System Integration of Flexible and Multifunctional Thin Film Sensors for Structural Health Monitoring

Greater information is needed on the state of civil infrastructure to ensure public safety and cost-efficient management. Lack of infrastructure investment and foreseeable funding challenges mandate a more intelligent approach to future maintenance of infrastructure systems. Much of the technology currently utilized to assess structural performance is based on discrete sensors. While such sensors can provide valuable data, they can lack sufficient resolution to accurately identify damage through inverse methods. Alternatively, technologies have shown promise for distributed, direct damage detection with flexible thin film and multifunctional polymer-nanocomposite materials. However, challenges remain as significant past work has focused on material optimization as opposed to sensing systems for damage detection. This dissertation offers novel methods for direct and distributed strain sensing by providing a fabrication methodology for broadly enabling thin film sensing technologies in structural health monitoring (SHM) applications. This fabrication methodology is presented initially as a set of materials and processes which are illustrated in analog circuit primitive forms including flexible, thin film capacitors, resistors, and inductors. Three sensing systems addressing specific SHM challenges are developed from this base of components and processes as specific illustrations of the broader fabrication approach. The first system developed is a fully integrated strain sensing system designed to enable the use of multifunctional materials in sensing applications. This is achieved through the development of an optimized fabrication approach applicable to many multifunctional materials. A layer-by-layer (LbL) deposited nanocomposite is incorporated with a lithography process to produce a sensing system. To illustrate the process, a strain sensing platform consisting of a nanocomposite film within an amplified Wheatstone bridge circuit is presented. The study reveals the material process is highly repeatable to produce fully integrated strain sensors with high linearity and sensitivity. The thin film strain sensors are robust and are capable of high strain measurements beyond 3,000 μϵ. The second system developed is an array of resistive distributed strain sensors and an associated algorithm to provide an alternative to electrical impedance tomography for spatial strain sensing. An LbL deposited polymer composite thin film is utilized as the piezoresistive sensing material. An inverse algorithm is presented and utilized for determining the resistance of array elements by electrically stimulating boundary nodes. Two polymer nanocomposite arrays are strain tested under cyclic loading. Both arrays functioned as networks of strain sensors confirming the viability of the approach and computational benefits for SHM. The third system developed is a thin film wireless threshold strain sensor for measuring strain in implanted and embedded applications. The wireless sensing system is comprised of two thin film, inductor-capacitor circuits, one of which included a fuse element. The sensor is fabricated on polyimide with metal layers used to pattern inductive antennas and a strain sensitive parallel plate capacitor. A titanium thin film fuse is designed to fail, or have a large resistance increase, when a strain threshold is exceeded. Three prototype systems are interrogated wirelessly while under increasing tensile strain. One of two sensor resonant peaks disappear at a strain threshold as designed, validating the sensing approach and thin film form for use in SHM systems. The fuse approach provides a platform for various systems and sensing elements. The reference peak remains intact and is used for continuous real-time strain sensing with a sensitivity of 0.5 and a noise floor below 50 microstrain.PHDCivil EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144183/1/arburt_1.pd

Overview of the Detection Theme Area for IVHM in NASA's Aviation Safety Program

No abstract availabl

Roadmap on semiconductor-cell biointerfaces.

This roadmap outlines the role semiconductor-based materials play in understanding the complex biophysical dynamics at multiple length scales, as well as the design and implementation of next-generation electronic, optoelectronic, and mechanical devices for biointerfaces. The roadmap emphasizes the advantages of semiconductor building blocks in interfacing, monitoring, and manipulating the activity of biological components, and discusses the possibility of using active semiconductor-cell interfaces for discovering new signaling processes in the biological world

NATURE-INSPIRED MATERIAL STRATEGIES TOWARDS FUNCTIONAL DEVICES

Naturally sourced, renewable biomaterials possess outstanding advantages for a multitude of biomedical applications owing to their biodegradability, biocompatibility, and excellent mechanical properties. Of interest in this dissertation are silk (protein) and chitin (polysaccharide) biopolymers for the fabrication of functional biodevices. One of the major challenges restricting these materials beyond their traditional usage as passive substrate materials is the ability to combine them with high-resolution fabrication techniques. Initial research work is directed towards the fabrication of micropatterned, flexible 2D substrates of silk fibroin and chitin using bench-top photolithographic techniques. Research is focused on imparting electrochemical properties to silk proteins using conducting polymers (PEDOT: PSS and PANI) and a naturally occurring semiconductor, eumelanin. The utility of conducting biomimetic composites in device applications was demonstrated by the fabrication of fully organic silk based flexible electrochemical biosensors. The biosensors display excellent detection of dopamine and ascorbic acid with high sensitivity. A flexible silk-PEDOT: PSS based temperature sensor is also demonstrated for the accurate monitoring of skin surface temperature. Finally, the challenge of conformability at the biological interface is addressed using structure-based design strategies. Inspiration from the Japanese art of paper cutting was taken for the formation of patterned cuts on silk fibroin films using photolithography. Micropatterned cuts can increase the conformability of films to soft biological interfaces by enhancing their strain tolerance. By doping with polyaniline (PANI), flexible, intrinsically conductive silk kirigami sheets could be fabricated. Such systems have potential in personalized healthcare monitoring devices, improving efficient disease detection and diagnosis

TFT & ULSIC: Interfacing large-area thin-film sensor arrays with CMOS circuits

Large-area, conformable sensing surfaces could find many applications by interfacing humans or machines users with their environment. Given the success of TFT backplanes for flat-panel displays, a promising approach is the fabrication of large integrated thin-film sensor arrays on single substrates. In thin-film technology the number of sensors can be made very large, and they can be deployed on rigid or flexible, conformably shapeable or even elastically stretchable substrates. Flat-panel displays suggest that TFT integration can be less costly than arrays made by placing and interconnecting discrete sensels. Equally important is that low-temperature thin-film technology can accommodate the diversity of materials required by the various sensor technologies. However, thin-film devices and circuits are slow. TFT circuits cannot compete directly with ULSI circuits in controlling large sensor arrays, or in signal processing and extracting the germane information from the huge number of signals that such arrays can generate. To combine the advantages of large-area integrated TFT circuits with the speed of ULSI circuits, we have been making hybrid systems that combine TFT and ULSIC [1]. Our work covers the range from thin-film device materials to subsystems implemented in thin-film technology, to co-designing and interfacing the large-area thin-film domain with the ULSIC domain. We have demonstrated systems for the sensing of mechanical strain [2], image detection [3], acoustic speaker localization [4], electro-encephalography [5], gestures [6], and patterns of pressure. Please click Additional Files below to see the full abstract

Algorithm for damage detection in wind turbine blades using a hybrid dense sensor network with feature level data fusion

Damage detection in wind turbine blades requires the ability to distinguish local faults over a global area. The implementation of dense sensor networks provides a solution to this local-global monitoring challenge. Here the authors propose a hybrid dense sensor network consisting of capacitive-based thin-film sensors for monitoring the additive strain over large areas and fiber Bragg grating sensors for enforcing boundary conditions. This hybrid dense sensor network is leveraged to derive a data-driven damage detection and localization method for wind turbine blades. In the proposed method, the blade\u27s complex geometry is divided into less geometrically complex sections. Orthogonal strain maps are reconstructed from the sectioned hybrid dense sensor network by assuming different bidirectional shape functions and are solved using the least squares estimator. The error between the estimated strain maps and measured strains is extracted to define damage detection features that are dependent on the selected shape functions. This technique fuses sensor data into a single damage detection feature, providing a simple and robust method for inspecting large numbers of sensors without the need for complex model driven approaches. Numerical simulations demonstrate the proposed method\u27s capability to distinguish healthy sections from possibly damaged sections on simplified 2D geometries

Research progress of flexible wearable stress sensor

Flexible wearable pressure sensors are widely used in health diagnosis, sports monitoring, rehabilitation medicine, entertainment, and other fields due to some factors such as the stretch ability, bendability, light weight, portability, and excellent electrical properties. In recent years, significant progress has been made in flexible pressure sensors, and a variety of flexible pressure sensors that able to measure health status have been applied to the pulse wave, movement, respiration, and electrocardiogram (ECG) detection. However, there are still many problems to be solved in the development of flexible pressure sensors. This article summarizes the development of flexible pressure sensors in recent years, from the working principle to the structural design of the flexible pressure sensors; designs to build a high-performance flexible pressure sensors; discusses the problems existing in current flexible pressure sensors and envisions the development trend of flexible pressure sensors in the future. Flexible pressure sensors with excellent flexibility, good biocompatibility, rapid response, high sensitivity, and multifunctional integration have shown a broad application prospects