Epidermal and Body-Worn Antennas

The work in this thesis focuses on flexible body-worn Electromagnetic Band-gap structures to remove body interference on the functionality of antennas and with compact UHF sensor tags designed for epidermal attachment and which are used in assisted living applications. Two passive sensing designs based on UHF RFID technology are presented. The first tag is mounted on the hard palette of the mouth and detects tongue position, while the second is a skin-mounted strain gauge. Both designs are proposed for wheelchair or computer mouse control applications. Measurements show the sensors can communicate over short ranges comparable with the distance expected between a patient’s mouth or face and a reader antenna. The mouth sensor is demonstrated to act as a tongue controlled switch, while the epidermal sensor is intended for eyebrow twitch control. Tests indicate both designs have a useful and repeatable sensing function, with more than 3 dB isolation in the switching case and approximately 0.25 dBm per percentage stretch in the strain gauge. Accurate arm and mouth models are used to simulate and validate the measurement results. Secondly, an investigation of how the system users can be trained with an appropriate repetition scheme to use the tongue control system efficiently are considered. The training method has been tested on 3 users and the improvement on the efficiency of using the system is also presented.