A Tightly Integrated Multilayer Battery Antenna for RFID Epidermal Applications

Maria Cristina Caccami,Gaetano Marrocco,John C Batchelor,Matteo P Hogan,Maria Alfredsson

doi:10.1109/tap.2017.2780899

Abstract

For the acceptance of biointegrated devices in daily life, radio systems must be developed, which are minimally invasive to the skin, and they must have ultralow-profile local power sources to support data-logging functionality without compromising shape conformability. This contribution proposes a tightly integrated multilayer battery-antenna system ( $65 \times 23$ mm2), that is, ultrathin (just $200~\mu \text{m}$ ), flexible, and lighter than 1 $g$ , making it suitable for epidermal applications. The negative electrode (anode) current collector of the battery is a radio frequency identification tag antenna coated by a conductive polymer (Pedot:PSS) working as anode material. Since the battery is a dynamic device, subjected to discharging, the antenna design must include the variable dielectric properties of the conductive polymer which are here first characterized in the UHF band for real charge/discharge battery conditions. The communication performance of the prototype composite device is hence evaluated through the measurement of the realized gain of the tag antenna (−19.6 dBi at 870 MHz) when it is placed directly onto a volunteer’s forearm. The read range of 1.3–3 m is suitable for occasional data download from the epidermal data logger when the user comes close to a reader-equipped gate.

Highlights

OVER the past decade, significant progress in the emerging field of bio-integrated wearable electronics has resulted in a new class of minimally invasive flexible and stretchable systems suitable to interface with the curved surfaces of the human body [1], [2]
Following the recent proof of concept simulations in [12] and [13], concerning a first attempt to achieve a composite batteryantenna structure for short-range communications, this contribution introduces the design and test of the first working example of a battery embedded into the antenna substrate, where a Radio Frequency Identification (RFID) tag is coated by a conductive polymer (Pedot:PSS) so that it may work as the anode of the battery
While Pedot:PSS has already been proposed for antenna fabrication, here it is doped with a variable amount of lithium ions during charging and discharging of the battery

Summary

Introduction

OVER the past decade, significant progress in the emerging field of bio-integrated wearable electronics has resulted in a new class of minimally invasive flexible and stretchable systems suitable to interface with the curved surfaces of the human body [1], [2]. It is still extremely challenging to design and fabricate a device capable of integrating an antenna and a battery that, besides providing the required capacity and discharge rate for wearable and wireless electronics, is sufficiently mechanically flexible [10], [11].

Results

Conclusion