This research project focuses on developing and validating innovative technologies for next-generation composite aircrafts and other large structures, with intrinsic sensing properties to provide complete structural damage awareness. The work is aimed at creating a paradigm shift in damage sensing through the development of the novel Triboluminescence and Photocatalysis (TriP) system that utilizes embedded triboluminescent (TL) sensors to provide real-time ubiquitous detection of crack initiation and growth at the material level. TL crystals will be used to manufacture "pain responsive" composite components containing a novel "nervous system" of embedded nano-optoelectronic (CTiN) rods. When stressed, triboluminescent crystals emit light, giving an indication of the location and extent of damage. The emitted light is absorbed by nano-electronic cells, which consists of nano-sized photocatalyst material in conjunction with carbon nanotubes to conduct as sensory pathways disseminating information to sensing stations. The underlying issues to be investigated are the placement of TL crystals, light conversion, and the subsequent transmission of electrical signals using the novel CTiN rods.
The project will develop confidence in aircraft structural health monitoring through systematic investigations of material systems for embedded sensing, embedded data transfer and utilization of sensory information, without compromising structural properties.
An overview chart of potential sensortype utilizing the triboluminescent (TL) material ZnS:Mn lead to two sensor types developed by the researchteam. The intrinsic optical fiber (ITOF) and the three-dimensional dye-sensitized solar cell (3D-DSC)device. The ITOF sensor is an attempt to solve these problems. The ITOF sensor was developed to enable effective side coupling of TL optical signals for damage detection and monitoring.The ITOF sensor consists of a polymer optical fiber (POF) with a highly sensitized section, known as thetriboluminescence sensory receptor (TSR). The TSR is made by mechanically removing the jacket in thatsection along the length of the POF, and coating with epoxy containing dispersed ZnS:Mn crystals. TheTL signals are then transmitted through the POF to a photodetector such as a photomultiplier tube(PMT) or a photodiode. The photodetector converts the TL optical signals into electrical signals that canbe analyzed by a computer system for damage characterization. The operation of the ITOF sensor is analogous to that of the sensory receptors in the human nervoussystem that are able to convert the energy of the stimuli into nerve impulses that can be transmittedthrough the neurons. The sensitized section of the ITOF acts like the sensory receptor of the HNS whilethe optical fiber acts like the neuron for transmitting the TL optical signal to the photodetectors. .This project has led to the development of the in-situ triboluminescent optical fiber (ITOF) sensor. Thisinnovative sensor system mimics the sensory receptor of the human nervous system with an integratedsensing and transmission system. The capability of the ITOF to provide real time damage monitoring incementitious composites like concrete structures (e.g. bridges, etc.) have been demonstrated. The research was featured in the November 2014 issue of physica status solidi (rapid research letters). "A high efficiency 3D photovoltaic microwire with carbon nanotubes (CNT)–quantum dot (QD) hybrid interface" was written by Dr. M. J. Uddin, Deborah E. Daramola, Ever Velasquez, Dr. Tarik J. Dickens, Jin Yan, Emily Hammel, Federico Cesano, and Dr. Okenwa I. Okoli. The article discusses an innovative hybrid quantum-dot sensitized photo¬voltaic carbon-nanotubes microyarn developed by the IME team using thermally stable and highly conductive carbon-nanotube yarns (CNYs). These three-dimensional photovoltaic cells show 5.93% photon-to-energy conversion efficiencies under standard AM 1.5 light intensity with high structural flexibility. The CNYs are highly inter-aligned, ultrastrong and flexible with excellent electrical conductivity, mechanical integrity and catalytic properties. The CNYs are coated with a quantum-dots (CdSe/CdS) incorporated TiO2 microfilm and intertwined with a second set of CNYs as the counter electrode. These cells are capable of efficiently harvesting incident photons regardless of direction and generating photocurrents with high efficiency and operational stability. This flexible 3D PV wire could potentially be woven into engineering textiles or reinforced fabrics for smart applications.
