## 4. Degradable Sensor Materials
On the other hand, the chronic toxicity experiment is designed to measure the impacts of exposure to medical devices, materials, and their extracts, which may occur either once or repeatedly over at least the majority of the experimental animal's lifespan. This long-term assessment helps in understanding the cumulative and delayed effects of these exposures. Implantation Reaction: The implantation experiment is employed to evaluate the local pathological effects of an implant on living tissues through both macroscopic and microscopic examinations. To conduct this experiment, the medical device is surgically implanted into a pre-determined site or tissue. It is crucial that the experimental time and route of exposure closely mimic those of the actual medical device or material, ensuring the relevance and accuracy of the results obtained. Degradation: For medical devices engineered to be absorbable, degradation experiments are essential. These experiments aim to comprehensively describe the mechanism of biodegradation, precisely determine the potential degradation rate, and identify the release of any potential toxic chemical substances. Depending on the specific requirements of the device, in vivo degradation experiments may be necessary to provide a more realistic assessment of the degradation process within a biological system. In the realm of practical medical and healthcare, biodegradable materials exhibit distinct advantages that traditional materials lack. For instance, biodegradable implants gradually undergo degradation and are assimilated by the human body subsequent to fulfilling their medical functions. This obviates the necessity for a secondary surgical procedure for removal, thereby alleviating the patient's pain and reducing medical expenses. Simultaneously, these materials demonstrate excellent biocompatibility, enabling them to coexist in harmony with human tissues. This effectively mitigates rejection reactions and inflammation. Post-usage, they can degrade spontaneously, minimizing long-term environmental contamination and the burden associated with medical waste disposal. In certain specific scenarios, biodegradable materials can also offer transient support for tissue regeneration. As the tissue recuperates, these materials gradually degrade, creating room for the growth of fresh tissue, which is conducive to tissue repair and regeneration. Nevertheless, these materials are not without certain limitations. For example, in comparison with traditional materials, biodegradable materials exhibit relatively inferior mechanical properties, and these properties tend to deteriorate more over time. When the device is required to be utilized for a specific duration or degrade at a specified rate, it is essential to meticulously design the composition and structure of the biodegradable material to fulfill the usage requirements. Even though the degradation products are non-toxic to the human body, they may still impact the physiological functions of local tissues. The degradable materials presented in this article are primarily classified into three categories: degradable metal materials, degradable silicon-based materials, and degradable polymer materials.