A cluster-optimization method for enhanced standing-wave acoustic fields: Stable levitation and pose manipulation of irregularly shaped objects

Acoustic levitation and manipulation with phased arrays have advanced significantly. However, achieving simultaneous stable levitation and dexterous pose control of irregularly shaped objects remains a challenge. This paper introduces a cluster-optimization method for generating a radially asymmetric enhanced standing-wave field (RA-ESWF) using opposed ultrasonic arrays. The method dynamically derives feature phase patterns from a field-phase mapping dataset, avoiding predefined templates, and integrates them with parametric optimization to decouple orientation-locking and positional-focusing functions. Experiments demonstrate that the RA-ESWF effectively balances strong levitation force with precise orientation control. It enables pose manipulation of objects with diverse shapes and sizes (including near-spherical and rod-like samples) while maintaining high angular stability (standard deviation: 0.614°) and positional precision (0.048 mm in X, 0.069 mm in Y). The proposed method extends the functionality of conventional opposed-array levitators and offers a robust, optimization-driven framework for advanced acoustic trapping and manipulation in applications such as micro-reactors, biological sample handling, and non-contact assembly.