## 6 SAR for Antennas on Human Body  
The SAR measures bodies' RF energy absorption from phones, antennas, and wireless devices. This statistic covers electromagnetic field safety issues. Pacemakers, implanted sensors, and wearable antennas for health monitoring are used for wireless data transfer. The absorption of electromagnetic energy by human tissues necessitates the careful design of wearable antennas, often made from flexible materials like textiles or polymers, to ensure compliance with SAR safety standards. Dielectric materials affect the SAR and EMF more than rigid substrates. The effects of body distance and antenna flexibility on the SAR can be due to various aspects; some of them are mentioned below:  
* Most antennas are placed near the skin and the SAR rises near the source because tissues absorb energy. High-performance, low-SAR antennas are crucial. A better antenna dissipates body energy. * Antenna design greatly affects the SAR. And, it varies by antenna size, shape, and frequency. Higher-frequency antennas increase the SAR because the body absorbs more radiation. For antenna efficiency and the SAR, designers must optimize location, ground planes, and materials. The international SAR monitors wearable antenna safety. Architects must consider regional codes and SAR-certified flat, bending, and twisting antennas. Figure 10: Illustration of inkjet printing process. * Flexible antennas are susceptible to environmental conditions such as heat, humidity, and perspiration, which can degrade their performance and influence SAR levels. Design strategies and robust testing protocols are necessary to ensure consistent SAR compliance under varying conditions of use. * The complex geometries and mobility of wearable antennas present significant challenges for SAR prediction and testing. Accurate SAR evaluation requires sophisticated algorithms and realistic human body models to simulate the interaction between antennas and biological tissues effectively. This study analyzes the various field properties of a recommended antenna along with gain, return loss, and the radiation pattern in a flat state with and without a body. When the body is not present, the return loss of the microstrip patch antenna is different, and when it is present, the return loss is different. The wattage per kilogram, or Watts/kg, is the unit of measurement used in the SAR. The SAR can also be conceptualized as an \"absorbed rate,\" which is related to the electric fields present in a specific area, i.e.,  
\[SAR=\frac{\sigma|E|}{\rho}\left(\frac{W}{Kg}\right) \tag{1}\]  
where E is the root mean square (r.m.s) of the electric field strength (V/m), and \(\sigma\) is the conductivity of the tissue (S/m) and \(\rho\) is the mass density of the human tissue. In certain fundamental studies, the SAR can be calculated as the rate of temperature rises in a specific location. The system's SAR distribution was for different antenna configurations. It was shown that in each of the four scenarios, the SAR was higher than necessary and needed to fall within the safer limit of 1.6 W/kg specified by the IEEE C95.1-1999 standard. According to the data, one gram of human body tissue could absorb more radiation than ten grams of other tissue. Although the conductivity of human body tissue was higher, at 5.8 GHz, than 2.45 GHz, the latter was subjected to more electromagnetic radiation. Additionally, the peak SAR for 1 g of human body tissue was 17.50 w/kg. Table 8 shows that the antenna's SAR, at 2.4 and 5.8 GHz frequencies, exceeded regulatory criteria, requiring extra measures to lower it to the safe limit [77]. Wearable flexible antennas were used to test the simulation results experimentally in various locations and motions. Proximity to the body reduced the antenna signal. Figure 11 shows space and flat-body antenna testing on phantom human muscle, fat, and skin at 2.4 GHz. SAR estimations can vary, but the sample volume average upper limit is 1.6 W/kg [88]. Human tissue absorbs electromagnetic field radiation, according to the SAR.