Spectral Fingerprint Investigation in the near Infra-Red to Distinguish Harmful Ethylene Glycol from Isopropanol in a Microchannel

Ethylene glycol (EG) and isopropanol (ISO) are among the major toxic alcohols that pose a risk to human health. However, it is important to distinguish them, since EG is more prone to cause renal failure, and can thus be more dangerous when ingested than ISO. Analysis of alcohols such as isopropanol and ethylene glycol generally can be performed with a complex chromatographic method. Here, we present an optical method based on absorption spectroscopy, performed remotely on EG-ISO mixtures filling a microchannel. Mixtures of ethylene glycol in isopropanol at different volume concentrations were analyzed in a contactless manner in a rectangular-section glass micro-capillary provided with integrated reflectors. Fiber-coupled broadband light in the wavelength range 1.3–1.7 µm crossed the microchannel multiple times before being directed towards an optical spectrum analyzer. The induced zig-zag path increased the fluid–light interaction length and enhanced the effect of optical absorption. A sophisticated theoretical model was developed and the results of our simulations were in very good agreement with the results of the experimental spectral measurements. Moreover, from the acquired data, we retrieved a responsivity parameter, defined as power ratio at two wavelengths, that is linearly related to the EG concentration in the alcoholic mixtures.

Assessing the mechanisms thought to govern ice and snow friction and their interplay with substrate brittle behavior

Sliding friction on ice and snow is characteristically low at temperatures common on Earth’s surface. This slipperiness underlies efficient sleds, winter sports, and the need for specialized tires. Friction can also play micro-mechanical role affecting ice compressive and crushing strengths. Researchers have proposed several mechanisms thought to govern ice and snow friction, but directly validating the underlying mechanics has been difficult. This may be changing, as instruments capable of micro-scale measurements and imaging are now being brought to bear on friction studies. Nevertheless, given the broad regimes of practical interest (interaction length, temperature, speed, pressure, slider properties, etc.), it may be unrealistic to expect that a single mechanism accounts for why ice and snow are slippery. Because bulk ice, and the ice grains that constitute snow, are solids near their melting point at terrestrial temperatures, most research has focused on whether a lubricating water film forms at the interface with a slider. However, ice is extremely brittle, and dry-contact abrasion and wear at the front of sliders could prevent or delay a transition to lubricated contact. Also, water is a poor lubricant, and lubricating films thick enough to separate surface asperities may not form for many systems of interest. This article aims to assess our knowledge of the mechanics underlying ice and snow friction.

Electro-Optical Biosensor Based on Embedded Double-Monolayer of Graphene Capacitor in Polymer Technology

In this work, we present an interferometric polymer-based electro-optical device, integrated with an embedded double-monolayer graphene capacitor for biosensing applications. An external voltage across the capacitor applies an electric field to the graphene layers modifying their surface charge density and the Fermi level position in these layers. This in turn changes the electro-optic properties of the graphene layers making absorption in the waveguide tunable with external voltages. Simultaneously, it is possible to appreciate that this phenomenon contributes to the maximization of the light-graphene interaction by evanescent wave in the sensing area. As a result, it is obtained large phase changes at the output of the interferometer, as a function of small variations in the refractive index in the cladding area, which significantly increasing the sensitivity of the device. The optimum interaction length obtained was 1.24 cm considering a cladding refractive index of 1.33. An absorption change of 129 dB/mm was demonstrated. This result combined with the photonic device based on polymer technology may enable a low-cost solution for biosensing applications in Point of Care (PoC) platform.

Emotional experiences in digitally mediated and in-person interactions: An experience-sampling study

As the ubiquity of digitally mediated communication grows, so does the number of questions about the costs and benefits of replacing in-person interactions with digital ones. In the present study, we used a daily diary design to examine how people’s emotional experiences vary across in-person, video-, phone-, and text-mediated interactions in day-to-day life. We hypothesized that individuals would report less positive affect and more negative affect after less life-like interactions (where in-person is defined as the most life-like and text-mediated as the least life- like). In line with this hypothesis, the analysis of 527 unique interactions reveals that people feel lonelier, sadder, less connected, less supported, and less happy following digitally mediated compared to in-person interactions. Additional analyses show that the links between communication mode and momentary experiences are independent of properties of individual interactions such as interaction length and overall quality of the interaction. These findings provide initial evidence that there may be inherent properties of common digital communication tools that make connection more challenging and point to important directions for future research.

Mid-infrared Nanoantennas as Ultrasensitive Vibrational Probes Assisted by Machine Learning and Hyperspectral Imaging

Infrared (IR) Spectroscopy has been developed for centuries and has been widely used to identify molecular structure from the massive information provided by IR fingerprint absorption, reflecting the vibration energy of the chemical bond. Due to the intrinsically weak light-matter interaction, IR spectroscopy serves low sensitivity and sizeable optical interaction length (~mm to ~cm) compared with other optical probes like Raman, florescent, and refractometry technology, which hinder the applications for ultra-sensitive biomolecular screening. Here, we report a new type of IR spectroscopy by wavelength gradient hook nanoantenna integrated with the microfluidic channel, enhancing the IR molecular absorption and bringing in refractometry function with ultrathin (~100 nm) optical interaction length. With the proof-of-concept demonstration of molecular recognition of mixed alcoholic liquids by machine learning and molecular fingerprint retrieving by hyperspectral images in one-time data acquisition, our work paves the way to advance, small-volume, real-time, ultra-sensitive, in-vitro biomolecular dynamic analysis in the aqueous environment.

Research on the characteristics of Klein–Cook parameter and diffraction efficiency of acousto-optic interaction for low-frequency ultrasonic in the liquid

We have investigated the characteristics of acousto-optic interaction for low-frequency ultrasonic wave in a liquid. Based on the coupling wave equation of acousto-optic interaction, the diffraction light characteristics for normal incidence at small parameter Q have been discussed. The parameter Q with respect to acousto-optic interaction length, ultrasonic frequency, water temperature, and the concentration of sucrose solution have been analyzed, which is an important physical quantity and reflects the degree of mismatch in the acousto-optic interaction. The diffraction efficiencies for different parameters Q, incident angles and phase shifts have been calculated. The results of our work provide theoretical basis for further study of the acousto-optic effect in the liquid.