The quick development of biomedical monitoring devices and the Internet of Things (IoT) has increased the need for communication systems that are not only compact and efficient but also capable of operating without frequent battery replacements. Energy-harvesting smart antennas offer a promising pathway by collecting energy from the surrounding environment, such as radio frequency (RF) signals, heat from the human body, and ambient light, and using it to power miniature sensors. This paper explores the theoretical foundations, design principles, and application opportunities of smart antennas based on advanced nanomaterials such as graphene, MXene, carbon nanotubes (CNTs), and flexible polymer composites. These materials allow antennas to be lightweight, highly conductive, flexible, and suitable for both wearable and implantable devices. The proposed antenna design shows reconfigurable behaviour they can adjust their frequency, polarisation, or beam direction depending on communication needs. Simulations based on electromagnetic and thermal multiphysics show how these Nanomaterial antennas perform when placed on the human body, exposed to varying environmental conditions, or used inside high-density IoT networks.