The demand for flexible wireless systems is rapidly increasing due to their diverse applications in health monitoring, telemedicine, wireless devices in daily life, tracking, patient diagnosis, and emergency rescue. Flexible electronic devices can be practical, low-profile, lightweight, disposable, inexpensive, and environmentally friendly. These devices must be bendable or even stretchable to integrate them with human body parts. Wearable devices, such as activity trackers, smartwatches, fitness bands, smart wears, augmented reality glasses, and fashion electronics are becoming an important part of the next generation of communication systems and Internet of Things (IoT) applications. An antenna is the most significant module of the wearable electronic system as the overall efficiency of the wireless link depends on it. Flexible antennas have been widely employed for on-body and off-body communication, wearable sensing systems, radio frequency identification (RFID), wireless body area network (WBAN), and ingestible and implantable applications. Therefore, they are important for the development of next-generation technologies for the improvement of human life.

Flexible antennas can be fabricated using nanoparticle inks, silver-nanoparticle inks, thin glasses, textile materials, metal foils, conductive polymers, graphene, plastics, or polymer substrates. The chosen substrate material must withstand mechanical deformations such as bending and twisting. The techniques commonly used for the fabrication of flexible antennas include inkjet printing, 3D printing, screen printing, chemical etching, and stitching or embroidery on the conductive textile. Unlike conventional antennas, which are usually placed in free space, the flexible antennas are positioned close to the human body under different bending conditions. As such, the design procedure for flexible antennas is different from customary antennas.

This Special Issue focuses on recent technological advancements in flexible antennas and sensors. Our aim is to cover different design aspects and measurement techniques of flexible and stretchable devices, in particular for use in microwave/mm-wave applications. We welcome both original research and review articles.

Potential topics include but are not limited to the following:

• 3D printed antennas
• 5G mm-wave antennas
• Artificial magnetic conductor (AMC) and electromagnetic bandgap metamaterial (EBG)-based antennas
• Conformal antennas for wireless power transfer systems
• Flexible metamaterials
• Frequency selective surface (FSS)-based antennas
• Implantable antennas
• Ink-jet printed antennas
• Low-profile antennas for IoT/ multiple-input and multiple-output (MIMO) systems
• Nano-antennas
• Radio-frequency identification (RFID) antennas
• Textile antennas
• Transparent antennas
• Wearable sensing systems