Microfluidic Chip Permanent Passivation Layer Acidic Fluid Resistance
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Solution Overview
Problem
Microfluidic dispensing devices with silicon substrates are incompatible with acidic reagents like hydrofluoric acid/nitric acid due to silicon etching, which contaminates samples in Life Sciences applications.
Innovation Solution
A microfluidic ejection chip with a silicon substrate featuring a fluid passageway covered by a permanent passivation layer, formed through deep reactive ion etching and fluorocarbon deposition, protects the silicon from acidic fluids by preventing chemical etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a silicon substrate is used in the microfluidic dispensing device, then the device achieves compact design and precise fluid jetting capability, but the silicon substrate is etched by acidic reagents (HF/HNO3), causing sample contamination
Solution Approach 1:
A passivation layer is introduced as an intermediary substance between the silicon substrate and the acidic reagent. This layer acts as a protective barrier that prevents direct contact between the HF/HNO3 mixture and the silicon, thereby eliminating etching and sample contamination while preserving the silicon substrate's structural integrity and fluid jetting precision
Solution Approach 2:
The microfluidic dispensing device transitions from a pure silicon substrate to a composite structure consisting of a silicon substrate combined with a passivation layer. This composite material system combines the advantages of silicon (precision, compactness) with the chemical resistance properties of the passivation layer, resolving the contradiction between manufacturing precision and chemical compatibility
2Adaptability or versatility
If the silicon substrate is exposed to acidic reagent for any purpose, then the reagent can be delivered through the device, but the acidic reagent chemically etches the silicon, resulting in silicon contamination of samples
Solution Approach 1:
The passivation layer serves as a protective intermediary that enables the device to handle acidic reagents without compromising sample purity. It allows chemical compatibility while maintaining reliability by preventing silicon dissolution and contamination
Solution Approach 2:
The passivation layer converts the harmful interaction between acid and silicon into a beneficial protective relationship. The acidic reagent, which would normally damage the silicon substrate, is now safely contained and delivered through the passivation layer, transforming a harmful chemical compatibility issue into a reliable dispensing capability
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 permanent passivation layer effectively shields the silicon substrate from acidic etching, ensuring accurate and contamination-free dispensing of reactive fluids, maximizing passivation layer thickness, and eliminating unnecessary cleaning steps.
Implementation Method 1
a permanent passivation layer to protect the silicon sidewall from exposure to an acidic fluid
Implementation Method 2
deep reactive ion etching
Implementation Method 3
fluorocarbon deposition
Data Source
AI summary
A method of generating a microfluidic ejection chip is provided. The method includes creating an opening in a silicon substrate through multiple iterations of a deep reactive ion etching process, forming a passivation layer over any exposed portion of silicon at the opening following each iteration of the deep reactive ion etching of the silicon substrate, and not removing the passivation layer at a conclusion of the etching of the silicon substrate to define a fluid passageway at the opening in the silicon substrate, such that the passivation layer is permanent on the silicon substrate at the opening.