Orders Of Magnitude Change Research Articles

Jamming Memory into Acoustically Trained Dense Suspensions under Shear

Systems driven far from equilibrium often retain structural memories of their processing history. This memory has, in some cases, been shown to dramatically alter the material response. For example, work hardening in crystalline metals can alter the hardness, yield strength, and tensile strength to prevent catastrophic failure. Whether memory of processing history can be similarly exploited in flowing systems, where significantly larger changes in structure should be possible, remains poorly understood. Here, we demonstrate a promising route to embedding such useful memories. We build on work showing that exposing a sheared dense suspension to acoustic perturbations of different power allows for dramatically tuning the sheared suspension viscosity and underlying structure. We find that, for sufficiently dense suspensions, upon removing the acoustic perturbations, the suspension shear jams with shear stress contributions from the maximum compressive and maximum extensive axes that reflect or “remember” the acoustic training. Because the contributions from these two orthogonal axes to the total shear stress are antagonistic, it is possible to tune the resulting suspension response in surprising ways. For example, we show that differently trained sheared suspensions exhibit (1) different susceptibility to the same acoustic perturbation, (2) orders of magnitude changes in their instantaneous viscosities upon shear reversal, and (3) even a shear stress that increases in magnitude upon shear cessation. We work through these examples to explain the underlying mechanisms governing each behavior. Then, to illustrate the power of this approach for controlling suspension properties, we demonstrate that flowing states well below the shear jamming threshold can be shear jammed via acoustic training. Collectively, our work paves the way for using acoustically induced memory in dense suspensions to generate rapidly and widely tunable materials. Published by the American Physical Society 2024

Modeling of rapid solidification in Laser Powder Bed Fusion processes

This paper addresses a numerical framework for modeling site-specific microstructure evolution in Laser Powder Bed Fusion (LPBF), where rapid solidification significantly influences the microstructure and properties of manufactured components. The fine microstructure and rapid solidification can enhance mechanical properties in final parts, yet pose challenges in controlling microstructure and addressing potential defects. In this study, an in-house developed free surface thermo-fluidic Computational Fluid Dynamics (CFD) model is coupled with a binary alloy phase-field model characterized by rapid solidification kinetics. The CFD model considers complex fluid flows related to Marangoni and recoil pressure, laser-material interactions, and rapid melting and solidification of the melt pool. A convergence study for the phase-field model is conducted, comparing simulated partition coefficients with the Continuous Growth Model (CGM) theory. The study investigates the individual effects of temperature gradients and solidification rates on simulated microstructure. Results indicate that, for the same order of magnitude change, the solidification rate has a more pronounced effect on microstructure than temperature gradients. The paper concludes with the simulation of site-specific microstructure evolution within the melt pool, comparing the results with experiments conducted at varied scanning speeds. The predicted microstructure aligns well with experimental measurements, suggesting the potential utility of the developed phase-field model in quantitative microstructural modeling. Overall, this work contributes to understanding microstructure evolution under rapid solidification conditions, providing a fundamental basis for optimizing the LPBF process.

Electric control of optically-induced magnetization dynamics in a van der Waals ferromagnetic semiconductor

Electric control of magnetization dynamics in two-dimensional (2D) magnetic materials is an essential step for the development of novel spintronic nanodevices. Electrostatic gating has been shown to greatly affect the static magnetic properties of some van der Waals magnets, but the control over their magnetization dynamics is still largely unexplored. Here we show that the optically-induced magnetization dynamics in the van der Waals ferromagnet Cr2Ge2Te6 can be effectively controlled by electrostatic gates, with a one order of magnitude change in the precession amplitude and over 10% change in the internal effective field. In contrast to the purely thermally-induced mechanisms previously reported for 2D magnets, we find that coherent opto-magnetic phenomena play a major role in the excitation of magnetization dynamics in Cr2Ge2Te6. Our work sets the first steps towards electric control over the magnetization dynamics in 2D ferromagnetic semiconductors, demonstrating their potential for applications in ultrafast opto-magnonic devices.

Ion transport induced room-temperature insulator-metal transition in single-crystalline Cu2Se.

Cu2Se is a superionic conductor above 414 K, with ionic conductivities reaching that of molten salts. The superionic behavior results from hopping Cu ions between different crystallographic sites within the Se scaffold. However, the properties of Cu2Se below 414 K are far less known due to experimental limitations imposed by the bulk or polycrystalline samples that have been available so far. Here, we report the synthesis of ultra-thin, large-area single crystalline Cu2Se samples using a chemical vapor deposition method. The as-synthesized Cu2Se crystals exhibit optically and electrically detectable and controllable robust phases at room temperature and above. We demonstrate that Cu ion vacancies can be manipulated to induce an insulator-metal transition, which exhibits 6 orders of magnitude change in the electrical resistance of two terminal devices, accompanied by an optical change in the phase configuration. Our experiments show that the high mobility of the liquid-like Cu ion vacancies in Cu2Se causes macroscopic ordering in the Cu vacancies. Consequently, phase distribution over the crystals is not dictated by the diffusive motion of the ions but by the local energy minima formed due to the phase transition. As a result, long-range vacancy ordering of the crystal below 414 K becomes optically observable at a micrometer scale. This work demonstrates that Cu2Se could be a prototypical system where long-range ordering properties can be studied via electrical and optical methods.

Phase Transition Engineering of Vanadium Dioxide Induced by Oxygen Vacancies

A reconfigurable optical functional system is a pioneering and comprehensive approach for portable future flexible electronics, irrespective of traditional silicon-based technology. VO2 shows tremendous temperature-dependent structural and electrical phase transitions as a complex correlated metal oxide, presenting it as a potential candidate for bolometers, thermal camouflage, and optoelectronics applications. However, the structural stability and high transition temperature restrict room-temperature applications. The present study reports the oxygen vacancies-assisted phase transition engineering in the VO2/muscovite heterostructure. The ion bombardment alters the oxygen stoichiometry of VO2/muscovite thin film at room temperature. A significant decrease in lattice constant has been observed during the transition of the insulating M1 (monoclinic) phase into the metallic R (tetragonal) phase, which was confirmed through high-resolution XRD. The change in oxygen vacancy concentration determined using X-ray photoelectron spectroscopy (XPS) actively suppressed and stabilized the epitaxial thin film of VO2 near room temperature. We investigated whether applying increasing power-mediated ion bombardment for a few minutes affects the oxygen vacancy formation on the VO2/muscovite film’s surface. Consequently, a change in KPFM and 4 orders of magnitude change in resistance of VO2 thin film have been observed. This report reveals the fundamental understanding of controlling the MIT in epitaxial VO2 thin film via facile and clean phase transition engineering techniques for advanced flexible electronic devices.

Programmable all-DNA hydrogels based on rolling circle and multiprimed chain amplification products.

Soft, biocompatible, and tunable materials offer biomedical engineers and material scientists programmable matrices for a variety of biomedical applications. In this regard, DNA hydrogels have emerged as highly promising biomaterials that offer programmable self-assembly, superior biocompatibility, and the presence of specific molecular identifiable structures. Many types of DNA hydrogels have been developed, yet the programmability of the DNA building blocks has not been fully exploited, and further efforts must be directed toward understanding how to finely tune their properties in a predictable manner. Herein, we develop physically crosslinked all-DNA hydrogels with tunable morphology and controllable biodegradation, based on rolling circle amplification and multiprimed chain amplification products. Through molecular engineering of the DNA sequences and their nano-/microscale architectures, the precursors self-assemble in a controlled manner to produce soft hydrogels in an efficient, cost-effective, and highly tunable manner. Notably, we develop a novel DNA microladder architecture that serves as a framework for modulating the hydrogel properties, including over an order of magnitude change in pore size and up to 50% change in biodegradation rate. Overall, we demonstrate how the properties of this DNA-based biomaterial can be tuned by modulating the amounts of rigid double-stranded DNA chains compared to flexible single-stranded DNA chains, as well as through the precursor architecture. Ultimately, this work opens new avenues for the development of programmable and biodegradable soft materials in which DNA functions not only as a store of genetic information but also as a versatile polymeric biomaterial and molecularly engineered macroscale scaffold.

Ultrathin VO2 grown with oxygen plasma molecular beam epitaxy on TiO2 (001) and Al2O3 (0001)

Bulk VO2 undergoes an insulator-to-metal transition (IMT) with up to five orders of magnitude change in the resistance at 340 K. However, when VO2 is deposited as a film on a substrate, the strain from the substrate can alter the IMT temperature, resistivity ratio of IMT, and hysteresis. Here, we present single-phase VO2 ultrathin films (thickness less than 20 nm) grown using oxygen plasma molecular beam epitaxy (MBE) on TiO2 (001) and Al2O3 (0001) substrates. First, we modify existing recipes employing ozone MBE and reproduce the best films from literature on TiO2 (001), maintaining an almost three orders of magnitude transition in a 12 nm thick film with TIMT of 308 K (296 K) upon warming (cooling). We then extend our recipe to Al2O3 (0001) substrates where we stabilize a 12 nm thin single-phase VO2 film and observe two orders of magnitude transition at 337 K (329 K) upon warming (cooling), expanding the possible growth methods for ultrathin VO2 films on Al2O3 (0001).

Growth mechanisms and anisotropic softness–dependent conductivity of orientation-controllable metal–organic framework nanofilms

Conductive metal-organic frameworks (cMOFs) manifest great potential in modern electrical devices due to their porous nature and the ability to conduct charges in a regular network. cMOFs applied in electrical devices normally hybridize with other materials, especially a substrate. Therefore, the precise control of the interface between cMOF and a substrate is particularly crucial. However, the unexplored interface chemistry of cMOFs makes the controlled synthesis and advanced characterization of high-quality thin films, particularly challenging. Herein, we report the development of a simplified synthesis method to grow "face-on" and "edge-on" cMOF nanofilms on substrates, and the establishment of operando characterization methodology using atomic force microscopy and X-ray, thereby demonstrating the relationship between the soft structure of surface-mounted oriented networks and their characteristic conductive functions. As a result, crystallinity of cMOF nanofilms with a thickness down to a few nanometers is obtained, the possible growth mechanisms are proposed, and the interesting anisotropic softness-dependent conducting properties (over 2 orders of magnitude change) of the cMOF are also illustrated.

Size-induced metal–insulator transition temperature decrease of VO2 nanoparticles obtained by laser irradiation in water

Vanadium dioxide (VO2) is a highly attractive and multifunctional material for technological applications due to its metal–insulator transition, which is accompanied by several orders of magnitude changes in electrical resistivity and optical transmissivity. In this work, we report on the metal–insulator transition of VO2 nanoparticles which are produced by a simple, efficient, and low-cost two-step preparation method based on infrared laser irradiation of V2O5 powder dispersed in water and subsequent stoichiometric stabilization by vacuum annealing at 773 K. VO2 nanoparticles have an average size of 36 nm with facet-like contours and undergo a structural phase transition from a monoclinic to a tetragonal phase, accompanied by a metal–insulator transition occurring around 323 K, which is about 17 K lower than bulk VO2. No evidence of the formation of intermediary metastable phases is observed. Our findings reveal that the size of VO2 nanoparticles is a key parameter to moving the transition closer to room temperature, which is important for many applications.

Regulating Exciton De-Trapping of Te4+ -Doped Zero-Dimensional Scandium-Halide Perovskite for Fluorescence Thermometry with Record High Time-Resolved Thermal Sensitivity.

Fluorescence thermometry has been propelled to the forefront of scientific attention due to its high spatial resolution and remote non-invasive detection. However, recent generations of thermometers still suffer from limited thermal sensitivity (Sr ) below 10% change per Kelvin. Herein, this work presents an ideal temperature-responsive fluorescence material through Te4+ -doped 0D Cs2 ScCl5 ·H2 O, in which isolated polyhedrons endow highly localized electronic structures, and the strong electron-phonon coupling facilitates the formation of self-trapped excitons (STEs). With rising temperature, the dramatic asymmetric expansion of the soft lattice induces increased defects, strong exciton-phonon coupling, and low thermal activation energy, which evokes a rapid de-trapping process of STEs, enabling several orders of magnitude changes in the fluorescence lifetime over a narrow temperature range. After regulating the de-trapping process with different Te4+ doping, a record-high Sr (27.36% K-1 ) of fluorescence lifetime-based detection is achieved at 325 K. The robust stability against multiple heating/cooling cycles and long-term measurements enables a low temperature uncertainty of 0.067 K. Further, the developed thermometers are demonstrated for the remote local monitoring of operating temperature on internal electronic components. It is believed that this work constitutes a solid step towards building the next generation of ultrasensitive thermometers based on low-dimensional metal halides.

Effect of florfenicol on nirS-type denitrifying communities structure of water in an aquatic microcosm model.

Florfenicol is used worldwide for its low side effects and strong bactericidal effect. Florfenicol is physicochemically stable and can persist in natural water bodies and affect water denitrification. Indoor aquatic microcosm models were constructed and water samples were collected at different florfenicol concentrations (0.1, 1, 10, and 100 mg/L) on days 0, 7, 30, and 60 to extract the microbial genome DNA and determine the water properties. qPCR and amplicon sequencing were used to study the dynamic changes of nirS gene and nirS-type denitrifying communities structure, diversity and abundance, respectively. The results showed that higher florfenicol concentrations caused accumulation of nitrate and ammonium nitrogen in water. Florfenicol stress caused orders of magnitude changes in nirS gene abundance, showing a trend of increasing first and then decreasing. 100 mg/L florfenicol addition led to a sustained increase of nirS gene abundance in water bodies. The florfenicol addition altered denitrifying community structure and suppressed the richness and diversity index of denitrifying bacteria in water body. Over time, the richness and diversity index gradually recovered. Proteobacteria was always the dominant denitrifying phylum in water. The relative abundance of Pseudomonas and beta proteobacterium showed obvious positive correlation with nirS gene abundance and were the dominant genera under florfenicol stress. Our study provided a scientific basis for the rational use of florfenicol in aquaculture to maintain a healthy and stable microecological environment, and also provided a preliminary understanding of the response characteristics of water denitrifying microorganisms to florfenicol exposure.

Tunable, thiol-ene, interpenetrating network hydrogels of norbornene-modified carboxymethyl cellulose and cellulose nanofibrils

Carboxymethyl cellulose modified with norbornene groups (NorCMC) and cellulose nanofibrils (CNFs) produced through mechanical refining without chemical pretreatment formed interpenetrating network hydrogels through a UV-light initiated thiol-ene reaction. The molar ratio of thiols in crosslinkers to norbornene groups off the NorCMC (T:N), total polymer weight percent in the hydrogel, and weight percent of CNFs of the total polymer content of the hydrogels were varied to control hydrogel properties. This method enabled orders of magnitude changes to behavior. Swelling in aqueous environments could be significant (>150 %) without CNFs to minimal (<15 %) with the use of 50 % CNFs. NorCMC and CNF networks interacted synergistically to create hydrogels with compression modulus values spanning 1 to 150 kPa - the values of most biological tissues. T:N and total polymer weight percent could be varied to create hydrogels with different CNF content, but the same compression modulus, targeting 10 and 100 kPa hydrogels and providing a system that can independently vary fibrillar content and bulk modulus. Analysis of the effective crosslinks, thiol-ene network mesh size, and burst release of the polymer indicated synergistic interactions of the NorCMC thiol-ene and CNFs networks. These interactions enhanced modulus and degradation control of the network under physiological conditions.

Ladder-type conjugated molecules as robust multi-state single-molecule switches

•Synthesis of a methylthio-functionalized, ladder-type oligoaniline derivative •Excellent stability and high molecular conductance in oxidized and protonated states •Robust switching of single-molecule conductance among three different states Ladder-type molecular structures greatly enhance the chemical stability of oligoaniline derivatives and impart well-defined physical properties to multiple molecular charge states. In this work, we characterize the charge transport properties of a ladder-type cyclohexadiene-1,4-diimine derivative at various protonation, lithiation, and oxidation states using single-molecule techniques. Our results show that a ladder-type oligoaniline derivative serves as a robust and reversible molecular switch with over two orders of magnitude changes in molecular conductance when controlled using chemical or electrochemical stimuli. Experimental results are complemented by molecular modeling using density functional theory (DFT) and nonequilibrium Green’s function-DFT (NEGF-DFT) to elucidate charge transport mechanisms at different molecular states. Overall, this work provides new strategies for advancing the stability, programmability, and efficiency of molecular charge transport using ladder-type single-molecule switches. Ladder-type molecular structures greatly enhance the chemical stability of oligoaniline derivatives and impart well-defined physical properties to multiple molecular charge states. In this work, we characterize the charge transport properties of a ladder-type cyclohexadiene-1,4-diimine derivative at various protonation, lithiation, and oxidation states using single-molecule techniques. Our results show that a ladder-type oligoaniline derivative serves as a robust and reversible molecular switch with over two orders of magnitude changes in molecular conductance when controlled using chemical or electrochemical stimuli. Experimental results are complemented by molecular modeling using density functional theory (DFT) and nonequilibrium Green’s function-DFT (NEGF-DFT) to elucidate charge transport mechanisms at different molecular states. Overall, this work provides new strategies for advancing the stability, programmability, and efficiency of molecular charge transport using ladder-type single-molecule switches.

Active control of terahertz waves based on hybrid VO2 periodic corrugated waveguides.

We describe a method for the active control of terahertz (THz) waves using hybrid vanadium dioxide (VO2) periodic corrugated waveguide. Unlike liquid crystals, graphene and semiconductors and other active materials, VO2 exhibits a unique insulator-metal transition characteristic by the electric fields, optical, and thermal pumps, resulting in five orders of magnitude changes in its conductivity. Our waveguide consists of two gold coated plates with the VO2-embedded periodic grooves, which are placed in parallel with the grooves face to face. Simulations show that this waveguide can realize mode switching by changing the conductivity of the embedded VO2 pads, whose mechanism is attributed to the local resonance induced by defect mode. Such a VO2-embedded hybrid THz waveguide is favorable in practical applications such as THz modulators, sensors and optical switches, and provides an innovative technique for manipulating THz waves.

Graphene Strain-Effect Transistor with Colossal ON/OFF Current Ratio Enabled by Reversible Nanocrack Formation in Metal Electrodes on Piezoelectric Substrates

Extraordinarily high carrier mobility in graphene has led to many remarkable discoveries in physics and at the same time invoked great interest in graphene-based electronic devices and sensors. However, the poor ON/OFF current ratio observed in graphene field-effect transistors has stymied its use in many applications. Here, we introduce a graphene strain-effect transistor (GSET) with a colossal ON/OFF current ratio in excess of 107 by exploiting strain-induced reversible nanocrack formation in the source/drain metal contacts with the help of a piezoelectric gate stack. GSETs also exhibit steep switching with a subthreshold swing (SS) < 1 mV/decade averaged over ∼6 orders of magnitude change in the source-to-drain current for both electron and hole branch amidst a finite hysteresis window. We also demonstrate high device yield and strain endurance for GSETs. We believe that GSETs can significantly expand the application space for graphene-based technologies beyond what is currently envisioned.

Tamm Plasmon Polaritons Hydrogen Sensors

AbstractTamm plasmon polariton (TPP) resonance can be excited within the stopband of a distributed Bragg reflector (DBR) by combining a thin metal film. When exposured to hydrogen gas, the TPP resonance feature is redshifted for the TPPs structure with palladium (Pd) on the top, due to hydrogen‐induced palladium lattice expansion. By utilizing a DBR‐side TPP structure, near‐zero reflectance can be achieved, leading to more than 3 orders of magnitude changes in reflectance compared to metal‐side TPP structure. The proposed TPP hydrogen structure enables the detection with low H2 concentration from 0.5% to 4%. Comparing to the only Pd film, TPP sensor has increased the sensitivity about 100% at visible wavelengths.

Effect of beneficial sweeps and background selection on genetic diversity in changing environments

Neutral theory predicts that the genetic diversity within a population is proportional to the effective population size. In contrast, the observed genetic diversity for various species vary in a narrow range for several orders of magnitude change in the population sizes (Lewontin’s paradox). The selective sweeps and background selection, reduce the genetic variation at the linked neutral sites and have been studied considering the environment to be selectively constant. However, in a natural population, the selective environment varies with time. Here, we investigate the impact of selective sweeps and background selection on neutral genetic diversity when the selection coefficient changes periodically over time. The reduction in genetic variation due to selective sweeps is known to depend on the conditional fixation time. Here, we find that the effect of changing environment on conditional mean fixation time is most substantial for the randomly mating population than the inbreeding population with arbitrary inbreeding coefficient. We also study the effect of background selection on neutral sites when the selection coefficient of linked deleterious mutation change periodically in time. In the slowly changing environment, we find that neutral heterozygosity is significantly different, and the site frequency spectrum has a different shape than that in the static environment.

Vertical and horizontal gene transfer tradeoffs direct plasmid fitness

Plasmid fitness is directed by two orthogonal processes—vertical transfer through cell division and horizontal transfer through conjugation. When considered individually, improvements in either mode of transfer can promote how well a plasmid spreads and persists. Together, however, the metabolic cost of conjugation could create a tradeoff that constrains plasmid evolution. Here, we present evidence for the presence, consequences, and molecular basis of a conjugation‐growth tradeoff across 40 plasmids derived from clinical Escherichia coli pathogens. We discover that most plasmids operate below a conjugation efficiency threshold for major growth effects, indicating strong natural selection for vertical transfer. Below this threshold, E. coli demonstrates a remarkable growth tolerance to over four orders of magnitude change in conjugation efficiency. This tolerance fades as nutrients become scarce and horizontal transfer attracts a greater share of host resources. Our results provide insight into evolutionary constraints directing plasmid fitness and strategies to combat the spread of antibiotic resistance.

An Ultra-steep Slope Two-dimensional Strain Effect Transistor.

We introduce a high-performance and ultra-steep slope switch, referred to as strain effect transistor (SET), with a subthreshold swing < 0.68 mV/decade at room temperature for 7 orders of magnitude change in the source-to-drain current based on atomically thin 1T'-MoTe2 as the channel material, piezoelectric lead zirconate titanate (PZT) as the gate dielectric, and nickel (Ni) as the source/drain contact metal. We exploit gate-voltage induced strain transduction in PZT leading to abrupt and reversible cracking of the metal contacts to achieve the abrupt switching. The SET also exhibits a low OFF-state current < 1 pA/μm, a high ON-state current > 1.8 mA/μm at a supply voltage of 1 V, a large current ON/OFF ratio > 1 × 109, and a high transconductance of > 100 μS/μm. The switching delay for the SET was found to be < 5 μs, and no device failure was observed even after 1 million (1 × 106) switching cycles.

Capturing the start point of the virus-cell interaction with high-speed 3D single-virus tracking.

The early stages of the virus-cell interaction have long evaded observation by existing microscopy methods due to the rapid diffusion of virions in the extracellular space and the large three-dimensional cellular structures involved. Here we present an active-feedback single-particle tracking method with simultaneous volumetric imaging of the live cell environment called 3D-TrIm to address this knowledge gap. 3D-TrIm captures the extracellular phase of the infectious cycle in what we believe is unprecedented detail. We report what are, to our knowledge, previously unobserved phenomena in the early stages of the virus-cell interaction, including skimming contact events at the millisecond timescale, orders of magnitude change in diffusion coefficient upon binding and cylindrical and linear diffusion modes along cellular protrusions. Finally, we demonstrate how this method can move single-particle tracking from simple monolayer culture toward more tissue-like conditions by tracking single virions in tightly packed epithelial cells. This multiresolution method presents opportunities for capturing fast, three-dimensional processes in biological systems.