Candidate: Majid Haji Bagheri
Date: April 6, 2026
Time: 11:00 AM
Location: Online
Supervisor: Professor Dayan Ban
All are welcome!
Abstract:
The proliferation of distributed sensors, wearable electronics, and the autonomous Internet of Things (IoT) systems has created a pressing demand for sustainable, maintenance-free power sources capable of operating in harsh and resource-constrained environments. While piezoelectric and triboelectric nanogenerators (PENGs and TENGs) offer a promising route for harvesting ambient mechanical energy, their practical deployment remains limited by material fragility, environmental instability, and temperature sensitivity, and reliance on toxic or non-recyclable components. My research addresses these challenges through the rational design of environmentally benign, mechanically robust, and thermally stable nanogenerator materials and architectures. The first part of this work introduces a self-healing, recyclable vitrimer composite (PI/GP30) engineered for high performance triboelectric energy harvesting. By combining enhanced dielectric properties, optimized interfacial charge transport, and dynamic covalent network chemistry, the composite enables durable TENG devices capable of stable output across wide temperature and humidity ranges. This platform supports wearable biomechanical harvesters, wireless signal transmission, and self-powered acoustic sensing integrated with real-time machine learning classification, demonstrating autonomous sensing in resource-limited environments.
The second part of my research focuses on lead-free piezoelectric nanogenerators with improved cryogenic stability. I report a two-dimensional Ruddlesden–Popper hybrid perovskite, (ATHP)₂SnCl₄, in which stereochemically active Sn²⁺ lone pairs induce pronounced lattice asymmetry and spontaneous polarization. When incorporated into a PVDF–TrFE matrix, the resulting nanocomposite exhibits significantly enhanced piezoelectric coefficients, increased power density, and stable operation down to cryogenic temperatures. Complementary work explores non-ferroelectric, structure-distortion-driven piezoelectric systems to suppress temperature-dependent extrinsic contributions and enable intrinsically stable electromechanical responses under sub-ambient conditions.
Together, these studies establish a materials-centric framework for designing durable, lead-free, and temperature-resilient nanogenerators. By integrating self-healing polymers, lone-pair-engineered hybrid perovskites, and intrinsic piezoelectric mechanisms, this research advances the development of self-powered electronic systems suitable for aerospace, polar, and other extreme environments.