Status and future prospects of non-contact levitation systems based on near-field acoustic levitation

Near-field acoustic levitation (NFAL) can achieve non-contact support by using high-frequency ultrasonic vibration to generate a squeeze film between a radiator and a levitated object. Owing to its independence from external gas supply and high-speed rotating equipment, as well as its weak dependence on the material properties of the levitation object, NFAL has become a promising approach for building a compact non-contact levitation system. Nevertheless, significant challenges remain in nonlinear mechanism modeling, solving, and enhancing the levitation force. In recent years, researchers are focusing on NFAL, especially nonlinear modeling, air-film lubrication theory, performance optimization, and system applications. This paper presents a comprehensive review from four perspectives: (i) NFAL fundamentals and operating mechanisms; (ii) air-film lubrication modeling and numerical solution methods; (iii) applications in non-contact platforms, bearings, and related precision support systems; and (iv) load-capacity enhancement and stability-improvement techniques. Typical NFAL-based platform and bearing architectures are summarized, together with their characteristic load capacity, stiffness, and dynamic response. Particular attention is given to power-accumulation strategies, structural and air-film co-design, and “air-film compensation” concepts for mitigating negative-pressure effects and improving stability. On this basis, the remaining challenges in multi-physics coupled modeling, high-load and high-stability operation, and engineering implementation are analyzed. The review is intended to provide systematic analysis and development suggestions for subsequent design optimization and engineering application.