Article
Physics, Multidisciplinary
Tao Gong, Inigo Liberal, Benjamin Spreng, Miguel Camacho, Nader Engheta, Jeremy N. Munday
Summary: The Casimir effect is a phenomenon where macroscopic metallic objects experience an attractive force due to vacuum fluctuation-induced interactions. This force is influenced by both plasmonic and photonic modes. In this study, we investigate the Casimir interaction between ultrathin films and find pronounced repulsive contributions to the force caused by highly confined and nearly dispersion-free epsilon-near-zero (ENZ) modes unique to ultrathin films. These contributions occur consistently around the ENZ frequency of the film regardless of interfilm separation. We also observe a thickness dependence of a figure of merit (FOM) for conductive thin films associated with ENZ modes, suggesting enhanced motion of objects induced by Casimir interactions for deeply nanoscale sizes.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
Tanja Schoger, Benjamin Spreng, Gert-Ludwig Ingold, Paulo A. Maia Neto, Serge Reynaud
Summary: We studied the Casimir interaction between two dielectric spheres immersed in a salted solution and found that this interaction exhibits universality properties at distances larger than the Debye screening length. This finding is important for the modeling of colloids and biological interfaces.
PHYSICAL REVIEW LETTERS
(2022)
Article
Multidisciplinary Sciences
Zhujing Xu, Peng Ju, Xingyu Gao, Kunhong Shen, Zubin Jacob, Tongcang Li
Summary: This study reports an experimental demonstration of Casimir force exerted among three objects, using a unique sphere-plate-sphere geometry. The research also proposes and demonstrates a three-terminal switchable architecture for opto-mechanical Casimir interactions which could lead to the development of a Casimir transistor with potential applications in sensing and information processing.
NATURE COMMUNICATIONS
(2022)
Article
Materials Science, Multidisciplinary
G. L. Klimchitskaya, V. M. Mostepanenko, O. Yu. Tsybin
Summary: In this study, the nonequilibrium Casimir-Polder force between a nanoparticle and a graphene sheet kept at different temperatures was examined using the formalism of the polarization tensor in the framework of a Dirac model. The results demonstrate that the magnitude of the force increases with the temperature of the graphene sheet. The impact of nonequilibrium conditions on the force becomes smaller at larger separations. Our findings reveal that for a graphene sheet with a lower temperature than the environment, the attractive Casimir-Polder force vanishes at a specific separation distance and becomes repulsive at larger distances. This effect has potential applications in fundamental graphene research and force control in bioelectronic microdevices.
Article
Nanoscience & Nanotechnology
Lina Zhang, Weibin Chen, Xinfeng Tan, Jianguo Jiao, Dan Guo, Jianbin Luo
Summary: This study demonstrates the nonmonotonic effect of Te vacancy defects on the friction of MoTe2. Increasing Te vacancy density leads to an overall increase in friction force, but the variation is nonmonotonic. The change in the maximum sliding energy barrier and uneven charge distribution are the main factors contributing to this effect.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Engineering, Marine
Weiye Ding, Tao Cai, Hongyue Sun, Xizeng Zhao, Yifan Fan
Summary: This study investigates the interactions between gravity currents and different types of horizontal cylinders and analyzes the hydrodynamic characteristics of the flow field around the cylinders. The results show that increasing the height of a cylinder increases the vorticity in the flow field and enhances the maximum dynamic pressure around the lower wall of the cylinder. The spacing between the cylinders affects the distribution of maximum dynamic pressure and vortices.
Article
Multidisciplinary Sciences
Wenlong Cao, Xueyan Wang, Yubo Liu, Yujie Yin, Jian Yang, Jianhui An
Summary: This study examines the aerodynamic characteristics and interference effects of chamfered square cylinders using large eddy simulation. The results show that the aerodynamic effects and interference effects of chamfered square cylinders are mainly controlled by the cross-wind interval and spacing.
SCIENTIFIC REPORTS
(2023)
Article
Materials Science, Multidisciplinary
Z. Babamahdi, V. B. Svetovoy, D. T. Yimam, B. J. Kooi, T. Banerjee, J. Moon, S. Oh, M. Enache, M. Stohr, G. Palasantzas
Summary: The film thickness plays a crucial role in determining the Casimir and electrostatic forces of topological insulating Bi2Se3 films. Thicker films can approach the genuine Casimir force after voltage compensation, while strong electrostatic effects lead to gradual deviation from theory in thinner films.
Article
Physics, Multidisciplinary
C. Romaniega
Summary: This study focuses on the electromagnetic Casimir-Lifshitz interaction between two bodies, specifically examining the fluctuation-induced pressure on the cavity wall. The research reveals that the sign of the pressure is independent of the geometry of the configuration.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Mathematics, Applied
F. Tajik, N. Allameh, A. A. Masoudi, G. Palasantzas
Summary: The study investigates the dynamical actuation of MEMS under the influence of Casimir forces between topological insulator plates, analyzing the impact of dielectric function and coating magnetization on the attractive and repulsive forces. The results show that the forces vary with the dielectric function and magnetization, affecting the stability and chaotic motion of the systems.
Article
Mechanics
Jia Tang, Yang Yang, Mingshui Li
Summary: This paper investigates the 2D AAFs of rectangular 5:1 cylinders within different turbulent flow fields. The 2D AAF is determined by removing the influence of the 3D effect from the traditional AAF, which can be derived based on the ratio of the one-dimensional fluctuating force spectrum to the one-dimensional turbulent wind spectrum. The traditional AAF values vary in response to the 3D effect and the dimensionless turbulent integral scale in different turbulent flow fields. The 2D AAF effectively reduces the discrepancies caused by the dimensionless turbulent integral scale.
Article
Optics
Joseph Durnin, Juliane Klatt, Robert Bennett, Stefan Yoshi Buhmann
Summary: Casimir-Polder interactions cause energy and momentum exchange between microscopic and macroscopic bodies. However, the dynamics of these effects have not been experimentally investigated because currently attainable atomic velocities are dominated by static effects. In this study, a more easily realizable setup involving a moving atom between two stationary plates is analyzed to establish the spectroscopic Casimir-Polder effects on the atom and their velocity dependence.
Article
Mathematics, Applied
Z. Dadi, A. A. Masoudi, F. Tajik, G. Palasantzas
Summary: This study discusses the stable actuation of a double beam torsional micro-actuator and focuses on finding the optimal distribution of electrostatic torque for maximum stable operation. The analysis shows the sensitivity of torque distribution on the optical properties of the moving component and the applied voltage. It is also demonstrated that applying the optimal torque distribution can reduce the possibility of chaotic motion and minimize the difference between systems with different optical contrast.
Article
Chemistry, Multidisciplinary
Oleg A. Vasilyev, Emanuele Marino, Bas B. Kluft, Peter Schall, Svyatoslav Kondrat
Summary: Fine-tuning interactions between particles can influence the structure of charged nanoparticles deposited on a substrate, with critical Casimir interactions decreasing significantly at the substrate. Experiments and simulations show self-assembly of nanoparticles into crystalline clusters and potential formation of fractal-like nanoparticle gels and bicontinuous phases. This research provides exciting opportunities for studying complex structures in optoelectronics and photonics.
Article
Astronomy & Astrophysics
Ivan A. Soldatenkov, Anastasiya A. Yakovenko, Vitaly B. Svetovoy
Summary: Technological progress has enabled precise measurements of small-scale forces, while the adhered cantilever method has provided more reliable data by avoiding pull-in instability.
Article
Biology
Julia Doelger, Arup K. Chakraborty, Mehran Kardar
Summary: The characteristic traits of virus families affect their ability to adapt to infect humans, spread novel human variants, and the risk of causing a global pandemic. The timing of virus spillover from animal reservoirs and global intervention efforts are crucial in preventing pandemics.
MATHEMATICAL BIOSCIENCES
(2022)
Article
Optics
Alec M. Hammond, Ardavan Oskooi, Mo Chen, Zin Lin, Steven G. Johnson, Stephen E. Ralph
Summary: We present a photonics topology optimization (TO) package that can address a wide range of practical photonics design problems. The package incorporates robustness and manufacturing constraints and can scale to large devices and massive parallelism. It employs a hybrid algorithm that solves multiple frequency-domain TO problems using a mature time-domain (FDTD) package and is enhanced by new filter-design sources and material-interpolation methods.
Article
Mechanics
I. Shukla, F. Wang, S. Mowlavi, A. Guyomard, X. Liang, S. G. Johnson, J. -c. Nave
Summary: Recent research has shown that feeding a silicon-in-silica coaxial fiber into a flame can result in the formation of silicon spheres with size controlled by feed speed. A reduced model to predict droplet size from feed speed has been derived, but quantitative validation has been challenging due to experimental uncertainties in parameter values and temperature profile. In this study, the reduced model was validated through three-dimensional simulations, showing excellent agreement across a range of feed speeds and constant capillary numbers at breakup location. This low-cost model is a useful tool for designing future experiments.
Article
Optics
Zin Lin, Raphael Pestourie, Charles Roques-Carmes, Zhaoyi Li, Federico Capasso, Marin Soljacic, Steven G. Johnson
Summary: We introduce end-to-end inverse design for multi-channel imaging, which involves optimizing a nanophotonic frontend and an image-processing backend to extract depth, spectral, and polarization channels from a single monochrome image. We demonstrate that subwavelength-scale metasurface designs can easily distinguish similar wavelength and polarization inputs, unlike diffractive optics. Our proposed technique combines a single-layer metasurface frontend with an efficient Tikhonov reconstruction backend, requiring only a grayscale sensor. Through spontaneous demultiplexing, our method achieves multi-channel imaging by separating different channels into distinct spatial domains on the sensor. We present large-area metasurface designs for multi-spectral imaging, depth-spectral imaging, and all-in-one spectro-polarimetric-depth imaging, demonstrating robust reconstruction performance.
Article
Physics, Applied
Mohammed Benzaouia, John D. Joannopoulos, Steven G. Johnson, Aristeidis Karalis
Summary: This study presents general analytical criteria for designing standard filters and demonstrates the method of designing filter devices through specific unitary coupling ratios. By solving a nonlinear optimization problem, filter design can be achieved, with a focus on elliptic filters for optimal performance.
PHYSICAL REVIEW APPLIED
(2022)
Article
Optics
Wenjie Yao, Francesc Verdugo, Henry O. Everit, Rasmus E. Christiansen, Steven G. Johnson
Summary: We propose a general framework for inverse design of nanopatterned surfaces that maximize surface-enhanced Raman spectra from randomly distributed molecules. Our optimized structures outperform coating with optimized spheres or bowtie structures by about 4 and 20 times, respectively, when considering nonlinear damage effects.
Article
Computer Science, Interdisciplinary Applications
Giuseppe Romano, Steven G. Johnson
Summary: In this study, a methodology for density-based topology optimization of non-Fourier thermal transport in nanostructures is introduced. It utilizes adjoint-based sensitivity analysis of the phonon Boltzmann transport equation (BTE) and a novel material interpolation technique called the transmission interpolation model (TIM). The approach is able to handle the interplay between real- and momentum-resolved material properties by parameterizing the material density with an interfacial transmission coefficient. This methodology allows for the systematic optimization of materials for heat management and conversion, as well as the design of devices where diffusive transport is not valid.
STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION
(2022)
Article
Nanoscience & Nanotechnology
Pengning Chao, Rodrick Kuate Defo, Sean Molesky, Alejandro Rodriguez
Summary: The local density of states (LDOS) plays a crucial role in photonics engineering. We propose a framework for evaluating upper bounds on LDOS in structured media, which can handle arbitrary bandwidths and considers wave scattering effects. We derive an analytical expression for the maximum LDOS and discover scaling laws for maximum LDOS enhancement, with implications on material selection and design applications.
Article
Optics
Mohammed Benzaouia, A. D. Stone, Steven G. Johnson
Summary: In this study, a general analysis is presented for finding and characterizing nonlinear exceptional point (EP) lasers above threshold. The stability of the EP laser is confirmed through numerical analysis, and a new method for characterizing the EP laser is proposed.
Article
Multidisciplinary Sciences
Andriy Goychuk, Deepti Kannan, Arup K. Chakraborty, Mehran Kardar
Summary: From proteins to chromosomes, polymers fold into specific conformations that control their biological function. Polymer folding has long been studied with equilibrium thermodynamics, yet intracellular organization and regulation involve energy-consuming, active processes. Signatures of activity have been measured in the context of chromatin motion, which shows spatial correlations and enhanced subdiffusion only in the presence of adenosine triphosphate. Moreover, chromatin motion varies with genomic coordinate, pointing toward a heterogeneous pattern of active processes along the sequence.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2023)
Article
Physics, Fluids & Plasmas
Daniel W. Swartz, Hyunseok Lee, Mehran Kardar, Kirill S. Korolev
Summary: This article presents a theory that integrates both competitive ability and colonization ability in mutant fitness. By solving mathematical equations, we identify three different regimes controlled by expansion rates, competitive abilities, or both, providing a simple framework for studying spatial competition.
Article
Optics
Sophie Fisher, Raphael Pestourie, Steven G. Johnson
Summary: This study presents a semianalytical framework for computing the coupling of radiative and guided waves in slowly varying surfaces. It fills the gap in current approximate methods by allowing the modeling of their coupling using a combination of two methods.
Article
Physics, Multidisciplinary
Lu Lu, Raphael Pestourie, Steven G. Johnson, Giuseppe Romano
Summary: This paper proposes a multifidelity neural operator based on deep neural networks, which can reduce the demand for high-fidelity data and achieve smaller errors in solving heat transport problems. By combining with genetic algorithms and topology optimization, it enables fast solvers and inverse design for the phonon Boltzmann transport equation (BTE).
PHYSICAL REVIEW RESEARCH
(2022)
Article
Physics, Fluids & Plasmas
Daniel W. Swartz, Bertrand Ottino-Loffler, Mehran Kardar
Summary: The Richards growth equation, frequently used in population modeling and pandemic forecasting, has been shown to emerge naturally from generic analytical growth rules in a distributed population with migration and stochastic growth rates. This connection provides a testable explanation for the fractional growth law observed in populations.
Article
Physics, Fluids & Plasmas
Julia Doelger, Mehran Kardar, Arup K. Chakraborty
Summary: There is currently a lack of effective long-term protective vaccines against viruses, such as seasonal influenza, that continuously evolve under immune pressure. Researchers have developed a computational method to infer the intrinsic mutational fitness landscape of viral proteins from yearly sequence data, which may have future implications in the design of immunization protocols.
