## 2 Result and Discussion
### Working Principle and Performance of SAVWS  
Figure 3a,c shows the circuit diagrams of the SAVWS. The load and S\({}_{2}\) were the wireless transmitter module and the MEMS switch, respectively. The PMS consisted of a BUCK circuit and an energy storage circuit. Therein, the BUCK circuit was composed of a rectifier bridge, series switch S\({}_{1}\), diode D\({}_{1}\), inductor L, and capacitor C\({}_{1}\). In addition, to better understand the workflow of SAVWS, the energy flow in this system is described below. The rectifier bridge converted the AC generated by E-TENG into DC, and the voltage signals from the rectifier bridge could control the working order of the S\({}_{1}\). When S\({}_{1}\) was turned on, the energy from E-TENG would be temporarily stored in L. After a moment, S\({}_{1}\) would turn off and the energy in L would be stored in C\({}_{1}\) through the loop of L, D\({}_{1}\), and C\({}_{1}\). Through this process, the energy produced by E-TENG would eventually be stored in the capacitor C\({}_{2}\) with high efficiency [16]. The Zener diode (D\({}_{2}\)) was added to protect C\({}_{2}\) from the damage of high voltage. Figure S5 shows a comparison of capacitor charging efficiency between the direct charge circuit with only one rectifier bridge and the PMS circuit. Figure 3b shows the waveforms of the U\({}_{0}\) and the I\({}_{0}\). The U\({}_{0}\) was the voltage of the C\({}_{2}\), which could demonstrate the working state of the transmitter module, and the I\({}_{0}\) was the current flowing through the transmitter. When the E-TENG continuously harvested vibrational energy and S\({}_{2}\) was in the closed state, the max value of I\({}_{0}\) and U\({}_{0}\) were 8.38 mA and 2.9 V, respectively. The time for the value of U\({}_{0}\) dropping from 2.9 V to 2 V, which was 103 ms, indicated the working time of the transmitter module. The maximum current of 8.38 mA and the extremely short working times demonstrated the low power consumption of the transmitter. The MEMS switch used in the system was voltage-sensitive and controlled by the output voltage of S-TENG, as shown in Figure 3c. Therein, the C\({}_{0}\) was connected at the gate and at the source of the MEMS switch to stabilize the MEMS state. When the voltage of C\({}_{0}\) reached the threshold, the drain and the source would be in a short-circuit state. The internal structure and microstructural diagram of the MEMS switch were shown in Figure S6. The relationship between the state of S\({}_{2}\) and the voltage of C\({}_{0}\) is shown in Figure 3d. The output voltage of the S-TENG with the mass of 700 g would turn on the MEMS switch under the vibration of acceleration of 2.5 m/s\({}^{2}\). When the vibration occurred, the voltage of C\({}_{0}\) would be raised to 60 V within 2.72 s and S\({}_{2}\) would turn on. After the vibration stopped, the voltage of C\({}_{0}\) would drop rapidly below 48 V within 450 ms and S\({}_{2}\) would turn off. It indicated that the voltage change in C\({}_{0}\) was not instantaneous, and there was a time delay between the state of S\({}_{2}\) and the voltage of C\({}_{0}\). What is more, the working time of the transmitter module was 103 ms. Thus, the response time of the system to abnormal acceleration was 2.82 s.  
The detailed workflow of the SAVWS is as follows. As the integrated vibrational TENG worked, the E-TENG and the S-TENG would start harvesting energy and monitoring the acceleration of vibration, respectively. When the acceleration of the vibration exceeded a certain value, the S-TENG would turn on the MEMS switch and wake up the transmitter module to send alarms. In addition, the acceleration value of turning on the MEMS switch, which was called the acceleration threshold, could change by the mass. Therefore, to realize the monitoring of various accelerations, the relationship between acceleration threshold and mass was studied. As shown in Figure 3e, the acceleration threshold increased with the raising of the mass.