Funnel-Shaped Inkjet Nozzles for Reduced Size Variation
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Solution Overview
Problem
Existing nozzle designs in inkjet print heads suffer from size variations, leading to print line width variations, air intake, and instability in droplet formation, which affect printing quality, resolution, and efficiency.
Innovation Solution
The development of a funnel-shaped nozzle with a curved top portion smoothly joined to a straight-walled bottom portion, fabricated using semiconductor processing techniques, which reduces size variations and ensures smooth fluid ejection by minimizing friction and air intake.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional nozzle designs are used, then manufacturing is simpler, but size variations occur leading to print line width variations and air intake
Solution Approach 1:
The nozzle is divided into two distinct functional sections: a curved top portion for fluid accumulation and a straight-walled bottom portion for stable jetting. This segmentation allows each section to optimize its specific function while maintaining overall manufacturing feasibility through standard semiconductor processing techniques.
Solution Approach 2:
The top portion of the nozzle features a curved profile that gradually converges toward the straight-walled bottom portion. This curvature eliminates sharp corners and discontinuities that cause air intake and flow instability, while the smooth transition is achieved through controlled reflow processing that rounds the nozzle opening.
2Reliability
If straight-walled nozzle design is used, then manufacturing is easier, but jetting straightness and droplet stability deteriorate
Solution Approach 1:
Different sections of the nozzle have different geometric qualities optimized for their specific functions: the top portion has a curved profile for smooth fluid convergence and accumulation, while the bottom portion has straight walls for stable, straight jetting. This local differentiation of geometric properties enhances overall jetting reliability.
Solution Approach 2:
The curved top portion acts as a preliminary preparation zone where fluid is smoothly guided and accumulated before entering the straight-walled jetting section. This preliminary action ensures that the fluid reaches the nozzle exit in a controlled, stable state, improving jetting straightness and droplet formation consistency.
3Loss of energy
If curved nozzle profile is used, then fluid friction is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The curved profile of the nozzle top portion is formed through a self-organizing reflow process where the photoresist material automatically rounds its own edges under controlled heating. This self-service mechanism naturally creates the desired curved geometry without requiring complex external tooling or multiple precision machining steps.
Solution Approach 2:
The manufacturing process utilizes parameter changes in the photoresist material properties during reflow - specifically, the material transitions from a rigid state during patterning to a viscous state during heating that allows surface tension to reshape the nozzle opening into a smooth curve, then returns to rigid state upon cooling to maintain the curved profile.
4Stability of the object's composition
If larger nozzle volume is used, then droplet formation stability improves, but air intake increases
Solution Approach 1:
The curved top portion of the nozzle creates a smooth, continuous fluid path that eliminates sharp corners and discontinuities where air could be entrained. The gradual convergence of the curved profile ensures that fluid flows smoothly without creating vacuum conditions that would draw air into the nozzle, while still providing sufficient volume for stable droplet formation.
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
The funnel-shaped nozzle achieves better jetting straightness, higher firing frequencies, lower driving voltages, and uniformity of drop shape and locations, enhancing printing quality and efficiency.
Implementation Method 1
the photoresist material in the layer softens and reflows under the influence of surface tension of the photoresist material
Implementation Method 2
an isotropic dry etching process is used to transform the straight-walled recess into the funnel-shaped recess
Implementation Method 3
the side surface of the funnel-shaped nozzle generates less friction on the fluid during fluid ejection
Data Source
AI summary
Techniques are provided for making a funnel-shaped nozzle in a substrate. The process can include forming a first opening having a first width in a top layer of a substrate, forming a patterned layer of photoresist on the top surface of the substrate, the patterned layer of photoresist including a second opening, the second opening having a second width larger than the first width, reflowing the patterned layer of photoresist to form curved side surfaces terminating on the top surface of the substrate, etching a second layer of the substrate through the first opening in the top layer of the substrate to form a straight-walled recess, the straight-walled recess having the first width and a side surface substantially perpendicular to the top surface of the semiconductor substrate.