Subsequently, the initial resistance value R0 of the MWNT sensor shown in the impedance analyzer at this time was recorded.(2)Gaseous SF6 decomposition product was passed into the sealed chamber through the inlet valve. Meanwhile, the resistance values R of the MWNT sensor were recorded until no change was observed. The resistance-change rate of the sensor, which is called the response of the sensor, was calculated as:��=(R?R0)/R0��100%(1)where R is the resistance value of the sensor after the injection of SF6 decomposition product gas, and R0 is the initial resistance value of the sensor under vacuum.(3)When the test was finished, SF6 decomposition product gas was pumped from the cylinder and N2 gas was passed into the cylinder to ensure that there was no residual gas present.

Evaporation is the transition from the liquid phase to the gas phase that occurs at temperatures below the boiling point, typically at ambient pressure [1]. Evaporation is related to properties of the fluid itself, the ambient environment and the surface on which the fluid is applied, and has diverse potential applications such as in climatography [2], cooling of electronic circuits [3] and even medical analysis of tears in the eyes [4]. Analysis of the formation, geometry and evaporation of fluid droplets can provide information on numerous properties of liquids including surface tension, viscosity, refractive index and chemical composition of solutions. In most cases, droplets are monitored through direct observation in contact angle goniometers, by micro-gravimeters, by atomic force microscopy, or using measurements of electrical capacitance [5�C8].

These methods provide high accuracy, however they often require sophisticated auxiliary equipment in the immediate vicinity of the fluid droplet.Optical fibers constitute an exceptional sensing platform [9]. They provide remote access to harsh environments, can be readily embedded within structures, and may serve as minimally-intrusive, bio-compatible probes. Fiber optic sensors Batimastat could offer simple, low-cost solutions for evaporation monitoring. The commonly observed quantities in fiber-optic fluid sensors are either refractive index or absorption spectrum. These observables provide rather limited information on evaporation dynamics and droplet behavior. Salazar-Haro and coauthors measured the reflection spectrum of a static droplet on the tip of an optical fiber to analyze the droplet geometry [10]. McMillan et al. used optical fibers in a capillary configuration in the monitoring of droplet formation [11].In this work, we demonstrate the monitoring of the evaporation dynamics of sub-nano-liter fluid volumes, from within in-line micro-cavities that are etched through optical fibers.