Assaf Ya'AKobovitz

The integration of graphene nanoplatelets (GnPs) into cementitious construction yields a multifunctional real‐time structural health monitoring (SHM) material for self‐sensing. Above a percolation threshold of 3.2 wt% GnP, a conductive network forms in the cementitious material, leading to a sharp decrease in electrical resistance (∼ 4 orders of magnitude) and a sensitive and stable sensory response under cyclic compressive loading. The values of fractional change in resistance (FCR) upon compression were found to be linearly correlated with stress, reaching 40% at a maximum stress of 11 MPa. The correlation between stress and resistance was calibrated using the stress sensitivity factor (SF = ((FCR)/( σ ))·100). The obtained SF was 3.6%/MPa, which is a significant improvement over previously reported studies (twice as high). The reproducible response was independent of the load direction with respect to orientation of the electrodes (parallel or perpendicular to the force direction). Currently used sensors mostly provide global information on large structures and are based on complex, fragile external devices such as cameras, lasers, or ultrasound sensors, which require extensive data analysis and operational overhead. In contrast, the findings of this study highlight the potential of the cementitious composite itself as a scalable, durable, and local sensor for SHM applications in concrete elements.

ReSe ₂ photodiodes present outstanding performances, that rely on their interactions with ambient oxygen. Indeed, they show high responsivity and external quantum efficiency (EQE).

We developed a process to build suspended Mo_1−xW_xS₂ nano-drumheads using a diffusion-based alloying process and investigated their mechanics via experiments and theoretical simulations.

Uncovering the material dissipation mechanisms of two-dimensional materials is essential for their implementation in advanced devices. While graphene resonators are highly attractive due to their high operational frequency and excellent durability, they dissipate a considerable amount of energy due to significant material dissipation associated with atomic friction manifested by the relative slipping of atomic layers. We mitigate the atomic friction by changing the atomic composition of the devices through the insertion of boron and nitride atoms that create polar interlayer bonds and, therefore, also reduce the energy dissipation. As a case study, we built boron carbonitride (BCN) foam cantilever devices and studied their frequency responses compared to those of their graphene counterparts. Indeed, we show that inserting boron and nitride atoms into the lattice improves the interlayer interactions and, thus, reduces the interlayer atomic friction. In addition, the air dissipation of BCN is also lower than that of graphene. Therefore, we pave the path for the development of BCN devices with tunable dissipation.

Understanding atomic friction within a liquid environment is crucial for engineering friction mechanisms and characterizing surfaces. It has been suggested that the lattice resolution of friction force microscope in liquid environments stems from a dry contact state, with all liquid molecules expelled from the area of closest approach between the tip and substrate. Here, we revisit this assertion by performing in-depth friction force microscopy experiments and molecular dynamics simulations of the influence of surrounding water molecules on the dynamic behavior of the nanotribological contact between an amorphous SiO₂ probe and a monolayer MoS₂ substrate. An analysis of simulation and experimental stick-slip patterns demonstrates the entrapment of water molecules at the contact interface. These trapped water molecules behave as an integral component of the probe and participate in its interaction with the substrate, affecting the dynamics of the probe and preventing long slips. Significantly, surrounding water from the capillary or layer exhibits a replenishing effect, acting as a water reservoir during sliding. This phenomenon facilitates the preservation of lattice-scale resolution across a range of applied normal loads.

We compress 2D WS ₂ using the buckling metrology, which demonstrated mechanical softening due to sequential atomic-scale buckling events. We tune the mechanics of WS ₂ and shed light on its fundamental physics.

The optical and photonic characteristics of monolayer transition metal dichalcogenides (TMDs) play a pivotal role in their functionality as solar cell materials, light-emitting diodes (LEDs), and other electro-optical applications. In this study, we reveal the impact of prolonged illumination on the luminescence properties and Raman spectra of monolayered MoS₂ and WS₂─a process known as "light soaking". We find a light-induced transition from the physisorption to the chemisorption of ambient O₂ and H₂O molecules. In parallel, we observe the activation and passivation of defect sites in the samples (depending on their initial defect density), which is attributed to the adsorbed ambient molecules and the resulting light-driven interactions with defect sites. Thus, we can control the active defect density of monolayered TMDs and shed light on the fundamental mechanisms underlying their luminescence properties. Therefore, this work clarifies the source of changes to the luminescence properties of TMDs and opens the path toward their integration into advanced applications that may be affected by light soaking, such as solar cells and energy devices.

We uncovered the elastic properties of two-dimensional rhenium disulfide (ReS ₂ ) and rhenium diselenide (ReSe ₂ ) and found that they are thickness-independent and can sustain large fracture strength and high stretchability.