# A Review of Multifunctional Antenna Designs for Internet of Things
## 2 Materials and Methods
### Biomedical Devices
#### 2.1.6. Discussions and Perspectives through Interdisciplinary Collaborations  
The aforementioned antennas are summarized in Table 1, which displays their most crucial parameters for these applications. It is evident that there is a trade-off between the size of the antenna and its gain, as electrically smaller antennas typically present low efficiency. Furthermore, in many cases, the operational bandwidth of the antenna is not mentioned, indicating a small bandwidth that leads to low data rates. To increase the data rate, multiple-band planar inverted-f antennas (PIFAs) have been investigated by different researchers [38; 39]. To further increase the gain and the antenna efficiency metamaterials may be used, as seen in [41]. Another way to enhance the efficiency and minimize the volume of the structure is by exploiting magnetoelectric (ME) materials, though this approach sacrifices bandwidth. In magnetoelectric antennas, radiation is achieved through the acoustic resonance of the antenna, which induces magnetic oscillations. This phenomenon is utilized to surpass the radiation bounds defined by Chu-Harrington's limit, particularly originating from the distance between the ground plane and the radiator [49]. It is important to highlight that this behavior is observed for general electrically small antennas due to the longer wavelengths. Despite these advantages, the efficiency of magnetoelectric antennas remains poor due to acoustic mismatches between the piezoelectric and magnetostrictive materials, as well as the low piezoelectric and piezomagnetic coefficients. In summary, the concept of magnetoelectric antennas appears to be more appealing at radio frequencies than in the microwave region based on current data. Figure 3: Measurement setup for simultaneous magnetic field sensing and energy harvesting of a magnetoelectric antenna presented in [44]. The most challenging task in designing wearable, and especially implantable, antennas is that they primarily operate in the near field due to the highly lossy dielectric medium of the human body. This medium absorbs electromagnetic waves, significantly affecting antenna performance. Therefore, designing an effective implantable or ingestible antenna requires precise measurements within the human body to verify its operation and ensure reliable communication. However, for practical and ethical reasons human test subjects (clinical trials) cannot be used in the initial stages of design. Consequently, phantoms made from materials that mimic human tissue, such as minced meat or agarose gel [37] or an agarose matrix [52], are used for testing. These phantoms allow researchers to simulate the electromagnetic environment of the human body, providing valuable insights into antenna performance without the need for live human trials. By using these realistic models, engineers can refine antenna designs to enhance their efficiency, safety, and effectiveness before moving on to more advanced testing stages. However, actual clinical trials to fully validate a device's functionality are performed in very few cases after the initial design stage. In this context, the optimal development and exploitation of antennas and wireless communication systems for biomedical devices cannot be achieved solely by engineers. Close collaboration with medical doctors and other healthcare professionals is essential to ensure continuous dialogue and bidirectional feedback throughout the design process. Such collaboration ensures that antenna designs meet both technical and clinical requirements, addressing practical healthcare challenges and patient needs. Although the importance of interdisciplinary collaboration is well understood, related efforts often lack systematic organization. This can lead to communication gaps and misaligned priorities between engineers and medical professionals. Establishing structured frameworks for collaboration, such as interdisciplinary teams and regular meetings, can enhance the integration of medical insights into the engineering design process.