Multifunctional sensing skin for structural health monitoring and biomechanical sensing

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Liu, Han
Major Professor
Laflamme, Simon
Cho, In-Ho
Day, Christopher
Bentil, Sarah A
Jiang, Shan
Committee Member
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Civil, Construction, and Environmental Engineering
Recent advances in hyperelastic materials and electronics have significantly impacted science and engineering, including the fields of civil, aerospace, and biomechanics. In particular, their soft and flexible properties enable the creation of smart sensors that can intelligently respond to the surroundings and provide compliant sensory feedback to conditional evaluation. In this dissertation, two types of newly developed sensing technologies for structural health monitoring (SHM) and biomechanical sensing are explored. The first sensing technology is a bio-inspired sensing skin and proposed by texturing the surface using corrugation patterns to significantly enhance sensing performance, term corrugated soft elastomeric capacitor (cSEC). As a type of large area electronics (LAE) with highly scalable properties, the cSEC is a flexible and ultra-compliant thin-film strain gauge capable of transducing surface strain into a measurable change in capacitance. It can be deployed as a dense sensor network (DSN) over large-scale structures for global monitoring and local diagnosis, analogous to biological skin. The electromechanical sensing property of the cSEC facilitates its application as a device to measure large strain found in biological processes. The second sensing technology is a modified version of the soft elastomeric capacitor technology that confers multifunctional sensing capabilities. It consists of a soft stretchable structural color film sandwiched between carbon nanotube electrodes. The sensor combines optical and capacitive sensing functions and exhibits a reversible and repeatable color change as well as a change in capacitance under external mechanical strain. This thesis investigates the use of both the cSEC and the multinational sensor for structural health monitoring applications. The sensing technology is combined with new signal processing algorithms enabling automatic detection, localization, and quantification of fatigue cracks on steel components. The cSEC is further extended towards smart bandage applications, where it is utilized to monitor and predict strain and stress present in sutured skin tissues. Overall, experimental results demonstrate that both the sensing skin technologies are successful at monitoring fatigue cracks as well as large strain and stresses in sutured biological skin, in particular using in vivo canine skin samples.
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