Multi-Pulse Waveform Control for Droplet Arrival Time Consistency
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Solution Overview
Problem
Existing droplet ejection technologies face challenges in achieving consistent droplet arrival times and variable drop sizes due to interference from residual pressures and flows, leading to inconsistent droplet formation and arrival on the target substrate.
Innovation Solution
The use of multi-pulse waveforms with specific drive pulses and cancellation edges, where the first subset includes a drive pulse near the beginning of the clock cycle and the second subset includes multiple drive pulses and cancel edges, allowing for controlled meniscus motion and consistent droplet arrival times across different sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single pulse waveform is used to eject droplets, then the device structure is simple, but the droplet arrival time consistency deteriorates due to residual pressure interference
Solution Approach 1:
The waveform is segmented into multiple pulses (first pulse, second pulse, third pulse) with specific timing relationships. The first pulse ejects a droplet, the second pulse (timed at or after the resonance period) ejects another droplet, and the third pulse compensates for residual pressure. This segmentation allows control over droplet ejection timing and size while maintaining arrival consistency.
Solution Approach 2:
The third pulse is introduced as a preliminary anti-action to counteract the residual pressure from the first pulse before it interferes with subsequent droplet ejection. By timing the third pulse appropriately, the system preemptively neutralizes the harmful residual pressure effects, ensuring consistent droplet formation and arrival times.
2Adaptability or versatility
If multiple pulses are used to form variable droplet sizes, then droplet size control is improved, but the droplet formation timing becomes inconsistent
Solution Approach 1:
The second pulse is timed to occur at or after the resonance period of the first pulse, which is a preliminary action that allows the first droplet to form and separate before the second pulse begins. This timing ensures that droplets of different sizes (formed by different pulse combinations) maintain consistent formation timing and arrival at the substrate.
Solution Approach 2:
The waveform utilizes periodic action based on the jet's natural resonance frequency. Pulses are timed in relation to the resonance period, creating a rhythmic pattern that ensures consistent droplet formation cycles regardless of droplet size variations. This periodic timing maintains synchronization across variable droplet sizes.
3Productivity
If the jet frequency increases beyond 25% of natural frequency, then the printing speed is improved, but the jet velocity variation increases due to residual pressure interference
Solution Approach 1:
The waveform design incorporates feedback by timing pulses based on the jet's natural resonance period. The system uses knowledge of the jet's dynamic response (resonance characteristics) to schedule subsequent pulses, effectively creating a feedback loop that maintains velocity consistency even at higher operating frequencies where residual pressure interference would normally be problematic.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances meniscus control, ensures consistent droplet arrival times, and improves droplet formation by compensating for the slower speed of smaller droplets, allowing them to arrive on target pixels simultaneously with larger droplets, thereby improving overall printing accuracy and efficiency.
Implementation Method 1
Each ink jet has a natural frequency which is related to the inverse of the period of a sound wave propagating through the length of the ejector
Implementation Method 2
The cancelling pulse is a shortened pulse that is timed so that the resulting pressure pulses arrive at the nozzle out of phase with the residual pressure from previous pulses
Implementation Method 3
Given that jets will have a dominant resonant frequency, the cancellation features are timed in units of resonance period Tc
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
Described herein is a method, apparatus, and system for driving a droplet ejection device with multi-pulse waveforms. In one embodiment, a method for driving a droplet ejection device having an actuator includes applying a first subset of a multi-pulse waveform to the actuator to cause the droplet ejection device to eject a first droplet of a fluid in response to the first subset. The method includes applying a second subset of the multi-pulse waveform to the actuator to cause the droplet ejection device to eject a second droplet of the fluid in response to the second subset. The first subset includes a drive pulse that is positioned in time near a beginning of a clock cycle of the first subset. The first droplet has a smaller volume than the second droplet.