2012 REU Projects
This paper briefly introduces ferromagnetic resonance and a few methods that have been used for FMR measurements focusing on planar transmission line perturbation. Specific focus is given to the analysis and design of a shorted microstrip, which provides a versatile and simple way of placing samples and accounting for the differences introduced by their magnetic properties. A method is given for the placement of a given thin film into the microstrip and then analyzed by observing the changes in the reflection parameters. The microstrip structure is discussed in detail including information about size of the dimensions and results are presented to show the functionality of the microstrip. Initial ferromagnetic resonance tests were unsuccessful and potential problems are presented with a few suggested solutions to these problems.
Faculty Mentor: Prof. Sayeef Salahuddin; Graduate Mentor: Debanjan Bhowmik; UC Berkeley Department of Electrical Engineering & Computer Science
Sandra Diaz, University of California, Merced, Materials Science Engineering
The ability to create an artificial genetic circuit that can sense a target chemical and respond correspondingly can open up a huge range of opportunites in industrial microbiology. While many efficient inducible expression systems are available for gram-negative and grampositive, there are no known systems in E.coli that can regulate gene expression according to C4N. We try to adapt a highly inducible regulator-promoter pair from Rhodococcus rhodochrous to DP10 E.coli to regulate the mCherry gene expression. A biplasmid system was created, the first expression plasmid is controlled by L-arabinose inducible pBAD promoter to tune the level of NitR transcription factor and the second reporter plasmid utilizes the NitR to achieve C4N-inducible mCherry signal repression.
Faulty Mentor: Jay Keasling; Graduate Mentor: Jingwei Zhang; UC Berkeley Department of Bioengineering
Roberto Falcón-‐Banchs, University of Puerto Rico, Mayaguez, Mechanical Engineering
This paper describes the development and integration of an on-‐chip loop-‐mediated isothermal amplification (LAMP) for the detection of lung cancer related miRNA’s. LAMP is a commonly used DNA amplification technique because of its simplicity (isothermal),this makes it ideal for the development of new point-‐of-‐care technologies. In our work we use miRNA’s as a primer for the LAMP reaction, making the detection of these lung cancer biomarkers very robust and sensitive. We present work on off-‐chip as well as on-‐chip LAMP reactions for the validation of the results. We utilized vacuum power which automates the sample loading and minimizes user interaction with the device, this results in a reduction of contamination. While in this study we don’t use whole blood samples, we expect the development of future devices that integrate blood-‐plasma separation so that the only input is whole blood.
Faculty Mentor: Luke Lee; Post Doc Mentor: Seung-min Park; UC Berkeley Department of Bioengineering
Trichloroethylene (TCE) is an organic solvent used in industry as a degreaser. Improper disposal results in soil, air and groundwater contamination. The metabolite of TCE, DCVC (a known toxin), has been shown to cause kidney cancer, but the mechanism and genes involved in renal toxicity are unclear. Therefore, we narrowed down the genes involved in toxicity, all of which were related to DNA repair. This lead to the hypothesis that TCE causes DNA damage that can promote carcinogenesis. A yeast model was used to conduct knock out and overexpression, studies after exposure to DCVC. The results suggest DNA repair genes play a role in DCVC toxicity. Overexpression of the repair protein, Rev3, showed recovery to the wild type strain of yeast whereas Rad18 showed no recovery. Both results suggest a highly important role in DCVC toxicity.
Faculty Mentor: Chris Vulpe; Graduate Mentor: Vanessa de la Rosa; UC Berkeley Department of Toxicology
An electromechanical Resistive Random-Access Memory device is proposed as one nonvolatile solution to the demand for an alternative to flash memory. Several specimens are prepared, based upon different dimensions and constitutive RRAM layers, and are tested using a Parametric Wafer Prober. Current and voltage plots are produced from hundreds of voltage sweeps across the circuits, with few producing acceptable results. Various complications are discussed with suggestions for further research.
Faculty Mentor: Tsu-Jae King Liu; Graduate Mentor: Wookhyun Kwon; UC Berkeley Department of Electrical Engineering & Computer Science
With the advancement of modern technology, the computer industry is constantly pushing for higher performing microchips and continually reducing chip size. As microchips are packed closer together, removing heat becomes the limiting design case. A novel method for removing this heat is through use of a micro loop heat pipe (mLHP). Proper mLHP operation requires that the circulating fluid be hermetically sealed within the device. Methods for hermetic sealing have been previously explored, but have rendered poor results. In this research, producing a better hermetic sealing method was explored and very promising results were observed. The bonding method produced as a result of this research repeatedly formed bonds capable of withstanding pressures higher than 30 psi all while maintaining a hermetic state.
Faculty Mentor: Al Pisano; Graduate Mentor: Gordon Hoople; UC Berkeley Department of Mechanical Engineering
Previous works have shown experimental evidence of negative capacitance behavior in ferroelec-tric materials. At very high temperatures, a ferroelectric in series with a dielectric capacitor results in overall capacitance enhancement. Application of epitaxial strain to the ferroelectric crystal struc-ture ne tunes the Curie temperature, and therefore, the negative capacitance temperature region. Barium Strontium Titanate (BSTO), which naturally has low Curie temperature, was grown on four dierent types of substrates via Pulse Laser Deposition. During epitaxial growth, BSTO’s a-lattice parameter adheres to that of the substrate. Epitaxy causes compressive/tensile strain on the ferro-electric crystal depending on the substrate’s a-lattice parameter. Characteristics, such as dielectric constant, polarization etc., were measured and analyzed with respect to theoretical predictions.
Faculty Mentor: Sayeef Salahuddin; Graduate Mentor: Asif Khan; UC Berkeley Department of Electrical Engineering & Computer Science
A key design criterion for soft contact lenses (SCLs) is that salt permeability (NaCl) should exceed 3 x 10-7 cm2/s at 35 °C, since below this value, on-eye lens movement is compromised. Thus, saline transport through SCLs is important to on-eye behavior. In this report, we seek to understand salt transport through SCLs, using soft-contact-lens material p(HEMA-co-MAA) hydrogels. Specifically, we measure salt permeability, swelling, and salt partitioning for hydrogels containing varying salinity, pH, HEMA/MAA ratio, and cross-linking density. Both swelling and salt partitioning increase with increasing pH and MAA amount, until plateaus are observed at approximately pH 8 (full MAA ionization) and 30 wt % MAA. However, as crosslinking density increases, swelling and salt partitioning decrease monotonically. Importantly, we find, in accordance with literature, that salt permeability increases with increasing water content.
Faculty Mentor: Clayton Radke; Graduate Student: Thomas Dursch; UC Berkeley Department of Chemistry
The solution to developing small, self-powering devises may lie with some of the smallest materials Mother Nature can provide: the bacteriophage (phage). Preliminary research has shown that the filamentous M13 wild-type phage can be deposited onto gold substrates and be used to generate electricity ,. Pulling speed and phage concentration has been varied, and the effects in the y-axis spacing and the hierarchical structures have been observed. A necessary step towards improving virus-based piezoelectric materials is to understand how to vary the structure of the thin films. We are now attempting to vary the spacing in the x-axis. Here, we have successfully engineered the filamentous fd-tet phage to express 4E proteins, and verified the results via DNA sequencing. The fd-tet phage is longer than the M13 phage, and the negative charges induced by the 4E proteins improve the piezoelectric properties of the films . We believe that the spacing in the x-axis is related to phage length, and we will use the genetically engineered fd-tet to test this hypothesis.
Faculty Mentor: Seung-Wuk Lee; Graduate Mentor: Dong Shin Choy; UC Berkeley Department of Bioengineering
We report on the humidity cross-sensitivity of a conductometric hydrogen sulfide gas sensor with a tungsten oxide nanoparticle network as the sensing material. Conductance of the network was monitored while heating the sensor using a micro-hotplate during exposures to mixtures of hydrogen sulfide, water vapor, and air. The sensor conductance increases when the
H2S concentration is increased. The sensitivity to H2S is decreased in the presence of humidity. The effect of humidity on H2S sensitivity is high between 0 and 24%. Between 24 to 68% humidity, we found that the sensitivity to H2S stabilizes.
Faculty Mentor: Alex Zettl; Research Scientist Mentor: Willi Mickelson; Graduate Mentor: Allen Sussman; UC Berkeley Department of Physics
The synthesis of silicon carbide nanowires has been performed by a chemical vapor deposition process using aluminum as both a catalyst and in-situ dopant. Wires were found on the edges and sometimes in strips on the leading edge of the samples. Many different growth parameters were attempted with varying results. Wires were characterized with a Raman Microscope and a low voltage Scanning Electron Microscope. Nanowires synthesized with this method of in-situ doping could be useful in optical and electrical nanodevices.
Faculty Mentor: Roya Maboudian; Graduate Mentor: John Alper; UC Berkeley Department of Chemical Engineering
The use of nanomaterials, including nanowires, in research and industry is growing, yet little is known about the toxicological implications of these materials. The present study examines the toxicity of four different silver nanowires to the freshwater cladoceran Daphnia magna, an indicator species, in media at pH 8.8. The nanowires are coated in inorganic amorphous aluminum-doped silica coating (SiO2). The toxicity of the nanowires varied by their dimensions – 2 µm (length) x 30 nm (diameter) or 20 µm x 60 nm. The acute LC50s of these two nanowires in media at pH 8.8 were compared to the acute LC50s in media at pH 7.4-7.8. The findings indicate that pH may affect the toxicity of silver nanowires to D. magna.
Faculty Mentor: Chris Vulpe; Graduate Mentor: Leona Scanlon; UC Berkeley Department of Toxicology