Overcoming the Miniaturization Challenge in Autoinjectors with Micro Springs & Precision Metal Components

Designs for modern autoinjectors are trending toward ever more portable, discreet, and ergonomic formats. Patients demand easy-to-carry devices, so engineers are drastically reducing the size and volume of internal components without sacrificing safety or functionality. A smaller device also uses less material and creates less post-use waste, enabling more sustainable designs. However, as space shrinks, it becomes harder to include critical safety mechanisms such as needle safeties, automatic retraction, and visual/audible indicators. Balancing extreme miniaturization with full performance has become a central engineering challenge for medical device designers.

Specific challenges include:

• Minimal space for internal activation, retraction, and locking mechanisms.
• Integrating sensors, batteries, or additional features without increasing device dimensions.
• Extremely tight dimensional tolerances are needed to ensure proper assembly and reliable operation.

Patients ultimately benefit from devices that are easy to carry, simple to use, and safe to dispose of. A truly compact autoinjector can improve user experience and treatment adherence by going almost unnoticed in daily life. But achieving a reduced format forces engineers to optimize every millimeter of the internal design. Crucially, safety features must still work flawlessly in a miniaturized device—for example, even the smallest autoinjector must lock and hide the needle after injection to prevent accidental needle sticks. This necessity for precision means each component must be manufactured with ultra-tight tolerances so that parts fit and function without fail in the limited space.

RPK Medical’s Solutions for Ultra-Compact Injectors

RPK Medical addresses these miniaturization challenges through innovative spring and metal component engineering:

• Micro Springs Optimized for Compact Spaces: Designing and manufacturing micro compression, wave, extension, or torsion springs optimized to perform in extremely compact geometries, and validating them via finite element analysis (FEA) before production. These mini precision springs deliver the required force within minimal space.
• Multi-Functional Metal Components: Developing stamped or deep-drawn metal parts with complex shapes that combine multiple functions into a single piece. For example, a single precision metal strip can serve as a spring, a locking mechanism, and a retention feature—saving space and assembly steps.
• Rapid Prototyping & Co-Engineering: Utilizing flexible manufacturing tools (e.g., modular molds and dies) to iterate component designs quickly during development. By co-engineering with the device manufacturer, RPK’s team jointly refines the autoinjector’s mechanical design, ensuring each metal component performs optimally within the space constraints and meets regulatory standards from the earliest project stages.

RPK Medical partners with pharmaceutical, CMOs and device manufacturers early in development to ensure that even the smallest autoinjectors maintain full functionality and patient safety. We invite you to collaborate with us and co-engineer the next generation of ultra-compact drug delivery devices.