Etching Process for Microneedle Patch Projections
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Solution Overview
Problem
Existing methods for producing needle patches for delivering bioactive materials are inefficient due to issues like concave profile projections, high breakage rates, and high production costs, primarily caused by fluorine/oxygen etching processes which result in a bullseye effect and require expensive hard masks.
Innovation Solution
A method using a passivant such as C4F8 and an etchant like SF6 to control the etching process, avoiding oxygen and employing organic photo-resists and Su-8 masks for better control over projection shape and reducing the bullseye effect, along with post-etch sharpening and coating techniques to enhance projection robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If fluorine/oxygen based etching is used to form deep high aspect ratio trenches, then etching depth is improved, but projection profile becomes concave with narrow tip liable to breakage
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using fluorocarbon-based passivant instead of oxygen-based passivant. This parameter change fundamentally alters the etching chemistry to produce convex projection profiles with broader tips that are resistant to breakage, while still achieving the required etching depth for effective skin penetration.
2Productivity
If fluorine/oxygen etching process is used, then etching capability is improved, but bullseye effect increases leading to high percentage of unusable patches
Solution Approach 1:
The patent modifies the etching process parameters by replacing oxygen-based passivation with fluorocarbon-based passivation. This change eliminates the bullseye effect that plagues conventional etching processes, resulting in uniform etching across the entire wafer surface and dramatically increasing the yield of usable patches from each wafer.
3Manufacturing precision
If hard mask material is used for etching, then etching control is improved, but mask cost and complexity increase
Solution Approach 1:
The patent replaces expensive, complex hard mask materials with a simple organic photoresist mask. This disposable mask approach is much easier to fabricate and apply, and the fluorocarbon-based etching process provides sufficient control without requiring the robustness of hard masks, thereby simplifying the overall manufacturing process.
4Ease of manufacture
If conventional etching process is used, then production cost is reduced, but projection breakage rate increases
Solution Approach 1:
The patent changes the fundamental chemistry of the etching process by using fluorocarbon-based passivation instead of oxygen-based passivation. This parameter change produces projections with convex profiles and broader tips that are inherently more resistant to breakage, improving reliability while maintaining cost-effectiveness through a simplified process that eliminates expensive hard masks.
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 allows for the production of robust, cost-effective needle patches with controlled profiles, reducing breakage and increasing the yield of usable patches, enabling efficient delivery of materials through the skin with improved physical properties.
Implementation Method 1
etching the substrate using an etchant and a passivant to thereby control the etching process and form the projections
Implementation Method 2
using an etchant and a passivant to thereby control the etching process
Data Source
AI summary
A method of producing projections on a patch including providing a mask on a substrate and etching the substrate using an etchant and a passivant to thereby control the etching process and form the projections, wherein the passivant does not include oxygen.