Injection Needle Assembly with Optimized Projection Length
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Solution Overview
Problem
The challenge lies in accurately injecting a small amount of vaccine into the epidermal layer or dermal layer near the epidermis, as the depth of the dermal layer can vary significantly with age, gender, and medical history, leading to difficulties in determining the optimal needle length, resulting in either vaccine leakage or inadequate immunocompetence due to injection into subcutaneous tissue with fewer dendritic cells.
Innovation Solution
A needle assembly with a needle having an outer diameter of 0.15 mm to 0.20 mm, a projection length of 0.50 mm to 1.25 mm, and a cutting face length of 0.30 mm to 0.75 mm, designed to securely inject a small amount of vaccine into the dermal layer near the epidermal layer, minimizing leakage and ensuring sufficient immunocompetence, even in individuals with thin skin such as infants and steroid-dosed patients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a needle with larger diameter is used for injection, then the needle strength and manufacturability are improved, but the injection precision into the thin epidermal layer deteriorates
Solution Approach 1:
The needle outer diameter is changed to a specific small range (0.15-0.20mm) to enable precise injection into the epidermal layer while maintaining sufficient strength through optimized geometric parameters and material properties
2Length of moving object
If the needle projection length is increased to reach the dermal layer, then the injection depth coverage is improved, but the risk of vaccine leakage into subcutaneous tissue increases
Solution Approach 1:
The needle projection length is optimized to a specific range (0.50-1.25mm) that ensures the needle tip reaches the dermal layer containing dendritic cells while preventing excessive penetration into subcutaneous tissue, thereby maintaining reliable injection accuracy
Solution Approach 2:
The needle hub includes an adjustment portion that allows the needle projection length to be adjusted, enabling adaptation to different skin thicknesses and target layer depths while maintaining reliable injection
3Quantity of substance
If a large amount of vaccine is injected into the skin upper layer, then the vaccine diffusion toward immunocompetent cells is improved, but the pain during injection increases
Solution Approach 1:
The needle outer diameter is reduced to 0.15-0.20mm, which decreases the mechanical trauma and pain during injection while maintaining effective vaccine delivery to immunocompetent cells in the skin upper layer
Data Source
Figure 1
Figure 2A~2E
Figure 3
AI summary
Provided is a needle assembly capable of injecting a chemical selectively into a skin upper layer, particularly a relatively shallow portion in a dermal layer near an epidermal layer to form a wheal without leakage of the chemical from a skin surface, and producing immunocompetence or the like even by an extremely small amount of the chemical. A needle assembly 10 includes: a needle 20 constituted by a needle tube that includes a needle hole 24 communicated from a needle tip 21 to a needle base end 23, and a cutting face 22 disposed at the needle tip 21; and a needle hub 30 that includes a tip 31c and a base end, and holds the needle 20 at the tip 31c. The needle hub 30 includes a needle tip side end face 31b from which the needle tip 21 projects. The needle 20 is configured such that an outer diameter ϕ1 is in a range from 0.15 mm (inclusive) to a length smaller than 0.20 mm, that a projection needle length L1 extending from the needle tip side end face 31b to the needle tip 21 ranges from 0.50 mm (inclusive) to 1.25 mm (inclusive), and that a needle body length L2 extending from the needle tip side end face 31b to the cutting face 22 ranges from 0.10 mm (inclusive) to 0.70 mm (inclusive).