This disclosure provides systems and methods relating to medical devices that utilize dynamically tunable antennas comprising a plurality of sub-wavelength antenna elements. In various embodiments, impedance elements associated with the sub-wavelength antenna elements are dynamically tuned to control radiation patterns of a tunable antenna, such as a metamaterial surface antenna technology (MSA-T) antenna. The radiation patterns produced by the tunable antenna are used, for example, for sending a control signal to an implanted medical device, directly controlling the movement of a medical device, causing a medical device to perform a specific function, powering a medical device, and/or otherwise interacting a medical device. In some embodiments, the implanted medical device may also include an antenna, such as an MSA-T antenna, for receiving and/or sending beam-formed electromagnetic radiation.