Structural Health Monitoring Using a New Type of Distributed Fiber Optic Smart Textiles in Combination with Optical Frequency Domain Reflectometry (OFDR): Taking a Pedestrian Bridge as Case Study.

Distributed fiber optic sensors (DFOS) have become a new method for continuously monitoring infrastructure status. However, the fiber's fragility and the installation's complexity are some of the main drawbacks of this monitoring approach. This paper aims to overcome this limitation by embedding a fiber optic sensor into a textile for a faster and easier installation process. To demonstrate its feasibility, the smart textile was installed on a pedestrian bridge at the University of Massachusetts Lowell. In addition, dynamic strain data were collected for two different years (2021 and 2022) using Optical Frequency Domain Reflectometry (OFDR) and compared, to determine the variability of the data after one year of installation. We determined that no significant change was observed in the response pattern, and the difference between the amplitude of both datasets was 14% (one person jumping on the bridge) and 43% (two people jumping) at the first frequency band. This result shows the proposed system's functionality after one year of installation, as well as its potential use for traffic monitoring.

Composite Bridge Girders Structure Health Monitoring Based on the Distributed Fiber Sensing Textile.

Distributed structure health monitoring has been a hot research topic in recent years, and optic fiber sensors are largely developed for the advantages of high sensitivity, better spatial resolution, and small sensor size. However, the limitation of fibers in installation and reliability has become one of the major drawbacks of this technology. This paper presents a fiber optic sensing textile and a new installation method inside bridge girders to address those shortcomings in fiber sensing systems. The sensing textile was utilized to monitor strain distribution in the Grist Mill Bridge located in Maine based on Brillouin Optical Time Domain Analysis (BOTDA). A modified slider was developed to increase the efficiency of installation in the confined bridge girders. The bridge girder's strain response was successfully recorded by the sensing textile during the loading tests that involved four trucks on the bridge. The sensing textile demonstrated the capability to differentiate separated loading locations. These results demonstrate a new way of installing fiber optic sensors and the potential applications of fiber optic sensing textiles in structural health monitoring.

Fiber Lateral Pressure Sensor Based on Vernier- Effect Improved Fabry-Perot Interferometer.

A fiber optic pressure sensor that can survive 2200 psi and 140 °C was developed. The sensor's pressure sensitivity was measured to be 14 times higher than bare FBG when tested inside stacks of ultra-high-molecular-weight polyethylene (UHMWPE) composite fabric. The sensitivity can be further improved 6-fold through the Vernier effect. Its tiny sensing length (hundreds of microns) and uniform outer diameter (125 µm) make it a suitable candidate for real-time point pressure monitoring under harsh environments with limited space, such as in composite-forming procedures.

Fiber Optic Sensing Textile for Strain Monitoring in Composite Substrates.

Composite polymers have become widely used in industries such as the aerospace, automobile, and civil construction industries. Continuous monitoring is essential to optimize the composite components' performance and durability. This paper describes the concept of a distributed fiber optic smart textile (DFOST) embedded into a composite panel that can be implemented during the fabrication process of bridges, planes, or vehicles without damaging the integrity of the composite. The smart textile used an embroidery method to create DFOST for easy installation between composite laminates. It also allows different layout patterns to provide two- or three-dimensional measurements. The DFOST system can then measure strain, temperature, and displacement changes, providing critical information for structural assessment. The DFOST was interrogated by using an optical frequency domain reflectometry (OFDR). It could measure strain variation during the dynamic and static test with a spatial resolution of 2 mm and a minimum strain resolution of 10 µÏµ. This paper focuses on the study of strain measurement.

Oropharyngeal swallowing hydrodynamics of thin and mildly thick liquids in an anatomically accurate throat-epiglottis model.

Understanding the mechanisms underlying dysphagia is crucial in devising effective, etiology-centered interventions. However, current clinical assessment and treatment of dysphagia are still more symptom-focused due to our limited understanding of the sophisticated symptom-etiology associations causing swallowing disorders. This study aimed to elucidate the mechanisms giving rise to penetration flows into the laryngeal vestibule that results in aspirations with varying symptoms. Methods: Anatomically accurate, transparent throat models were prepared with a 45° down flapped epiglottis to simulate the instant of laryngeal closure during swallowing. Fluid bolus dynamics were visualized with fluorescent dye from lateral, rear, front, and endoscopic directions to capture key hydrodynamic features leading to aspiration. Three influencing factors, fluid consistency, liquid dispensing site, and dispensing speed, were systemically evaluated on their roles in liquid aspirations. Results: Three aspiration mechanisms were identified, with liquid bolus entering the airway through (a) the interarytenoid notch (notch overflow), (b) cuneiform tubercle recesses (recess overflow), and (c) off-edge flow underneath the epiglottis (off-edge capillary flow). Of the three factors considered, liquid viscosity has the most significant impact on aspiration rate, followed by the liquid dispensing site and the dispensing speed. Water had one order of magnitude higher aspiration risks than 1% w/v methyl cellulose solution, a mildly thick liquid. Anterior dispensing had higher chances for aspiration than posterior oropharyngeal dispensing for both liquids and dispensing speeds considered. The effects of dispending speed varied. A lower speed increased aspiration for anterior-dispensed liquids due to increased off-edge capillary flows, while it significantly reduced aspiration for posterior-dispensed liquids due to reduced notch overflows. Visualizing swallowing hydrodynamics from multiple orientations facilitates detailed site-specific inspections of aspiration mechanisms.