Compliant Mechanisms in Aseptic Pharmaceutical Manufacturing
Feasibility Study on Flexure-Based Design for Particle Elimination in Sterile Environments
M.C. van Ingen (TU Delft - Mechanical Engineering)
F.G.J. Broeren – Mentor (TU Delft - Mechanical Engineering)
A.H.A. Stienen – Graduation committee member (TU Delft - Mechanical Engineering)
Nicolo' Vacchi – Mentor (Novo Nordisk A/S)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
Aseptic pharmaceutical manufacturing demands ultra-clean automation to safeguard product integrity and patient safety, yet traditional rigid body mechanisms generate particles, require lubricants, and are difficult to sterilize. Compliant mechanisms (CMs), achieving motion through elastic deformation of monolithic structures, offer a compelling alternative by inherently eliminating these contamination sources. However, their feasibility within the strict constraints of Grade A aseptic environments remains underexplored.
This Master's thesis investigates the design, analysis, and preliminary validation of a flexure-based compliant gripping mechanism for sterile handling of pharmaceutical components, developed in collaboration with Novo Nordisk. The research employed a systematic approach, integrating analytical stiffness modeling (including refined corner-filleted arc leaf flexures), Pseudo-Rigid Body Models (PRBMs) for gripper kinematics, and Finite Element Analysis (FEA) for stress and kinematic performance. A cleanroom-compatible voice coil actuator (VCA) drove the system, which included a compliant linear guide mechanism (LGM) and a two-fingered gripping mechanism (GM), complemented by an aseptic bayonet locking system. Preliminary validation involved prototyping (in Al7075) and cleanability assessment via riboflavin testing.
Results demonstrated strong agreement between analytical (13.00 N/mm) and FEA (13.45 N/mm) predictions for LGM stiffness, validating the accuracy of the refined flexure models. Modal analysis confirmed robust dynamic stability, with the first axial mode (84.196 Hz) well separated from parasitic modes. The GM achieved a 7.5 mm gripping motion from a 4 mm VCA input, with optimized tapered flexures reducing peak von Mises stresses by approximately 35$\%$. The monolithic design inherently eliminated particle-generating elements, and riboflavin tests showed high cleanability, identifying minor geometric refinements for optimal aseptic compliance. The design was subsequently re-optimized for pharmaceutical compatible material Super Duplex, preserving validated performance.
This study successfully demonstrates the viability of compliant mechanisms as a critical enabling technology for next generation automation in aseptic pharmaceutical manufacturing. By inherently minimizing particle generation, simplifying sterilization, and ensuring cleanroom compatibility, these mechanisms promise enhanced sterility assurance and improved efficiency, paving the way for advanced pharmaceutical production.