Reliable CNT thermoelectric modules enabled by flexible printed circuit board integration for self-powered IoT sensors

Carbon nanotube (CNT)-based thermoelectric (TE) materials have emerged as promising candidates for low-grade heat harvesting in self-powered Internet of Things (IoT) devices. However, the practical deployment of CNT-film TE modules has been hindered by two critical fabrication challenges, namely short circuits caused by the CNT whiskers that are generated during film dicing, and structural misalignment arising from manual stacking. In this study, a reliable TE module architecture is presented, which integrates n-type CNT films with a flexible printed circuit board (F-PCB) substrate, the latter of which functions simultaneously as an electrical interconnect and an effective insulating layer. A 50-pair TE module fabricated using this approach exhibited an open-circuit voltage of >20 mV and a maximum output power of >20 μW under a temperature difference of ~50 K. When connected to a commercial direct current (DC)-to-DC converter, the module successfully powered a Bluetooth Low Energy (BLE) temperature sensor, enabling real-time wireless data transmission to a smartphone. These results demonstrate that F-PCB-integrated CNT TE modules offer a high-yield, robust, and practical solution for sustainable self-powered IoT sensing technologies. • n-Type CNT films were integrated with an F-PCB substrate to produce a TE module • F-PCB functions as an electrical interconnect and an effective insulating layer • A 50-pair TE module delivered >20 mV and >20 μW under a 50 K temperature gradient • The TE module powered a BLE temperature sensor via a commercial DC-to-DC converter • This module offers robust, practical solutions for self-powered IoT sensing applications