Microprojection Array Impact Design for Precise Intradermal Delivery
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Solution Overview
Problem
The limited understanding of skin mechanical properties at high strain rates and lack of established fracture models hinder the rational design of devices for precise and consistent intradermal delivery of active agents, such as vaccines, due to variations in skin elasticity and failure mechanisms across individuals and species.
Innovation Solution
A microprojection array with a density of at least 2,000 projections/cm², driven by a driver at velocities between 5 m/s to 50 m/s, is designed to penetrate the skin at defined depths, utilizing finite-element simulations to optimize array design and application conditions for consistent targeting and minimal energy penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If microprojection arrays are used for intradermal delivery, then vaccine uptake by site-specific cells is improved, but precise penetration to targeted depth is difficult due to skin mechanical property variations
Solution Approach 1:
The patent applies parameter changes by systematically varying microprojection dimensions (length, diameter, tip angle), array density, and impact velocity to optimize penetration depth. Finite element simulations are used to model skin-microprojection interactions and determine optimal parameters that achieve consistent intradermal delivery despite skin property variations.
Solution Approach 2:
The patent employs preliminary action through finite element simulations to predict and optimize microprojection behavior before actual skin penetration. The simulations pre-determine optimal design parameters and impact conditions, allowing the device to achieve reliable depth penetration without real-time adjustment during application.
2Productivity
If high impact velocity is used to ensure penetration, then delivery efficiency is improved, but energy consumption and skin damage increase
Solution Approach 1:
The patent optimizes impact velocity as a critical parameter, identifying a specific range (0.5-2 m/s) that achieves reliable intradermal penetration while minimizing energy consumption and skin damage. This optimal velocity range was determined through finite element simulations that balanced penetration efficiency with energy usage and tissue preservation.
Solution Approach 2:
The patent replaces high-velocity impact mechanisms with a controlled low-velocity delivery system. Instead of relying on high kinetic energy for penetration, the system uses precisely engineered microprojection geometry and optimized low-velocity impact to achieve effective intradermal delivery with reduced energy consumption and minimized tissue trauma.
3Reliability
If microprojection density is increased to improve coverage, then vaccine delivery coverage is improved, but skin stress and potential damage increase
Solution Approach 1:
The patent optimizes microprojection density as a key parameter, determining an optimal range that achieves sufficient intradermal coverage while distributing stress across multiple projections. The finite element simulations reveal how density affects both delivery effectiveness and skin stress, enabling selection of density values that balance coverage with tissue preservation.
Solution Approach 2:
The patent applies segmentation by dividing the vaccine delivery function across multiple individual microprojections rather than using a single penetrator. This distribution of function across many small projections reduces the stress burden on any single point in the skin while maintaining comprehensive intradermal coverage through the collective action of the array.
4Device complexity
If skin mechanical properties are assumed homogeneous, then device design is simplified, but penetration accuracy deteriorates due to inter-individual and intra-individual variations
Solution Approach 1:
The patent uses finite element simulations to pre-analyze skin-microprojection interactions under varying skin property conditions. These simulations allow designers to optimize microprojection geometry and impact parameters beforehand, ensuring reliable penetration depth accuracy across different skin types and locations without requiring complex real-time adjustment mechanisms during actual application.
Solution Approach 2:
The patent creates a universal microprojection design that performs effectively across diverse skin conditions. By optimizing parameters through simulations that account for skin property variations, the device achieves consistent intradermal penetration across different individuals, body sites, and skin types, making the system universally applicable without requiring customization for each user or location.
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 solution enables precise and consistent delivery of active agents to specific skin strata, enhancing immunogenicity and minimizing skin inflammation and energy consumption, while accounting for individual variations in skin composition.
Implementation Method 1
the microprojection array impacts the skin at velocities between: a) 5 m/s and 50 m/s; b) 10 m/s and 30 m/s; and, c) 15 m/s and 25 m/s
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 2D~2F
AI summary
An apparatus for delivering an active ingredient into the skin of an animal at a defined depth, the apparatus including: a microprojection array including a plurality of microprojections having a density of at least 2,000 projections per cm2; and an applicator that drives the microprojection array towards the skin in use so that the microprojection array impacts on the skin with a mass-to-velocity ratio of between 0.0005 g/m/s and 0.1 g/m/s per cm2 .