We report on the electrical characterization of single MXene Ti3C2Tx flakes (where T is a surface termination) and demonstrate the metallic nature of their conductivities. We also show that the carrier density can be modulated by an external gate voltage. The density of free carriers is estimated to be 8 ± 3 × 1021 cm−3 while their mobility is estimated to be 0.7 ± 0.2 cm2/V s. Electrical measurements, in the presence of a magnetic field, show a small, but clearly discernable, quadratic increase in conductance at 2.5 K.

Herein we report on how to render Ti 3 C 2 T x (MXene) monolayers deposited on SiO 2 /Si wafers, with different SiO 2 thicknesses, visible. Inputting the effective thickness of a Ti 3 C 2 T x monolayer (1 ± 0.2 nm) measured by atomic force microscopy, and its refractive index into a Fresnel-law-based simulation software, we show that the optical contrast of Ti 3 C 2 T x monolayers deposited on SiO 2 /Si wafers depends on the SiO 2 thickness, number of MXene layers, and the light's wavelength. The highest contrast was found for SiO 2 thicknesses around 220 nm. Simulations for other substrates, namely, Al 2 O 3 /Si, HfO 2 /Si, Si 3 N 4 /Si and Al 2 O 3 /Al, are presented as supplementary information. IMPACT STATEMENTThe experimental and simulated color contrasts between Ti 3 C 2 T x (MXene) monoflakes deposited on SiO 2 of various thicknesses-under an optical microscope-were obtained for the first time. ARTICLE HISTORY

Measles is one of the most infectious airborne viruses worldwide. With a basic reproduction rate between 12-18, this virus is six times more infectious than the SARS-CoV-2 Alpha variant and similar to the SARS-CoV-2 Omicron variant. Even though a cheap and effective vaccine is available, measles is still common in developing countries. To date, sporadic outbreaks are also reported in developed countries, primarily due to non-vaccinated people. This work presents a point-of-care (POC) biosensing device capable of detecting measles virions (MV) in human saliva. The device is a surface-acoustic-wave (SAW) based lab-on-a-chip (LOC), smaller than a €1-cent coin, in which SAWs are used both for sensing and fluid recirculation. The biosensing detection performance of this system is tested and device sensitivity and selectivity are assessed. The SAW-LOC with MV loaded in healthy, whole human saliva is finally validated. The experimental results also highlight a crucial aspect of the biosensing process: the interactions between probing and target species during incubation with or without fluid mixing. The presented findings are promising for realizing a POC platform for measles diagnosis and may serve as a guideline for designing new microfluidics-based biosensing systems.

Vertical arrays of sealed nanofluidic channels, in which both cross-sectional dimensions are controllable down to 10 nm, were fabricated by selective side etching of a SiGe heterostructure comprised of layers of alternating Ge fractions. Capillary filling of these nanochannel arrays with fluorescent dye solutions was investigated using a confocal microscope. The feasibility of using nanochannels for size-based separation of biomolecules was demonstrated by imaging aggregates of tagged amyloid-beta peptide. The ability to integrate a large number of nanochannels shows promise for high throughput applications involving lab-on-a-chip systems.

Measles Sensing Measles is one of the most infectious airborne viruses worldwide, and it is still common in developing countries. In article number 2201958, Marco Cecchini and co‐workers present a point‐of‐care biosensing lab‐on‐a‐chip based on surface‐acoustic‐waves for detecting measles virions in human saliva. The presented findings may serve as a guideline for designing new microfluidics‐based biosensing systems.