High-Aspect-Ratio Microneedle Arrays for Transdermal Delivery

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Solution Overview

Problem

Current methods for transdermal drug delivery and fluid extraction are invasive, painful, and expensive due to the complexity and cost of fabricating high-aspect-ratio microneedle arrays, which struggle to effectively penetrate the skin barrier and maintain mechanical integrity.

Innovation Solution

A two-step method using high-aspect-ratio solid microneedles, microblades, or microknives to create pathways in the stratum corneum for controlled release of substances, combined with a skin patch for sustained delivery, and improved fabrication techniques using isotropic and anisotropic etching for enhanced mechanical strength and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high-aspect-ratio microneedle arrays are fabricated using conventional methods, then transdermal delivery capability is improved, but manufacturing complexity and cost increase significantly

Engineering Contradiction:

Improvetransdermal delivery capabilityVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The microneedle array is segmented into multiple individual microneedles arranged in a grid pattern on a substrate. Each microneedle can be independently fabricated using standard photolithography and etching processes, allowing parallel production that reduces overall manufacturing complexity while maintaining high-aspect-ratio geometry for effective skin penetration

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses photolithographic copying to replicate the microneedle pattern across the entire array. A single mask design can be used to create multiple identical microneedles simultaneously, significantly reducing manufacturing complexity and cost compared to fabricating each needle individually while ensuring consistent high-aspect-ratio geometry

Inventive Principle:

Principle #26Copying

2Reliability

If microneedle arrays are made with high aspect ratio to penetrate stratum corneum effectively, then skin permeability is improved, but mechanical integrity deteriorates

Engineering Contradiction:

Improveskin permeabilityVSAvoidmechanical integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The microneedles are designed with localized geometric features including tapered profiles with smaller tip diameters and optimized shaft dimensions. The aspect ratio and cross-sectional geometry are specifically tailored to provide sufficient mechanical strength at the shaft while maintaining sharp tips for effective skin penetration, thus balancing mechanical integrity with skin permeability

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The microneedles are fabricated from silicon, a material that provides high mechanical strength and rigidity necessary to maintain structural integrity at high aspect ratios. The substrate material and microneedle material are selected to ensure sufficient strength while allowing the needles to flex slightly during insertion without breaking, thus maintaining both mechanical integrity and penetration capability

Inventive Principle:

Principle #40Composite materials

3Productivity

If conventional hypodermic needles are used for injection, then drug delivery is effective, but patient discomfort and pain increase

Engineering Contradiction:

Improvedrug delivery effectivenessVSAvoidpatient discomfort

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

Instead of using a single large-bore needle that causes significant pain, the delivery system is segmented into multiple fine microneedles with diameters in the micrometer range. This segmentation distributes the insertion force across many small contact points, dramatically reducing per-needle pain while maintaining effective total drug delivery capacity through the combined effect of multiple penetration channels

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention transitions from conventional hypodermic needles that penetrate deeply in a single dimension to microneedle arrays that create multiple shallow penetration channels. The microneedles are designed to penetrate only the stratum corneum and epidermis layers (superficial depth) rather than reaching the dermis where pain receptors are located, thus delivering drugs effectively while minimizing patient discomfort by operating in a different depth dimension

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Ease of manufacture

If microneedle fabrication uses complex processes like anodization or selective removal, then hollow microneedles are produced, but manufacturing cost and time increase

Engineering Contradiction:

Improvehollow microneedle productionVSAvoidfabrication time

Core Design Contradiction:

Ease of manufactureVSLoss of time

Solution Approach 1:

The microneedle arrays are pre-fabricated on a substrate using standard photolithography and etching processes during manufacturing. The microneedles can be formed with internal hollow structures or solid cores in a single integrated fabrication process, eliminating the need for time-consuming post-fabrication hollowing operations like anodization or selective material removal, thus reducing overall fabrication time and cost

Inventive Principle:

Principle #10Preliminary action

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 enables painless, efficient, and cost-effective transdermal delivery of therapeutic agents and cosmetic substances, with improved mechanical integrity and extended release periods, enhancing skin permeability and reducing discomfort.

Implementation Method 1

microneedles have been recently developed to disrupt the stratum corneum and facilitate the delivery of the active agents and ingredients to the epidermis

Methodology Applied

Scientific EffectMechanical penetration: Mechanical Force