The loss of the sense of smell has not produced as many technological developments to mitigate the inconvenience it causes compared to the loss of vision or hearing. Anosmia or hyposmia concerns approximately 20% of the current European population and is associated with a loss of quality of life and an increased rate of household accidents. Restoring olfaction would therefore be beneficial, but it represents a technological challenge. Electrical stimulation of the nasal cavity triggers sensations that may be helpful to patients in detecting environmental odorant stimuli. We present an electrical stimulator fabricated using commercial flexible PCB technology and compare two different placement designs: A standard design based on existing medical technology that uses a metallic rod, bent to ensure contact with the nasal cavity; and a self-holding design featuring two magnets, placed across the nasal septum to ensure contact. The detection thresholds were measured for both configurations on seven normosmic individuals and show a good correlation between the two designs.

Introduction The olfactory and trigeminal system are closely interlinked. Existing literature has primarily focused on characterizing trigeminal stimulation through mechanical and chemical stimulation, neglecting thermal stimulation thus far. The present study aimed to characterize the intranasal sensitivity to heat and the expression of trigeminal receptors (transient receptor potential channels, TRP). Methods A total of 20 healthy participants (aged 21-27 years, 11 women) were screened for olfactory function and trigeminal sensitivity using several tests. Under endoscopic control, a thermal stimulator was placed in 7 intranasal locations: anterior septum, lateral vestibulum, interior nose tip, lower turbinate, middle septum, middle turbinate, and olfactory cleft to determine the thermal threshold. Nasal swabs were obtained in 3 different locations (anterior septum, middle turbinate, olfactory cleft) to analyze the expression of trigeminal receptors TRP: TRPV1, TRPV3, TRPA1, TRPM8. Results The thermal threshold differed between locations (p = 0.018), with a trend for a higher threshold at the anterior septum (p = 0.092). There were no differences in quantitative receptor expression (p = 0.46) at the different sites. The highest overall receptor RNA expression was detected for TRPV1 over all sites (p<0.001). The expression of TRPV3 was highest at the anterior septum compared to the middle turbinate or the olfactory cleft. The thermal sensitivity correlated with olfactory sensitivity and results from tests were related to trigeminal function like intensity ratings of ammonium, a questionnaire regarding trigeminal function, nasal patency, and CO(2 )thresholds. However, no correlation was found between receptor expression and psychophysical measures of trigeminal function. Discussion This study provided the first insights about intranasal thermal sensitivity and suggested the presence of topographical differences in thermal thresholds. There was no correlation between thermal sensitivity and trigeminal mRNA receptor expression. However, thermal sensitivity was found to be associated with psychophysical measures of trigeminal and olfactory function.

Liquids confined down to the atomic scale can show radically new properties. However, only indirect and ensemble measurements operate in such extreme confinement, calling for novel optical approaches that enable direct imaging at the molecular level. Here we harness fluorescence originating from single-photon emitters at the surface of hexagonal boron nitride for molecular imaging and sensing in nanometrically confined liquids. The emission originates from the chemisorption of organic solvent molecules onto native surface defects, revealing single-molecule dynamics at the interface through the spatially correlated activation of neighbouring defects. Emitter spectra further offer a direct readout of the local dielectric properties, unveiling increasing dielectric order under nanometre-scale confinement. Liquid-activated native hexagonal boron nitride defects bridge the gap between solid-state nanophotonics and nanofluidics, opening new avenues for nanoscale sensing and optofluidics.

While interference colors have been known for a long time, conventional color filters have large spatial dimensions and cannot be used to create compact pixelized color pictures. Here we report a simple yet elegant interference-based method of creating microscopic structural color pixels using a single-mask process using standard UV photolithography on an all-dielectric substrate. The technology makes use of the varied aperture-controlled physical deposition rate of low-temperature silicon dioxide inside a hollow cavity to create a thin-film stack with the controlled bottom layer thickness. The stack defines which wavelengths of the reflected light interfere constructively, and thus the cavities act as micrometer-scale pixels of a predefined color. Combinations of such pixels produce vibrant colorful pictures visible to the naked eye. Being fully CMOS-compatible, wafer-scale, and not requiring costly electron-beam lithography, such a method paves the way toward large scale applications of structural colors in commercial products.

We report a new approach to controllable thermal stimulation of a single living cell and its compartments. The technique is based on the use of a single polycrystalline diamond particle containing silicon-vacancy (SiV) color centers. Due to the presence of amorphous carbon at its intercrystalline boundaries, such a particle is an efficient light absorber and becomes a local heat source when illuminated by a laser. Furthermore, the temperature of such a local heater is tracked by the spectral shift of the zero-phonon line of SiV centers. Thus, the diamond particle acts simultaneously as a heater and a thermometer. In the current work, we demonstrate the ability of such a Diamond Heater-Thermometer (DHT) to locally alter the temperature, one of the numerous parameters that play a decisive role for the living organisms at the nanoscale. In particular, we show that the local heating of 11–12 °C relative to the ambient temperature (22 °C) next to individual HeLa cells and neurons, isolated from the mouse hippocampus, leads to a change in the intracellular distribution of the concentration of free calcium ions. For individual HeLa cells, a long-term (about 30 s) increase in the integral intensity of Fluo-4 NW fluorescence by about three times is observed, which characterizes an increase in the [Ca 2+ ] cyt concentration of free calcium in the cytoplasm. Heating near mouse hippocampal neurons also caused a calcium surge—an increase in the intensity of Fluo-4 NW fluorescence by 30% and a duration of ~ 0.4 ms.

In this work, we develop and study superconducting materials for a broadband microwave single-photon detector for wide-range applications in superconducting quantum devices. Ideal materials of this type should have a superconducting gap of the order of 10 GHz (0.2 K), and possess a normal sheet resistance of the order of 50 Omega . We find that Ti/Pt bilayers are good candidates: it enables to vary the superconducting transition temperature in a wide range, from 0.1 to 0.4 K, and the sheet resistance in the range from 10 to 50 Omega. We present a proof-of-principle demonstration of a low-level microwave power detector based on a nanobridge made of a designed Ti/Pt bilayer. The response to the absorbed microwave power is consistent with the picture of the kinetic inductance detection in superconductors. The extracted response time corresponds to the recombination of quasiparticles with the emission of a photon to the microwave line.

Hexagonal boron nitride (hBN) has emerged as a promising material platform for nanophotonics and quantum sensing, hosting optically active defects with exceptional properties such as high brightness and large spectral tuning. However, precise control over deterministic spatial positioning of emitters in hBN remained elusive for a long time, limiting their proper correlative characterization and applications in hybrid devices. Recently, focused ion beam (FIB) systems proved to be useful to engineer several types of spatially defined emitters with various structural and photophysical properties. Here we systematically explore the physical processes leading to the creation of optically active defects in hBN using FIB and find that beam-substrate interaction plays a key role in the formation of defects. These findings are confirmed using transmission electron microscopy, which reveals local mechanical deterioration of the hBN layers and local amorphization of ion beam irradiated hBN. Additionally, we show that, upon exposure to water, amorphized hBN undergoes a structural and optical transition between two defect types with distinctive emission properties. Moreover, using super-resolution optical microscopy combined with atomic force microscopy, we pinpoint the exact location of emitters within the defect sites, confirming the role of defected edges as primary sources of fluorescent emission. This lays the foundation for FIB-assisted engineering of optically active defects in hBN with high spatial and spectral control for applications ranging from integrated photonics, to nanoscale sensing, and to nanofluidics.

Our understanding of the dynamics of charge transfer between solid surfaces and liquid electrolytes has been hampered by the difficulties in obtaining interface, charge, and solvent-specific information at both high spatial and temporal resolution. Here, we measure at the single charge scale the dynamics of protons at the interface between an hBN crystal and binary mixtures of water and organic amphiphilic solvents (alcohols and acetone), evidencing a marked influence of solvation on interfacial dynamics. Applying single-molecule localization microscopy to emissive crystal defects, we observe correlated activation between adjacent ionizable surface defects, mediated by the transport of single excess protons along the solid/liquid interface. Solvent content has a nontrivial effect on interfacial dynamics, leading at intermediate water fraction to an increased surface diffusivity, as well as an increased affinity of the proton charges to the solid surface. Our measurements evidence the notable role of solvation on interfacial proton charge transport.

The Josephson junction as a switching detector of weak signals is investigated in presence of noise in the frame of rotating pendulum model. The parameter range, where the detection can be more efficient, is found. It has been demonstrated, that with decrease of the signal power the double minima of the mean switching time and the standard deviation are transformed into a single minimum, which corresponds to interplay between noise suppression and resonant activation regimes. The resonant nature of escape allows to detect weak signals, whose amplitudes are weaker than the difference between critical cur-rent and bias current of a Josephson junction. With decrease of damping an efficient detection becomes possible even at subharmonics of the resonance frequency. (c) 2021 Elsevier Ltd. All rights reserved.

Adapting optical microscopy methods for nanoscale characterization of defects in two-dimensional (2D) materials is a vital step for photonic on-chip devices. To increase the analysis throughput, waveguide-based on-chip imaging platforms have been recently developed. Their inherent disadvantage, however, is the necessity to transfer the 2D material from the growth substrate to the imaging chip which introduces contamination, potentially altering the characterization results. Here we present a unique approach to circumvent these shortfalls by directly growing a widely-used 2D material (hexagonal boron nitride, hBN) on silicon nitride chips, and optically characterizing the defects in the intact as-grown material. We compare the direct growth approach to the standard wet transfer method, and confirm the clear advantages of the direct growth. While demonstrated with hBN in the current work, the method is easily extendable to other 2D materials.

Aqueous proton transport at interfaces is ubiquitous and crucial for a number of fields, ranging from cellular transport and signalling, to catalysis and membrane science. However, due to their light mass, small size and high chemical reactivity, uncovering the surface transport of single protons at room temperature and in an aqueous environment has so far remained out-of-reach of conventional atomic-scale surface science techniques, such as scanning tunnelling microscopy. Here, we use single-molecule localization microscopy to resolve optically the transport of individual excess protons at the interface of hexagonal boron nitride crystals and aqueous solutions at room temperature. Single excess proton trajectories are revealed by the successive protonation and activation of optically active defects at the surface of the crystal. Our observations demonstrate, at the single-molecule scale, that the solid/water interface provides a preferential pathway for lateral proton transport, with broad implications for molecular charge transport at liquid interfaces.

Single-molecule localization microscopy (SMLM) is a powerful tool that is routinely used for nanoscale optical imaging of biological samples. Recently, this approach has been applied to study optically active defects in two-dimensional (2D) materials. Such defects can not only alter the mechanical and optoelectronic properties of 2D materials but also bring new functionalities, which make them a promising platform for integrated nanophotonics and quantum sensing. Most SMLM approaches, however, provide a field of view limited to similar to 50 x 50 mu m(2), which is not sufficient for high-throughput characterization of 2D materials. Moreover, the 2D materials themselves pose an additional challenge as their nanometer-scale thickness prevents efficient far-field excitation of optically active defects. To overcome these limitations, we present here a waveguide-based platform for large field-of-view imaging of 2D materials via total internal reflection excitation. We use this platform to perform large-scale characterization of point defects in chemical vapor deposition-grown hexagonal boron nitride on an area of up to 100 x 1000 mu m(2) and demonstrate its potential for correlative imaging and high throughput characterization of defects in 2D materials.

Super-resolution microscopies based on the localization of single molecules have been widely adopted due to their demonstrated performance and their accessibility resulting from open software and simple hardware. The PAINT method for localization microscopy offers improved resolution over photoswitching methods, since it is less prone to sparse sampling of structures and provides higher localization precision. Here, we show that waveguides enable increased throughput and data quality for PAINT, by generating a highly uniform ~100 × 2000 µm 2 area evanescent field for TIRF illumination. To achieve this, we designed and fabricated waveguides optimized for efficient light coupling and propagation, incorporating a carefully engineered input facet and taper. We also developed a stable, low-cost microscope and 3D-printable waveguide chip holder for easy alignment and imaging. We demonstrate the capabilities of our open platform by using DNA-PAINT to image multiple whole cells or hundreds of origami structures in a single field of view.

Temperature is a widely known phenomenon, which plays an extremely important role in biological systems. Its behavior on the macro-scale has been quite well investigated and understood, thanks to the availability of reliable and precise thermometers such as thermocouples and infrared cameras. However, temperature measurements on the subcellular scale present an ongoing challenge due to the absence of universal nanoscale temperature sensors. Recent work on fluorescent nanodiamonds has revealed their unique ability to measure temperature with high spatial and temporal resolution, of particular importance in the intracellular environment. This review summarizes recent progress in the field and highlights the future directions for intracellular temperature sensing using fluorescent nanodiamonds.

Point defects can have significant impact on the mechanical, electronic, and optical properties of materials. The development of robust, multidimensional, high-throughput, and large-scale characterization techniques of defects is thus crucial for the establishment of integrated nanophotonic technologies and material growth optimization. Here, we demonstrate the potential of wide-field spectral single-molecule localization microscopy (SMLM) for the determination of ensemble spectral properties as well as the characterization of spatial, spectral, and temporal dynamics of single defects in chemical vapor deposition (CVD)-grown and irradiated exfoliated hexagonal boron-nitride materials. We characterize the heterogeneous spectral response of our samples and identify at least two types of defects in CVD-grown materials, while irradiated exfoliated flakes show predominantly only one type of defects. We analyze the blinking kinetics and spectral emission for each type of defects and discuss their implications with respect to the observed spectral heterogeneity of our samples. Our study shows the potential of wide-field spectral SMLM techniques in material science and paves the way toward the quantitative multidimensional mapping of defect properties.

Fluorescent nanoparticles with optically robust luminescence are imperative to applications in imaging and labeling. Here we demonstrate that hexagonal boron nitride (hBN) nanoparticles can be reliably produced using a scalable cryogenic exfoliation technique with sizes below 10 nm. The particles exhibit bright fluorescence generated by color centers that act as atomic-size quantum emitters. We analyze their optical properties, including emission wavelength, photon-statistics, and photodynamics, and show that they are suitable for far-field super-resolution fluorescence nanoscopy. Our results provide a foundation for exploration of hBN nanoparticles as candidates for bioimaging, labeling, as well as biomarkers that are suitable for quantum sensing.

We have successfully applied the resistance grid technique to measure the disintegration speed in a special type of glass objects, widely known as Prince Rupert's drops. We use a fast digital oscilloscope and a simple electrical circuit, glued to the surface of the drops, to detect the voltage changes, corresponding to the breaks in the specific parts of the drops. The results obtained using this method are in good qualitative and quantitative agreement with theoretical predictions and previously published data. Moreover, the proposed experimental setup does not include any expensive equipment (such as a high-speed camera) and can therefore be widely used in high schools and universities.

We discuss the known construction of two interacting superconducting circuits based on Josephson junctions, which can be precisely engineered and easily controlled. In particular, we use the parametric excitation of two circuits realized by an instant change of the qubit coupling to study entropic and information properties of the density matrix of a composite system. We obtain the density matrix from the initial thermal state and perform its analysis in the approximation of small perturbation parameter and sufficiently low temperature. We also check the subadditivity condition for this system both for the von Neumann entropy and deformed entropies and check the dependence of mutual information on the system temperature. Finally, we discuss the applicability of this approach to describe the two coupled superconducting qubits as harmonic oscillators with limited Hilbert space.

We verify the new entropic and information inequalities for noncomposite systems using an experimental 5×5 density matrix of the qudit state measured by the tomographic method in a multilevel superconducting circuit. These inequalities are well known for bipartite and tripartite systems but have never been tested for superconducting qudits. Entropic inequalities can also be used to evaluate the accuracy of experimental data and the value of mutual information deduced from them and characterize correlations between different degrees of freedom in a noncomposite system.