Optimized piezoelectric energy harvesters for performance robust operation in periodic vibration environments
By: Wen Cai
Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210, USA
Energy harvesters with a wide frequency range, long lifetime, and high output power are preferred in power supply for wireless devices. Motivated to guide the design of a robust energy harvesting platform in a confined space, an analytical model adopted the Euler-Bernoulli beam theory for a laminated beam is first presented to predict the nonlinear response. Then with the existing model a multi-objectives optimization method based on the genetic algorithm considering the frequency range, strain level, and output power is proposed to learn the influence of nonlinearity, beam shape, and tip mass on the robust design. The optimization results indicate that a tapered beam with minor monostable nonlinearity, mounted a relatively small mass at the free end will be the best option for the robust system design. In addition, for the multi-objective problem, the weights assigned to different cost functions will influence the dominant factor in the optimization, which will in turn affect the final optimal design. Comparing with the other two objectives, the cost function for the voltage is more sensitive to the change of weights.
Targeted mode attenuation and broadband vibration control with optimized elastomeric metamaterials
By: Sih-Ling Yeh
Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210, USA
This study investigates the broadband vibration attenuation mechanism of optimal cylindrical metamaterial inclusions embedded within a hollow tubular beam. The optimal metamaterial inclusions are obtained by leveraging a genetic algorithm with an analytical model of the system. The analytical model is formulated on an energy method and approximately solved by the Ritz method. Experimental efforts affirm that the model identifies the optimal metamaterial inclusions to best provide broadband vibration control capability and the sensitivities of the design parameters. The parameters, including the radius bulk metamaterial layer, open angle ratio, and Young’s modulus of the porous metamaterial layer, have greater influence on tuning dynamic stiffness than the other parameters, such as the number of the radially arrayed beams in the porous metamaterial layer and Young’s modulus of the bulk metamaterial layer. Furthermore, the starting mode of the inclusion for greater attenuations is associated with the frequency of the tuned-mass-damper-like behaviors, which can be tuned by the Young’s modulus of the metamaterial inclusions. The detailed displacements, determined by finite element analysis, suggest that the starting mode is coupled with lateral translation and shear deformation. Results from this research give the insight on the most influential vibration attenuation mechanisms by elastomeric metamaterials.
Investigating the Effect of Thermoelectric Processing on Ionic Aggregation in Thermoplastic Ionomers
By: Prasant Vijayaraghavan
Ionomers are a class of polymers which contain a small fraction of charged groups in the polymer backbone. These ionic groups aggregate (termed ionic aggregates) to form temporary cross-links that break apart over the ionic dissociation temperature and re-aggregate on cooling, influencing the mechanical properties of these polymers. In addition to enhanced mechanical properties, some ionomers also exhibit self-healing behavior. The self-healing behavior is a consequence of weakly bonded ionic aggregates breaking apart and re-aggregating after puncture or a ballistic impact. The structure and properties of ionomers have been studied over the last several decades; however, there is a lack of understanding of the influence of an electrostatic field on ionic aggregate morphology. Characterizing the effect of temperature and electric field on the formation and structure of these ionic aggregates will lead to preparation of ionomers with enhanced structural properties. This work focuses on Surlyn® 8940 which is a poly-ethelene methacryclic acid co-polymer in which a fraction of the carboxylic acid is terminated by sodium. In this work, Surlyn® is thermoelectrically processed over its ionic dissociation temperature in the presence of a strong electrostatic field. Thermal, X-ray and Infrared studies are performed on the ionomer to study the effect of the thermoelectric processing. It is shown that the application of a thermoelectric field leads to increase in the ionic aggregate order in these materials and reduction in crystal size distribution.
By: Dr. Belinda Hurley
The OSU Libraries spend many millions each year to provide resources that are not freely available online. Belinda Hurley, OSU Libraries’ liaison for Physical Sciences and Engineering, will present an overview of available resources and services to those new to the OSU Libraries system.
Engineering DNA Origami Structures On Cell Surface for Detection of Cancer Biomarkers in Cellular Microenvironment
By: Melika Shahhosseini
Cancer cells exhibit specific gene mutations, such as mutations in the tumor suppressor gene BRCA1 that are observed in breast cancer. Circulating tumor DNA (ctDNA) are the mutated genes that are released by dead cancer cells into blood circulation, which presents a potential marker for early stage diagnosis. There are currently multiple methods to detect ctDNAs for early cancer diagnosis, normally by performing liquid biopsies. However, current detection methods have limitations such as demand for specialized equipment, low sensitivity and insufficient specificity. Furthermore, none of the available techniques provide in-situ detection, which may provide the additional benefit of elucidating mechanisms of cancer progression mediated by ctDNA. To address these limitations, we aim to exploit cells as sensing platforms by engineering their cell membranes to detect ctDNA in-situ with fluorescence based reporting. DNA origami is self-assembly of geometric complex nanostructures using DNA as building blocks. We recently reported a highly novel approach to engineer cell-membrane function by embedding DNA-origami nanodevices onto the cell surface via cholesterol-conjugated oligonucleotides as amphiphilic anchors . We programmed DNA origami nanodevices to detect presence of 2 different DNA sequence (targets) on the cell surface by emitting fluorescence signal in two different channels. Preliminary results show that introduction of each DNA target at 1μM, increases fluorescence signal by 50%. Also, structures are able to simultaneously detect two target DNA sequences over a broad range of concentrations (1nM to 1μM). Preliminary results also suggest we can detect binding events on individual cells, and in some cases with sub-cellular resolution. Therefore, we expect that implementing DNA origami structures on cell membranes will enable us to profile the spatiotemporal distribution of ctDNA in cellular microenvironment. For future steps, we plan to incorporate multiple cancer-related aptamers into DNA structures to enable simultaneous detection of multiple cancer biomarkers. Specifically, we are interested in detection of combinations of different cancer related genes with other cancer biomarkers (e.g. platelet-derived growth factor and pH) in cellular microenvironment. This technique can be implemented as a highly sensitive liquid biopsy method for early detection of cancer.
Electric Fields Control Motility of Metastatic Breast Cancer Cells
By: Ayush Garg
The onset of metastasis in breast cancer patients reduces their survival rates from over 90% to less than 20%. The key to stopping and treating metastatic breast lesions lies in understanding the mechanisms that regulate cancer cell migration. Mechanisms that regulate cancer cell migration in response to chemical cues, mechanical cues, physical cues etc. have been widely studied but effects of electric fields on motility are not well understood. While previous direct current electric field (dc EF) studies have shown directional galvanotactic migratory response in various cancer cells, the underlying mechanisms regulating this responses are still unclear. Here we show that by applying non-contact induced electric fields (iEFs, field strength < 100 µV/cm), we can directionally increase spontaneous migration rate of MDA-MB-231 cells. We found that this directional response was Akt dependent. Further, iEFs directionally hindered epidermal growth factor (EGF) induced migration of MDA-MB-231s by inhibiting EGFR phosphorylation, adversely impacting normal mitochondrial function, and disrupting actin polarization. Finally, we found that combined treatment of iEFs with MK2206 (an Akt inhibitor), resulted in ~21% slower migration speeds compared to untreated controls. Taken collectively, this body of results represents a significant step toward identifying how low frequency (< 1 MHz) iEFs interact with mammalian breast cancer cells and the possible governing mechanisms controlling their migratory responses. The results presented here could lay the foundation for exploring non-contact and new therapeutic approaches that may be used in a stand-alone manner or in conjunction with chemotherapy such as an Akt inhibitor based strategy.
Measurements of N2(A3Σ+u, v) Kinetics in Nonequilibrium Plasmas and Nonequilibrium Hypersonic Flows
By: Elijah Jans
Understanding the impact that real gas effects have behind strong shock waves is critical for design of hypersonic vehicles. These real gas effects cause nonequilibrium energy transfer and chemical kinetics that need to be understood for predictive modeling of flows over hypersonic vehicles. To experimental study these effects use of several optical diagonistics techniques will be presented with recent laboratory results.
Thermal transport across GaN and SiC Interface
by Vinay Chauhan
Noon – 12:30pm E525
The heat flux in GaN based high-electron mobility transistors (HEMTs) can reach up to a few kW/cm2 which can lead to failure of devices in case of poor heat dissipation. The thermal interface resistance between the GaN and the substrate material is the major obstruction in the heat flow path, mainly effected by the thermal conductivity of the substrate and the lattice mismatch. The previously developed models showed good concurrence of thermal interface resistance with experimental data at high temperatures (>300 K) but failed to follow the physics at low temperatures. The proposed experiments will enable us to find the reliable thermal properties related to the interface, and thus help in improving and developing the models.