Adjoint-based optimization of open-loop control for microfluidics of an inkjet printhead

Area of Science:

• Fluid Dynamics
• Acoustics
• Microfluidics

Background:

• Drop-on-demand inkjet printing relies on precise fluid control.
• Acoustic reverberations within printheads can negatively impact droplet ejection and print quality.
• Minimizing energy in microfluidic systems is crucial for efficiency.

Purpose of the Study:

• To determine the optimal actuator velocity profile for canceling acoustic reverberations in inkjet printheads.
• To ensure a specific meniscus state at a defined time after droplet ejection.
• To minimize the total energy of the oscillating flow and surface energy in the microchannel.

Main Methods:

• Formulation of an optimization problem to minimize total system energy (acoustic and surface energy).
• Utilized an adjoint method for efficient gradient computation of the cost function.
• Employed a gradient-based optimization algorithm to find the optimal actuator velocity profile.

Main Results:

• The optimal actuator profile effectively cancels acoustic reverberations within the printhead.
• Actuator action initially reduces surface energy by extracting fluid, followed by wave generation to cancel reverberations.
• Both tested inkjet printhead mechanisms achieved over a 100-fold reduction in total system energy compared to uncontrolled cases.

Conclusions:

• The developed methodology successfully optimizes actuator velocity for acoustic cancellation in inkjet printheads.
• This approach enhances control over the meniscus state and reduces overall system energy.
• Significant energy reduction demonstrates the potential for improved efficiency and performance in drop-on-demand inkjet systems.