Bound states in the continuum (BICs) are a fascinating class of eigenstates that trap energy within the continuum, enabling breakthroughs in ultra-low-threshold lasing, high-$Q$ sensing, and advanced wave-matter interactions. However, their stringent symmetry requirements hinder practical integration, especially in acoustic and electromechanical systems where efficient mode excitation is challenging. Here, we demonstrate deployable nanoelectromechanical quasi-BICs on suspended lithium niobate thin films, enabled by nanoscale Lamb wave phononic crystals operating at gigahertz frequencies. By exploiting the decoupling of symmetric ($S$) and antisymmetric ($A$) Lamb wave modes, we create a robust framework for BICs. Controlled mirror symmetry breaking induces targeted coupling between the $S$ and $A$ modes, resulting in quasi-BICs that preserve high-$Q$ characteristics and can be excited by traveling waves, eliminating the need for specialized excitation schemes. Our approach enables the multiplexing of quasi-BIC resonators along a single transmission line, each corresponding to a unique frequency and spatial position. This Letter presents a scalable route for the on-chip integration of BICs, bridging the gap between theoretical concepts and practical nanoelectromechanical devices, and opening new avenues in advanced signal processing, high-precision sensing, and quantum acoustics.

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• Acoustic metamaterials
• Acoustic wave phenomena
• Bound states in the continuum
• Elastic waves
• Mechanical & acoustical properties
• Phononic crystals
• Thin films
• Cavity resonators
• Elastic wave theory
• Surface acoustic wave