MEMS Inkjet Printhead Polymer Coating for Hydrophobic Surface Control
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Solution Overview
Problem
Inkjet printheads fabricated using MEMS techniques face challenges in achieving a hydrophobic ink ejection face while maintaining hydrophilic nozzle chambers, as existing processes often remove hydrophobic materials and result in undesirable hydrophobization of nozzle chamber walls, affecting ink pressure and flooding.
Innovation Solution
A method involving a polymer coating resistant to oxidative plasma, such as polydimethylsiloxane (PDMS) or perfluorinated polyethylene (PFPE), is applied to the printhead, which is photopatternable and has a Young's modulus of less than 1000 MPa, allowing for a hydrophobic front face and hydrophilic nozzle chambers, and is used as an etch mask or deposited after nozzle etching to prevent removal during ashing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hydrophobic coating is applied to the printhead to create a hydrophobic ink ejection face, then ink flooding is prevented, but the hydrophobic coating is removed by oxidative plasma during fabrication, resulting in a hydrophilic surface
Solution Approach 1:
The patent applies the hydrophobic coating early in the fabrication process, before the oxidative plasma treatment steps. This preliminary application ensures the coating is present to perform its function while recognizing it will be removed later, requiring reapplication or alternative protection strategies throughout the fabrication sequence.
Solution Approach 2:
The patent introduces a sacrificial layer or protective mask that mediates between the hydrophobic coating and the oxidative plasma. This intermediary protects the coating during specific fabrication steps, allowing the coating to survive the plasma treatment while still enabling the necessary manufacturing processes.
2Ease of manufacture
If standard MEMS fabrication techniques are used, then manufacturing simplicity is maintained, but hydrophobic materials are removed by ashing processes, affecting surface characteristics
Solution Approach 1:
The patent applies different surface treatments to different regions of the printhead. The ink ejection face receives a hydrophobic coating while the nozzle chamber walls maintain their natural hydrophilic properties. This local differentiation allows each region to have the surface characteristics needed for its specific function.
Solution Approach 2:
The patent modifies the fabrication process parameters, specifically the ashing conditions and timing, to preserve the hydrophobic coating. By adjusting these parameters, the process maintains manufacturing simplicity while achieving the desired surface characteristic retention through controlled exposure conditions.
3Reliability
If hydrophobic coating is applied to the entire printhead, then ink flooding is prevented, but nozzle chamber walls become hydrophobized, affecting ink pressure and ejection efficiency
Solution Approach 1:
The patent selectively applies the hydrophobic coating only to the ink ejection face and nozzle openings, while leaving the nozzle chamber walls untreated and naturally hydrophilic. This localized application prevents ink flooding at the ejection surface while maintaining proper capillary action and ink pressure within the chambers.
Solution Approach 2:
The patent divides the printhead surface into distinct functional zones: a hydrophobic zone at the ink ejection face for flooding prevention, and hydrophilic zones in the nozzle chambers for proper ink flow and pressure management. This segmentation allows each region to optimize its performance for its specific function.
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 maintains the desired surface characteristics, preventing ink flooding and ensuring efficient ink ejection while allowing for reliable and long-term operation of inkjet printheads.
Implementation Method 1
A method involving a polymer coating resistant to oxidative plasma, such as polydimethylsiloxane (PDMS) or perfluorinated polyethylene (PFPE), is applied to the printhead
Implementation Method 2
A method involving a polymer coating resistant to oxidative plasma, such as polydimethylsiloxane (PDMS) or perfluorinated polyethylene (PFPE), is applied to the printhead, which is photopatternable
Data Source
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AI summary
A method of fabricating a plurality of MEMS integrated circuits from a wafer having a MEMS layer formed on a frontside thereof and a polymer coating over said MEMS layer, said polymer coating having a plurality of frontside dicing streets defined therethrough, said method comprising the steps of: (a) releasably attaching a first holding means to said polymer coating; and (b) performing at least one operation on a backside of the wafer, said at least one operation including etching a plurality of backside dicing streets through the wafer, each backside dicing street meeting with a respective frontside dicing street, thereby providing the plurality of MEMS integrated circuits releasably attached to said first holding means, wherein each MEMS integrated circuit comprises a respective polymer coating.