Kirigami structures, or paper cutting patterns, have more expansive design freedom than other approaches, making it is easy to fabricate sensors with different performances. Kirigami 16, 17, 18, 19, honeycomb 20, 21, 22, and helical 23, 24, 25 structures, as well as metamaterials 26 that enable stretching, have been studied. Therefore, structural design is often studied to attain stretchability 15. Polyvinylidene (PVDF) is the most popular piezoelectric polymer material owing to its high piezoelectric performance, ductility, flexibility, and biocompatibility however, it is still not stretchable. Piezoelectric polymers have been studied to develop stretchable sensors. These characteristics render their use in applications related to the human body challenging. Second, piezoelectric materials with high piezoelectric coefficient, such as lead zirconate titanate (PZT), are rigid, fragile, and lack biocompatibility. Therefore, it is necessary to improve the measurement circuit design of piezoelectric strain sensors. In addition, the measurement system cannot follow the rapid increase in voltage thus, it cannot fully measure the actual voltage generated by the piezoelectric materials. The voltage drop is mainly due to the measurement circuit. This prevents utilization of piezoelectric materials in strain sensing applications because it is difficult to measure a transient output voltage. First, the generated voltage dissipates to the surroundings such that the voltage peak appears only for a short duration when the strain is applied. However, piezoelectric materials for strain sensing applications have two drawbacks that limit their applications, primarily to pressure sensors. Therefore, piezoelectric materials are promising for strain sensing applications. The output voltage produced with strain can be used as a power source for additional functions such as wireless communication. Unlike piezoresistive sensors, active sensing is possible with piezoelectric sensors. Piezoelectric-based sensors can accurately measure rapid strain changes without latency. The sensing mechanisms for stretchable sensors are piezoresistive 2, 3, 4, 5, 6, piezocapacitive 7, 8, 9, and piezoelectric 10, 11, 12, 13, 14, with the piezoelectric mechanism being the most advantageous. Therefore, it is essential to develop sensors with tunable sensing performance. Pulse sensing requires higher sensitivity than detection of bending motion. For example, a sensor attached to an elbow requires higher stretchability than that required for a finger. Additionally, it is crucial to optimize sensor performance according to the target application because different sensor properties, such as stretchability and sensitivity, are required depending on the body part and application. Flexibility and stretchability are required for human body applications, and the demand for such sensors is increasing 1. Wearable sensors are becoming increasingly important in various applications such as health monitoring and artificial reality (AR)/virtual reality (VR) technology. Finally, the fabricated sensor was successfully applied in a haptic glove for playing musical instruments. A piezoelectric kirigami sensor was constructed with a sensitivity of 9.86 V/cm 2 and a stretchability of 320.8%, higher than those of previously reported kirigami piezoelectric strain sensors. A sensor voltage measurement circuit was also designed, amplifying the output voltage 86.5 times by improving measurement accuracy. The electromechanical properties of sensors with four different kirigami patterns were analyzed. Using finite element analysis, the sensing performance was evaluated, and the kirigami patterns were optimized. In this study, we developed a high performance kirigami piezoelectric strain sensor. Stretchability, sensitivity, and tunability are crucial sensor properties stretchability and sensitivity ensure user comfort and accurate sensing performance, while tunability is essential for implementing sensors in diverse applications with different ranges of motion. Wearable technology requires high-performance sensors with properties such as small size, flexibility, and wireless communication.
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