## 1 Introduction
Nevertheless, wireless signals experience significant attenuation within the human body, and precise external equipment is indispensable for signal reception and processing [2]. Piezoelectric sensors possess the distinct advantage of self-power supply, obviating the need for a battery. They exhibit a relatively rapid response speed, rendering them highly suitable for dynamic monitoring applications. Nevertheless, these sensors are not without limitations. Specifically, the output signal is feeble and necessitates amplification, and piezoelectric materials may elicit rejection reactions when in contact with human tissues. Consequently, it is of paramount importance to select different principles based on the location of the target signal and the characteristics of the device. To accomplish the all-day measurement of physiological signals, the crux lies in the realization of wireless communication and wireless power supply, along with the real-time transmission of the measured data to the terminal. At present, the commonly employed medical detection devices are typically connected to the equipment via wires or optical cables. This connection approach is straightforward, practical, and cost-effective, and it can effectively mitigate external interference. Nevertheless, it is evident that this method is not applicable to implantable devices, as it will impose significant inconvenience on the subjects. Furthermore, continuous monitoring becomes unfeasible when the subjects engage in certain activities. The utilization of wireless communication can concurrently address these two issues. For individuals at potential disease risk, including those who require blood glucose, blood pressure [2; 3; 4], and intracranial pressure [5; 6] monitoring, implantable devices empower them to perform round-the-clock monitoring in their daily lives, obviating the necessity of regular hospital visits for such monitoring. This approach not only mitigates the disruption to patients' daily routines but also facilitates the collection of human physiological data under real-world conditions, which holds great significance for disease surveillance and prevention. The choice of wireless transmission and wireless power supply techniques is a pivotal determinant in attaining optimal sensing performance without disrupting the wearer's normal daily activities. Given the diverse locations of various implanted devices, the interference they encounter also varies significantly. Consequently, the suitable communication methods also diverge accordingly. Regarding active devices, technologies including Near Field Communication (NFC), Bluetooth, Radio Frequency Identification (RFID), and infrared can be utilized. In the case of passive devices, data transmission can be accomplished via ultrasonic energy transmission or electromagnetic induction coupling (LC resonance) approaches. Each communication method makes use of electrical signals within specific frequency bands, and the absorption and scattering of these signals in human tissues also differ. Devices implanted beneath the skin are subject to relatively less interference. Consequently, they necessitate a shorter communication range and lower power consumption. In contrast, sensors implanted deep within the human body, such as in arteries or vital organs, are confronted with more interference and thus demand higher power to attain a longer communication distance. This calls for designers to meticulously select the communication method and frequency band. Simultaneously, they should also endeavor to prevent electromagnetic radiation and thermal damage to the human body resulting from high-power data transmission. The power supply unit constitutes a crucial component of wireless sensors. Nevertheless, the capacity of batteries remains relatively constrained. In the case of long-term implanted devices, multiple surgical procedures may be necessary to replace the battery, which can inflict harm on the wearer. Regarding biodegradable electronic devices, chemical batteries are non-biodegradable.