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Metal-organic frameworks (MOFs) have the advantages of tunable pore sizes and porosity and have demonstrated unique advantages for various applications. This study synthesized composite MOF nanomaterials by modifying MOF801 or AlOOH with UIO66. The composite nanomaterials, UIO66/MOF801 and UIO66/AlOOH showed increased Zeta potential than their pristine form, AlOOH, UIO66 and MOF801. For the first time, the composite MOFs were used to fabricate filter paper-based evaporation-driven power generators for spontaneous electricity generation. The MOFs-KBF membrane was constructed by coating filter paper (10 × 50 mm) with composite MOFs and conductive Ketjen Black. The UIO66/MOF801 decorated device achieved a maximum open circuit voltage of 0.329 ± 0.005 V and maximum output power of 2.253 μW. The influence of salt concentration (0.1–0.5 M) on power generation was also analyzed and discussed. Finally, as a proof-of-concept application, the device was employed as a salinity sensor to realize remote monitoring of salinity. This work demonstrated the potential of flexible MOF composites for spontaneous power generation from water evaporation and provides a potential way to enhance the performance of evaporation-driven power generators. [ABSTRACT FROM AUTHOR]

Chefs frequently rely on their taste to assess the content and flavor of dishes during cooking. While tasting the food, the mastication process also provides continuous feedback by exposing the taste receptors to food at various stages of chewing. Since different ingredients of the dish undergo specific changes during chewing, the mastication helps to understand the food content. The current methods of electronic tasting, on the contrary, always use a single taste snapshot of a homogenized sample. We propose a robotic setup that uses the mixing to imitate mastication and tastes the dish at two different mastication phases. Each tasting is done using a conductance probe measuring conductance at multiple, spatially distributed points. This data is used to classify 9 varieties of scrambled eggs with tomatoes. We test four different tasting methods and analyze the resulting classification performance, showing a significant improvement over tasting homogenized samples. The experimental results show that tasting at two states of mechanical processing of the food increased classification F1 score to 0.93 in comparison to the traditional tasting of a homogenized sample resulting in F1 score of 0.55. We attribute this performance increase to the fact that different dishes are affected differently by the mixing process, and have different spatial distributions of the salinity. It helps the robot to distinguish between dishes of the same average salinity, but different content of ingredients. This work demonstrates that mastication plays an important role in robotic tasting and implementing it can improve the tasting ability of robotic chefs.

Quartz crystal microbalance (QCM) has been used as a resonant sensing platform for chemical, biological, and mechanical events detection. Specifically, QCMs have shown great potential towards a particle sensing as the added mass induces a linear shift in resonant frequency. Although a QCM is an economic solution for the mass sensing of solid thin films, QCMs generally become unreliable for in-liquid particles analysis due to a rather complex fluidic motions and coffee ring effect of liquid droplets. Specifically, uncontrollable agglomerations of particles hinder a stable QCM operation and ultimately limit its mass sensitivity. This paper presents the integration of a layer of Carbon Nanotubes (CNTs) on a QCM for an accurate sensing of the ion concentration in liquid, or salinity. The integrated CNT layer induces a controllable nm-resolution roughness on QCMs, and such roughness affects the nucleation behavior of ionic particles and adhesion parameters, ultimately improving the particle adhesion for a stable QCM operation. CNT-QCMs exhibit a mass sensing range of up to over $10 ~\mu \text{g}$ with about 40 pg measurement resolution. Moreover, CNT-QCMs maintain higher quality factor (${Q}$) compared to the bare QCM, and such improvement in ${Q}$ could directly determine the power budget and noise performances of the QCM integrated oscillators or sensor systems. We believe our work can contribute to build an advanced sensor system for water quality monitoring and detection of liquid ion concentration in semiconductor fabrication processes. [ABSTRACT FROM AUTHOR]

In this paper, we report a novel and compact sensor based on an optic microfiber coupler interferometer (OMCI) for seawater salinity application. The OMCI device is fabricated by connecting Faraday rotating mirrors to the two out-ports of the microfiber coupler, respectively. The sensor signal processing is based on a wavelength demodulation technique. We theoretically analyze the sensing characteristics with different device structure parameters. Besides, the results show that the date reading error decreases with the thinner waist region and longer arm difference. Through the experiment, the reflection spectra red-shifted as the sea water salinity increased; the highest response sensitivity of the OMCI salinity sensor reached 303.7 pm/‰ for a range of 16.6–23.8‰, and the resolution was less than 0.03‰. This study provides a new technical solution for the development of practical optical fiber seawater salinity sensors.

A simple, high-sensitivity, and low-cost optical sensor for the measurement of temperature and salinity in seawater is demonstrated based on a microfiber directional coupler. The shifts of sensing dips are highly sensitive to the change of salinity and temperature in seawater with highest sensitivities at 930 pm/% and -160 pm/°C for coupler assembled by 3.79and 2.20-μm-diameter fibers. The temperature sensitivity can be further improved to -1130 pm/°C for smaller fibers with diameters of 3.50 and 1.35 μm. To keep the stable structure in liquid, a methodology of coating using ethyl cellulose ethoce film is proposed. By ethyl cellulose ethoce solvent coating on the coupling area, the coupler can be operated stably in seawater. The sensor demonstrated here is easy to construct, is low cost, is high sensitivity, and is compatible with the optical fiber system, which may find applications in developing miniature and multifunction optical sensors used in seawater and other liquid surroundings.

Seawater salinity is a critical physical parameter in oceanography, affecting ocean circulation, marine ecosystems, and climate. However, current salinity measurement methods have limitations in terms of efficiency, convenience, and integration. Therefore, the development of advanced salinity measurement technology is crucial for ocean exploration and research. In this study, we designed a high-sensitivity ocean refractive index sensor using the guided-mode resonance, which exhibits superior performance in terms of transmission efficiency (approximately 1), full width at half maximum (0.210 nm), and figure of merit (5675.924). Furthermore, we obtained a set of optimized parameters by conducting a systematic study on the relationship between different structural parameters and resonance wavelength, which significantly improves the performance. Additionally, the variation trend of resonance wavelength with the change of refractive index in seawater was studied, which demonstrates that our optimized scheme achieves highly sensitive seawater salinity measurement with good process tolerance, polarization insensitivity, and a wide wavelength working interval. This high-sensitivity ocean refractive index sensor has great potential for a wide range of applications in future ocean exploration studies, such as ocean environment monitoring, marine ecology management, and oceanographic research. • Refractive index sensing in a simple 2D grating structure. • FOM can be flexibly controlled by geometric parameters and incidence angle. • The object under test with a small refractive index difference can also be detected. [ABSTRACT FROM AUTHOR]

The microfiber knot-type ring resonator is widely used in sensing, and the resonant mode is an essential concern. In this paper, resonant mode characteristics of microfiber knot-type ring resonator are studied theoretically. Results show that resonant mode split occurs when the deviation angle is large enough under the condition that the input is linearly or elliptically polarized light. Moreover, in the case that the input is partially polarized light, the resonant peak positions of split modes are identical with those in the case of inputting linearly or elliptically polarized light under the same deviation angle. The split mode characteristic is further studied by salinity sensing simulation and experiment. The split modes have the same free spectral range, and their resonant peak shifts have the same response to salinity changing. The experimental split mode characteristic is in good agreement with theoretical simulating, which demonstrates the resonant mode split theory of the microfiber knot-type ring resonator. The analysis on resonant mode presented here may offer useful references for sensing applications.

A simple, high-sensitivity, and low-cost optical sensor for the measurement of temperature and salinity in seawater is demonstrated based on a microfiber directional coupler. The shifts of sensing dips are highly sensitive to the change of salinity and temperature in seawater with highest sensitivities at 930 pm/‰ and -160 pm/ ^{\circ}C for coupler assembled by 3.79- and 2.20- \mu\text{m}- diameter fibers. The temperature sensitivity can be further improved to -1130 pm/ ^{\circ}C for smaller fibers with diameters of 3.50 and 1.35 \mu\text{m}$. To keep the stable structure in liquid, a methodology of coating using ethyl cellulose ethoce film is proposed. By ethyl cellulose ethoce solvent coating on the coupling area, the coupler can be operated stably in seawater. The sensor demonstrated here is easy to construct, is low cost, is high sensitivity, and is compatible with the optical fiber system, which may find applications in developing miniature and multifunction optical sensors used in seawater and other liquid surroundings. [ABSTRACT FROM PUBLISHER]

Salinity is an indispensable parameter for various applications such as biomedical diagnostics, environmental chemical analysis, marine monitoring, etc. Miniaturized salinity sensors have significant potential in portable applications in various scenarios and designs with highly desirable features of convenience, reliability, economy, and high sensitivity and also the capability of real-time measurements. Herein, we demonstrate a highly refractive index-sensitive sensor based on a microscale III-nitride chip that consists of a light emitter and a photodetector. This highly monolithically integrated chip shows an excellent sensitivity of salinity of 2606 nA/(mol/L) (or 446 nA/%) and a response time of 0.243 s. In addition, wireless communication technologies can be easily integrated with the sensing device, which enables automatic remote control for data collection and postprocessing. Remarkably, a polymer-based antifouling coating on the surface of the sensing chip has been established to significantly improve its long-term stability in mimicked marine water. The demonstrated ultrasensitive, ultracompact, cost-effective, fast response, wireless-compatible, and easy-to-use features endow the current device with a huge potential for in situ salinity sensing under varying environmental conditions.

In this paper, we report a novel and compact sensor based on an optic microfiber coupler interferometer (OMCI) for seawater salinity application. The OMCI device is fabricated by connecting Faraday rotating mirrors to the two out-ports of the microfiber coupler, respectively. The sensor signal processing is based on a wavelength demodulation technique. We theoretically analyze the sensing characteristics with different device structure parameters. Besides, the results show that the date reading error decreases with the thinner waist region and longer arm difference. Through the experiment, the reflection spectra red-shifted as the sea water salinity increased; the highest response sensitivity of the OMCI salinity sensor reached 303.7 pm/‰ for a range of 16.6–23.8‰, and the resolution was less than 0.03‰. This study provides a new technical solution for the development of practical optical fiber seawater salinity sensors. [ABSTRACT FROM AUTHOR]