**4. Conclusions**

A compact textile UWB planar monopole antenna integrated with an MTMUCA featuring ENG and NZRI properties was proposed and studied. The MTM-integrated antenna prototype was fabricated using flexible polymer viscose-wool felt as the substrate (since it provides easier fabrication with sufficient flexibility) and Shieldit SuperTM as the conductive element. The proposed MTMUC structure consists of a unique combination of square- and nonagonal-shaped CSRR-type MTMs. The proposed MTMUCA and MT-MUC exhibited SNG properties in different frequency bands. The MTMUCA structure featured an 11.68 GHz ENG bandwidth and an 8.5 GHz NZRI bandwidth. This work also presented an equivalent circuit design to illustrate the principles of the overall structure. The implementation of the MTMUCA into the antenna design was proven experimentally to improve the antenna gain, efficiency, and bandwidth. Measurements showed an FBW of up to 138.84%, from 2.63 to 14.57 GHz, with a peak gain and total efficiency of 4.4 dBi and 80%, respectively. The proposed design can potentially be applied for wearable applications, where future research could be carried out to investigate the feasibility of on-body application, specifically for breast cancer detection.

**Author Contributions:** Conceptualization, K.H., M.J. and T.S.; design methodology, K.H., M.N.O. and P.J.S.; software, K.H. and H.A.R.; validation, K.H. and T.S.; formal analysis, K.H. and M.N.M.Y.; investigation, K.H.; design optimization, S.S.A.-B.; metamaterial characterization, K.H. and M.N.O.; numerical calculation and data interpretation, M.A.A. and H.A.R.; resources, M.N.O.; writing original draft preparation, K.H., T.S. and M.J.; writing—review and editing, T.S., P.J.S. and S.S.A.-B.; visualization, K.H. and M.N.M.Y.; supervision, T.S. and M.J.; project administration, M.N.M.Y.; funding acquisition, M.A.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the Deanship of Scientific Research at Prince Sattam bin Abdulaziz University, Saudi Arabia.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** This study did not report any data.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

