Recirculation Passage for Uniform Droplet Ejection
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Solution Overview
Problem
Fluid ejection devices face challenges in achieving uniform droplet size and direction due to contamination and air bubbles, which affect the consistency and efficiency of fluid deposition on a medium.
Innovation Solution
The implementation of a recirculation passage system that is fluidically connected to the nozzle and descender, with high impedance at the firing pulse frequency, helps to prevent contamination and air bubbles by circulating deaerated fluid, minimizing energy loss, and ensuring uniform fluid flow, thereby promoting consistent droplet ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a recirculation passage is added to circulate fluid near the nozzle, then uniformity of droplet ejection is improved, but device complexity increases
Solution Approach 1:
The recirculation passage is integrated into the substrate itself rather than being a separate component, merging the recirculation function with the existing substrate structure. This reduces overall device complexity while achieving the goal of uniform droplet ejection through fluid circulation near the nozzle.
Solution Approach 2:
The recirculation passage is positioned within the substrate in close proximity to the nozzle, nesting the recirculation function within the existing device architecture. The passage is configured to be closer to the nozzle than the pumping chamber, creating a nested arrangement that improves droplet uniformity without adding external complexity.
2Manufacturing precision
If recirculation passage is placed close to nozzle, then droplet uniformity is improved, but risk of contamination increases
Solution Approach 1:
The recirculation passage converts the potential harm of close proximity (contamination risk) into a benefit by actively circulating deaerated fluid through the passage. This continuous circulation prevents contamination and air bubbles from affecting the nozzle, while the close placement maintains uniform droplet ejection.
Solution Approach 2:
The recirculation passage enables continuous circulation of fluid near the nozzle, maintaining a constant flow that prevents contamination and air bubbles from accumulating. This continuous action ensures both droplet uniformity and contamination prevention simultaneously.
3Loss of energy
If recirculation passage has high impedance at firing pulse frequency, then energy loss is minimized, but fluid flow restriction increases
Solution Approach 1:
The recirculation passage is designed with frequency-dependent impedance characteristics that are dynamic rather than static. At the firing pulse frequency, the passage presents high impedance to minimize energy loss, while at other frequencies it allows adequate fluid flow. This dynamic impedance behavior resolves the contradiction between energy conservation and fluid flow requirements.
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 solution enhances the uniformity of fluid droplet ejection, reduces the time required to refill the nozzle, and facilitates self-priming, ensuring consistent droplet size, speed, and direction across multiple nozzles, while preventing drying and contamination.
Implementation Method 1
circulating deaerated fluid through the recirculation passage prevents contamination and air bubbles from interfering with droplet ejection
Implementation Method 2
A recirculation passage can be formed in the substrate and fluidically connected to the descender, the recirculation passage being closer to the nozzle than the pumping chamber and having an impedance at the firing pulse frequency substantially higher than the impedance of the nozzle
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A system for ejecting droplets of a fluid is described. The system includes a substrate having a flow path body that includes a fluid pumping chamber, a descender fluidically connected to the fluid pumping chamber, and a nozzle fluidically connected to the descender. The nozzle is arranged to eject droplets of fluid through an outlet formed in an outer substrate surface. The flow path body also includes a recirculation passage fluidically connected to the descender. The system for ejecting droplets of a fluid also includes a fluid supply tank fluidically connected to the fluid pumping chamber, a fluid return tank fluidically connected to the recirculation passage, and a pump fluidically connecting the fluid return tank and the fluid supply tank. In some implementations, a flow of fluid through the flow path body is at a flow rate sufficient to force air bubbles or contaminants through the flow path body.