Multifunctional Mechano-Luminescent-Optoelectronic Composites for Self-Powered Strain Sensing

Advances in Mechanical Engineering

Shen

2019

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Surface buckling (wrinkling) driven by mechanical instability is commonly observed in thin-film structures with a compliant substrate. The resulting undulation, while sometimes undesirable, has been increasingly exploited to enhance mechanical and/or functional performances of many thin film devices. In this study a practical finite element modeling approach is introduced to simulate wrinkle formation in thin films atop a compliant substrate. The proposed technique is robust and easy to implement, and it overcomes typical challenges in computationally modeling the buckling instability. Using a two-dimensional geometry under the plane strain or generalized plane strain conditions, with randomly distributed imperfections bearing different material properties at the film/substrate interface, we demonstrate the model's capability in triggering surface instability during direct compression and out-of-plane tensile loading. With sufficient mesh refinement, the predicted wrinkling wavelength, amplitude, and critical strain to activate wrinkle formation are shown to be close to analytical solutions. The effect of imperfection distribution is systematically studied, and a valid range of imperfection spacing is identified. The present numerical approach can be applied to predicting buckling instability in the design and analysis of thin film/compliant substrate systems over a wide range of material and geometric conditions. Directions for future studies are also discussed.

Section: Introductionmentioning

confidence: 99%

Direct numerical simulation of buckling instability of thin films on a compliant substrate

Nikravesh

Advances in Mechanical Engineering

Shen

2019

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“…To overcome the intrinsic limitations of the piezoresistive strain sensors, researchers suggested novel flexible strain sensor technologies [ 2 , 5 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. Piezoelectric materials-based strain sensors showed decent features in strain sensing performance [ 13 , 14 ].…”

Section: Introductionmentioning

confidence: 99%

“…Of many multifunctional composites employed for devising self-powered strain sensors, multifunctional mechano-luminescence-optoelectronic (MLO) composites were recently proposed to sense tensile strain using direct current (DC) [ 11 , 20 ]. DC (i.e., electrical energy) was generated from the MLO composites subjected to cyclic tensile loading and unloading (i.e., mechanical energy).…”

Section: Introductionmentioning

confidence: 99%

Corrugated Photoactive Thin Films for Flexible Strain Sensor

Mongare

2018

Materials

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In this study, a flexible strain sensor is devised using corrugated bilayer thin films consisting of poly(3-hexylthiophene) (P3HT) and poly(3,4-ethylenedioxythiophene)-polystyrene(sulfonate) (PEDOT:PSS). In previous studies, the P3HT-based photoactive non-corrugated thin film was shown to generate direct current (DC) under broadband light, and the generated DC voltage varied with applied tensile strain. Yet, the mechanical resiliency and strain sensing range of the P3HT-based thin film strain sensor were limited due to brittle non-corrugated thin film constituents. To address this issue, it is aimed to design a mechanically resilient strain sensor using corrugated thin film constituents. Buckling is induced to form corrugation in the thin films by applying pre-strain to the substrate, where the thin films are deposited, and releasing the pre-strain afterwards. It is known that corrugated thin film constituents exhibit different optical and electronic properties from non-corrugated ones. Therefore, to design the flexible strain sensor, it was studied to understand how the applied pre-strain and thickness of the PEDOT:PSS conductive thin film affects the optical and electrical properties. In addition, strain effect was investigated on the optical and electrical properties of the corrugated thin film constituents. Finally, flexible strain sensors are fabricated by following the design guideline, which is suggested from the studies on the corrugated thin film constituents, and the DC voltage strain sensing capability of the flexible strain sensors was validated. As a result, the flexible strain sensor exhibited a tensile strain sensing range up to 5% at a frequency up to 15 Hz with a maximum gauge factor ~7.

“…To overcome the intrinsic limitations of the piezoresistive strain sensors, researchers have studied to suggest novel flexible strain sensor technologies [2,[10][11][12][13][14][15][16][17][18][19]. Piezoelectric materials-based strain sensors showed impressive strain sensing performance [13,14].…”

Section: Introductionmentioning

confidence: 99%

“…Multifunctional mechano-luminescence-optoelectronic (MLO) composites were proposed to sense tensile strain using direct current (DC) voltage generated from the MLO composites under cyclic tensile loading and unloading [11,20]. The MLO composites consist of two functional components, such as mechano-optoelectronic (MO) poly(3-hexthylthiophene) (P3HT)-based thin film sensor and ML ZnS:Cu-embedded elastomeric composites.…”

Section: Introductionmentioning

confidence: 99%

Corrugated Photoactive Thin Films for Flexible Strain Sensor

Mongare

2018

Preprint

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In this study, a flexible strain sensor is devised using corrugated poly(3-hexylthiophene) (P3HT) thin film. In the previous studies, the P3HT-based photoactive thin film was shown to generate direct current (DC) under broadband light, and the generated DC voltage varied with applied tensile strain. Yet, the mechanical resiliency and strain sensing range of the P3HT-based thin film strain sensor were limited due to relatively more brittle thin film constituent—poly(3,4-ethylenedioxythiophene)-polystyrene(sulfonate) (PEDOT:PSS) conductive thin film as a bottom electrode. To address this issue, it is aimed to design mechanically resilient strain sensor using corrugated thin film constituents. Buckling is induced to form corrugation in the thin films by applying pre-strain to the substrate, where the thin films are deposited, and releasing the pre-strain afterwards. It is known that corrugated thin film constituents exhibit different optical and electronic properties from non-corrugated ones. Therefore, to optimize design of the flexible strain sensor, it was studied to understand how the applied pre-strain and thickness of the PEDOT:PSS thin film affect the optical and electrical properties. Also, pre-strain effect on light absorptivity of the corrugated P3HT-based thin films was studied. In addition, strain effect was investigated on the optical and electrical properties of the corrugated thin film constituents. Finally, flexible strain sensors are fabricated by following the design guideline, which is suggested from the studies on the corrugated thin film constituents, and DC voltage strain sensing capability was validated. As a result, flexible strain sensor exhibited tensile strain sensing range up to 5% at frequency up to 15 Hz with maximum gage factor ~7.