*Article* **Dielectric Characterization of Non-Conductive Fabrics for Temperature Sensing through Resonating Antenna Structures**

### **Isidoro Ibanez-Labiano \* and Akram Alomainy**

School of Electronic Engineering and Computer Science, Queen Mary University of London, London E1 4NS, UK; a.alomainy@qmul.ac.uk

**\*** Correspondence: i.ibanezlabiano@qmul.ac.uk; Tel.: +44-747-980-4581

Received: 13 February 2020; Accepted: 9 March 2020; Published: 11 March 2020

**Abstract:** Seamless integration of electronics within clothing is key for further development of e fficient and convenient wearable technologies. Therefore, the characterization of textile and fabric materials under environmental changes and other parametric variations is an important requirement. To our knowledge, this paper presents for the first time the evaluation of dielectric characterization over temperature for non-conductive textiles using resonating structures. The paper describes the e ffects of temperature variations on the dielectric properties of non-conductive fabrics and how this can be derived from the performance e ffects of a simple microstrip patch antenna. Organic cotton was chosen as the main substrate for this research due to its broad presence in daily clothing. A dedicated measurement setup is developed to allow reliable and repeatable measurements, isolating the textile samples from external factors. This work shows an approximately linear relation between temperature and textile's dielectric constant, giving to fabric-based antennas temperature sensing properties with capability up to 1 degree Celsius at millimeter-wave frequencies.

**Keywords:** material characterization; smart clothing; temperature sensing; wearable technology
