Publications

2018
X. Xu, Kwon, H., Gawlik, B., Estakhri, N. M., Alu, A., Sreenivasan, S. V., and Dodabalapur, A., “Enhanced Photoresponse in Metasurface-Integrated Organic Photodetectors,” Nano Lett., vol. 18, no. 6, pp. 3362-3367, 2018. DOIAbstract
In this work, we experimentally demonstrate metasurface-enhanced photoresponse in organic photodetectors. We have designed and integrated a metasurface with broadband functionality into an organic photodetector, with the goal of significantly increasing the absorption of light and generated photocurrent from 560 up to 690 nm. We discuss how the metasurface can be integrated with the fabrication of an organic photodiode. Our results show large gains in responsivity from 1.5x to 2X between 560 and 690 nm.
E. Fleming, Kholmanov, I., and Shi, L., “Enhanced specific surface and thermal conductivity in ultrathin graphite foams grown by chemical vapor deposition on sintered nickel powder templates,” Carbon, vol. 136, pp. 380-386, 2018. Publisher's Version
J. Chen, Kim, J., Poudel, N., Hou, B., Shen, L., Shi, H., Shi, L., and Cronin, S., “Enhanced thermoelectric efficiency in topological insulator Bi2Te3 nanoplates via atomic layer deposition-based surface passivation,” Applied Physics Letters, vol. 113, pp. 083904, 2018. Publisher's Version
W. Lin, Bergquist, A. M., Mohanty, K. K., and Werth, C. J., “Environmental impacts of replacing slickwater with low/no-water fracturing fluids for shale gas recovery,” ACS Sustainable Chemistry & Engineering, vol. 6, no. 6, pp. 7515-7524, 2018. Publisher's VersionAbstract
The environmental impacts of a typical hydraulic fracturing operation for shale gas recovery were evaluated using life cycle assessment, with energy demands for well drilling and fracturing determined from GHGfrack model. Dominant environmental impacts stem from well construction, which are >63% in all categories (e.g., global warming and eutrophication), and mainly due to diesel fuel combustion and steel production. The relative impacts related to water use (i.e., fracturing fluid components, water/wastewater transportation, and wastewater disposal) are relatively small, ranging from 5 to 22% of total impacts in all categories; freshwater consumption for fracturing is also a small fraction of available water resources for the shale play considered. The impacts of replacing slickwater with CO2 or CH4-foam fracturing fluid (≤10 vol % water) were evaluated; total impacts decrease <12%, and relative impacts related to water use decrease to 2–9% of total impacts. Hence, switching to a foam-based fracturing fluid can substantially decrease water-related impacts (>60%) but has only marginal effects on total environmental impacts. Changes in lateral well length, produced to fresh-water ratios, fracturing fluid composition, and LCA control volume do not change these findings. More benefits could potentially be realized by considering water versus foam-related impacts of ecological health and energy production.
J. K. Bean, Bhandari, S., Bilotto, A., and Hildebrandt Ruiz, L., “Formation of Particulate Matter from the Oxidation of Evaporated Hydraulic Fracturing Wastewater,” Environmental Science & Technology, vol. 52, no. 8, pp. 4960-4968, 2018. Publisher's Version
M. Sivaguru, Saw, J. J., Jr., J. W. C., Lieske, J. C., Krambeck, A. E., Romero, M. F., Chia, N., Schwaderer, A. L., Alcalde, R. E., Bruce, W. J., Wildman, D. E., Fried, G. A., Werth, C. J., Reeder, R. J., Sanford, R. A., and Fouke, B. W., “Geobiology reveals how human kidney stones dissolve in vivo,” Scientific Reports, vol. 8, pp. 13731, 2018. Publisher's VersionAbstract
More than 10% of the global human population is now afflicted with kidney stones, which are commonly associated with other significant health problems including diabetes, hypertension and obesity. Nearly 70% of these stones are primarily composed of calcium oxalate, a mineral previously assumed to be effectively insoluble within the kidney. This has limited currently available treatment options to painful passage and/or invasive surgical procedures. We analyze kidney stone thin sections with a combination of optical techniques, which include bright field, polarization, confocal and super-resolution nanometer-scale auto-fluorescence microscopy. Here we demonstrate using interdisciplinary geology and biology (geobiology) approaches that calcium oxalate stones undergo multiple events of dissolution as they crystallize and grow within the kidney. These observations open a fundamentally new paradigm for clinical approaches that include in vivo stone dissolution and identify high-frequency layering of organic matter and minerals as a template for biomineralization in natural and engineered settings.
I. Shovkun and Espinoza, N. D., “Geomechanical implications of dissolution of mineralized natural fractures in shale formations,” Journal of Petroleum Science and Engineering, vol. 160, pp. 555–564, 2018. Publisher's Version
A. Malinverno, Cook, A. E., Daigle, H., and Oryan, B., “Glacial cycles influence marine methane hydrate formation,” Geophysical Research Letters, vol. 45, no. 2, pp. 724-732, 2018. Publisher's VersionAbstract
Methane hydrates in fine‐grained continental slope sediments often occupy isolated depth intervals surrounded by hydrate‐free sediments. As they are not connected to deep gas sources, these hydrate deposits have been interpreted as sourced by in situ microbial methane. We investigate here the hypothesis that these isolated hydrate accumulations form preferentially in sediments deposited during Pleistocene glacial lowstands that contain relatively large amounts of labile particulate organic carbon, leading to enhanced microbial methanogenesis. To test this hypothesis, we apply an advection‐diffusion‐reaction model with a time‐dependent organic carbon deposition controlled by glacioeustatic sea level variations. In the model, hydrate forms in sediments with greater organic carbon content deposited during the penultimate glacial cycle (~120–240 ka). The model predictions match hydrate‐bearing intervals detected in three sites drilled on the northern Gulf of Mexico continental slope, supporting the hypothesis of hydrate formation driven by enhanced organic carbon burial during glacial lowstands.
Google Scholar Profile”. 2018. Link to Google Scholar
C. Faxon, Dhulipala, S. V., Allen, D. T., and Hildebrandt Ruiz, L., “Heterogeneous Production of Cl2 from Particulate Chloride Measured in Environmental Chamber Experiments,” American Institute of Chemical Engineers Journal, Futures Issue: Reaction Engineering, Kinetics, and Catalysis, 2018. Publisher's Version
L. L. Worthington, Daigle, H., Clary, Wesley, A., Gulick, S. P. S., and Montelli, A., “High sedimentation rates and thrust fault modulation: insights from ocean drilling offshore the St. Elias Mountains, southern Alaska,” Earth and Planetary Science Letters, vol. 483, pp. 1-12, 2018. Publisher's VersionAbstract
The southern Alaskan margin offshore the St. Elias Mountains has experienced the highest recorded offshore sediment accumulation rates globally. Combined with high uplift rates, active convergence and extensive temperate glaciation, the margin provides a superb setting for evaluating competing influences of tectonic and surface processes on orogen development. We correlate results from Integrated Ocean Drilling Program (IODP) Expedition 341 Sites U1420 and U1421 with regional seismic data to determine the spatial and temporal evolution of the Pamplona Zone fold-thrust belt that forms the offshore St. Elias deformation front on the continental shelf. Our mapping shows that the pattern of active faulting changed from distributed across the shelf to localized away from the primary glacial depocenter over ∼300–780 kyrs, following an order-of-magnitude increase in sediment accumulation rates. Simple Coulomb stress calculations show that the suppression of faulting is partially controlled by the change in sediment accumulation rates which created a differential pore pressure regime between the underlying, faulted strata and the overlying, undeformed sediments.
Z. Pan, Xu, X., Chung, C. -jui, Dalir, H., Yan, H., Chen, K., Wang, Y., Jia, B., and Chen, R. T., “High-Speed Modulator Based on Electro-Optic Polymer Infiltrated Subwavelength Grating Waveguide Ring Resonator,” Laser & Photonics Reviews, 2018. Publisher's VersionAbstract
Silicon‐organic hybrid integrated devices show great potential in high‐speed optical interconnects and sensors. In this paper, a high‐speed modulator based on an electro‐optic (EO) polymer (SEO125) infiltrated sub‐wavelength grating (SWG) waveguide ring resonator is presented. The core of the SWG waveguide consists of periodically arranged silicon pillars along the light propagation direction, which provides large mode volume overlap with EO polymer. The optimized SWG shows a mode volume overlap of 36.2% with a silicon duty cycle of 0.7. The 3‐dB modulation bandwidth of the fabricated modulator is measured to be larger than 40 GHz occupying an area of 70 μm x 29 μm, which is the largest bandwidth and the most compact footprint that has been demonstrated for ring resonators on the silicon‐organic hybrid platform.
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In-plane thermal conductivity measurement with nanosecond grating imaging tehchnique
J. Jeong, Chen, K., Walker, E. S., Roy, N., He, F., Liu, P., Willson, G. C., Cullinan, M., Bank, S. R., and Wang, Y., “In-plane thermal conductivity measurement with nanosecond grating imaging tehchnique,” Nanoscale and Microscale Thermophyical Engineering, vol. 22, no. 2, pp. 83-96, 2018. Publisher's VersionAbstract
We develop a nanosecond grating imaging (NGI) technique to measure in-plane thermal transport properties in bulk and thin-film samples. Based on nanosecond time-domain thermoreflectance (ns-TDTR), NGI incorporates a photomask with periodic metal strips patterned on a transparent dielectric substrate to generate grating images of pump and probe lasers on the sample surface, which induces heat conduction along both cross- and in-plane directions. Analytical and numerical models have been developed to extract thermal conductivities in both bulk and thin-film samples from NGI measurements. This newly developed technique is used to determine thickness-dependent in-plane thermal conductivities (κx) in Cu nano-films, which agree well with the electron thermal conductivity values converted from four-point electrical conductivity measurements using the Wiedemamn–Franz law, as well as previously reported experimental values. The κx measured with NGI in an 8 nm x 8 nm GaAs/AlAs superlattice (SL) is about 10.2 W/m⋅K, larger than the cross-plane thermal conductivity (8.8 W/m⋅K), indicating the anisotropic thermal transport in the SL structure. The uncertainty of the measured κx is about 25% in the Cu film and less than 5% in SL. Sensitivity analysis suggests that, with the careful selection of proper substrate and interface resistance, the uncertainty of κx in Cu nano-films can be as low as 5%, showing the potential of the NGI technique to determine κx in thin films with improved accuracy. By simply installing a photomask into ns-TDTR, NGI provides a convenient, fast, and cost-effective method to measure the in-plane thermal conductivities in a wide range of structures and materials.
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F. Meng, Jing, Z., Ferreira, R., Ren, P., and Zhang, F., “Investigating the Association Mechanism between Rafoxanide and Povidone,” Langmuir, 2018.
D. S. Choi, Poudel, N., Park, S., Akinwande, D., Cronin, S. B., Watanabe, K., Taniguchi, T., Yao, Z., and Shi, L., “Large Reduction of Hot Spot Temperature in Graphene Electronic Devices with Heat-Spreading Hexagonal Boron Nitride,” ACS Applied Materials & Interfaces, vol. 10 , pp. 11101–11107, 2018. Publisher's Version
X. Tian and Daigle, H., “Machine-learning-based object detection in images for reservoir characterization: a case study of fracture detection in shales,” The Leading Edge, vol. 37, no. 6, pp. 435-442, 2018. Publisher's VersionAbstract
Imaging tools are widely used in the petroleum industry to investigate structural features of reservoir rocks directly at multiple scales. Quantitative image analysis is often used to determine various rock properties, but it requires significant time and effort, particularly to analyze a large number of samples. Automated object detection represents a potential solution to this efficiency problem. This method uses computers to efficiently provide quantitative information for thousands of images. Automated fracture detection in scanning electron microscope (SEM) images is presented as an example to show the workflow of using advanced deep-learning tools for quantitative rock characterization. First, an automatic object-detection method is presented for fast identification and characterization of microfractures in shales. Using this approach, we analyzed 100 SEM images obtained from deformed and intact samples of a carbonate-rich shale and a siliceous shale with the goal of analyzing the abundance and characteristics of microfractures generated during hydraulic fracturing. Most of the fractures are detected with about 90% success rate relative to manual picking. Second, we obtained statistics of length and areal porosities of these fractures. The experimentally deformed samples had slightly more detectable microfractures (1.8 fractures/image on average compared to 1.6 fractures/image), and the microfractures induced by shear deformation tend to be short (<50 μm) in the Eagle Ford and long in the siliceous samples, presumably because of differences in rock fabric. In future work, this approach will be applied to characterize the shape and size of mineral grains and to analyze relationships between fractures and minerals.
C. Griffith and Daigle, H., “Manipulation of Pickering emulsion rheology using hydrophilically modified silica nanoparticles in brine,” Journal of Colloid and Interface Science, vol. 509, pp. 132-139, 2018. Publisher's VersionAbstract
Previous work on Pickering emulsions has shown that bromohexadecane-in-water emulsions (50% oil) stabilized with fumed and spherical particles modified with hexadecyl groups develop a noticeable zero shear elastic storage modulus (G′0) of 200 Pa and 9 Pa, respectively, while in just 50 mM NaCl. This high G′0 can be problematic for subsurface applications where brine salinities are higher and on the order of 600 mM NaCl. High reservoir salinity coupled with low formation pressure drops could prevent an emulsion with a high G′0 from propagating deep into formation. It is hypothesized that G′0 of an emulsion can be minimized by using sterically stabilized silica nanoparticles modified with the hydrophilic silane (3-glycidyloxypropyl)trimethoxysilane (glymo).
Z. Jing, Liu, C., Qi, R., and Ren, P., “Many-body effect determines the selectivity for Ca2+ and Mg2+ in proteins,” Proceedings of the National Academy of Sciences, vol. 115, pp. E7495–E7501, 2018.
J. A. Valdez and Tinney, C. E., “Measurements of a Mach 3 jet using high-speed optical flow techniques,” AIAA/CEAS Aeroacoustics Conference, AIAA Paper 2018-3148. Atlanta, Georgia, USA, 2018.Abstract
The design and construction of various high-speed digital optical flow techniques forstudying the aeroacoustics and turbulence dynamics, as it relates to supersonic/hypersonicflow phenomena, is discussed. The three systems comprise retroreflective shadowgraphy, a z-type schlieren and a focused schlieren system. The performance of the three systems are examined using an axisymmetric Mach 3 flow, which has received considerable attention at the University of Texas at Austin for understanding the sound produced by flows with supersonic convective acoustic Mach numbers. Various techniques to aid in the setup of optical elements in conjunction with the high resolution digital cameras, capable of producing a million frames per second, are described. Various analysis methods are then employed (wavenumer-frequency transforms and wavelet analysis) to quantify the dynamical nature of the flow and sound field produced by this supersonic nozzle.
Z. Jing and Ren, P., “Mechanism of selectivity for magnesium and calcium in proteins,” in ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 2018, vol. 255.

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