Microneedle Array Geometry for Low-Force Skin Insertion
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Solution Overview
Problem
Existing microneedle arrays face challenges in inserting and securing themselves in the skin, leading to potential damage, discomfort, and instability over time, which affects their ability to continuously monitor interstitial fluid analytes and perform drug delivery applications.
Innovation Solution
A wearable device with a microneedle array featuring an off-center tip, indention, and sills, made of electrically insulative materials, is designed to facilitate easier insertion and secure locking, utilizing microfluidic channels and electrical interconnections for stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If microneedles are made sharp and rigid for effective skin piercing, then insertion capability is improved, but microneedles become prone to damage and cause user discomfort
Solution Approach 1:
The microneedle is designed with dynamic flexibility, allowing it to bend during insertion to navigate tissue barriers and then return to its original shape to maintain structural integrity. This dynamic behavior enables the microneedle to be both sharp enough for effective piercing and resilient enough to avoid damage
Solution Approach 2:
The microneedle's mechanical properties are optimized by changing parameters such as tip geometry, body thickness, and material composition. The tip is made sharp for penetration while the body maintains appropriate flexibility through controlled thickness and material selection, resolving the contradiction between insertion capability and structural integrity
2Reliability
If microneedles are inserted deeply for stable analyte monitoring, then sensing stability is improved, but microneedles lose correct depth and become unstable over time
Solution Approach 1:
The microneedle is segmented into distinct functional regions: a sharp tip for insertion, a flexible body for navigation and depth maintenance, and a base for anchoring. This segmentation allows each region to perform its specific function optimally, with the body region maintaining correct depth through its mechanical properties over the device's operational lifetime
Solution Approach 2:
The microneedle's body exhibits dynamic mechanical properties that allow it to adapt to tissue movements while maintaining stable positioning. The flexibility enables the microneedle to accommodate tissue deformation without losing depth, ensuring continuous stable monitoring over time
3Force
If microneedles are made flexible for easy insertion, then insertion force is reduced, but microneedles lack the strength to pierce the protective skin barrier
Solution Approach 1:
The microneedle is designed with non-uniform properties along its length: the tip region is made sharp and sufficiently rigid for barrier piercing, while the body region is optimized for flexibility to reduce insertion force. This local differentiation of mechanical properties allows the microneedle to pierce the skin barrier effectively while requiring minimal insertion force
Solution Approach 2:
The microneedle exhibits asymmetric geometry with a sharp, rigid tip and a more flexible, thicker body. This asymmetric design creates a gradient in mechanical properties that enables the tip to concentrate force for barrier penetration while the body provides flexibility and structural support, resolving the contradiction between insertion force and piercing 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 improved microneedle array reduces insertion force, minimizes tissue damage, enhances stability, and ensures continuous monitoring of analytes with reduced biofouling and inflammatory response, supporting both sensing and drug delivery functions.
Implementation Method 1
at least some of the microneedles being configured as electrochemical sensor electrodes to detect an electrical signal from a reaction with a target analyte in a biofluid
Data Source
AI summary
Disclosed is a wearable device with improvements to microneedles in a microneedle array including an off-center tip, a deflection guide indention, amorphous cavities which help the microneedles to bend during insertion into the skin. As the microneedles bend back after insertion, a number of sills extending from the microneedles help to hold the microneedles in place. Less damage is done to the microneedles and the surrounding tissue, thus reducing inflammation.