LiNi0.5Mn1.5O4 (LNMO) is a promising cathode material owing to its high operating potential of 4.75 V vs. Li+/Li. However, the high potential triggers interfacial instability, such as electrolyte oxidation. A mechanically robust cathode-electrolyte interphase (CEI) is essential for maintaining structural integrity and ensuring reliable performance of high-voltage lithium-ion batteries. CEI layer thickness is often under 20 nm, making the assessment of its elastic properties challenging. We applied an amplitude-modulated/frequency-modulated scanning force microscopy method to enable quantitative mechanical characterization of thin CEI layers on rough composite electrode surfaces. We systematically varied the number of battery cycles and investigated the morphology and elastic modulus of the interphase layers on LNMO cathodes. The pristine crystalline LNMO surface exhibited an elastic modulus of approximately 126 +/- 20 GPa, whereas the binder/carbon (b/c) regions had a modulus of 1.9 +/- 0.1 GPa. After only 5 cycles the elastic modulus on LNMO decreased to 3.2 +/- 1.2 GPa, indicating an LNMO passivation by CEI growth. After 200 cycles, the elastic modulus became homogeneous with the moduli on the LNMO and b/c regions reaching 3.9 +/- 0.8 GPa and 3.9 +/- 0.4 GPa, respectively. This mechanical convergence is supported by a convergence in chemical composition of the interphase between the LNMO and b/c regions. We also observed a compositional shift from ether-rich oligomers to a more oxidized, carbonyl-rich organic network. The final stabilized modulus of approximate to 4 GPa reflects an organic-dominated interphase with enhanced intermolecular interactions. Inorganic species are likely buried beneath the organic-rich top layer. This work provides understanding of interfacial stability and establishes a robust and reproducible framework for quantifying the elastic modulus of interphase layers within composite electrodes, providing insights for the design of stable high-voltage battery systems.

Water drops spontaneously become electrically charged when moving on different surfaces, such as plant leaves, insect wings, building walls, window glass and plastic1-9. This process, known as contact or sliding electrification, is analogous to tribocharging between solids10-13. The electric potential of water drops charged in this way can exceed 1 kV (refs. 14-16). A vital but as yet unanswered question is whether the charge in water drops causes corrosion. Here we analyse the effect of series of water drops hitting metal surfaces, which are protected by a non-conductive coating. Before hitting the coated metal, the drops acquire a charge spontaneously by sliding over an insulating surface. We demonstrated that these charged drops can cause the coating to break down electrically and lead to corrosion of the metal. As spontaneously charged water drops form naturally, this previously overlooked corrosion mechanism may contribute to the degradation of cultural heritage sites, buildings, ships, cars and other metal components. Our findings can improve anticorrosion strategies and emphasize the need for protective materials capable of resisting charge-induced damage from water drops.

Water drops sliding on hydrophobic surfaces spontaneously separate charges at their rear. It is unclear how this charge separation affects the contact angles of a sliding drop. We slide grounded and insulated drops on hydrophobic surfaces at low capillary numbers (≤10^{-4}). We find that the drop charge leads to spontaneous electrowetting that decreases the contact angles. The deposited charges lead to a surface charge effect and decrease the contact angle. Both phenomena compensate each other at the receding contact line, resulting in an insignificant change in the receding contact angle of a sliding drop.

Nanodiamonds hosting colour centres are promising building blocks for quantum technologies, enabling advances in quantum computation1,2, nanoscale NMR spectroscopy3-6, single-spin magnetometry7,8, wide-field quantum imaging9 and single-photon sources10,11. However, the controlled bottom-up synthesis of ultrasmall and structurally uniform nanodiamonds has remained a challenge, with existing methods producing heterogeneous materials that vary in size, morphology, impurity content and defect quality. Here we show that well-defined, hydrogen-terminated molecular nanographenes serve as chemically confined precursors for high-pressure, high-temperature synthesis of ultrasmall (3-4 nm), monodisperse and highly crystalline molecular nanodiamonds with only a single sp2 surface reconstruction and produced on a milligram scale. The same bottom-up platform also enables a two-component strategy for incorporating silicon- and germanium-based colour centres during synthesis, yielding SiV- and GeV- emitters without ion implantation, irradiation or post-treatment. Because the nanographene precursor defines both the confined carbon framework and the hydrogen content, this approach provides intrinsic, precursor-level control over nanodiamond size and composition, particularly in the low-nanometre regime relevant for biological and quantum sensing. Molecular nanographenes, ultralarge polycyclic aromatic hydrocarbons, therefore, establish a scalable and modular route to high-quality molecular and fluorescent nanodiamonds and offer a general design principle for tailored quantum materials and nanoscale devices.

Programmable drop sliding on surfaces is of interest for microfluidics, self‐cleaning surfaces, water harvesting, or drop nanoreactors. While drop movement along gradients on surfaces or on slippery surfaces has been demonstrated, achieving programmable movement of drops on nanoporous surfaces without structural or chemical gradients requires different mechanisms of symmetry breaking. Using a hydrophilic mesoporous film, we investigate direction‐controlled drop sliding of aqueous salt solutions. We observe drop sliding using an aqueous NaCF3SO3 solution drop together with symmetry breaking through local airflow. The direction in which the drop moves is controlled by evaporation‐induced, asymmetric salt distribution. We investigate how the macroscopic static contact angle below 10°, the use of a continuous airflow, and varying salt concentrations allow the speed, distance, and direction of the drop to be programmed. The motive force increased with increasing NaCF3SO3 concentration in the drop and reaches 7 µN for 5 µL drops. The tuning of the drop direction and speed, driven by asymmetric airflow and controlled by ion concentration and airflow intensity‐induced local evaporation, provides a new perspective and mechanistic approach to programmable fluid drop transport, especially on mesoporous surfaces.

A robust alternative method to measure receding contact angles is suggested.

Kelvin probe force microscopy (KPFM) provides an established and reliable measurement of the work function of electronic conductors under equilibrium conditions. A less used but highly versatile application of KPFM is the characterization of electrochemical devices in operation, i.e., devices under nonequilibrium conditions. We derive the KPFM signal interpretation from basic considerations of the Volta potential and its relation to the surface potential, chemical potential of electrons, Galvani potential, and work function. As a key experiment for understanding operando measurements at electrochemical cells, we investigate a Hebb-Wagner solid-state polarization cell (HWC), constructed with a mixed ionic-electronic conductor (MIEC). Using a model-type MIEC based on amorphous Li3PO4, we illustrate how different potentials used in electrochemistry contribute to the KPFM signal. We show that KPFM measurements correspond to the inner electric (Galvani) potential profile along the HWC, once specific assumptions are valid. Consequently, KPFM can be very valuable in the investigation of solid electrolytes in operating electrochemical cells. Such cells are suitable models for all-solid-state batteries, candidates for future high energy density batteries.

The wetting behavior of drops on natural and industrial surfaces is determined by the advancing and receding contact angles. They are commonly measured by the sessile drop technique, also called goniometry, which doses liquid through a solid needle. Consequently, this method requires substantial drop volumes, long contact times, tends to be user-dependent, and is difficult to automate. Here, we propose the stood-up drop (SUD) technique as an alternative to measure receding contact angles. The method consists of depositing a liquid drop on a surface by a short liquid jet, at which it spreads radially forming a pancake-shaped film. Then the liquid retracts, forming a spherical cap drop shape (stood-up drop). At this quasi-equilibrium state, the contact angle (θ_SUD) closely resembles the receding contact angle measured by goniometry. Our method is suitable for a wide variety of surfaces from hydrophilic to hydrophobic, overcoming typical complications of goniometry such as needle-induced distortion of the drop shape, and it reduces user dependence. We delineate when the receding contact angle can be obtained by the stood-up method using Volume-of-Fluid (VoF) simulations that systematically vary viscosity, contact angle, and deposited drop volume. Finally, we provide simple scaling criteria to predict when the stood-up drop technique works.

High-speed video recordings are crucial for investigating drop dynamics and their interactions with surfaces. Measuring the width of sliding drops, a key parameter linked to frictional forces, requires additional equipment like cameras or mirrors, complicating experimental setups and limiting observable areas. This study introduces a novel method that simplifies the measurement process by employing artificial neural networks to estimate millimeter-scale drop width directly from side-view video data. Our approach processes raw video footage to dynamically identify features most indicative of drop width. By treating drop behavior as an extrinsic time-series problem, our model effectively captures temporal dependencies in video sequences. We propose a VGG8-inspired architecture optimized for small and low information density video datasets. This architecture is combined with our novel position invariant video processing methodology that efficiently removes non-essential regions, reducing computation time by 84 m (1.7 m. Code and data are open-sourced at: https://github.com/shumaly/position_invariant_cnn_transformer .

Cylindrical polymer brushes (CPBs) enable remarkable control over nanoparticle properties solely through sequential polymerization. The spatial dimensions and functionality of the resulting polymeric nanoparticles can be adjusted by the ratio of backbone to side chain length and the chemical nature of both parts. In this work, we present a convenient and straightforward synthetic pathway to polypept(o)ide-based CPBs using a "grafting-from" strategy utilizing poly-l-lysine (pLys) as the macroinitiator backbone and polysarcosine (pSar) as the side chain. End-capping of pSar chains with azido-butyric acid pentafluorophenyl ester enables facile surface functionalization by click chemistry (e.g., dye labeling). This strategy allows for straightforward control over nanoparticle size (Rh from 12 to 41 nm), shape (aspect ratio from 1.7 to 8.3), and molecular weights (from 350 to 2980 kg mol-1). Despite the high grafting density of pSar side chains from the pLys backbone (>85%), enzymatic degradation is feasible by the natural protease B fromStreptomyces griseusand enables the analysis of pSar side chains upon cleavage (Đ = 1.03-1.04). Interestingly, these CPBs exhibit thermal stability in phosphate-buffered saline at elevated temperatures (60 °C for 24 h) and display notable circulation in zebrafish embryos (up to 3 days). Therefore, CPBs based on polypept(o)ides not only allow for precise tuning of size, shape, and surface functionality but also display high biocompatibility and extended circulation time in zebrafish, leveraging the stealth-like properties of pSar.

Cylindrical bottlebrush polymers (CBPs) enable the precise adjustment of nanoparticle properties such as size, shape, and functionality exclusively by polymer synthesis. In addition, block copolymer side chains enable direct access to core–shell structure. In this study, the synthesis of polypept(o)ides‐based core–shell CBPs is presented through a “grafting‐from” strategy. While, poly‐lysine (pLys) serves as the backbone, poly(γ‐benzyl‐ l ‐glutamic acid)‐block‐polysarcosine (pGlu(OBn)‐ b ‐pSar) copolymers form the side chains. This approach enables the synthesis of core–shell nanoparticles, referred as core–shell brushes (CSBs), with hydrodynamic radius ( R h ) from 17 to 70 nm, and molecular weights (1320–4000 kg mol −1 ) with dispersity indices ≈1.3 as determined by size‐exclusion chromatography. Dasatinib is chosen as a drug molecule model to explore the potential of such synthetical CSBs as a platform for drug encapsulation by π – π ‐interactions. An overall loading efficiency of 10% is achieved, which also displayed sustained release within 72 h, cellular uptake into human glioblastoma (U‐87 MG) cells, and drug‐related therapeutic efficacy. While drug release can be further optimized by covalent drug attachment, these results establish a strong foundation for the use of CSBs in nanomedicine.

Neurological diseases and neural injuries are prevalent but difficult to treat because of the complexity of the neural environment. To unravel this complexity, simple cell culture models are required that allow the study of individual aspects of the neural environment under defined conditions. In this work, we developed stable coatings of bioactive peptides via photoimmobilization through a thiol-ene reaction on glass substrates suitable for long-term culture of neural cells. The substrates were modified with thiol groups via chemical vapor deposition to obtain a homogeneous layer, followed by the immobilization of neural active peptides bearing vinyl groups. Subsequently, human neuroblastoma cells were shown to stably adhere to and grow on the modified substrates. The results establish a facile fabrication route for patternable and peptide-functionalized substrates for the culturing of neural cells without an additional antifouling treatment.

It has been discovered during the last decade that when water drops slide on hydrophobic surfaces, they spontaneously leave negative charges along the drop path. The drops become positively charged with a potential of 1 kV. This process, called slide electrification, influences drop motion and alters contact angles. Here, a third effect of slide electrification is demonstrated: the preferential deposition of dissolved solutes with positive charges. To illustrate this, water drops containing dissolved charged fluorophore ions are allowed to slide down a tilted hydrophobic surface, and their track is imaged. Two perylene derivatives are applied as fluorophores, one chromophore carrying positive charges, PDI+, and one carrying negative charges, PDI─. PDI+ is deposited at a concentration as low as 0.5 µm. In contrast, PDI─ is only deposited above 5 µm. Experiments using grounded drops or a hydrophobic coating on a conducting substrate indicate that the electric field generated from the negative surface charges behind the drop causes a preferential deposition of the dissolved ions near the interface. This hypothesis also agrees with Kelvin probe measurements. Complex biomolecules deposition e.g. DNA can be also affected by this. These findings contribute to a better understanding of mass transfer processes at interfaces.

Wetting phenomena have been studied quantitatively for more than 200 years, but there remain many fundamental questions that are not understood. For example, the speed of a water drop sliding down an inclined plane cannot be predicted. A drop that slides down a surface experiences a resistance. We call this resistance drop friction. It is still debated how and where energy is dissipated in a sliding drop. Particularly for the most common liquid, water, there have been considerable advances in the understanding of wetting, driven by the development of new physical, preparative and theoretical methods. Water is a special liquid, owing to its polar nature, its tendency to form hydrogen bonds, the self-ionization into OH− and H3O+, its low viscosity and its high surface tension. In recent years, water–surface interactions due to adaptation, spontaneous electrostatic charging and deformation on elastomers have been identified as important processes that increase drop friction. They may be responsible for drop friction even on seemingly smooth, homogeneous and rigid surfaces. The dynamic wetting of sliding drops, particularly of water, remains poorly understood. New experimental techniques have shown that, in addition to viscous dissipation, other energy dissipation mechanisms such as adaptation, electrostatic charging and deformation can contribute significantly and affect the motion of the drops.

Contact line friction (CLF) of bubbles is ubiquitous, from bubbles on a beer glass to H2 bubbles sliding over electrodes in electrolysis. However, a fundamental understanding of CLF of bubbles is still missing, mainly due to the challenge of precisely controlling bubble sliding. For example, it is not clear how bubbles start sliding and how CLF of bubbles depends on velocity. We therefore developed a bubble friction force instrument to directly measure bubble CLF. This force develops from a static regime, through a transition, to a kinetic regime. This entire process is quantitatively described by a modified Kawasaki-Furmidge equation. Bubble CLF was measured for velocities from 0.2 micron/s to 2 mm/s, revealing a transition from a constant CLF regime below about 60 micron/s to a velocity-dependent CLF regime on surfaces with various wettability. The velocity dependence stems from interfacial adaptation governed by the liquid ionic environment with a relaxation time of around 10 microsecond. Moreover, CLF of bubbles can be measured on hydrophilic surfaces and under a challenging H2 atmosphere, overcoming the limitations of current droplet-based methods. Our results provide a quantitative basis for understanding CLF of bubbles with relevance to many applications, including bubble manipulation and electrochemistry.

The current controversies about the role of space charge layers hinder the development of better solid-solid interfaces and, thus, the improvement of solid-state batteries (ASSBs). To overcome this, we have combined high spatial resolution and nondestructive techniques, operando heterodyne Kelvin probe force microscopy (KPFM), and operando nuclear reaction analysis (NRA) to conduct a study of space charge layers in ASSBs. A model thin-film ASSB was fabricated from lithium (Li)|Li3PO4 (LPO)|LiCoO2 (LCO) for this study. This battery excels due to negligible interfacial defects and side reactions. For a working battery voltage range from 3.0 to 4.3 V vs Li/Li+, a space charge layer mainly exists at the LPO|LCO interface. This space charge layer with a width <50 nm arises from the redistribution of Li-ions at the interface. We clarified controversial views on the role of space charge layers in ASSBs by quantitatively determining the interfacial space charge layer resistance and found a maximum value between 18.4 and 19.1 Ω cm2 at 4.3 V vs Li/Li+. The absolute value of interfacial resistance from space charge layer formation is much smaller compared with the bulk solid electrolyte resistance in the fabricated thin-film ASSB. By employing KPFM and NRA techniques in ASSB research, our knowledge of space charge layer evolution at the solid electrolyte electrode interface is more comprehensive, even beyond the investigation of space charge layers.

High speed side-view videos of sliding drops enable researchers to investigate drop dynamics and surface properties. However, understanding the physics of sliding requires knowledge of the drop width. A front-view perspective of the drop is necessary. In particular, the drop’s width is a crucial parameter owing to its association with the friction force. Incorporating extra cameras or mirrors to monitor changes in the width of drops from a front-view perspective is cumbersome and limits the viewing area. This limitation impedes a comprehensive analysis of sliding drops, especially when they interact with surface defects. Our study explores the use of various regression and multivariate sequence analysis (MSA) models to estimate the drop width at a solid surface solely from side-view videos. This approach eliminates the need to incorporate additional equipment into the experimental setup. In addition, it ensures an unlimited viewing area of sliding drops. The Long Short Term Memory (LSTM) model with a 20 sliding window size has the best performance with the lowest root mean square error (RMSE) of 67 µm. Within the spectrum of drop widths in our dataset, ranging from 1.6 to 4.4 mm, this RMSE indicates that we can predict the width of sliding drops with an error of 2.4%. Furthermore, the applied LSTM model provides a drop width across the whole sliding length of 5 cm, previously unattainable.

Slide electrification of drops is mostly investigated on tilted plate setups. Hence, the drop charging at low sliding velocity remains unclear. We overcome the limitations by developing an electro drop friction force instrument (eDoFFI). Using eDoFFI, we investigate slide electrification at the onset of drop sliding and at low sliding velocities <= 1 cm s(-1). The novelty of eDoFFI is the simultaneous measurements of the drop discharging current and the friction force acting on the drop. The eDoFFI tool facilitates control on drop length and width using differently shaped rings. Hereby, slide electrification experiments with the defined drop length-to-width ratios >1 and <1 are realized. We find that width of the drop is the main geometrical parameter which determines drop discharging current and charge separation. We combine Kawasaki-Furmidge friction force equation with our finding on drop discharging current. This combination facilitates the direct measurement of surface charge density (sigma) deposited behind the drop. We calculate sigma approximate to 45 mu C m(-2) on Trichloro(1H,1H,2H,2H-perfluorooctyl)silane (PFOTS) and approximate to 20 mu C m(-2) on Trichloro(octyl)silane (OTS) coated glass surfaces. We find that the charge separation by moving drops is independent of sliding velocity <= 1 cm s(-1). The reverse sliding of drop along the same scanline facilitates calculation of the surface neutralization time constant. The eDoFFI links two scientific communities: one which focuses on the friction forces and one which focuses on the slide electrification of drops.