Standing Wave Droplet Ejection for High Viscosity Liquids

The patent replaces the conventional pressure-based mechanical ejection system with an acoustic field-based system. A standing wave acoustic field is generated using a piezoelectric element that vibrates at a specific frequency, creating acoustic radiation pressure to detach droplets from the nozzle tip. This substitution allows precise control of droplet ejection without the pressure control issues that affect droplet size precision when handling high viscosity liquids.

The patent utilizes mechanical vibration through a piezoelectric element that generates high-frequency vibrations (typically 20-100 kHz) at the nozzle tip. These vibrations create a standing wave acoustic field that applies periodic acoustic radiation pressure to the droplet, enabling controlled detachment. The vibration frequency and amplitude can be precisely controlled to achieve consistent droplet size and ejection timing, resolving the contradiction between ejection capability and size control precision.

The patent employs periodic acoustic vibration at a specific frequency to create cyclic acoustic radiation pressure. The piezoelectric element vibrates continuously at a controlled frequency, creating periodic compression and rarefaction cycles in the liquid. This periodic action allows precise control of droplet detachment timing - droplets are ejected only at specific phases of the vibration cycle when acoustic pressure exceeds surface tension forces, preventing continuous ejection and maintaining printing quality.

The high-frequency mechanical vibrations generated by the piezoelectric element create a standing wave acoustic field that applies periodic forces to the droplet. This vibration-based mechanism provides precise temporal control over droplet detachment, allowing single droplet ejection at controlled intervals rather than continuous ejection, thereby maintaining high printing quality even for high viscosity liquids.