Micro-Needle Arrays with Inclined Tips for Skin Penetration
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Solution Overview
Problem
Existing micro-needle technologies face challenges in achieving appropriate penetration of the outer skin layer, specifically the stratum corneum, without deep penetration that could interfere with nerves, and often result in inefficiencies and discomfort during medical applications.
Innovation Solution
A method involving anisotropic etching processes on single crystalline substrates to create micro-needles with inclined tips, allowing for improved penetration and manufacturing efficiency, including the use of SOI wafers for precise control and the ability to produce both solid and hollow needles with varied geometries for medical and electrical applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ordinary syringes are used for drug administration, then the injection can be performed, but it causes pain and discomfort to the patient
Solution Approach 1:
The invention divides the needle structure into multiple discrete micro-needles arranged in arrays (e.g., 6x6, 12x12 configurations), where each micro-needle is a separate penetrating element. This segmentation allows the device to penetrate skin with minimal pain while maintaining structural integrity through the array configuration, directly addressing the patient comfort issue without requiring complex single-needle designs
Solution Approach 2:
The invention replaces the traditional mechanical syringe needle penetration mechanism with a micro-needle array system that relies on distributed mechanical action across multiple points. This substitution reduces the force concentration at any single point, thereby reducing pain and discomfort while achieving effective drug delivery through the skin barrier
2Object-affected harmful factors
If micro-needles are used to reduce patient pain, then patient comfort is improved, but achieving appropriate penetration depth without interfering with nerves becomes difficult
Solution Approach 1:
The invention employs anisotropic etching processes that exploit crystal plane orientation dependencies to precisely control the length and geometry of micro-needles. By adjusting etching parameters (time, temperature, chemical composition) and crystal orientation, the penetration depth can be precisely tuned to penetrate the stratum corneum effectively while stopping before reaching nerve layers, thus achieving both patient comfort and controlled penetration depth
Solution Approach 2:
The micro-needles are pre-formed with specific lengths and geometries (including inclined tips resembling cannulas) before application. This preliminary formation through controlled anisotropic etching ensures that when applied to skin, the needles have the exact penetration depth required to breach the stratum corneum without risking deeper penetration into nerve-containing layers, thereby solving the depth control precision issue
3Productivity
If conventional etching methods are used for micro-needle fabrication, then manufacturing can be performed, but the yield and manufacturing efficiency are reduced
Solution Approach 1:
The invention replaces mechanical drilling or cutting methods with chemical anisotropic etching processes that exploit crystal plane orientation. This substitution enables high-yield batch fabrication of micro-needles with precise geometries (including inclined tips) directly on silicon wafers, simultaneously improving manufacturing efficiency and geometric precision without the limitations of mechanical methods
Solution Approach 2:
The invention utilizes changes in etching parameters (chemical composition, temperature, time) and crystal orientation angles to precisely control micro-needle geometry during fabrication. By optimizing these parameters, the process achieves high manufacturing yield while producing micro-needles with the required precision for effective skin penetration, resolving the contradiction between productivity and precision
4Ease of manufacture
If micro-needles with vertical tips are used, then manufacturing is simpler, but penetration effectiveness through the stratum corneum is reduced
Solution Approach 1:
The invention introduces asymmetry in the tip geometry of micro-needles by creating inclined tip surfaces through anisotropic etching, rather than using symmetric vertical tips. This asymmetric geometry enhances penetration effectiveness by reducing resistance at the tip-skin interface, while the asymmetry is achieved through controlled crystal plane exposure during etching, maintaining manufacturing feasibility through standardized semiconductor processing techniques
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 method enables effective penetration of the stratum corneum, reducing patient discomfort and improving the yield of micro-needle production, while allowing for both medical drug delivery and electrical measurements with enhanced precision and efficiency.
Implementation Method 1
an anisotropic, crystal plane dependent etch forming the inclined surface(s)
Data Source
AI summary
The invention relates in a general aspect to a method of making vertically protruding elements on a substrate, said elements having a tip comprising at least one inclined surface and an elongated body portion extending between said substrate and said tip. The method comprises an anisotropic, crystal plane dependent etch forming said inclined surface(s); and an anisotropic, non crystal plane dependent etch forming said elongated body portion; combined with suitable patterning processes defining said protruding elements to have a predetermined base geometry.