A theoretical framework is presented for a core-shell particle architecture that integrates piezoelectric transduction, memristive state storage, and conductive encapsulation within a single structure of 200 nm to 50 µm diameter. The particle consists of a piezoelectric core (BaTiO₃), a memristive first shell (HfO₂ or Ag₂S), and an electrically conductive second shell (graphene/rGO). An external ultrasound field (20 kHz–20 MHz) activates the piezoelectric core via the direct piezoelectric effect; the resulting electrical voltage is distributed across the memristive shell through capacitive coupling and induces a nonvolatile resistance state change. An analytical electromechanical model is developed that accounts for (i) acoustic stress amplification through impedance mismatch (stress concentration factor SCF ≈ 1.9), (ii) piezoelectric voltage generation scaling linearly with core diameter, (iii) capacitive voltage division across the spherical core-shell geometry, (iv) flexoelectric polarization bias arising from strain gradients at the curved interface, and (v) the energy balance for both direct switching and cumulative sub-threshold regimes. For a representative configuration—a 10-µm BaTiO₃ core with a 30-nm Ag₂S electrochemical metallization (ECM) shell under high-intensity focused ultrasound (100 W/cm²)—the model predicts a shell voltage of approximately 71.5 mV, exceeding the experimentally reported switching threshold of Ag₂S-based ECM cells (30–100 mV, switching energy ≈18 fJ). The flexoelectric effect at the curved BaTiO₃/Ag₂S interface provides an additional permanent bias estimated at 5–25 mV, reducing the effective switching threshold. The proposed architecture would enable wireless, battery-free, nonvolatile information storage at the single-particle level, with potential applications in structural health monitoring, biomedical sensing, physical unclonable functions, environmental monitoring, and radiation dosimetry.
Baran Dindar (Sun,) studied this question.