Selective, Robust, and Precision Manipulation of Particles in Complex Environments With Ultrasonic Phased Transducer Array and Microscope

The noncontact acoustic manipulation of particles, biosamples, droplets, and air bubbles has emerged as a promising technology in the fields of biology, chemistry, medicine, etc. The noncontact nature offers significant advantages in terms of biocompatibility, contamination free, and material versatility. However, current noncontact acoustic manipulation techniques still lack adequate selectivity, robustness, and precision controllability in complex environments. To this end, in this article, we propose an automated noncontact manipulation system that leverages a high-density ultrasonic phased transducer array in combination with a microscope to further optimize and enhance the controllability and flexibility of noncontact particle manipulation. This work presents several notable contributions. First, we successfully realized selective particle manipulation, allowing instantaneous interaction with users to perform user-designated and objective-oriented manipulation tasks. Second, we integrated a closed-loop control strategy into the system that effectively mitigates misalignment errors induced by the trapping stiffness heterogeneity of acoustic trap and enables automated precision position control of particles in complex environments (in 30-mm-wide workspace, positioning precision is 1/40 of the wavelength). Third, we proposed a reconfigurable acoustic trap design method, named pseudovortex trap, featuring real-time computing and trapping particles larger than the wavelength. The system setup, the calibration specifics, the acoustic trap design methodology, and the corresponding visual servo control scheme (in terms of selective trapping, precision positioning, and dynamic trajectory planning) are given in detail in the article. Meanwhile, the trapping stiffness and the manipulation stability are also analyzed in this work. Experimental results well demonstrated the effectiveness of the proposed system.