Synergistic Trimodal Stimuli-Induced Impedance Matching in Polydopamine-Functionalized Magnetoelectric Nanogenerators: Toward Efficient Charge Generation and Hybrid Energy Harvesting

Abstract A trimodal piezo-pyro-magnetoelectric nanogenerator (PPyMENG) is introduced, comprising an electrospun poly(vinylidene fluoride) (PVF2) nanofiber mat uniformly embedded with polydopamine-coated cobalt ferrite (PCFO) nanoparticles to integrate piezo-, pyro-, and magnetoelectric responses in a single compatible platform. In the PVPCF composite nanofiber mat, the electroactive β-crystalline phase provides coupled piezo- and pyroelectric functionality. The magnetoelectric pathway arises from the coupling between the molecular ferroelectric dipoles of PVF2 and the uniformly distributed magnetostrictive PCFO nanoparticles, establishing three parallel energy-conversion channels that collectively reshape the impedance-matching landscape. For instance, simultaneous mode activation reduces the internal resistance from 1.9 MΩ (under mechanical stimuli alone) to 700 kΩ under the combined excitation of mechanical, thermal, and magnetic stimuli, corresponding to a net decrease of 63%, accompanied by a 176% enhancement in output power density. Quantitative analysis reveals a remarkable Yang’s coupling factor of kC,Q = 5.6, substantially exceeding simple additive expectations and confirming strong cooperative interactions among the three energy transduction mechanisms. A generalized Thevenin-equivalent circuit with three resistive–capacitive branches captures the load–power profile across operating conditions, thereby validating architecture-level impedance modulation as a route to robust output power under variable stimuli. These findings reveal that multistimuli coupling can be leveraged to program internal resistance via parallel pathway activation and synergy-enhanced charge generation, providing a framework for power optimization in flexible autonomous systems.