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Needle-punching conditions determine the structure of nonwoven fabrics and the structure determines their tensile properties. However, the structural parameters of nonwoven fabrics and the relationship between these parameters and tensile properties have not been quantitatively analyzed. Therefore, we analyzed the structure of needle-punched nonwoven fabrics by X-ray computed tomography (XCT). The relationships between the needle-punching conditions, tensile properties, and structural parameters, such as fiber-volume fraction and three-dimensional fiber orientation, were investigated. The fiber-volume fraction in the middle layer of the fabric was clearly larger than that of the bulk above a compression ratio of 1.4. With increasing needle penetration depth, the fibers tended to become oriented both parallel and perpendicular to the normal direction of the fabric plane while avoiding the intermediate direction. A linear relationship was found between the obtained volume fraction of fibers oriented in the normal direction and the tensile strength of the fabric. These results demonstrate that XCT image analysis is effective to evaluate the structure of needle-punched nonwoven fabrics and to design the properties of nonwoven fabrics.

A mouthguard (MG) controller with a wireless data transmitter was developed for unconstrained control of external devices. The MG controller was composed of three pairs of a pressure sensor and a Bluetooth low energy (BLE) wireless data logger for the upper and lower jaws. The pressure sensors and the BLE data loggers were sandwiched by two dental MG materials so that they were not exposed in the oral environment. Pressure applied to the sensor was measured as a resistance change, and an algorithm that exploited the sensor output to regulate the control of an external device, such as a smart device, was developed. The pressure sensor encapsulated in the MG material showed a dynamic range of 1.7-29 N. In an experiment using a jaw phantom, the response time to applied occlusal pressure was 0.18 s. Finally, the use of the measured pressure to manipulate a pointer in a smart device application was demonstrated. The results indicate that the developed MG controller enables the manipulation of devices in one's vicinity via occlusion.

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