Optical Fiber Sensor for Monitoring the Evaporation of Ethanol-Water Mixtures

Attaining Tailored Wicking Behavior with Additive Manufacturing

Additive manufacturing (AM) has opened a new pathway to create customized wicking materials. With lower manufacturing costs and a larger design space than many alternatives for wicking, AM is of particular value in fields such as thermal management and microfluidics. Fluid propagation during wicking in porous media, however, has largely remained limited to Washburnian (t ) behavior, and optimizing these materials for wicking in a variety of use cases presents a challenge. In this work, we present a method of tailoring wicking behavior to an arbitrary target function of propagation distance versus time, achieved through the use of AM to create nonuniform porous materials. Layers of parallel lines, each successive layer rotated 90° from the last, form a gridded structure with a spatially varying unit cell size for which analytical models for the capillary pressure and solid fraction and a semianalytical model for permeability were found. These models were validated with capillary rise experiments for spatially uniform porous materials over a range of solid fractions from 0.4 to 0.9. Leveraging these models and representing a nonuniform porous material as a series of Ohmic fluidic resistors, we created an inverse design algorithm that generates a wicking material with spatially varying parameters to achieve a specified target function for fluid propagation as a function of time. These materials can exhibit atypical wicking behavior, including fluid propagation displaying simple linear and piecewise linear relationships with time rather than the conventional Washburn relationship.

Environmental Monitoring: A Comprehensive Review on Optical Waveguide and Fiber-Based Sensors

Globally, there is active development of photonic sensors incorporating multidisciplinary research. The ultimate objective is to develop small, low-cost, sensitive, selective, quick, durable, remote-controllable sensors that are resistant to electromagnetic interference. Different photonic sensor designs and advances in photonic frameworks have shown the possibility to realize these capabilities. In this review paper, the latest developments in the field of optical waveguide and fiber-based sensors which can serve for environmental monitoring are discussed. Several important topics such as toxic gas, water quality, indoor environment, and natural disaster monitoring are reviewed.

Optical Identification of Parenteral Nutrition Solutions Exploiting Refractive Index Sensing

Parenteral artificial nutrition (PAN) is a lifesaving treatment for a large population of patients affected by different diseases, and it consists of intravenous injection of nutritive fluids by means of infusion pumps. Wrong PAN solutions are, unfortunately, often administered, thus threatening the patients' well-being. Here, we report an optofluidic label-free sensor that can distinguish PAN solutions on the basis of their volumetric refractive index (RI). In our system, a monochromatic light beam, generated by a laser diode, travels obliquely through a transparent, square-section polystyrene channel, is then back-reflected by a mirror, and finally exits the channel in a position that depends on the filling fluid RI. The displacement of the output light spot ΔXexperim is easily detected with a linear, 1-D position sensitive detector (PSD). We initially calibrated the sensor with water-glucose solutions demonstrating a sensitivity S = ΔXexperim/Δn = 13,960 µm/RIU. We then clearly distinguished six commercial PAN solutions, commonly administered to patients. To the best of our knowledge, this is the first reported healthcare sensing platform for remote contactless recognition of PAN fluids, which could be inserted into infusion pumps to improve treatment safety, by checking the compliance to the prescription of the fluid actually delivered to the patient.