High-order modal acoustic wave driving vertical jetting of droplets on 128° Y–X LiNbO₃

Abstract: The vertical jetting of droplets is crucial for printing applications in the fields of microelectronics and biomedicine, and acoustic-driven droplet jetting technology could be a potential technique for achieving this purpose. Currently, a nearly vertical jetting can be realized using standing Rayleigh surface acoustic wave (SAW) by superimposing at least two rows of symmetrically distributed traveling SAW generated from two opposite inter-digital transducers (IDTs). In this study, a high-order modal acoustic wave driving vertical jetting of droplets on 128° Y–X LiNbO_3, which is prominently distinct from the traditional Rayleigh SAW-generated droplet jetting phenomenon, is reported. Experimental testing and finite element simulation calculation were performed to analyze the high-order modal acoustic wave characteristics and corresponding streaming phenomenon that explains these different mechanisms from Rayleigh SAW. Furthermore, we reorganized the experimental jetting data to systematically analyze the effects of different parameters such as input RF power, duration time, acoustic wave frequency, and initial liquid volume on the droplet jetting behavior. Finally, both on the upper and/or lower surface of the double polished piezoelectric substrate, a droplet array jetting method is proposed and realized using a high-order modal acoustic wave with a frequency of 29.7 MHz. Graphic abstract: [Figure not available: see fulltext.]