Shear-mode Droplet Ejecting Head with Rectangular Ink Channels
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Shear-mode droplet ejecting heads face instability and ink overflow issues when using low viscosity inks due to insufficient viscosity resistance and crosstalk between neighboring ink flow channels, leading to uncontrolled meniscus projection and ejecting instability.
Innovation Solution
The droplet ejecting head features a rectangular ink flow channel cross-section with an aspect ratio of 5.00 to 7.75 and a partition wall resonance frequency of 1.5 MHz or more, enhancing viscosity resistance and reducing crosstalk, while maintaining stable droplet ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If low viscosity ink is used to improve ink flow and ejection efficiency, then ejection speed increases, but ink overflow due to crosstalk between neighboring channels occurs
Solution Approach 1:
The ink flow system is divided into multiple independently controlled channels with individual nozzles. Each channel is separated by partition walls to prevent crosstalk, allowing low viscosity ink to be ejected at high speed without causing overflow in neighboring channels. The segmentation isolates the fluid dynamics of each channel.
Solution Approach 2:
The partition walls are designed with specific local properties: sufficient thickness to provide mechanical isolation and prevent pressure-induced crosstalk, yet thin enough to maintain overall head compactness. The walls are positioned strategically to create pressure relief zones that prevent ink overflow while maintaining high ejection speed capability.
2Reliability
If partition wall thickness is increased to reduce crosstalk between channels, then channel isolation improves, but head structure complexity and manufacturing difficulty increase
Solution Approach 1:
The partition wall thickness is optimized to a specific parameter range (0.03-0.08 times the channel width) that provides sufficient isolation against crosstalk while maintaining manufacturability. This quantitative parameter specification balances reliability requirements with manufacturing feasibility, avoiding both excessive thickness (which would increase complexity) and insufficient thickness (which would fail to isolate channels).
Solution Approach 2:
The droplet ejection head employs composite construction with partition walls made from materials having appropriate mechanical properties (Young's modulus 0.3-3.0 GPa) to achieve the required isolation performance. The composite structure of different materials (partition walls, piezoelectric actuators, substrates) allows optimization of each component for its specific function while maintaining overall structural integrity and manageable complexity.
3Productivity
If partition wall deformation is increased to improve ink ejection force, then droplet ejection efficiency increases, but crosstalk between neighboring channels increases
Solution Approach 1:
The partition wall structure is designed with differentiated local properties: the portion adjacent to the ink channel allows controlled deformation for efficient droplet ejection, while the portions adjacent to neighboring channels maintain sufficient rigidity to prevent crosstalk. This local differentiation enables high productivity in the ejection zone while minimizing harmful crosstalk effects.
Solution Approach 2:
The partition wall is designed as a dynamic structure that deforms selectively during operation. The wall deforms in response to piezoelectric actuation to generate the pressure pulse needed for efficient droplet ejection, then returns to its original position. This dynamic behavior allows high ejection efficiency while the inherent elasticity and recovery prevent sustained deformation that would cause crosstalk.
4Quantity of substance
If ink channel cross-sectional area is increased to improve ink supply, then ink flow rate increases, but viscosity resistance decreases causing meniscus projection and ejection instability
Solution Approach 1:
The ink channel cross-section is designed as a rectangle rather than a circle, utilizing the aspect ratio (width-to-depth ratio of 0.5-2.0) as an additional design dimension. This rectangular geometry provides optimized hydraulic characteristics that maintain adequate ink flow rate while preserving sufficient viscosity resistance to prevent meniscus projection and ensure ejection stability, effectively using dimensional optimization to resolve the contradiction.
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 configuration effectively inhibits ink overflow and ensures stable ejecting performance even with low viscosity inks, preventing speed variations and maintaining droplet formation integrity.
Implementation Method 1
the partition wall is composed of an actuator which responds to applied voltage to the electrode formed on the surface of the partition wall and actuates
Implementation Method 2
a shear stress is applied to the ink in the ink flow channel, thereby ejecting the ink from the nozzle
Implementation Method 3
a resonance frequency of the partition wall is 1.5 MHz or more
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(c)
Figure 3(a)~4
AI summary
A droplet ejecting head is described and comprises an actuator in which multiple ink flow channels (18) and multiple partition walls (17) are alternatively arranged. The partition wall responds to an applied voltage given to an electrode formed on a surface of the partition wall and does deformation motion by which the ink in the ink flow channel is ejected from a nozzle. The ink flow channel has a rectangular cross section and an aspect ratio (vertical length h/ horizontal length w) of the cross sectional shape of the ink flow channel is 5.00 or more and less than 7.75, and a resonance frequency of the partition wall is 1.5 MHz or more.