Article
Mechanics
Dege Li, Yi Cao, Bingfang Huang, Xinlei Wu, Guofang Hu, Xiaolong Wang, Yonghong Liu, Yanzhen Zhang
Summary: The breakup process of an inviscid liquid bridge sandwiched between two coaxial rods is investigated, with a focus on its profile close to rupture and its influence on subsequent breakup behaviors. The profile of the liquid bridge undergoes a transition from symmetry to asymmetry as the distance between the rods increases. A critical slenderness is found above which the liquid bridge becomes asymmetric and exhibits a well-fitted profile of a sine wave cycle. Experimental and theoretical results show that the ratio of bridge length to equivalent radius is always 2 pi for the asymmetric bridge close to rupture. The influence of slenderness on the time interval between asymmetric pinch-off events, velocity, destination, and size of the satellite droplet is explored.
Article
Mechanics
Christian Diddens, Yaxing Li, Detlef Lohse
Summary: Recent studies have shown that in evaporating binary sessile and pendant droplets, gravity and natural convection can be the dominant driving mechanisms for flow. A quasi-stationary model has been derived and validated to predict the prevalence and intriguing interaction of Rayleigh and/or Marangoni convection based on a phase diagram for the flow field expressed in terms of the Rayleigh and Marangoni numbers.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Polymer Science
Nandini Bhandaru, Rabibrata Mukherjee
Summary: In this study, dewetting of a thin polymer bilayer consisting of a stacked polystyrene (PS) film on top of a topographically patterned poly(methyl methacrylate) (PMMA) bottom layer on a nonwettable substrate results in a myriad of partially or fully ordered patterns. The local thicknesses of the thinnest parts of both layers collectively influence the evolution pathway and extent of ordering in the final dewetted features. Different values of h(R-PMMA) and h(T-PS) lead to different morphologies of ordered structures during the dewetting process.
Article
Nanoscience & Nanotechnology
Linh Quy Ly, Alison Joy Fulton, Stephanie Nicole Bonvicini, Yujun Shi
Summary: This study systematically explored two different methods for dewetting of silver thin films, PLiD and TD, and found that both methods can produce silver NPs of similar size, with PLiD showing better size uniformity for thinner films. On the other hand, TD produced larger silver NPs for thicker films.
Article
Chemistry, Physical
Palash Dhara, Rabibrata Mukherjee
Summary: This paper reports on the morphology, phase separation, instability, and dewetting of Polymer dispersed liquid crystal (PDLC) thin film comprising nematic liquid crystal, 4-n-pentyl-4'-cyanobiphenyl (5CB), and Polystyrene (PS). It is found that the thickness and composition of the film play a crucial role in their properties, and topographically patterned substrates can help align the phase-separated LC domains.
JOURNAL OF MOLECULAR LIQUIDS
(2021)
Article
Chemistry, Physical
Wei-Shao Wei, Joonwoo Jeong, Peter J. Collings, A. G. Yodh
Summary: The liquid crystalline phases of matter are visually stunning and determined by various factors including bulk LC elasticity, surface anchoring conditions, and confinement geometry. In this study, we explore the defect textures of the smectic LC phase in unique confining geometries and find that a complex range of director configurations can arise from a single system, depending on sample processing procedures. Our findings shed light on the assembly mechanisms and suggest new routes for fabricating complex soft material structures.
Article
Chemistry, Physical
Stefan Luding, Kianoosh Taghizadeh, Chao Cheng, Lou Kondic
Summary: This study examines the evolution of dense granular systems in three dimensions during slow compression and decompression. It finds that the transitions in the system involve both smooth and continuous reversible events, as well as fast and discontinuous irreversible events. The analysis using persistent homology reveals that kinetic energy is correlated with the strength of rearrangements, while global mechanical measures, such as pressure, are strongly correlated with the evolution of topological measures quantifying loops in the force network. Surprisingly, some transitions are detected by persistent homology even when particle motion or rearrangement is weak or not observed at all.
Article
Nanoscience & Nanotechnology
David A. Garfinkel, Vasudevan Iyer, Robyn Seils, Grace Pakeltis, Marc R. Bourgeois, Andrew W. Rossi, Clay Klein, Benjamin J. Lawrie, David J. Masiello, Philip D. Rack
Summary: Trimer meta-atoms composed of three gold rods were fabricated and their near-field plasmonic responses were characterized. The magnetic and electric modes of the trimer structure could be tuned by changing the length of the rods. The study also found that the intensity of the electric mode increased more than expected, while the magnetic mode showed the expected tilt dependence. This research opens up new possibilities for studying the nanoscale excited-state of other magnetic meta-atom structures.
ACS APPLIED NANO MATERIALS
(2022)
Article
Nanoscience & Nanotechnology
David A. Garfinkel, Nan Tang, Grace Pakeltis, Reece Emery, Ilia N. Ivanov, Dustin A. Gilbert, Philip D. Rack
Summary: The magnetic and optical properties of AuxCo1-x thin films and nanoparticles can be tuned by controlling their chemical composition and morphology. Annealing leads to phase separation and enhances the magnetic properties. The optical properties are greatly influenced by the chemical morphology, where phase separation enhances the quality factor and optical absorption.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Engineering, Chemical
B. Gu, L. Kondic, L. J. Cummings
Summary: The study demonstrates that the variations in porosity of membrane filters, induced by changes in pore radii or random pore networks, significantly affect their performance. Additionally, network and pore size variations play a role, particularly when pore radii variations are significant.
JOURNAL OF MEMBRANE SCIENCE
(2022)
Article
Instruments & Instrumentation
Leo Saturday, Chris Luck, Leslie Wilson, Jason D. Fowlkes, Philip D. Rack, Nicholas J. Evans
Summary: This study presents a method to simulate the Spallation Neutron Source and characterize the thermal failure of NCD foils. A test stand with in situ diagnostics is used to track foil sublimation and thinning, and a COMSOL simulation is developed to assess potential changes to the NCD film and predict foil temperatures under different beam conditions.
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT
(2022)
Article
Chemistry, Multidisciplinary
Sumeer R. Khanna, Michael G. Stanford, Ivan V. Vlassiouk, Philip D. Rack
Summary: In this study, CuxN1-x alloy thin films were used as catalysts for graphene growth at atmospheric pressure. By adjusting the alloy composition, the growth of graphene was controlled. The results showed that graphene primarily grew as a single layer when the Cu concentration (x) was above 69 at.%.
Article
Chemistry, Multidisciplinary
Jason D. Fowlkes, Robert Winkler, Philip D. Rack, Harald Plank
Summary: This article presents an electron dose compensation strategy, called DBEA, to address the structural artifact issue caused by temperature gradient in 3D nanoprinting using focused electron beam-induced deposition. By modulating the electron dose, the deviations caused by temperature variations can be corrected, thus improving the printing accuracy.
Article
Chemistry, Multidisciplinary
John Lasseter, Philip D. D. Rack, Steven J. J. Randolph
Summary: This study demonstrates the selective growth of high-purity gold films onto nanoscale 3D architectures using the Me2Au (acac) precursor and pulsed laser pyrolytic chemical vapor deposition. The high thermal resistance of the nanoscale geometries enables selective deposition. The effects of laser irradiance, pulse width, and precursor pressure on the growth rate were explored, and feature-targeting resolutions of approximately 100 and 5 μm were achieved using diode lasers coupled to multimode (915 nm) and single mode (785 nm) fiber optics, respectively. Finite element thermal modeling was used to rationalize the experimental results.
Article
Physics, Fluids & Plasmas
Binan Gu, Lou Kondic, Linda J. Cummings
Summary: Pore-size gradients are used to enhance the performance of membrane filters by increasing filter lifetime and improving the utilization of membrane pore volume. In this study, we investigated the impact of pore-size gradients on the efficiency of a membrane filter with interconnected tubelike pores using mathematical modeling. Our results suggest that there is an optimal pore-radius gradient that maximizes filter efficiency, independent of the maximum pore length. Additionally, filters with longer characteristic pore length perform better.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Education, Special
Jason D. Fowlkes, Robert Winkler, Philip D. Rack, Harald Plank
Summary: 3D nanoprinting using focused electron beam-induced deposition is susceptible to structural distortions caused by temperature gradients. In this study, an electron dose compensation strategy called the Decelerating Beam Exposure Algorithm (DBEA) is proposed to correct for nanowire bending during computer-aided design. The DBEA utilizes an analytical solution derived from 3D nanoprinting simulations to offset undesired heating effects. This compensation strategy has the potential to improve the fidelity of 3D nanoscale printing.
RESEARCH IN AUTISM SPECTRUM DISORDERS
(2023)
Article
Chemistry, Multidisciplinary
Jason D. Fowlkes, Robert Winkler, Philip D. Rack, Harald Plank
Summary: 3D nanoprinting using focused electron beam-induced deposition often results in structural artifacts caused by temperature gradients during the deposition process. Researchers have developed an electron dose compensation strategy to correct for these artifacts and improve the precision of 3D nanoprinting.
Article
Physics, Fluids & Plasmas
Rituparna Basak, Ryan Kozlowski, Luis A. Pugnaloni, M. Kramar, Joshua E. S. Socolar, C. Manuel Carlevaro, Lou Kondic
Summary: In this study, quasi-two-dimensional experiments were conducted with photoelastic particles confined to an annular region. It was found that an intruder constrained to move in a circular path halfway between the annular walls experiences stick-slip dynamics. The response of the granular medium to the driven intruder was discussed, with a focus on the evolution of the force network during sticking periods. The analysis of the force networks using topological measures based on persistence diagrams revealed identifiable slip precursors and characteristic features in the dynamics.
Article
Materials Science, Multidisciplinary
Timothy G. Lach, Chinthaka M. Silva, Yufan Zhou, Walker L. Boldman, Philip D. Rack, William J. Weber, Yanwen Zhang
Summary: This study investigates the behavior of two sets of near-equiatomic CoCrCuFeNi thin films under irradiation in different environments. The results demonstrate the influence of composition and environmental exposure on the stability of high entropy alloys under radiation, providing insights into controlling these behaviors.
NPJ MATERIALS DEGRADATION
(2022)
Article
Physics, Fluids & Plasmas
Luis A. Pugnaloni, C. Manuel Carlevaro, Ryan Kozlowski, Hu Zheng, Lou Kondic, Joshua E. S. Socolar
Summary: Experiments and simulations of an intruder dragged by a spring through a two-dimensional annulus of granular material show robust force fluctuations. A simple model predicts the relationship between the critical packing fraction and the width and diameter of the annulus, allowing for a data collapse. These findings challenge theories of mechanical failure in amorphous materials.
Article
Chemistry, Physical
Miroslav Kramar, Chao Cheng, Rituparna Basak, Lou Kondic
Summary: This article studies a granular particle system subjected to externally applied shear stress and investigates the evolution of system behavior before a slip event. The study finds that system behavior measures can be divided into two groups: global measures and time-dependent measures. The time-dependent measures show significant changes and increased fluctuations before a slip event occurs.