Based on material from Saskia Sichermann, Samuel Cruz Vanegas, and Rubén Ramos García, Optics Department, Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE)
Introduction
Researchers at the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) are developing a needle-free injector capable of drug delivery through the skin using high-velocity liquid jets. To successfully penetrate human skin, these jets must reach speeds of approximately 150 m/s. The team’s existing additive manufacturing tools, however, could not produce the smooth, highly precise internal features required to generate stable, high-speed jets.
The prototype relies on a 500 µm diameter cylindrical exit nozzle through which fluid is accelerated. The smoothness of the interior walls is critical: even micrometer sized variations in surface roughness can destabilize the jet, limit velocity, and prevent consistent penetration. INAOE’s internal 3D printing capability did not offer high enough resolution to produce these micro-scale geometries with the surface quality needed for functional testing.
The goal was to fabricate a micrometer-scale exit capable of producing stable, high-speed jets suitable for transdermal drug delivery. Achieving repeatable, smooth internal surfaces inside such a small channel represented the primary barrier to performance.
Unlocking Performance Through Micro-Precision
The team turned to Boston Micro Fabrication’s micro-precision 3D printing platform, leveraging its Projection Micro Stereolithography (PµSL) technology. BMF’s ability to print with very high resolution, exceptional surface smoothness, and material clarity enabled successful manufacturing of the injector’s most critical component. This was the first time the team could produce a nozzle with sufficient dimensional accuracy and smooth interior walls to meet the performance requirements of the study.
Process
The researchers submitted designs to BMF for production, focusing on achieving:
- 500 µm diameter cylindrical exits with even, repeatable geometry
- Ultra-smooth internal surfaces to promote jet stability
- Material clarity to support evaluation and visualization
BMF printed multiple prototypes, allowing direct comparison between parts made using INAOE’s existing equipment.
Results
The impact of improved print resolution and surface quality was immediate and dramatic:
• Jets from INAOE-printed parts reached maximum velocities of approximately 30 m/s
• Jets from BMF-printed parts achieved velocities up to 200 m/s, using the same input energy
With BMF-printed components, the prototype surpassed the 150 m/s threshold required to penetrate human skin—an outcome previously considered unreachable with available fabrication methods. The enhanced performance paves the way for follow-on studies examining penetration depth, dose delivery, and jet stability across different skin layers.
