## 1 Introduction
As a result, various sensors can be deployed on the human body to track these essential indicators. Body-worn sensors can store data related to these physiological metrics. Technology advancements have also introduced new tools to markets, including smart clothing, smart rings, and smart glasses [6]. According to the IEEE Std 802.15, the frequency range supported by WBANs must comply with the requirements of regulatory medical and communication organizations. These include the Industrial, Scientific, and Medical (ISM) (90-928 MHz, 950-958 MHz, 2360-2400 MHz, 2400-2483.5 MHz), ultra-wideband (3.1-10 GHz), and Medical Implant Communications Service (MICS) (402-405 MHz) frequency ranges. Recently, millimeter-wave (mm) bands have also been added to the list of frequency bands for development and implementation of WBAN communication systems [7; 8]. The frequency bands of wearable antennas are described in Table 1.  
This study discusses the use of flexible materials, including textiles and polymers, in the design of wearable antennas. The study emphasizes their use in a wide range of applications and their long-term durability, mechanical reliability, and performance under changing environmental stress conditions. Developing such knowledge is important for wearable antenna systems' practical and challenging operation. Existing fabrication techniques, such as inkjet and screen printing, require additional advancements to enhance scalability, cost-effectiveness, and precision for the mass production of wearable antennas. A lot of research is being performed on ways to lower the specific absorption rate (SAR), but it is still hard to find the best balance between lowering the SAR and keeping an antenna's efficiency and functionality when it is being bent and deformed in practical scenarios. The major contributions of this review are as follows:  
* We investigate wearable antenna design, materials, and structural adaptability to ensure compatibility with WBANs and real-time applications. * We evaluate the impact of bending, deformation, and proximity to human tissues on critical antenna parameters, such as gain, return loss, bandwidth, and the SAR. * We analyze the role of flexible materials like textiles, polymers, and conductive composites in improving antenna functionality while exploring fabrication methods like inkjet printing and screen printing for scalable production. * We examine techniques such as metamaterials, EBG structures, and FSSs to reduce SAR levels while maintaining antenna efficiency and safety. \begin{table}
\begin{tabular}{c c c} \hline \hline
**S. No.** & **Frequency** & **Applications** \\ \hline
1. & 402–405 MHz & Medical Implant Communications Service (MICS) \\ \hline
2. & 402–405 MHz, 863–950 MHz & Wireless Medicals Telemetry Services (WMTS) \\ \hline
3. & 902–928 MHz, 950–958 MHz, 2360–2400 MHz, 2400–2483.5 MHz & Industrial, Scientific, and Medical (ISM) \\ \hline
4. & 3.1–10 GHz & Ultra-Wideband \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Frequency range for ISM bands [9]. * We explore the potential applications of wearable antennas in healthcare, the IoT, and next-generation communication systems, emphasizing their role in enhancing real-time monitoring and wireless communication. This study explores various aspects of wearable antennas, focusing on their development, manufacturing, testing, and applications. The review article is organized as follows: Section 2 discusses types of flexible wearable antennas using textiles, polymers, and microwave imaging antennas. Section 3 discusses the selection of material used for designing wearable antennas. Section 4 describes the bending effect of wearable antennas. Section 5 shifts focus to fabricating techniques such as screen printing, inkjet printing, and embroidery.