Dr. Chao-Shih Liu Profile

Dr. Chao-Shih Liu

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Proceedings Article | 10 April 2008 Paper

An offset multilayered optic sensor for shear and pressure measurement

Chao-Shih Liu, Gai-Wen Chou, Yi-Lang Lyu, Per Reinhall, Wei-Chih Wang

Proceedings Volume 6935, 69351B (2008) https://doi.org/10.1117/12.775616

KEYWORDS: Optical fibers, Sensors, Neural networks, Signal attenuation, Fiber optics sensors, Evolutionary algorithms, Optical sensors, Multilayers, Light emitting diodes, Defense technologies

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Simultaneous recording of shear and pressure is an important requirement for study the causes of foot ulceration. In order to obtain a more robust and meaningful picture of what is occurring on the plantar surface of the foot, we have developed a multi-layered optical bend loss sensor that can be accommodated for shear and pressure measurement of an extended area. The sensor is made of two layers of crisscross fiberoptic sensor array separated by an elastomeric layer. Each sensing layer has multiple fibers molded into a thin polydimethylsiloxane (PDMS) substrate to form a mesh array. The top layer uses 6 fibers to create a 3 by 3 mesh with 9 intersection points and the bottom layer uses 8 fibers to create a 4 by 4 mesh with 16 intersection points. The space between the adjacent fibers is 0.5cm. Measuring changes of light intensity transmitted through the fiber provides information about the force induced changes of the fiber's radius of curvature. Pressure is measured based on the force induced light loss from the two affected crossing fibers divided by each sensing area. Shear was measured based on the relative position changes on these pressure points between the two fiber mesh layers. The design is an offset layout because the intersection points of the top and bottom layer are offset by 0.25 cm which can increase the shear sensing sensitivity. For testing the sensor with various loading condition, a neural network algorithm is induced to identify the loading pattern and the shear direction. Three loading patterns with 5 different loading directions were tested and a >90% accuracy was obtained using an algorithm using 2 neural networks.

Proceedings Article | 11 April 2007 Paper

Design of a multi-layered optical bend loss sensor for pressure and shear sensing

Chao-Shih Liu, Gia Wen Chou, Xin Liang, Per Reinhall, Wei-Chih Wang

Proceedings Volume 6532, 65321P (2007) https://doi.org/10.1117/12.714720

KEYWORDS: Sensors, Fiber optics sensors, Optical fibers, Signal attenuation, Composites, Linear filtering, Optical sensors, Mechanical sensors, Fiber optics, Magnetic sensors

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A multi-layered optical bend loss sensor for pressure and shear sensing is presented. This design is based on the characteristic of optical bend loss. When external forces applied to the sensor, the optical fibers will bend and cause the light to escape from the fiber. The amount of light attenuation depends on the amount of bending occurred on the fiber. In our previous study, the sensor is composed of two layers of fiber optic mesh sensors that are molded into a thin polydimethyl siloxane (PDMS) substrate. Measuring changes of light intensity transmitted through the fiber provides information about the changes of the fiber's radius of curvature. The new design induces an elastomeric layer to separate the two optical fiber meshes. Pressure is measured based on the force induced light loss from the two affected crossing fibers. Shear was measured based on the relative position changes on these pressure points between the two fiber mesh layers. The additional elastomeric layer provides mobility in the lateral direction to improve the shear sensing. Preliminary testing on the new multi-layered sensor under normal and shear loading is encouraging. By adding the gel layer, when the applied force is 5N, the maximum attenuation is 30% at the top layer and 3% at the bottom layer. For the shear force detection, shifting of loading point at bottom layer was also observed from the experiment.

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