Exploitation of Transparent Conductive Oxides in the Implementation of a Window-Integrated Wireless Sensor Node

TL;DR

This paper explores using transparent conductive oxides, specifically AZO, to develop energy-harvesting thermoelectric generators and transparent antennas for window-integrated wireless sensor nodes, enabling energy autonomy and transparency.

Contribution

It presents practical implementations of AZO-coated substrates for thermoelectric power generation and transparent antennas, advancing energy-autonomous and visually unobtrusive sensor nodes.

Findings

Flexible AZO TEG produces 1.6 μW at 43 K temperature difference.

Transparent RFID antenna achieves -9.1 dB efficiency at 900 MHz.

Bluetooth antennas show efficiencies between -3.8 dB and -0.4 dB.

Abstract

Exploitation of transparent conductive oxides (TCO) to implement an energy-autonomous sensor node for a wireless sensor network (WSN) is studied and a practical solution presented. In the practical implementations, flexible and rigid substrates that is polyimide and glass, are coated with TCO, namely aluminum doped zinc oxide (AZO). AZO-coated flexible substrates are used to form thermoelectric generators (TEG) that produce electricity for the sensor electronics of the node from thermal gradients on a window. As the second solution to utilize AZO, its conductive properties are exploited to implement transparent antennas for the sensor node. Antennas for a UHF RFID transponder and the Bluetooth radio of the node are implemented. A prototype of a flexible transparent TEG, with the area of 67 cm2 when folded, was measured to produce power of 1.6 uW with a temperature difference of 43 K. A radiation efficiency of -9.1 dB was measured for the transparent RFID antenna prototype with the center frequency of 900 MHz. Radiation efficiencies between -3.8 dB and -0.4 dB, depending on the substrate, were obtained for the 2.45 GHz Bluetooth antenna.