Nanomaterial Based Flexible & Smart Sensing Architectures

Abstract

Sensors that translate physical phenomena into digital data are foundational to the era of digital transformation. As connectivity and decision-making increasingly rely on high-quality big data, developing sensors capable of acquiring accurate and reliable data at scale has become essential. However, conventional sensor technologies often fall short in supporting massive-scale, ubiquitous monitoring because they face major challenges: their rigidity limits wide applications such as wearable healthcare; their widespread deployment raises serious energy consumption concerns; and their simplistic designs cannot meet the complex functional demands of emerging technologies like Internet of thing (IoT), Industry 4.0, big data, artificial intelligence (AI), and robotics. This thesis addresses these challenges through the development of flexible, self-powered, and multifunctional sensing systems based on advanced nanomaterials.
Thermoelectric (TE) technology is identified as an ideal energy source for powering electronic systems, given its clean nature and high adaptability to sensing applications, particularly due to the vast amount of wasted heat in the environment. First, flexible TE films are developed based on carbon nanotubes (CNTs) and silver selenide (Ag2Se). CNTs are widely used in advanced electronic sensing and connection systems owing to their intrinsic flexibility and excellent electrical conductivity. To enable self-powered sensing, the thermoelectric properties of CNTs are enhanced through the in-situ polymerization of polyaniline (PANI) on their surfaces, improving both TE performance and mechanical reliability. In addition, emerging nanomaterials such as Ag2Se are investigated due to their superior room-temperature TE performance, attributed to their "phonon-liquid electron-crystal" behavior. Flexible Ag2Se films are fabricated via a low-temperature fusing process, which not only enhances electrical conductivity by improving nanoparticle connectivity but also increases the Seebeck coefficient through intensive energy filtering effects enabled by preserved grain boundaries.
Furthermore, a multifunctional energy source and dual-functional sensor are developed based on an ionic thermoelectric system. This system achieves continuous energy output through redox reactions at the electrodes and functions as a dual sensor for temperature and strain, advancing the development of smart, self-sustained sensing systems. To further enhance the intelligence of electronic systems, the field-effect modulation of CNT emissivity is explored, enabling tunable infrared properties for wearable applications. This approach opens new possibilities for infrared cloaking and radiative cooling technologies. Overall, this work demonstrates that developing nanomaterials can overcome critical limitations in current sensor technologies, contributing to the advancement of flexible, intelligent, and self-powered sensing systems essential for the digital and data-driven future.

Date of Award	2025
Original language	American English
Supervisor	Lianxi Zheng (Supervisor)