A disposable bioreactor is designed consisting out two identical shells that are fabricated via a two component, hard and soft, injection molding technique. In the bioreactor an autologous-cell-seeded scaffold can be placed for culturing (growing and conditioning) and testing tissue-engineered heart valves. The soft polymer is used for membranes, that drive the fluid flow, and for the steering valves and the sealings. The hard polymer comprises the casing parts that hold the soft parts in place. The steering valves are used for directing the fluid flow and controlling the closing pressure exerted on the growing heart valve. Air pressure actuation is used because of its flexibility, simplicity and reliability. Different spherical membrane geometries are evaluated in their performance to realize a reproducible deformation. Relaxation of flow-induced orientation inside the membrane results in buckling and tilting, which makes ultrasonic position measuring troublesome. The problem is solved by developing a membrane geometry that allows high volume displacements combined with relaxation to a neutral geometry as it is initially molded. The bioreactor is successfully tested, imitating the cardiac pressures and cardiac flows needed during the culturing and testing of tissue-engineered heart valves.

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Gas assisted injection moulding (GAIM) is a technique that is successfully used for compensating shrinkage during injection moulding of thick walled but still accurate products with low levels of internal stresses and frozen-in orientation. In this study the authors apply GAIM in moulding 28 mm thick products combining the technique with two component injection moulding: 2C-GAIM. Next, the authors used a movable insert as a local shrinkage compensating device, making the use of gas superfluous: the component, component, compliance, compensating for shrinkage technology is born. It is used for injection moulding robust and accurate transparent polymer products aiming to introduce multifunctionality, to apply hard and soft polymers, and differently coloured polymers, for improved visibility of text or design lines, and moulding text even inside a product for improved aesthetics.

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