A noncontact air-floating system with pneumatically modulated excitation for controllable vibration of flexible substrates

Abstract

Vibration can promote droplet spreading, accelerate liquid leveling, and improve liquid-film morphology, but most existing excitation methods rely on contact. In precision manufacturing of flexible substrates, however, contact is often prohibited. To address this limitation, this work proposes a pneumatically modulated air-floating system that enables controllable noncontact vibration while maintaining stable levitation. A numerical model is established to analyze air film pressure fluctuations and the resulting dynamic load response under periodic negative-pressure modulation. The results show that the effective vibration bandwidth is governed mainly by the pneumatic transmission path rather than by the air film alone. The chamber-free air film does not act as a simple low-pass element and may exhibit high-frequency gain, whereas the combined vacuum chamber and constriction introduce a pronounced low-pass filtering effect, with chamber depth playing the dominant role in roll-off behavior. Experiments on a glass substrate under square-wave negative-pressure switching from 5 to 50 Hz confirm stable and repeatable noncontact vibration, with a broadly tunable amplitude ranging from several micrometers to several hundred micrometers. In addition, vibration-assisted experiments show that the introduced vibration accelerates droplet spreading and facilitates local edge reshaping of a liquid film with an initially uneven boundary. Compared with the non-vibration case, the normalized spreading area under vibration increased by approximately 28% at 120 s, and the local edge irregularity was further suppressed during vibration. These results suggest the potential of the proposed system for accelerating liquid leveling and improving process efficiency in coating, UV-curing, and related liquid-film processes involving delicate flexible substrates.