. Here, diaphorase (DI) (E.C. 1.6.99) is covalently attached to the magnetic micro-beads (2.7 mum) and integrated into a short section of a microchip fabricated from PDMS. DI converts non-fluorescent resazurin to fluorescent resorufin in the presence of nicotinamide adenine dinucleotide phosphate (NADH). In this work, an embedded magnet holds the micro-beads in place within the microchannel while a solution of resazurin and NADH in buffer is flowed through the beads. Incorporation of the micro-beads into the microchannel requires only a few minutes and offers well-defined spatial resolution and reproducibility. At a flow rate of 41.2 microL/h, a stable state for the enzyme reaction in the microfluidic format was achieved within 50 s. The maximum conversion of the reaction was obtained at a concentration of 1.25 mM NADH. The reaction yield is affected by ZnCl(2) and at concentrations in excess of 90.0 mM, the activity of DI was almost double without ZnCl(2). At 5.2 mM potassium chloride, the activity of DI reached its maximum value. Overall, the conversion of resazurin in microfluidic format was more than twice than that in a batch assay.

Development of microfluidic chips for heterogeneous receptor-ligand interaction studies.

A simple microfluidic-based technique to quantitate the binding affinity between the glycopeptide antibiotics teicoplanin from Actinoplanes teicomyceticus and vancomycin from Streptomyces orientalis and 5-carboxyfluorescein-D-Ala-D-Ala-D-Ala (5-FAM-(DA)(3)) is described. In this work, (3-aminopropyl)triethoxysilane is used to modify the surfaces of a series of microchannels, and each channel is subsequently exposed to a solution of antibiotic for a few minutes. The antibiotic is retained after washing through electrostatic interactions, and the series of channels are subsequently exposed to an increasing concentration of 5-FAM-(DA)(3) followed by washing to exclude any nonspecific binding. The extent of fluorescence is quantified using a microscope fitted with a CCD camera. The binding constants for the interaction of teicoplanin and vancomycin with the fluorescent peptide were determined to be 6.03 +/- 0.97 x 10(4) and 4.93 +/- 1.13 x 10(4) M(-1), respectively, in good agreement with previous data. The ease of quantifying the extent of interaction in this microchip technique may prove powerful for exploration of a myriad of receptor-ligand pairs.

Use of magnetic beads to study the interaction of ristocetin with peptides and bacteria.

BACKGROUND: We aimed to develop and validate sensitive fluorescence techniques to assess the binding of magnetic microbeads derivatized with ristocetin from Amycolatopsis lurida to carboxyfluorescein-labeled D-Ala-D-Ala-D-Ala and in competition with Staphylococcus aureus bacteria. Glycopeptide antibiotics have been widely used to treat bacterial infections. However, new antibiotics are needed because of growing bacterial resistance and serious side effects. To screen potential candidates for new antibiotics, there is a great demand for sensitive, fast and inexpensive techniques to analyze the interactions between these molecules and bacterial cells. RESULTS: Fluorometry, an in-house fluorescent instrument and fluorescence microscopy were used to determine binding constants of 2.75 × 10(4), 2.21 × 10(4) and 0.81 × 10(4) M(-1), respectively, for the interaction between ristocetin and the labeled peptide. CONCLUSION: The methods detailed herein have been successfully applied to assess the binding of carboxyfluorescein- labeled D-Ala-D-Ala-D-Ala to ristocetin on microspheres. The magnetic bead-based immunoassay could be used to detect bacteria at low concentrations.

Microchip DNA electrophoresis with automated whole-gel scanning detection.

Gel electrophoresis continues to play an important role in miniaturized bioanalytical systems, both as a stand alone technique and as a key component of integrated lab-on-a-chip diagnostics. Most implementations of microchip electrophoresis employ finish-line detection methods whereby fluorescently labeled analytes are observed as they migrate past a fixed detection point near the end of the separation channel. But tradeoffs may exist between the simultaneous goals of maximizing resolution (normally achieved by using longer separation channels) and maximizing the size range of analytes that can be studied (where shorter separation distances reduce the time required for the slowest analytes to reach the detector). Here we show how the miniaturized format can offer new opportunities to employ alternative detection schemes that can help address these issues by introducing an automated whole-gel scanning detection system that enables the progress of microchip-based gel electrophoresis of DNA to be continuously monitored along an entire microchannel. This permits flexibility to selectively observe smaller faster moving fragments during the early stages of the separation before they have experienced significant diffusive broadening, while allowing the larger slower moving fragments to be observed later in the run when they can be better resolved but without the need for them to travel the entire length of the separation channel. Whole-gel scanning also provides a continuous and detailed picture of the electrophoresis process as it unfolds, allowing fundamental physical parameters associated with DNA migration phenomena (e.g., mobility, diffusive broadening) to be rapidly and accurately measured in a single experiment. These capabilities are challenging to implement using finish-line methods, and make it possible to envision a platform capable of enabling separation performance to be rapidly screened in a wide range of gel matrix materials and operating conditions, even allowing separation and matrix characterization steps to be performed simultaneously in a single self-calibrating experiment.

Separation performance of single-stranded DNA electrophoresis in photopolymerized cross-linked polyacrylamide gels.

Considerable effort has been directed toward optimizing performance and maximizing throughput in ssDNA electrophoresis because it is a critical analytical step in a variety of genomic assays. Ultimately, it would be desirable to quantitatively determine the achievable level of separation resolution directly from measurements of fundamental physical properties associated with the gel matrix rather than by the trial and error process often employed. Unfortunately, this predictive capability is currently lacking, due in large part to the need for a more detailed understanding of the fundamental parameters governing separation performance (mobility, diffusion, and dispersion). We seek to address this issue by systematically characterizing electrophoretic mobility, diffusion, and dispersion behavior of ssDNA fragments in the 70-1,000 base range in a photopolymerized cross-linked polyacrylamide matrix using a slab gel DNA sequencer. Data are collected for gel concentrations of 6, 9, and 12%T at electric fields ranging from 15 to 40 V/cm, and resolution predictions are compared with corresponding experimentally measured values. The data exhibit a transition from behavior consistent with the Ogston model for small fragments to behavior in agreement with the biased reptation model at larger fragment sizes. Mobility data are also used to estimate the mean gel pore size and compare the predictions of several models.

Microfabricated electrophoresis systems for DNA sequencing and genotyping applications: current technology and future directions.

Many routine genomic-analysis assays rely on gel electrophoresis to perform size-selective fractionation of DNA fragments in the size range below 1 kb in length. Over the past decade, impressive progress has been made towards the development of microfabricated electrophoresis systems to conduct these assays in a microfluidic lab-on-a-chip format. Since these devices are inexpensive, require only nanolitre sample volumes, and do not rely on the availability of a pre-existing laboratory infrastructure, they are readily deployable in remote field locations for use in a variety of medical and biosensing applications. The design and construction of microfabricated electrophoresis devices poses a variety of challenges, including the need to achieve high-resolution separations over distances of a few centimetres or less, and the need to easily interface with additional microfluidic components to produce self-contained integrated DNA-analysis systems. In this paper, we review recent efforts to develop devices to satisfy these requirements and live up to the promise of fulfilling the growing need for inexpensive portable genomic-analysis equipment.