Smart implants are envisioned to revolutionize personal health care by assessing physiological processes, for example, upon wound healing, and communicating these data to a patient or medical doctor. The compactness of the implants is crucial to minimize discomfort during and after implantation. The key challenge in realizing small-sized smart implants is high-volume cost- and time-efficient fabrication of a compact but efficient antenna, which is impedance matched to 50 Ω, as imposed by the requirements of modern electronics. Here, we propose a novel route to realize arrays of 5.5-mm-long normal mode helical antennas operating in the industry-scientific-medical radio bands at 5.8 and 2.4 GHz, relying on a self-assembly process that enables large-scale high-yield fabrication of devices. We demonstrate the transmission and receiving signals between helical antennas and the communication between an antenna and a smartphone. Furthermore, we successfully access the response of an antenna embedded in a tooth, mimicking a dental implant. With a diameter of ~0.2 mm, these antennas are readily implantable using standard medical syringes, highlighting their suitability for in-body implant applications. Helical antennas that are just 5.5 millimetres long have been developed for use in smart medical implants by scientists in Germany. Smart implants are set to transform personal health care by monitoring physiological processes and relaying data to medical workers. It is critical for such implants to be compact, but miniaturizing antenna has proved challenging. Now, researchers based in Dresden have applied strain engineering to polymer–metal heterostructures to achieve large scale high yield fabrication of compact helical antennas that are about five times smaller than conventional two-dimensional dipole antennas. They demonstrate transmission and reception of signals between a pair of antennas as well as between an antenna and smartphone. They also show that the antenna can be addressed when embedded in a tooth model. The small size of the antennas permits them to be implanted using standard medical syringes. We fabricated compact helical antenna operating in the industry-scientific-medical radio band. With a total length of only 5.5 mm, it is about five times smaller compared with the conventional dipole antenna. The transmission and receiving signals between helical antennas and the communication between a helical antenna and a smartphone is reported. Owing to the shape and dimensions, we successfully demonstrate the possibility to address the antenna, when embedded in a tooth, as well as to implant the antenna using standard medical syringes. These demonstrations highlight the potential of helical antennas for medical applications as components of smart system implants.