Transparent Epidermal Antenna for Unobtrusive Human-Centric Internet of Things Applications

• Published in: IEEE internet of things journal Vol. 11; no. 1; p. 1
• Main Authors: Simorangkir, Roy B. V. B., Gawade, Dinesh R., Hannon, Tim, Donovan, Paul, Kumar, Sanjeev, Rather, Nadeem, Moloudian, Gholamhosein, O'Flynn, Brendan, Buckley, John L.
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.01.2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Antennas; Conductive textile; Electronics; epidermal antenna; Epidermis; Far fields; Field tests; flexible antenna; Internet of Things; Internet of Things (IoT); Phantoms; Polydimethylsiloxane; polydimethylsiloxane (PDMS); Prototypes; Radiation; Textile composites; Textiles; transparent antenna; Ultrahigh frequencies; unobtrusive; wearable antenna; Wireless communication; Wireless sensor networks
• DOI: 10.1109/JIOT.2023.3288994
• ISSN: 2327-4662

The concept of optical transparency in antennas for epidermal electronics is demonstrated in this work as a means of improving the long-term comfort-of-wear level and possibly opening up a wider range of applications. In contrast to previous attempts, the epidermal antenna transparency is achieved by employing dielectric and conductive materials that are both transparent and flexible (i.e., polydimethylsiloxane-transparent conductive textile composite) via a non-clean room procedure that is relatively simpler and less expensive. To demonstrate the concept, a modified rectangular loop epidermal antenna for an arm-worn wireless sensing system operating at 868 MHz Ultra High Frequency (UHF) band is designed. Through a systematic numerical investigation, an interesting radiation response of the loop epidermal antenna as the result of two opposing mechanisms of radiation and loss is revealed, which dictates a specific design guideline for the loop when attached to the body compared to that in free space. Two antenna prototypes were fabricated with the developed transparent composite and its non-transparent counterpart. Then, comprehensive characterizations comparing both epidermal antenna prototypes were carried out, including antenna return loss and far-field tests on a human forearm phantom, and indoor wireless connectivity tests using a human test subject. By showing similar performance between the two prototypes, the study provides a convincing demonstration of the applicability of the developed transparent composite for the class of epidermal antenna and the capability of a transparent antenna to enable wireless connectivity in the context of epidermal electronics.