AMOLF Institutional Repository
Not a member yet
1351 research outputs found
Sort by
Quantification of Mobile Ions in Perovskite Solar Cells with Thermally Activated Ion Current Measurements
Full text linkMobile ions play a key role in the degradation of perovskite solar cells, making their quantification essential for enhancing device stability. Various electrical measurements have been applied to characterize mobile ions. However, discerning between different ionic migration processes can be difficult. Furthermore, multiple measurements at different temperatures are usually required to probe different ions and their activation energies. Here, we demonstrate a new characterization technique based on measuring the thermally activated ion current (TAIC) of perovskite solar cells. The method reveals density, diffusion coefficient, and activation energy of mobile ions within a single temperature sweep and offers an intuitive way to distinguish mobile ion species. We apply the TAIC technique to quantify mobile ions of MAPbI3 and triple-cation perovskite solar cells. We find a higher activation energy and a lower diffusion coefficient in the triple-cation devices. TAIC measurements are a simple yet powerful tool to better understand ion migration in perovskite solar cells
Cellular anatomy of arbuscular mycorrhizal fungi
Full text linkArbuscular mycorrhizal (AM) fungi are ancient plant mutualists that are ubiquitous across terrestrial ecosystems. These fungi are unique among most eukaryotes because they form multinucleate, open-pipe mycelial networks, where nutrients, organelles, and chemical signals move bidirectionally across a continuous cytoplasm. AM fungi play a crucial role in ecosystem functioning by supporting plant growth, mediating ecosystem diversity, and contributing to carbon cycling. It is estimated that plant communities allocate ∼3.93 Gt CO2e to AM fungi every year, much of which is stored as lipids inside the fungal network. Despite their ecological significance, the cellular biology of AM fungi remains underexplored. Here, we synthesise the current knowledge on AM fungal cellular structure and organisation. We examine AM fungal development at different biological levels — the hypha and its content, hyphal networks and AM fungal spores — and explore key cellular dynamics. This includes cell wall composition, cytoplasmic contents, nuclear and lipid organisation and dynamics, network architecture, and connectivity. We highlight how their unique cellular arrangement enables complex cytoplasmic flow and nutrient exchange processes across their open-pipe mycelial networks. We discuss how both established and novel techniques, including microscopy, culturing, and high-throughput image analysis, are helping to resolve previously unknown aspects of AM fungal biology. By comparing these insights with established knowledge in other, well-studied filamentous fungi, we identify critical knowledge gaps and propose questions for future research to further our understanding of fundamental AM fungal cell biology and its contributions to ecosystem health
Stochastic Thermodynamics of a Linear Optical Cavity Driven On Resonance
Full text linkWe present a complete framework of stochastic thermodynamics for a single-mode linear optical cavity driven on resonance. We first show that the steady-state intracavity field follows the equilibrium Boltzmann distribution. The effective temperature is given by the noise variance, and the equilibration rate is the dissipation rate. Next, we derive expressions for internal energy, work, heat, and free energy of light in a cavity and formulate the first and second laws of thermodynamics for this system. We then analyze fluctuations in work and heat and show that they obey universal statistical relations known as fluctuation theorems. Finite time corrections to the fluctuation theorems are also discussed. Additionally, we show that work fluctuations obey Crooks’ fluctuation theorem which is a paradigm for understanding emergent phenomena and estimating free energy differences. The significance of our results is twofold. On one hand, our work positions optical cavities as a unique platform for fundamental studies of stochastic thermodynamics. On the other hand, our work paves the way for improving the energy efficiency and information processing capabilities of laser-driven optical resonators using a thermodynamics based prescription
Lactate controls cancer stemness and plasticity through epigenetic regulation
Full text linkTumors arise from uncontrolled cell proliferation driven by mutations in genes that regulate stem cell renewal and differentiation. Intestinal tumors, however, retain some hierarchical organization, maintaining both cancer stem cells (CSCs) and cancer differentiated cells (CDCs). This heterogeneity, coupled with cellular plasticity enabling CDCs to revert to CSCs, contributes to therapy resistance and relapse. Using genetically encoded fluorescent reporters in human tumor organoids, combined with our machine-learning-based cell tracker, CellPhenTracker, we simultaneously traced cell-type specification, metabolic changes, and reconstructed cell lineage trajectories during tumor organoid development. Our findings reveal distinctive metabolic phenotypes in CSCs and CDCs. We find that lactate regulates tumor dynamics, suppressing CSC differentiation and inducing dedifferentiation into a proliferative CSC state. Mechanistically, lactate increases histone acetylation, epigenetically activating MYC. Given that lactate's regulation of MYC depends on the bromodomain-containing protein 4 (BRD4), targeting cancer metabolism and BRD4 inhibitors emerge as a promising strategy to prevent tumor relapse
Regulating Airflow Using Hybrid LCN for Soft Pneumatic Circuits
Full text linkBeing flexible and adaptive to various environments, soft robotics shows promise as a more robust alternative in many applications compared to traditional, rigid robotics. Of many employable different actuation strategies, pneumatically driven soft robotics have gained attraction owing to their relative straightforward manufacturing and capability to produce significant force to their environment upon interaction. To enable more autonomous pneumatic systems, however, there is an emerging need for developing smarter fluidic elements responding to environmental cues, to provide embodied control and regulation. Herein, a liquid crystal network (LCN)-based fluid regulator is designed to impart stimuli responsiveness and regulation into fluidic circuits by combining radially aligned nematic and nonaligned isotropic LCNs. Assisted by a finite element method, the thermoresponsiveness of the LCN is discussed. Finally, the regulating behavior of the responsive pneumatic regulator is demonstrated, which alters its fluidic resistance with changing temperature. This work emphasizes the potential of advancing responsive soft robotics that can interact with their environment through multiphysical stimuli
Hysteresis in Perovskite Devices: Understanding the Abrupt Resistive Switching Mechanism
Full text linkHalide perovskite devices exhibit diverse current–voltage hysteresis behaviors, driven by distinct mechanisms that can enhance or hinder performance, making their understanding crucial. Among these, abrupt switching is particularly relevant for memristive operation and reverse-bias breakdown in solar cells. In this work, we identify four distinct hysteresis responses: capacitive, inductive, hysteresis-free, and abrupt switching. All four behaviors are clearly observed via cyclic voltammetry in a simple perovskite device with silver contacts. Real-time photoluminescence microscopy shows that continuous bias and illumination progressively modify the perovskite–electrode interface, transforming inductive into hysteresis-free behavior and supporting its interfacial origin. Further stress leads to filament formation, with abrupt switching occurring only when a filament bridges the electrodes, forming a reversible short circuit. This switching arises from dynamic contact at the filament-electrode interface. Conductive AFM and electron microscopy reveal that the filaments are highly conductive and composed of metallic silver. Transient and impedance measurements effectively differentiate the hysteresis modes. Similar responses are found in gold-contacted devices, though abrupt switching is restricted to nanometer-scale gaps between the electrodes, suggesting the formation of smaller, less stable filaments due to the lower reactivity of gold. These findings provide valuable insights for advancing switching and understanding hysteresis in perovskite-based devices
Reliable determination of sub-nanometer gaps in plasmonic gold dimers for correlation to their optical properties
Full text linkAccurately characterizing sub-nanometer gaps in plasmonic nanoparticle dimers is essential for understanding their optical properties, particularly in the transition from classical to quantum plasmonic behavior. While two-dimensional (scanning) transmission electron microscopy imaging provides high spatial resolution, it lacks the three-dimensional (3D) morphological information needed to reliably extract gap sizes. In this work, we combine electron tomography with a robust data analysis workflow to quantify interparticle gaps in gold nanosphere dimers with sub-nanometer precision. We show that gap size estimates are highly sensitive to reconstruction algorithms, segmentation thresholds, and meshing parameters. To overcome this, we introduce a model-fitting approach based on convolving a step function with a Gaussian, enabling consistent and accurate gap measurements even in the absence of a known ground truth. Validation on simulated datasets confirms pixel-level accuracy, and application to experimental data demonstrates the robustness and general applicability of the method. The resulting 3D reconstructions are directly integrated into electromagnetic simulations, allowing reliable interpretation of the optical response of the dimer. This workflow offers a broadly applicable strategy for correlating morphology and optical function in plasmonic systems and provides a crucial step toward resolving quantum effects in nanoscale light-matter interactions
Uncovering Hidden Resonances in Non‐Hermitian Systems with Scattering Thresholds
Full text linkThe points where diffraction orders emerge or vanish in the propagating spectrum of periodic non-Hermitian systems are referred to as scattering thresholds. Close to these branch points, resonances from different Riemann sheets can tremendously impact the optical response. However, these resonances are so far elusive for two reasons. First, their contribution to the signal is partially obscured, and second, they are inaccessible for standard computational methods. Here, the interplay of scattering thresholds with resonances is explored and a multi-valued rational approximation is introduced to access the hidden resonances. The theoretical and numerical approach is used to analyze the resonances of a plasmonic line grating. This work elegantly explains the occurrence of pronounced spectral features at scattering thresholds applicable to many nanophotonic systems of contemporary and future interest
Roadmap for Quantum Nanophotonics with Free Electrons
No full textOver the past century, continuous advancements in electron microscopy have enabled the synthesis, control, and characterization of high-quality free-electron beams. These probes carry an evanescent electromagnetic field that can drive localized excitations and provide high-resolution information on material structures and their optical responses, currently reaching the sub-Å and few-meV regime. Moreover, combining free electrons with pulsed light sources in ultrafast electron microscopy adds temporal resolution in the subfemtosecond range while offering enhanced control of the electron wave function. Beyond their exceptional capabilities for time-resolved spectromicroscopy, free electrons are emerging as powerful tools in quantum nanophotonics, on par with photons in their ability to carry and transfer quantum information, create entanglement within and with a specimen, and reveal previously inaccessible details on nanoscale quantum phenomena. This Roadmap outlines the current state of this rapidly evolving field, highlights key challenges and opportunities, and discusses future directions through a collection of topical sections prepared by leading experts
Self-aligning polar active matter
Full text linkSelf-alignment describes the property of a polar active unit to align or antialign its orientation toward its velocity. In contrast to mutual alignment, where the headings of multiple active units tend to directly align with each other - as in the Vicsek model - self-alignment impacts the dynamics at the individual level by coupling the rotation and displacements of each active unit. This enriches the dynamics even in the absence of interactions and allows, for example, a single self-propelled particle to orbit in a harmonic potential. At the collective level, self-alignment modifies the nature of the transition to collective motion already in the mean-field description and can lead to other forms of self-organization such as collective actuation in dense or solid elastic assemblies of active units. This has significant implications for the study of dense biological systems, metamaterials, and swarm robotics. Here a number of models are reviewed that were introduced independently to describe the previously overlooked property of self-alignment and some of its experimental realizations are identified. The aim of this review is threefold: (i) to underline the importance of self-alignment in active systems, especially in the context of dense populations of active units and active solids; (ii) to provide a unified mathematical and conceptual framework for the description of self-aligning systems; and (iii) to discuss the common features and specific differences of the existing models of self-alignment. The review concludes by discussing promising research avenues in which the concept of self-alignment could play a significant role