Microneedle Manufacturing via Dicing and Etching
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Solution Overview
Problem
Existing methods for manufacturing microneedles face challenges in producing needles with desired lengths and sharp tips, often resulting in broken needles due to stress concentration at the base and difficulty in achieving high aspect ratios and sharp tips, especially when using materials like silicon that require precise etching and orientation-dependent properties.
Innovation Solution
The method involves forming grooves on a substrate using a dicing blade with controlled angles and chamfered edges to create microneedles with gentle slopes at the base, allowing for the production of microneedles with varied shapes and taper angles, and using isotropic etching to sharpen the tips without material limitations, enabling the use of biocompatible materials and reducing production costs through replication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etching is used to manufacture microneedles, then the microneedles can be formed with sharp tips, but the process requires highly purified single crystal material and the taper angle and point angle are determined by crystal orientation properties, making it difficult to design appropriate shapes
Solution Approach 1:
The patent replaces the chemical wet etching process with a mechanical dicing process using a dicing blade. This substitution allows the microneedle geometry to be controlled by the physical cutting action and blade parameters rather than crystal orientation, enabling flexible design of taper angles and point angles while maintaining sharp tips. The mechanical dicing process can be applied to various materials regardless of crystal structure.
Solution Approach 2:
The patent changes the controlling parameters from crystal orientation angles to dicing blade parameters (blade angle, cutting depth, feeding rate). By adjusting these mechanical parameters, the taper angle and point angle of microneedles can be freely designed without being constrained by material crystal properties, thus improving design flexibility while maintaining manufacturing precision.
2Shape
If wire cutting method is used to manufacture microneedles, then the size and shape can be controlled by changing cutting angles, but the microneedle has a trapezoidal cone shape with a flat plane on the apex, impairing piercing performance
Solution Approach 1:
The patent applies preliminary action by forming grooves at specific positions and depths before the final cutting stage. The dicing blade first creates guiding grooves that define the microneedle boundaries, then completes the cutting to form the sharp apex. This preliminary groove formation ensures precise geometric control while enabling the blade to converge to a sharp point without creating a flat apex.
Solution Approach 2:
Instead of cutting horizontally from the base as in wire cutting, the patent inverts the approach by cutting vertically downward from the top surface to form the microneedle apex. This inverted cutting direction allows the dicing blade to converge to a sharp point at the apex while maintaining control over the microneedle's overall shape and dimensions.
3Productivity
If transcription molding method is used to manufacture microneedles, then fine structures can be manufactured with low cost in large scale, but a master plate having inversed shape is necessary, making the manufacturing process quite complicated for structures with high aspect ratio and sharp tip
Solution Approach 1:
The patent uses dicing to directly form the microneedle shape on the substrate, creating a positive replica rather than requiring an inversed master plate. The dicing blade cuts the microneedle geometry directly, eliminating the need for complex master plate fabrication and inversion processes, thus reducing overall process complexity while maintaining scalability.
Solution Approach 2:
The patent extracts the microneedle formation step from the complex transcription molding process by using direct dicing. This separates the microneedle shaping operation into an independent mechanical cutting process, eliminating the need for master plate fabrication, material deposition, and demolding steps, thereby simplifying the manufacturing process while preserving mass production capability.
4Length of moving object
If microneedle has sufficient length for penetrating corneal layer and epidermis, then drug solution can permeate under the skin, but the needle base experiences stress concentration making it prone to breakage
Solution Approach 1:
The patent applies curvature by forming a rounded base geometry at the microneedle substrate interface instead of a sharp corner. The dicing process creates a curved transition zone between the microneedle shaft and the substrate, which distributes stress more evenly during penetration, reducing stress concentration and preventing breakage of long microneedles.
Solution Approach 2:
The patent applies local quality by providing different geometric characteristics at different parts of the microneedle: a sharp apex for effective skin penetration and a rounded base for stress distribution. This local differentiation of geometric properties allows the microneedle to simultaneously achieve sufficient length for deep penetration while maintaining strength and resistance to breakage at the vulnerable base region.
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 manufacture of microneedles with improved piercing performance, reduced breakage, and increased design flexibility, enabling efficient drug delivery and sampling while using materials harmless to the body, with enhanced productivity and cost-effectiveness.
Implementation Method 1
grooves are formed by grinding using a dicing blade
Implementation Method 2
applying isotropic etching from the back surface of the wafer
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(e)
Figure 3~4
AI summary
The invention regards a method of manufacturing a microneedle comprising steps of: forming a plurality of first linear grooves on a substrate (10) in parallel to one another along a first direction using grinding; and forming a plurality of second linear grooves on the substrate in parallel to one another in a second direction intersecting the first direction using grinding. At least one of the step of forming a plurality of first linear grooves and the step of forming a plurality of second linear grooves includes: forming first stage grooves using a first dicing blade (16); processing the first stage grooves by tracing the first stage grooves using a second dicing blade (17) having a side sudace different from that of the first dicing blade (16) to thereby form second stage grooves.