## 2 Types of Flexible Wearable Antennas
### Microwave Imaging Antennas  
A microwave imaging antenna uses microwave frequencies to image or map environments. Microwave imaging employs antennas to receive and broadcast microwave radiation to make images or identify things. Industrial testing, medical imaging, and security can utilize customized designs and technology. This antenna transmits and receives microwave signals for imaging and structure detection. Medical imaging, security screening, nondestructive testing, etc., are industrial uses. Frequency range microwaves typically \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Ref.** & \begin{tabular}{c} **Antenna Type** \\ **and Shape** \\ \end{tabular} & \
\begin{tabular}{c} **Dimension** \\ **(a)** \\ \end{tabular} &
\begin{tabular}{c} **Substrate** \\ **Material** \\ \end{tabular} & **Frequency (GHz)** & **Gain (dB)** & **Application** \\ \hline
[18] & \
\begin{tabular}{c} Wearable Textile \\ Antenna \\ \end{tabular} & 0.24 \(\times\) 0.24 & Textile Materials & 2.4–2.5 & 3.5 &
\begin{tabular}{c} Healthcare and \\ Communication \\ \end{tabular} \\ \hline
[19] & \
\begin{tabular}{c} UWB Patch \\ Antenna \\ \end{tabular} & 0.21 \(\times\) 0.26 & Denim Substrate & 3.1–10.6 & 6.2 &
\begin{tabular}{c} Early Breast Cancer \\ Detection \\ \end{tabular} \\ \hline
[20] &
\begin{tabular}{c} Dual-Band Patch \\ Antenna \\ \end{tabular} & 0.17 \(\times\) 0.17 & Poly-Cotton Textile & 5.8 and 8.3 & 8.73 and 4.64 & Wearable Monitoring \\ \hline
[21] & \begin{tabular}{c} Frequency \\ Selective Surface \\ Textile Antenna \\ \end{tabular} & 0.3 \(\times\) 0.42 & \
\begin{tabular}{c} Textile-Based PSS \\ Reflector \\ \end{tabular} & 1.5–6.0 & Not specified &
\begin{tabular}{c} Wearable Body Area \\ Network \\ \end{tabular} \\ \hline
[22] & \begin{tabular}{c} Dual-Band Textile \\ Antenna \\ \end{tabular} & 0.18 \(\times\) 0.18 & \
\begin{tabular}{c} Conductive Textile \\ Layers \\ \end{tabular} & 0.868 and 2.4 & Not specified &
\begin{tabular}{c} Military, Industrial, \\ and Telemedicine \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Textile-based antennas and their applications. range from 300 MHz to 300 GHz [27], with the selection of imaging frequency governed by the application's resolution and functional requirements. Due to its non-ionizing radiation, ultra-wideband microwave imaging is becoming important for cancer diagnosis. System efficiency depends on antenna performance [28]. This article discusses advancements in microwave imaging systems' high-directivity sensors. For cancer diagnosis, it emphasizes antenna designs near the body. Due to its benefits over conventional imaging methods, microwave imaging is popular. In-depth biological tissue investigations for cancer diagnosis are beneficial. This study focuses on optimizing the material, size, bandwidth, and pulse propagation of UWB microwave imaging antennas, which form the core components of these imaging systems. Among the antenna designs examined, the Vivaldi antenna is highlighted for its efficacy in breast cancer diagnosis. The number of components affects array quality, and water and electrical properties distinguish healthy and cancerous tissues. Imaging systems often employ antipodal Vivaldi antennas (AVA) operating in the 2.4-12 GHz frequency range, known for their omnidirectional radiation patterns and suitability for adaptive radar applications. Balanced antipodal Vivaldi antennas (BAVA) and AVA antenna designs show energy flow density and performance [29]. Figure 2 shows how high-gain antennas and meta-surfaces can detect several breast cancers in microwave imaging. Microwave imaging safely and accurately detect breast abnormalities, making it a beneficial early breast cancer screening and treatment option. Microwave imaging is essential for breast health monitoring because normal and cancerous cells have different electrical characteristics. Microwave imaging is better than X-ray, ultrasound, and magnetic resonance imaging [30].