Singh User Day Poster Presentation and Competition

Posters are alphabetized by the presenting author’s last name (bold); numbers refer to easel number. Presenters are assigned to one of four periods during User Day to be at their posters to discuss their work; they are welcome to be at their posters for any additional periods.

Poster Session time periods are:

9:45 – 10:15 am
12:00 – 12:30 pm
12:30 – 1:00 pm
2:30 – 3:00 pm

Jump to poster number:

1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27

1. Micro-patterning highly uniform and conductive tracks of silver nanoparticle ink via inkjet printing (12-12:30)

Inayat Bajwa, Amal Abbas, Hiromichi Yamamoto
inayat.bajwa@gmail.com

Drop-on-demand inkjet printing provides a cost and time effective additive process for fabrication of flexible electronic circuits. However, poor resolution, non-uniform morphology and low conductivity of printed conductive metal features hugely restricts its lucrativeness. In this study, a FUJIFILM Dimatix (DMP-2831) inkjet printer with 10 pL nozzles was used to print precise and highly conductive tracks of Ag nanoparticle ink on polyethylene terephthalate (PET) and polyimide (PI) films. The printer employs a piezoelectric element that drives current through the nozzles, ejecting droplets on the substrate according to the predefined digital design. After printing, the substrate was thermally sintered to remove organic solvents and fuse the Ag nanoparticles together to form conductive tracks. A modified interlacing method, where the design is broken down into sub patterns and printed sequentially, was used in combination with an optimized drop spacing and drop frequency setting for that pattern to obtain high resolution features without any overlapping droplets. The waveform was customized to restrict the size of drops though the nozzle and achieve features as small as 20-50 um. Lower resistivity was achieved though thermal sintering and a strategic multilayer printing technique. Printed features also displayed exceptional adhesion and mechanical stability on substrates. These highly conductive Ag nanoparticle tracks will be used to print low cost antennas with increased read distance for radio frequency identification (RFID) tags.

Keywords: inkjet printing, silver nanoparticle ink, flexible electronics

 

2. Direct Investigation of the Roles of Decorin in Cartilage Pericellular Matrix via Immunofluorescence-guided AFM (2:30-3 pm)

Daphney R. Chery, Samuel J. Rozans, Biao Han, Ling Qin, David E. Birk, Renato V. Iozzo, Motomi Enomoto-Iwamoto, Lin Han
dc679@drexel.edu

The pericellular matrix (PCM) of cartilage is a ≈ 5 µm-thick layer surrounding each chondrocyte, which regulates the biomechanical microenvironment of chondrocytes, and the territorial and interritorial extracellular matrices (T/IT-ECM) between cell lacunae are directly responsible for overall mechanical functions . The PCM is composed of localized collagen VI in the form of beaded filaments and perlecan, as well as other non-fibrillar proteins. Currently, the exact contribution of each molecular constituent to the PCM properties is unclear. Our recent studies discovered the indispensable roles of decorin in the properties of articular cartilage ECM. To this end, we hypothesize that decorin also exerts an important role to the PCM properties. Immunofluorescense-(IF)  images detected distinctive rings of collagen VI -concentrated PCM surrounding each chondrocyte in both WT and Dcn-/- murine cartilage. Guided by the IF-imaging, from each nanoindentation modulus map, the regions corresponding to the T/IT-ECM versus PCM were registered via our custom Matlab program, and analyzed. Within each genotype and age, modulus of the PCM was found to be significantly lower than that of the T/IT-ECM. When compared across genotypes, both the PCM and T/IT-ECM of Dcn-/- cartilage had significantly lower moduli than WT at both ages. In addition, in WT cartilage, the impacts of maturation were apparent in the modulus increase from 2 weeks to 3 months of age in both the PCM and the T/IT-ECM. For Dcn-/- mice, however, while a significant increase was observed in the T/IT-ECM, the modulus of PCM was similar between the two ages.

Keywords:  pericellular matrix, extracellular matrix, nanomechanics, decorin

3. Improving the temporal resolution of nanopore recordings (9:45-10:15 am)

Chen-chi Chien, Siddharth Shekar, David Niedzwiecki, Kenneth Shepard, Marija Drndic
chienc@sas.upenn.edu

Solid-state nanopores are being pursued for a number of applications including, most notably, DNA sequencing. One of the challenges that nanopores present is the fast rate at which molecules translocate. Significant improvements in the measurement bandwidth can be obtained through the optimization of detection electronics and reduction in nanopore membrane capacitance. We present a low-noise, custom-designed complementary metal-oxide-semiconductor (CMOS) amplifier chip capable of recording translocation dynamics in nanopores at bandwidths up to 10 MHz. We integrate state-of- the-art silicon nitride nanopores with this amplifier to achieve signal to noise ratios (SNRs) of better than 10 at 5 MHz bandwidth in ssDNA translocation experiments. We observe transient features with durations as short as 200 ns in some translocation events, features that would have been hidden at lower recording bandwidths. We also use our platform to record ssDNA translocation through glass-passivated silicon-nitride nanopores with membrane capacitances of less than 1 pF, further extending the achievable recording bandwidth. At these speeds, the potential exists to realize free-running DNA sequencing using solid-state nanopores.

Keywords:   nanopore, DNA sequencing, fast recordings

 

4. Electro-kinetics in fast oxygen conductor: grain growth & grain-size transition (12:30-1 pm)

Yanhao Dong and I-Wei Chen
dongya@seas.upenn.edu

The kinetics of mass transport is central to ceramic processing and device stability. In the present work, the effect of electrical and hydrogen reduction on the grain growth behavior of doped zirconia and ceria has been investigated. Faster grain growth has been observed under reducing conditions in all cases. The results firmly establish that a depressed local oxygen potential can enhance cation kinetics in fluorite-structured oxide ceramics. Meanwhile, a large electrical current can create a graded microstructure with a dramatic grain-size transition across the length of the sample. Most surprisingly, 100× grain size contrast and correspondingly 104× kinetics enhancement can be readily achieved in tetragonal and cubic zirconia, with or without segregated solutes dragging the grain boundary motion. The large electrical driving force further leads to Rayleigh-type instability and filamentary grain growth, creating finger-like grain structures with a huge (>100) aspect ratio. Lastly, micro Raman analysis indicates that huge tetragonal grains of doped zirconia are unexpectedly stable under reduction, where classical theory indicates a phase transformation when the grains are above a critical size.

Keywords: Zirconia, Ceria, Grain growth, Reduction, Field-assisted sintering, Raman spectrum

 

5. Engineering single-photon sources in hexagonal boron nitride (12-12:30 pm)

Annemarie Exarhos, Jennifer Saouaf, David Hopper, Richard Grote, Audrius Alkauskas, Lee Bassett
exarhosa@seas.upenn.edu

Defect engineering in solid state systems is a rapidly progressing field with applications for quantum information processing, nanophotonics, nanoscale sensing, and other quantum technologies.  While the majority of efforts to date have focused on three-dimensional wide-bandgap semiconductors such as diamond and silicon carbide, low-dimensional materials hosting single spins and single-photon sources can provide unique functionality due to intrinsic spatial confinement and the ability to create multifunctional layered materials.  One such example is hexagonal boron nitride (h-BN), which hosts isolated single-photon sources exhibiting visible fluorescence at room temperature.  Studies on defect creation via electron bombardment and annealing of exfoliated h-BN on various substrates indicate strong substrate interaction effects.  Spectral, temporal, polarization, and spatial characteristics of the defects’ optical emission in suspended, single-crystal h-BN films aid in understanding the physics underlying h-BN’s quantum emission.  Defect emission spectra reveal similarities in vibronic coupling despite widely-varying fluorescence wavelengths, and a statistical analysis of their polarized emission patterns indicates a correlation between the optical dipole orientations of some defects and the primitive crystallographic axes of the single-crystal h-BN film. These measurements constrain possible defect models, and, moreover, suggest that several classes of emitters can exist simultaneously in freestanding h-BN.  This new understanding of single-photon emission in h-BN will aid in the development of precision quantum sensors for nanoscale biological and chemical applications.

Keywords: hexagonal boron nitride; fluorescent defect; single-photon emission; single crystal

 

6. Plasmon resonances in self-assembled two-dimensional Au nanocrystal metamolecules (2:30-3 pm)

Nicholas J. Greybush, Iñigo Liberal, Ludivine Malassis, James M. Kikkawa, Nader Engheta, Christopher B. Murray, and Cherie R. Kagan
greybush@seas.upenn.edu

We explore the evolution of plasmonic modes in two-dimensional nanocrystal oligomer “metamolecules” as the number of nanocrystals is systematically varied. Precise, hexagonally-ordered Au nanocrystal oligomers with 1–31 members are assembled via capillary forces into polygonal topographic templates defined using electron-beam lithography. The visible and near-infrared scattering response of individual oligomers is measured by spatially-resolved, polarized darkfield scattering spectroscopy. The response is highly sensitive to in-plane versus out-of-plane incident polarization, and we observe an exponentially saturating red-shift in plasmon resonance wavelength as the number of nanocrystals per oligomer increases, in agreement with theoretical predictions. Simulations further elucidate the modes supported by the oligomers, including electric dipole and magnetic dipole responses. The single-oligomer sensitivity of our measurements also enables an analysis of the role of positional disorder in determining the oligomers’ optical properties. The progression of structures studied here advances our understanding of fundamental plasmonic interactions in the transition regime between few-member plasmonic metamolecules and extended two-dimensional arrays.

Keywords: plasmonics, template-assisted self-assembly, darkfield scattering spectroscopy, metamaterials, oligomer clusters, magnetic plasmon, polarization

 

7. Diamond nanofabrication for quantum information science (12:30-1 pm)

Richard Grote, David Hopper, Sam Parks, Annemarie Exarhos, Lee Bassett
rgrote@seas.upenn.edu

Recent advances in materials growth techniques have resulted in commercially available high-purity single-crystal diamond substrates, creating the potential for a new class of electronic and photonic devices that utilize diamond’s unique material properties. Diamond’s wide bandgap and large thermal conductivity have been utilized for high-current capacity transistors and Raman lasers with performances that are unmatched in other systems.  Beyond its bulk properties, diamond is also host to fluorescent spin defects which can generate single-photons. One point defect in particular, the nitrogen-vacancy center, is particularly interesting as it can be used as a room temperature qubit for quantum information processing and precision nanoscale sensing.
Owing to its  unique capabilities for use in future quantum technologies, we have developed a library of nanofabrication techniques for diamond using a combination of patterning (photolithography, electron beam lithography, and focused ion beam milling), dry etching (reactive ion etching), dielectric deposition (plasma-enhanced chemical vapor deposition) of SiO2 and Si3N4, and shaping using laser micromachining.   We use these techniques to fabricate quantum photonic devices including solid immersion lenses coupled to individual nitrogen-vacancy centers, fin waveguides for planar lightwave circuits on diamond, and surface patterning for high-sensitivity magnetometry.

Keywords: diamond, quantum, nanofabrication

 

8. Decorin Plays an Indispensable Role in Cartilage Poroelasticity at the Nanoscale (12-12:30 pm)

Biao Han, Qing Li, Mei Sun, Hadi T. Nia, Ramin Oftadeh, Basak Doyran, Ling Qin, Renato V. Iozzo, David E. Birk, and Lin Han
bh462@drexel.edu

Poroelasticity is the dominant mechanism for energy dissipation and impact force protection in articular cartilage during high frequency activities, such as jumping and impactful loading. It is governed by the interactions between water molecules and glycosaminoglycan (GAG) side chains of aggrecan. The collagen fibrillar network serves as a scaffold that holds aggrecan aggregates. To this day, while the roles of aggrecan and collagen are well understood, it remains unclear how quantitatively minor molecules, such as small leucine rich proteoglycans (SLRPs), contribute to cartilage poroelasticity. This study examined the role of decorin, the most abundant SLRP in cartilage, in the poroelastic mechanical properties of cartilage. AFM-based nanorheometric test was applied to study the time-dependent nanomechanics of wild-type (WT) and decorin-null (Dcn-/-) murine cartilage in both intact and CS-GAG-depleted forms. From the mechanical tests and associated finite-element modelling(FEM), we found that WT and Dcn-/- cartilage had significant differences in the frequency-dependent spectra of |E*| and δ, indicating their distinctive poroelastic characteristics. In comparison to the WT control, besides having a lower elastic modulus, Dcn-/- cartilage showed significantly weaker poroelastic properties including lower self-stiffening ratio and higher hydraulic permeability. In addition, the fiber-reinforced FEM extracted significantly lower pore pressure in Dcn-/- cartilage. On the other hand, as expected, for each genotype, CS-GAG-depletion resulted in significant weaken. Meanwhile, SEM and TEM imaging detected significant variations in the collagen structure, where Dcn-/- cartilage showed larger collagen fibril diameters both on the surface and in middle/deep zones.

Keywords: decorin, AFM, nanomechanics, GAG, aggrecan, collagen, finite-element method

 

9. A NIR fluorescence-MRI-CT-DE mammography multimodal nanoparticle contrast agent for breast cancer detection (9:45-10:15 am)

Jessica Hsu, Renee Hastings, Pratap Naha, Kristen Lau, Peter Chhour, Walter Witschey, Elizabeth MacDonald, Andrew Maidment, David Cormode
jesshsu@seas.upenn.edu

Multimodal imaging nanoprobes, which combine the unique advantages of each imaging technique, can offset the limitations of a single imaging modality and provide more detailed information for accurate imaging diagnosis. Due to the low-sensitivity of conventional mammography for women with dense breasts, contrast-enhanced imaging modalities such as magnetic resonance imaging (MRI), computed tomography (CT), optical imaging and dual energy mammography (DEM) are being explored as alternative screening tools for these women. Herein, we present a novel multimodal imaging nanoprobe where a near infrared fluorescent dye (DiR), silver sulfide nanoparticles (Ag2S-NP) and iron oxide nanoparticles (IO-NP) are encapsulated within the hydrophobic core of micelles formed from phospholipids. We have previously shown silver nanoparticles (AgNP) to provide contrast for DEM and CT. Therefore, we hypothesized this nanoprobe can serve as a DEM, CT and MRI contrast agent and as a fluorescence optical imaging probe that provides high spatial resolution and high sensitivity. We have completed nanoscale characterization of this nanoprobe and examined its contrast properties for DEM, CT, MRI and fluorescence imaging, and evaluated its biocompatibility in vitro.

Keywords: silver sulfide; iron oxide; DIR; nanoprobe; breast cancer

 

10. Model-assisted development of micro-fabricated 3D Ni(OH)2 electrodes with rapid charging capabilities (2:30-3 pm)

Chenpeng Huang, Andac Armutlulu, Sue Ann Bidstrup Allen, and Mark Allen
huach@seas.upenn.edu

Three-dimensional (3D) nickel hydroxide electrodes based on laminated structures were prepared via an electrochemical route combined with microfabrication technologies. The electrodes exhibited enhanced rate capabilities owing to their large surface area and reduced diffusion and conduction path lengths for the charge transfer. Highly laminated electrodes enabled areal capacities as high as 2.43 mAh cm-2. When charged at fast rates of 150C, the electrodes were able to deliver more than 50% of their initial capacity. The electrochemical performance of the fabricated electrodes was predicted with close approximation by means of a mathematical model developed by employing fundamental mass transport and reaction kinetics principles. This model was used to optimize the characteristic dimensions of the electrodes and make projections of performance for various energy and power needs.

Keywords: Energy storage, 3D batteries, Modeling

 

11. Quantitative microwave impedance microscopy with effective medium approximations (12-12:30 pm)

Timothy S. Jones, Carlos R. Pérez, and Jorge J. Santiago-Avilés
jonests@seas.upenn.edu

Microwave impedance microscopy (MIM) is a scanning probe technique to measure local changes in tip-sample admittance. The imaginary part of the reported change is calibrated with finite element simulations and physical measurements of a standard capacitive sample, and thereafter the output ΔY is given a reference value in siemens. Simulations also provide a means of extracting sample conductivity and permittivity from admittance, a procedure verified by comparing the estimated permittivity of polytetrafluoroethlyene (PTFE) to the accepted value. Finally, the well-known effective medium approximation of Bruggeman is considered as a means of estimating the volume fractions of the constituents in inhomogeneous two-phase systems. Specifically, we consider the estimation of porosity in nanostructured carbons.

Keywords: microwave impedance microscopy, carbon, inhomogeneity

 

12. Defining the mechanism by which Kingella kingae adheres to host cells (12:30-1 pm)

Brad Kern, Eric Porsch, Katherine Rempe, and Joseph St. Geme
kernb@chop.edu

Kingella kingae is a gram-negative pediatric pathogen that initiates infection by colonizing the posterior pharynx.  Adherence to host cells is an important first step in colonization.  Previous work by our lab has shown that K. kingae expresses three surface factors that mediate or modulate adherence to host cells: type IV pili (T4P), polysaccharide capsule, and a trimeric autotransporter adhesin named Knh.  Based on this work we developed a model of K. kingae adherence: T4P initiate contact with the host cell and mediate weak adherence.  T4P then retract, causing the capsule to be displaced, exposing Knh to the host cell, allowing Knh to mediate strong adherence to the host cell.  This model suggests three fundamental hypotheses: 1) Knh mediates stronger adherence to host cells than do T4P, 2) capsule is deeper than Knh is long, and 3) capsule is displaced on the side of the bacteria in closest contact with the host cell.  We tested these hypotheses using flow adherence assays, atomic force microscopy (AFM), and transmission electron microscopy (TEM).  Our results support our model of K. kingae adherence to host cells and suggests future studies using nanoscale characterization methods.

Keywords: bacterial adherence, polysaccharide capsule, type IV pili, trimeric autotransporter adhesin, Kingella, atomic force microscopy

 

13. Surface tension-driven assembly of metallic nanosheets at the liquid-air interface: application to highly laminated magnetic cores (2:30-3 pm)

Jooncheol Kim, Minsoo Kim and Mark Allen
novamagic@gmail.com

This paper presents a fabrication technique to develop highly laminated structures comprising stacked thin films, in which the structures are based on surface tension-driven assembly at the liquid-air interface.  When multiple metallic films are removed from a liquid solution, there is a surface tension-driven coalescence and self-alignment of the wetted films, resulting in thick metallic microstuctures comprised of many layers of metallic nanosheets after evaporation of the liquid.  If the liquid contains a dissolved material, each sheet can further be coated with the material prior to assembly. Based on this technique, we developed laminated structures comprising hundreds of nanoscale layers of alternating metallic film and non-conducting polymer.  Electroplated Co44Ni37Fe19 (Cobalt-Nickel-Iron alloy) and a commercial Novec 1700 solution (3M, Minnesota) were utilized for the metallic film and the liquid solution, respectively. Theoretical analysis and experimental results were compared, demonstrating a critical gap between the metallic films, below which capillary force is sufficient for driving self‑assembly of the films. As an exemplary application of this technique, highly laminated magnetic cores comprising 600 layers of 500 nm thick CoNiFe that are insulated by 100 nm thick polymer were prepared. A 15-turn toroidal inductor with the fabricated magnetic core exhibited a constant inductance of 2.5 μH up to 30 MHz with a quality factor over 70 at 1 MHz.

Keywords: Ferromagnetic materials, Nanolaminations, Surface tension-driven assembly

 

14. Compression and recovery of carbon nanotube foams described as a phase transition (12:30-1 pm)

Xiaojun Liang, Jungho Shin, Daniel Magagnosc, Yijie Jiang, Sei Jin Park, A. John Hart, Kevin T. Turner, Daniel S. Gianola, Prashant K. Purohit
liangxj_156@163.com

In this paper we describe experiments and a phase transition based continuum model for the compression of carbon nanotube (CNT) forests, or foams. Our model is inspired by the observation of one or more propagating interfaces across which densified and rarefied phases of the CNT forests co-exist. We use a quasi-static version of the Abeyaratne-Knowles theory of phase transitions for continua with a stick-slip type kinetic law and a nucleation criterion based on the critical stress for buckling of CNT forests to describe the formation and propagation of these interfaces in uniaxial compression experiments. We consider pillars made from bare CNTs, as well as those coated with different thicknesses of alumina using atomic layer deposition (ALD). The effect of ALD coating thickness on the parameters entering the phase transition model are described. We also carry out nanoindentation experiments on the CNT forests and interpret the load-indentation data by incorporating a constitutive law allowing for phase transitions into solutions for the indentation of a linearly elastic half-space. Even though the state of stress in a nanoindentation experiment is more complex than that in a uniaxial compression test, we find that the parameters obtained from fitting the nanoindentation experiments are close to those from uniaxial compression. Our nanoindentation experiments also reveal dissipation which, we believe, has its origins in inter-fiber contacts in the densified phase. Our models could therefore aid the design of CNT forests to have engineered mechanical properties, and guide further understanding of their behavior under large deformations.

Keywords: nanoindentation, CNT foams, phase transition

 

15. Two-layer plate nanocardboard (9:45-10:15 am)

Chen Lin, Sam Nicaise, Jonathan Bryan, Eric Lu, Keivan Davami, John Cortes, Drew E. Lilley, Igor Bargatin
chenlin1@seas.upenn.edu

We report the fabrication and characterization of ultrathin, shape-recovering and flat plates made out of two alumina layers. The two ultrathin (about 60-nm-thick) alumina layers deposited using atomic layer deposition, one flat and the other corrugated, form a joined structure which is reminiscent of honeycomb sandwich plates. The vertical hexagonal walls connecting the top and bottom layers can limit the shear of these two layers with respect to each other. The two-layer plates therefore offer a high bending stiffness while still possessing extremely low areal density (~0.5 g/m2). It is shown by finite element simulations that the bending stiffness increases quadratically with the plate height at first, 10-9-10-8 Nm for plate heights of 1-10 um  (qualitatively supported by the atomic force microscope measurements of the bending stiffnesses of 1-um-tall and 3-um-tall two-layer cantilevered plates), and then saturates when the height is above ~10 um. Moreover, our two-layer plates can recover their original shapes after extremely sharp bending deformations without displaying any sign of fracture or damage. We also report the development of new metamaterials-based fabrication processes for making two-layer sandwich structures, which feature both larger spacing between the top and bottom layers, higher manufacturing throughput, and lower cost. Unprecedented properties of these two-layer alumina plates allow applications in testing of nanoscale strength enhancement and as structural elements in flying microflyers.

Keywords: two-layer plate, mechanical metamaterials, atomic layer deposition, bending stiffness, robustness

 

16. NanoMAST-3D: a nanoscale magnetically-activated, spatially-targeted drug delivery device for crossing the blood-brain barrier (12-12:30 pm)

Jessica Liu, Andrew Tsourkas, and David Issadore
jessicafliu@gmail.com

Current drug delivery methods often suffer from poor specificity and off-target effects. To improve the spatial control over drug delivery, we have developed a Nanoscale Magnetically-Activated Spatially-Targeted Drug Delivery Device (nanoMAST-3D) that allows controlled release of drugs from liposomes with millimeter-scale precision. Our device utilizes an alternating magnetic field (AMF) to control the release of drugs from thermally-sensitive liposomes via super paramagnetic iron oxide nanoparticles (SPIONs). In an AMF, the SPIONs generate local heating to destabilize the liposomal membrane and release liposomal contents. To limit AMF-mediated heating to a desired location, a strong static magnetic field with a sharp zero point is superimposed over the AMF. At the zero point, the AMF dominates, allow the SPIONs to trigger drug release from the liposomes; elsewhere, the strong static field dominates, pinning the magnetic moment within the SPIONs and thus suppressing AMF-mediated drug release. Because there is no inherent limit on how small the zero point in the static field can be, spatial targeting is in theory limited by diffusion alone. This MRI-inspired system would allow for non-invasive spatial targeting of drug release at the zero point of a strong static field. Magnetically activated location-specific drug release could decrease the severe systemic side effects of chemotherapeutic and other drugs while bypassing the risks of more invasive targeting methods such as direct injection.

Keywords: targeted drug delivery, superparamagnetic iron oxide nanoparticles, magnetic hyperthermia, neuroengineering

 

17. Controlled sculpture of black phosphorus nanoribbons (12:30-1 pm)

Paul Masih Das, Gopinath Danda, Andrew Cupo, William Parkin, Liangbo Liang, Neerav Kharche, Xi Ling, Shengxi Huang, Mildred S. Dresselhaus, Vincent Meunier, and Marija Drndić
pmasi@sas.upenn.edu

Black phosphorus (BP) is a highly anisotropic allotrope of phosphorus with great promise for fast functional electronics and optoelectronics. We demonstrate the controlled structural modification of few-layer BP along arbitrary crystal directions with sub-nanometer precision for the formation of few-nanometer-wide armchair and zigzag BP nanoribbons. Nanoribbons are fabricated, along with nanopores and nanogaps, using a combination of mechanical–liquid exfoliation and in situ transmission electron microscopy (TEM) and scanning TEM nanosculpting. We predict that the few-nanometer-wide BP nanoribbons realized experimentally possess clear one-dimensional quantum confinement, even when the systems are made up of a few layers. The demonstration of this procedure is key for the development of BP-based electronics, optoelectronics, thermoelectrics, and other applications in reduced dimensions.

Keywords: Black phosphorus, phosphorene, nanoribbons, density functional theory, transmission electron microscopy

 

18. Nanoscale adhesion modified by shear-stress-assisted chemical reactions (9:45-10:15 am)

Zachary B. Milne, Tevis D. B. Jacobs, Rob Carpick
zmilne@seas.upenn.edu

Despite a wealth of information regarding macroscale friction, adhesion, and wear, fundamental understanding of these phenomena on the nanoscale is still a topic of hot pursuit in research. Our recent in situ studies have found the measured Bradley-limit work of adhesion is exponentially dependent on the normal stress in the contact interface. Furthermore, the adhesion grows logarithmically with sliding speed. We believe this is evidence that atoms in the contact bond more readily due to the local shear-forces, or friction, in the interface. These bonds supplement the intrinsic work of adhesion due to Van-der-Waals forces, thus increasing the measured work of adhesion proportionally to the sliding speed and normal stress. Our findings complement recent results for chemically induced nanoscale wear and friction, fitting well in the theoretical and experimental framework of chemical kinetics which has been shown to describe these separate but dependent phenomena surprisingly well.

Keywords: tribology adhesion friction wear nanoscale

 

19. Superconductivity in palladium patterned topological insulator Bi2Se3 (12:30-1 pm)

Jerome T. Mlack, Atikur Rahman, Gopinath Danda, Natalia Drichko, Sarah Friedensen, Marija Drndic, Nina Markovic
jmlack@sas.upenn.edu

We pattern Bi2Se3 nanostructures with palladium using thermal annealing which causes the Bi2Se3 to absorb the palladium. This process results in superconductivity in the patterned regions, with unpatterned regions remaining normal Bi2Se3, as measured using a dilution refrigerator. In order to understand the material changes from this process, we analyze annealed samples using a variety of techniques including EDS, SAED, AFM, and Raman spectroscopy.

Keywords: Topological insulator, superconductivity, nanodevices, materials analysis

 

20. Sequentially-layered corrugated nanoplates for mechanical metamaterials (12-12:30 pm)

Samuel M. Nicaise, Zachary Stillman, Mohsen Azadi, Chen Lin, Daeyeon Lee, Igor Bargatin
snicaise@seas.upenn.edu

Composite three-dimensional (3D) nanostructures have been developed for various applications, including biomimetics, optoelectronic devices, mechanical coatings, and gas sensors. Many mechanical 3D nanostructures have shown a high stiffness-to-weight ratio, negative Poisson’s ratio, or large range in elastic deformation. Our recent work leveraged microscale periodic cellular honeycomb structures to produce plates that sustained large deformations, though were prone to defect-based fracture. We present the fabrication and mechanical characterization of new nanometer-thick mechanical plates composed of alternating layers of rigid alumina and more flexible polyelectrolyte multilayers (PEMs). Our work targets remarkably light-weight, macroscale-area mechanical metamaterial plates that have the rigidity equal to or greater than a sheet of defect-free alumina, with strength amplification provided by the limited fracture propagation at proximal oxide-polymer interfaces. Fabrication included sequential deposition of alumina thin films by atomic layer deposition and poly(acrylic acid)/poly(allylamine hydrochloride) PEM by layer-by-layer (LbL) deposition. In varying the number of deposition cycles, we controlled the film thicknesses to single-nanometers, and thus accumulated 3-11 layers. We thereafter released the plates from the silicon substrate with post-process etching. To provide many times greater stiffness (force-displacement slope of 3000 N/m with cyclic tensile loading) over otherwise planar (non-patterned) plates, the substrate was patterned by photolithography with microscale, cellular honeycomb corrugation. This work is a novel example of mechanical metamaterials with all-film continuous layers, realizing rigidity that was previously out-of-reach.

Keywords: layer-by-layer deposition, metamaterial, nanocardboard, atomic layer deposition, MEMS, composites

 

21. Magnetic nanopore-based sorting for ultra-sensitive HIV viral load detection (2:30-3 pm)

Nishal Shah, Farida Shaheen, Yanjie Yi, Jin A Ko, Ronald Collman, David Issadore
nishal@seas.upenn.edu

Despite the resources invested in HIV infection research, no cures have been found partially due to an inability to evaluate low viral loads. Limits of detection (LOD) have reached ~20 virions/mL, but require special equipment and extensive purification. To address this challenge, we harness the inherent lack of magnetic signal in blood to develop a diagnostic tool that achieves ultra-high sensitivity (5 virions/ml) in a portable platform. Our device immunomagnetically captures HIV in blood using track-etched nanopore filters coated with permalloy, a magnetic nickel-iron alloy. With an enormous density (10^7/cm2) of nanoscale pores, d < 1 um, we achieve high throughput while maintaining extraordinary selectivity and sensitivity.
The device is composed of a reservoir for sample input and a series of polycarbonate filters coated with permalloy and gold. We use two-step antibody labeling to tag HIV (AT2-inactivated NL43) with anti-CD44 and magnetic nanoparticles (50 nm). Currently, the virus is spiked into healthy human plasma sample and then run through the device at 10 ml/hr. After filtration, we lyse the captured virions on-chip, and isolate the viral RNA  and perform RT-qPCR off-chip. From this experiments, we determined an enrichment of ~50 between our starting and final concentrations and an LOD of ~30 virions/mL. We are now proceeding to test the device with clinical samples from patients with different viral load levels.

Keywords: magnetic sorting, nanoparticles, HIV, nanoscale trapping

 

22. Phase transitions in torsionally constrained DNA (12-12:30 pm)

Jaspreet Singh, Prashant Purohit
sinjas@seas.upenn.edu

Experimental studies on single molecules of DNA using optical tweezers have reported a rich variety of phase transitions including coexistence of three phases, in a torsionally constrained molecule. A comprehensive knowledge of these phase transitions is useful for unraveling the in-vivo and in-vitro behavior of DNA. Our objective is to understand the phase transitions in a torsionally constrained molecule when it is pulled using optical or magnetic tweezers. We borrow the foundational concepts from
the Zimm-Bragg helix-coil transition theory and merge them with the ideas from the theory of fluctuating elastic rods to model the mechanics of DNA. We employ the Poisson-Boltzmann equation to account for the electrostatic interactions between the ions and the negatively charged phosphate backbone of DNA. The fact that phase transitions are strongly cooperative manifests itself in the sigmoidal nature of the resultant force- displacement curves. Using our model, we calculate the force and moment corresponding to the over-stretching transition characterized by a 70% jump in the contour length of the molecule and examine the effect of salt concentration on this transition. We also deduce conditions under
which the co-existence of B-, S- and P-DNA is possible.

Keywords: Phase transitions, DNA, elastic rods, triple point

 

23. Utilization of MEMS techniques to deterministically engineer high power lithium ion battery electrodes (12:30-1 pm)

Mike Synodis, Dr. Sue Ann Bidstrup Allen, Dr. Mark Allen, Dr. Andac Armutlulu
msynodis@seas.upenn.edu

Rechargeable, or secondary batteries, are required to power almost all of today’s increasingly complex technology. In most current commercial systems, high charge and discharge rates lead to increased kinetic resistances and reduced capacity retention, while increasing electrode size and active material mass can increase energy storage but reduce power density. In order to optimize both energy storage and power performance, the battery electrodes must be designed to minimize the kinetic resistances of both electron and ion transport within the system while maintaining the infrastructure to hold a large amount of active material. Additionally, it is necessary for these electrodes to be deterministically engineered in order to have potential for high volume manufacturing. In this study, micro-machining and electroplating techniques are utilized to design a fabrication process that deterministically engineers electrodes and achieves the goal of both high power and high energy density performance. The fabrication process maximizes the surface area of the electrodes, while the multilayer approach enables the manufacture to be repeatable and scalable, even up to volumes on the order of a cubic centimeter. This size and performance versatility of these electrodes make them ideal candidates for use in a wide array of applications.  The electrodes are characterized via galvanostatic charge and discharge at various dimensions and C rates.

Keywords: Energy, Batteries, Microfabrication, MEMS

 

24. Effect of gold nanoparticle size and coating for cell labeling of monocytes (9:45-10:15 am)

Peter Chhour, Johoon Kim, Alfredo Tovar, Victor A. Ferrari, David P. Cormode
alfredot@seas.upenn.edu

Tracking cells in-vivo is a promising and informative option to monitor cell migration, differentiation, and cell viability to improve cell therapies without using invasive procedures. Our project focuses on gold nanoparticles (AuNP) as a reporter for x-ray computed tomography (CT). We investigated the effect of size and surface functionality of the AuNP on monocyte uptake and viability. AuNP from 15 to 150 nm in diameter were synthesized and coated with different capping ligands. This resulted in 44 different AuNP formulations that were used in in vitro cytotoxicity and uptake studies using the RAW 264.7 monocyte line. Most of the formulations were found to be biocompatible, with the exception of some 150 nm PEG functionalized particles that caused reductions in cell viability at higher concentrations. Uptake was found to be high in AuNP formulations coated with straight-chain hydrocarbon with distal carboxylic acids (11-MUA and 16-MHA). Formulations with 50 to 75 nm diameter coated with 2000 MW poly(ethylene-glycol) carboxylic acid ligands (PCOOH) also exhibited high uptake. On the other hand, 15, 25, 100, and 250 nm PCOOH AuNP formulations showed low uptake, revealing an interrelation between size and surface functionality. These data show that highly negatively charged carboxylic acid coatings for AuNP create the highest degree of uptake of AuNP in monocytes in a size and ligand dependent relationship.

Keywords: gold nanoparticles, monocytes, cell tracking, computed tomography, size, uptake

 

25. Lassoing saddle splay and the geometrical control of topological defects (12-12:30 pm)

Lisa Tran, Maxim O. Lavrentovich, Daniel A. Beller, Ningwei Li, Kathleen J. Stebe, Randall D. Kamien
ltran@sas.upenn.edu

Systems with holes, such as colloidal handlebodies and toroidal droplets, have been studied in the nematic liquid crystal (NLC) 4-cyano-4′-pentylbiphenyl (5CB): both point and ring topological defects can occur within each hole and around the system, while conserving the system’s overall topological charge. However, what has not been fully appreciated is the ability to manipulate the hole geometry with homeotropic (perpendicular) anchoring conditions to induce complex, saddle-like deformations. We exploit this by creating an array of holes suspended in an NLC cell with oriented planar (parallel) anchoring at the cell boundaries. We study both 5CB and a binary mixture of bicyclohexane derivatives (CCN-47 and CCN-55). Through simulations and experiments, we study how the bulk saddle deformations of each hole interact to create novel defect structures, including an array of disclination lines, reminiscent of those found in liquid crystal blue phases. The line locations are tunable via the NLC elastic constants, the cell geometry, and the size and spacing of holes in the array. This research lays the groundwork for the control of complex elastic deformations of varying length scales via geometrical cues in materials that are renowned in the display industry for their stability and ease of manipulability.

Keywords: liquid crystals, topological defects

 

26. Ultra-high throughput detection (ɸ > 100 mL/hr) of fluorescent droplets on a cell phone using time domain encoded optofluidics (9:45-10:15 am)

Venkata R. Yelleswarapu, David Issadore
vraviy@gmail.com

Abstract not available for publication. Please visit poster.

Keywords: digital assays droplet microfluidics pcr cell phone parallel high throughput point of care portable

 

27. Biodegradable electrical interconnects for transient implantable systems (2:30-3 pm)

Tao Zhang, Melissa Tsang, Mark Allen
taozhan@seas.upenn.edu

This study presents the development and characterization of biodegradable electrical interconnects comprising biodegradable conductive polymer composites for use in transient implantable systems. The biodegradable conductive composites were developed using iron (Fe) microparticles as the conductive filler and polycaprolactone (PCL) as the insulating matrix. The electrical resistivity, mechanical and electrochemical properties of the composites were investigated during physiological degradation. The electrical percolation threshold was found at 17% Fe volume fraction, but higher volume fractions exhibited more stable resistivity throughout degradation. An electrical lifetime of over 20 days was achieved with 40% Fe composites, where the average resistivity was 0.3 Ω·cm. Biodegradable electrical interconnects based on 40%vf Fe-PCL composites were successfully micropattened in daisy-chain structures to illustrate process compatibility of these materials.

Keywords: Fe-PCL composites, biodegradable electrical interconnect