The solution structure and the stability of a tungsten emitter operating in vacuum are numerically investigated. A one-dimensional nonlinear electrothermal model is developed by combining the reformulated general thermal-field emission model with the thermal balance over the emitter. Two solutions have been identified, one stable and one unstable. The key factor for this monostable behavior, as compared with the bistability of carbon nanotubes, is the quadratic dependence of the electric resistivity on the temperature, which drives the Joule heating term out of thermal equilibrium once the instability threshold (singular point) is exceeded. The model may explain the experimentally observed bending (change of slope) of the current-voltage curves, predicting the existence of two break points, the first one signifying the departure from linearity on a Millikan–Lauritzen plot, and the second one on the path to the instability threshold and the thermal runaway. The second break point is a key feature of the present combined electrothermal model that cannot be explained by space charge or dynamic image forces effects as it is determined by the departure from the equilibrium between heat dissipation and heat generation.

Atomic force microscopy (AFM) enables high-resolution imaging and quantitative force measurement, which are critical for understanding nanoscale mechanical, chemical, and biological interactions. In dynamic AFM modes, however, interaction forces are not directly measured; they must be mathematically reconstructed from observables such as the amplitude, phase, or frequency shift. Many reconstruction techniques have been proposed over the last two decades, but they rely on different assumptions and have been applied inconsistently, limiting reproducibility and cross-study comparison. Here, we systematically evaluate major force reconstruction methods in both frequency- and amplitude-modulation AFM, detailing their theoretical foundations, performance regimes, and sources of error. To support benchmarking and reproducibility, we introduce an open-source software package that unifies all widely used methods, enabling side-by-side comparisons across different formulations. This work represents a critical step toward achieving consistent and interpretable AFM force spectroscopy, thereby supporting the more reliable application of AFM in fields ranging from materials science to biophysics.

To migrate efficiently through tissues, cells must transit through small constrictions within the extracellular matrix. However, in vivo environments are geometrically, mechanically, and chemically complex, and it has been difficult to understand how each of these parameters contribute to the propulsive strategy utilized by cells in different confining environments. To address this, we employed a sacrificial micromolding approach to generate polymer substrates with tunable stiffness, controlled adhesivity, and user-defined microscale geometries. We combined this together with live-cell imaging and three-dimensional traction force microscopy to quantify the forces that cells use to transit through constricting channels. Surprisingly, rather than enlarging the constriction via pushing forces, we observe that mesenchymal cells migrating through compliant constrictions generate inwardly directed contractile forces that decrease the size of the opening and pull the channel walls closed around the nucleus. This had the effect of increasing nuclear deformation compared to cells migrating through comparably sized rigid confinements. Additionally, the nucleus took longer to transit through compliant constrictions compared to similarly sized rigid constrictions. These findings show that nuclear deformation during confined migration can be accomplished by internal cytoskeletal machinery rather than by reactive forces from the substrate, and our approach provides a mechanism to test between different models for how cells translocate their nucleus through narrow constrictions. The methods, analysis, and results presented here will be useful to understand how cells choose between propulsive strategies in different physical environments.

Background: Impaired balance is one of the most common and functionally limiting problems in children with cerebral palsy (CP), significantly affecting their motor abilities and quality of life. Although force platforms are considered the gold standard for evaluating postural stability, they are often costly, non-portable, and require specialized laboratory environments, limiting their accessibility in routine clinical settings. Objective: This study aimed to develop a novel software program based on image processing techniques to assess static balance in children with CP and to evaluate its validity against traditional force platform measurements. Methods: A total of 83 children aged 5–15 years (63 with CP, GMFCS levels I–II; 20 healthy controls) participated. Static balance was assessed under four different standing conditions using both a force platform and a newly developed video-based software tool. The software utilized the frame difference method to detect center of mass movements, and parameters such as velocity and total displacement were calculated. Correlation analyses were conducted between the image processing and force platform data. Results: The software demonstrated moderate to strong positive correlations with force platform parameters in the majority of test conditions, particularly when participants stood with eyes open. In more challenging balance scenarios (e.g., eyes closed, feet together), correlations were weaker but still significant. Conclusions: The findings suggest that this image-based software is a valid, low-cost, and portable alternative for static balance assessment in children with CP. It has the potential for use in diverse clinical or home settings, supporting individualized rehabilitation strategies.

Cell behavior and cell fate are impacted by electric currents or fields that are endogenous or externally applied. Static electric signals can be applied in customized microfluidic devices to mimic the electric environment in slow physiological processes such as development, wound healing, and homeostasis. An important class of cellular electric studies is the control of cell migration by static in-plane galvanic currents in simple microfluidic channels mimicking wound currents, with current densities of ~0.1-1000 A/m2. However, due to incompatible geometry, these devices are not appropriate to study electric effects in tissue homeostasis, where cells adopt apico-basal polarity and a transepithelial potential difference (TEPD). Here, we detail a unique microfluidic-based device that applies physiological ion currents perpendicular to the plane of confluent epithelial cell layers to perturb the TEPD and investigate electrical regulation of tissue steady states. The setup is made from a two-layer UV-curable polymer embedded with soft, polyacrylamide gel substrate coated with extracellular-matrix protein of choice. This microfluidic device provides the correct geometry and permeable substrate to induce a relatively uniform ion current across the cell layers of centimetric-scale. The setup is compatible with confocal live-cell imaging and Traction Force Microscopy to infer mechanical stresses induced by the transepithelial currents. Strikingly, the proliferation, extrusion and migration of cells are collectively influenced within the confluent epithelium depending on the direction of ion current, inducing a new tissue state characterized by different cell-cell interaction strengths, cell events (death and proliferation), and tissue structures. The electrically controlled cell behaviors can be understood as an electrically induced mechanical stress and cell response. This novel microfluidic device and protocol provide the tool and documentation required for the mechanobiology and bioengineering communities to study electric effects in tissue homeostasis and develop novel tissue engineering applications.

The artificial intelligence (AI) can accelerate the meta‐optics design by rapidly predicting the transmission coefficients of individual meta‐atoms. However, extensive optimization iterations are usually required to complete the desired metasurface consisting of massive meta‐atoms. For designing meta‐holography, any change to the target image forces the whole process to repeat, resulting in lengthy computation time. Here, a physics‐driven self‐supervised network (PDSS‐Net) built upon AI‐assisted optimization frameworks are proposed to further expedite the design process. The encoder‐decoder module introduced into the PDSS‐Net can establish a mapping between the input holographic images and the output structural parameters of all meta‐atoms. After self‐supervised training, the network learns this mapping and enables iteration‐free inference for inputs beyond the training dataset. The design of 2K‐resolution, three‐wavelength‐multiplexed meta‐holograms is completed within one second, achieving a computational speedup exceeding 1000‐fold over conventional optimization‐based approaches. By retraining, more complex tasks are achieved as demonstrated in the design of both the wavelength‐polarization‐depth multiplexed scalar and vectorial meta‐holograms. This iteration‐free computational paradigm with adaptability in typical multiplexed meta‐optics can be applied to the intelligent design of multifunctional metasurfaces, facilitating large‐scale applications of meta‐devices.

Nanoscale field emitters develop strong curvature-induced transverse confinement under applied electrostatic fields, a physical effect absent in conventional Fowler–Nordheim-type models. In this work, we show that this confinement introduces geometric zero-point energy that effectively raises the potential barrier encountered by tunneling electrons. As a result, the tunneling probability is suppressed through a semiclassical correction to the Gamow exponent. By modeling the quantum state of the tunneling electron with a Gaussian ansatz that captures its transverse confinement, we derive a correction term, ε, that scales as ε∼(λR)−1/2(I/νF), where λ is the tunneling length, R is the apex radius of the emitter, I a barrier integral influenced by geometry and image forces, and νF the Burgess–Kroemer–Houston function. This curvature-induced transverse quantization alters the predicted local emission current due to the exponential sensitivity of tunneling probabilities. In large emitter arrays, it leads to measurable deviations in total current that can affect device performance and spatial resolution. These findings highlight the need for improved field emission models that incorporate the quantum confinement effects associated with the classical transverse curvature of the electrostatic potential around the emitter apex, particularly in applications, such as vacuum nanoelectronics, high-precision lithography, and compact electron sources.

Abstract Magnetoelectric nanoparticles (MENPs) show promise for targeted cancer therapy due to their magnetoelectric properties and selective interaction with biological systems. Experimental evidence highlights their high‐specificity, field‐controlled targeting of cancer cells without bioreagents, yet the physical mechanisms remain unclear. This study explores MENPs’ selective affinity for malignant tissue, focusing on conductivity and capacitance differences. A MATLAB simulation is developed to model MENP interactions with cancer and healthy cell membranes from intravenous injection to targeting. The framework integrated Brownian motion, intermolecular forces—van der Waals attraction, Coulombic repulsion, and dipole image forces—parameterized with literature‐derived electrical properties. Magnetic field effects are simulated in 3D tensor form to assess targeting specificity. MATLAB simulations revealed that MENPs’ surface charge minimizes protein adsorption, enhancing circulation time, while the enhanced permeability retention effect aids tumor accumulation. Cancer cells’ lower negative charge reduces repulsion, enabling closer MENP approach. At short distances, higher membrane capacitance in cancer cells amplifies dipole image forces, increasing attachment compared to healthy cells. Simulated force profiles and particle distributions confirmed a specificity factor favoring cancer cells, enhanced by magnetic modulation. These findings underscore MENPs’ potential for cancer‐specific targeting. The framework provides a theoretical foundation for optimizing MENP design and advancing their therapeutic application.

Since the 1940s, infrared (IR) spectroscopy has been a reference technique for quantitative and qualitative analysis of organic materials (1). Modern IR spectroscopy now offers diverse non-destructive methods that adapt to various sample types, geometries, phases, and textures. By measuring how light interacts with matter at specific wavelengths, IR spectroscopy generates spectra with unique signatures, crucial for chemical identification. However, its spatial resolution is limited by the diffraction of light, restricting it to the micrometer scale when coupled to microscopy imaging (2).To overcome this, in 1995, Wickramasinghe’s group introduced a groundbreaking combination of atomic force microscopy (AFM) with IR spectroscopy, achieving sub-10 nm spatially resolved chemical imaging (3). This development advanced further with the advent of photoinduced force microscopy (PiFM) in 2010, a tip-based, light-independent technique that enables high-resolution nanoscale chemical contrast (4). PiFM is now recognized as a leading-edge tool in surface nanospectroscopy and nanochemical metrology (5).In this presentation, I showcase PiFM’s unparalleled capabilities in characterizing on-surface synthesized organic nanofilms derived from electrochemical reduction of aryl diazonium salts on glassy carbon and template-stripped gold surfaces. Using both bulk and localized electrochemical deposition techniques within a three-electrode setup and scanning electrochemical cell microscopy, we achieved tunable nanofilm properties by varying salt functional groups and solvents (6). This work presents the first simultaneous nanochemical identification and nanoimaging of these organic nanofilms with spatial resolution down to ~5–7 nm. Detailed analysis of the molecular densities, structures, and morphologies of these films using electrochemical and spectroscopy techniques provides novel insights into grafted nanofilms’ surface and interface electrochemistry applicable to electronics, optics, coatings, sensing, and beyond.(1) Thomas, N. C., The early history of spectroscopy. Journal of Chemical Education 1991, 68 (8), 631, 10.1021/ed068p631.(2) Shen, J.; Noh, B.-I.; Chen, P.; Dai, S., Scanning Probe Nano-Infrared Imaging and Spectroscopy of Biochemical and Natural Materials. Small Science 2024, 2400297, 10.1002/smsc.202400297.(3) Zenhausern, F.; Martin, Y.; Wickramasinghe, H. K., Scanning Interferometric Apertureless Microscopy: Optical Imaging at 10 Angstrom Resolution. Science 1995, 269 (5227), 1083-1085, 10.1126/science.269.5227.1083.(4) Rajapaksa, I.; Uenal, K.; Wickramasinghe, H. K., Image force microscopy of molecular resonance: A microscope principle. Applied Physics Letters 2010, 97 (7), 073121, 10.1063/1.3480608.(5) Jafari, M.; Nowak, D. B.; Huang, S.; Carlos Abrego, J.; Yu, T.; Du, Z.; Hammouti, B.; Jeffali, F.; Touzani, R.; Ma, D.; Siaj, M., Photo-induced force microscopy applied to electronic devices and biosensors. Materials Today: Proceedings 2023, 72, 3904-3910, 10.1016/j.matpr.2022.10.216.(6) Jafari, M.; Salek, S.; Goubert, G.; Byers, J. C.; Siaj, M., Photo-Induced Force Microscopy-Based Spectroscopy and Chemical Mapping of Grafted Electrochemically Reduced Aryl Diazonium Salts. The Journal of Physical Chemistry C 2024, 10.1021/acs.jpcc.4c04226.Graphical Figure 1

Integrin tensions are important force signals mediating platelet adhesion and contraction, and may also participate in platelet activation in response to substrate stiffness, a process referred as platelet stiffness sensing. Here, we characterized integrin tensions during platelet adhesion and stiffness sensing by simultaneously imaging force signals and associated cellular structures at submicron resolution. Our findings identified two distinct mechanisms governing integrin tension generation in platelets. Actomyosin contraction, regulated by MLCK but not ROCK (contrary to nucleated cells), generates integrin tensions in a focal adhesion (FA)-like pattern at the platelet's central region. Independently, F-actin polymerization, mediated by Rac1 and Arp2/3, produces integrin tensions in a ring-like pattern at the cell periphery. We further tested platelet activation on elastic substrates while imaging or restricting integrin tensions. The results indicate that although substrate stiffness strongly modulates integrin tensions in preactivated platelets, this modulation may not play a primary role in platelet stiffness sensing.

Intermediate filaments are key regulators of cell mechanics. Vimentin, a type of intermediate filament expressed in mesenchymal cells and involved in migration, forms a dense network in the cytoplasm that is constantly remodeling through filament transport, elongation/shortening, and subunit exchange. While it is known that filament elongation involves end-to-end annealing, the reverse process of filament shortening by fragmentation remains unclear. Here, we use a combination of in vitro reconstitution, probed by fluorescence imaging and atomic force microscopy, with theoretical modeling to uncover the molecular mechanism involved in filament breakage. We first show that vimentin filaments are composed of two populations of subunits, half of which are exchangeable and half immobile. We also show that the exchangeable subunits are tetramers. Furthermore, we reveal a mechanism of continuous filament self-repair, where a soluble pool of vimentin tetramers in equilibrium with the filaments is essential to maintain filament integrity. Filaments break due to local fluctuations in the number of tetramers per cross-section, induced by the constant subunit exchange. We determine that a filament tends to break if approximately four tetramers are removed from the same filament cross-section. Finally, we analyze the dynamics of association/dissociation and fragmentation to estimate the binding energy of a tetramer to a complete versus a partially disassembled filament. Our results provide a comprehensive description of vimentin turnover and reveal the link between subunit exchange and fragmentation.

Measuring contractile forces in vascular smooth muscle cells.

Achieving both high precision and efficiency in edge devices presents a notable challenge in neuromorphic computing. Conventional neuristors typically operate with fixed computational precision, forcing a trade-off between accuracy and efficiency when addressing tasks of varying complexity. To overcome this limitation, we propose a Schottky barrier neuristor that combines high-efficiency nonlinear logic with high-precision linear operations within a single device. A distinctive global bottom gate modulates the Schottky barrier, maintaining a linear relationship between gate voltage and transconductance. Furthermore, electrostatic doping-induced image force effects, alongside an optimized source-drain work function, enable uniform and symmetric n-/p-type modulation, enhancing the driving capability. This innovative design supports the development of reconfigurable digital-analogue units, requiring only one-fifth the number of devices needed for nonlinear functions compared to silicon. Simulations demonstrate that an accelerator based on this device achieves 98.3% accuracy and an energy efficiency of 1359.62 TOPS/W.

The enzyme SMPDL3b in podocytes decouples proteinuria from chronic kidney disease progression in experimental Alport Syndrome.

Systematic review of biomechanical forces associated with carotid plaque disruption and stroke.

Non-semantic features or semantic-agnostic features, which are irrelevant to image context but sensitive to image manipulations, are recognized as evidential to Image Manipulation Localization (IML). Since manual labels are impossible, existing works rely on handcrafted methods to extract non-semantic features. Handcrafted non-semantic features jeopardize IML model's generalization ability in unseen or complex scenarios. Therefore, for IML, the elephant in the room is: How to adaptively extract non-semantic features? Non-semantic features are context-irrelevant and manipulation-sensitive. That is, within an image, they are consistent across patches unless manipulation occurs. Then, spare and discrete interactions among image patches are sufficient for extracting non-semantic features. However, image semantics vary drastically on different patches, requiring dense and continuous interactions among image patches for learning semantic representations. Hence, in this paper, we propose a Sparse Vision Transformer (SparseViT), which reformulates the dense, global self-attention in ViT into a sparse, discrete manner. Such sparse self-attention breaks image semantics and forces SparseViT to adaptively extract non-semantic features for images. Besides, compared with existing IML models, the sparse self-attention mechanism largely reduced the model size (max 80% in FLOPs), achieving stunning parameter efficiency and computation reduction. Extensive experiments demonstrate that, without any handcrafted feature extractors, SparseViT is superior in both generalization and efficiency across benchmark datasets.

Plant absorption is important for the entry of many pollutants into food chains. Although terrestrial microplastics (MPs) can be absorbed by the roots1,2, their upward translocation is slow1. Meanwhile, atmospheric MPs are widely present3,4, but strong evidence on their direct absorption by plants is still lacking. Here, analyses using mass spectrometry detection show the widespread occurrence of polyethylene terephthalate (PET) and polystyrene (PS) polymers and oligomers in plant leaves, and identify that their levels increase with atmospheric concentrations and the leaf growth duration. The concentrations of PET and PS polymers can reach up to 104 ng per g dry weight in leaves at the high-pollution areas studied, such as the Dacron factory and a landfill site, and 102-103 ng per g dry weight of PET and PS can be detected in the open-air-grown leafy vegetables. Nano-sized PET and PS particles in the leaves were visually detected by hyperspectral imaging and atomic force microscopy-infrared spectroscopy. Absorption of the proactively exposed non-labelled, fluorescently labelled or europium-labelled plastic particles by maize (Zea mays L.) leaves through stomatal pathways, as well as their translocation to the vascular tissue through the apoplastic pathway, and accumulation in trichomes was identified using hyperspectral imaging, confocal microscopy and laser-ablation inductively coupled plasma mass spectrometry. Our results demonstrate that the absorption and accumulation of atmospheric MPs by plant leaves occur widely in the environment, and this should not be neglected when assessing the exposure of humans and other organisms to environmental MPs.

The microvascular basement membrane (mvBM) is crucial in maintaining vascular integrity and function and, therefore, key to the health of major organs. However, the complex nature and the intricate interplay of biochemical and biomechanical factors that regulate the mvBM functional dynamics make it difficult to study. Here, we present a novel and highly tunable in vitro model of the human mvBM, enabling a bottom‐up approach to assemble a composite model of the microvascular wall and explore microvascular dynamics and interactions with circulating neutrophils in real time. An electrospun polyethylene glycol (PEG)‐based fibrillar network mimics the mvBM with adjustable nanofiber diameter, orientation, and density. The fidelity of the model to the human mvBM's topography and mechanics was verified through second harmonic generation imaging and atomic force microscopy. PEG was functionalized with bioactive moieties to enable endothelial cell (EC) and pericyte (PC) attachment, through which neutrophil interactions with the microvascular wall model were observed. The model, coupled with 4D microscopy, revealed nuanced and dynamic neutrophil behavior when interacting with the microvascular wall, demonstrating its utility in characterizing cell–cell interactions. As such, the model can be employed in the exploration of inflammatory and microvascular‐related diseases. Therefore, this innovative approach represents a significant advancement in vascular biology research, holding profound implications for understanding mvBM dynamics in both health and disease.

A surface piezoelectricity model generalizing the Steigmann–Ogden model for linear elastic solids is described starting from a rigorous variational approach. The boundary and tip conditions on surface-energetic material surfaces are presented. The model is applied to the problem for a one-phase or a two-phase piezoelectric circular fiber in a piezoelectric infinite matrix. The piezoelectric materials are assumed to have a 6-mm hexagonal crystal symmetry. The problem is solved analytically using the complex variable approach. The boundaries between different materials possess surface piezoelectric energy. The matrix is subjected to a far-field loading and contains a piezoelectric screw dislocation. The effective moduli of the piezoelectric composites reinforced by one-phase or two-phase circular fibers are obtained using the Maxwell’s far-field methodology. The results are compared with the generalized self-consistent scheme. An image force on the dislocation is computed using the generalized Peach–Koehler formula. Numerical examples and parametric studies are presented.

We modify the traditional linear-elastic field of an edge dislocation. The modifications stem from symmetry and energy requirements imposed in terms of embedded (deformed) coordinates. These requirements are satisfied if a line force is added to the dislocation field. The modification to the stress field is expressed by coefficients that are a function only of Poisson's ratio. Qualitatively, the field of the dislocation is increased in the glide direction and decreased in the climb direction. There are small changes to the field of a screw dislocation that do not entail the addition of a line force. Effects of nonlinearity, anisotropic elasticity, and image forces are briefly considered.