# Wireless Power Transfer Approaches for Medical Implants: A Review
## 3 Consideration for Design of Medical implants and Related Regulations  
Developments in wireless technology for medical devices are elevating the provision of healthcare with lower expenses. Wireless telecommunications can be used for both wearable and implantable applications, such as DBSs, tracking of vital signs, measuring biological parameters, and cardiac rhythm control. The main advantage of wireless technology compared to landline networks is that the patient is not required to be linked to a certain location by cables [117]. Despite advances in biomedical implants such as the pacemaker, cochlear implant, and nerve stimulator, these devices need to be improved in terms of miniaturization, the biocompatibility of materials, sources of electric charge, and wireless communication. To develop an effective IMD, the doctor, the patient, and the technician must collaborate in collecting coherent initial information about different aspects of the device. In particular, the user's satisfaction, the doctor's technical priorities, and the workability of the model are necessary to be considered in the design process [118]. There are important factors for designing medical implants. Since an electric device is implanted inside the human body, the organisms around the device may react to it. To avoid such an issue, the device should be made up of or coated by biocompatible materials. Moreover, the medical implants should have appropriate packaging to isolate components of the device from body tissue. Another factor is the structure of the design itself. Before the design, enough data should be collected from patients, engineers, and previous designs, along with their advantages and drawbacks [118]. The United States' medical devices market is regulated by three different organizations: the Federal Communications Commission (FCC), the Food and Drug Administration (FDA), and the Centers for Medicare and Medicaid Services (CMS). Wireless medical instruments can be classified into two categories: short-range, such as inductive implants and medical body area networks, and long-range, such as wireless medical telemetry (WMTS). According to the FCC, short-range technology sends data to local receivers and long-range technology sends user data to a remote spot [117]. The FDA's mission is to check if the proposed medical devices guarantee the factors of safeness and effectiveness for patient usage. The FDA divides medical devices into three classifications based on the risk factor. Class I includes the lowest-risk devices, and without FDA prior authorization, medical devices in this class may be advertised. The medical devices using wireless technologies are usually considered in Class II. The highest-risk medical devices fall under Class III and clinical trials are mandatory to get FDA approval. The FCC and FDA must permit before wireless medical devices can be marketed in the United States. It is worth mentioning that the FDA and FCC have distinct criteria, and one agency's authorization does not simply ensure the other's consent [117]. The designers of medical implants are currently dealing with challenges in materials, output power, size miniaturization, the efficiency of the wireless link, and cybersecurity [118]. There are different types of cyber-attacks, including theft of protected health information and execution of fraudulent device commands, which require appropriate cybersecurity mechanisms [119]. It is crucial to have a broad perspective of different aspects of wireless techniques before choosing the tactic for any specific applications. Figure 10 shows a comparison between the collected research papers for different approaches: the maximum dimension of a receiver, power transfer efficiency, and frequency. From Figure 10a,b, it can be seen that most of the ultrasound-based WPT systems work at a low operating frequency, ranging from a few hundred kHz up to few MHz.