Date of Award

6-2008

Degree Name

MS in Engineering - Biomedical Engineering

Department

Biomedical and General Engineering

Advisor

Lily Laiho

Abstract

The growing field of tissue engineering requires the design and verification of an environmentally-controlled sterile incubator volume. As this technology advances and the field of cell printing emerges, the need for such a volume increases. This volume shall maintain post-deposition cell viability of printed cells, by maintaining volume sterility and controlling temperature. This becomes more important as more delicate cells are used. Sterility maintenance prevents contamination of the cells, while temperature regulation maintains the optimum temperature for cell viability. Several existing incubator systems are capable of regulating environmental conditions, but none are designed to function with a moving cell deposition head.

The Sterile Incubator Volume System was developed to accommodate cell printing needs. The primary challenge was to create a sterile volume, with environmental conditions suitable for cell growth; it must interface with a moving deposition head. Numerous engineering practices were included in this design process: defining design inputs and outputs, brainstorming, using decision matrices, considering manufacturing constraints, prototyping, and testing.

The final design consists of a portable, self-contained volume capable of maintaining cell viability for at least 4 hours. This environment features feedback-regulated temperature, which is controlled via an external feedback loop by a proportional-integral-derivative (P-I-D) temperature controller. This configuration optimizes temperature regulation while minimizing the risk of contamination from external elements by placing the heating element external to the sterile volume. The volume is compact (6" x 6" x 2"), with an easily removable snap-fit lid for simple assembly and disassembly in a sterile hood. A latex cover maintains sterility inside the container while allowing adequate movement of the deposition syringe. A septum permits the syringe to penetrate the latex and be removed without compromising the interior sterility of the volume.

The design was verified through a series of tests, including temperature and pH regulation, resterilizability, evaporation, cell viability and systems integration trials. Temperature, pH, resterilzability and evaporation tests yielded quantitative data; while the cell viability and systems integration tests compared cells from the Sterile Incubator Volume System to control cells (from a commercial incubator). These tests verified that the system can maintain cell viability for up to 4 hours; it follows that the allowable cell print time will increase, due to optimized conditions for the cells during deposition and experimentation. These trials found cell viability in the Sterile Incubator Volume System to be comparable to cells from the commercial incubator. This design is simple, autonomous, and can be integrated into most existing tissue engineering and cell culture experiments with minor changes.

The potential for maintaining cell viability could be further enhanced by future developments, including humidity and carbon dioxide regulation, expanding the volume size, and creating additional print-head interface variations to increase the diversity of the printed assemblies. These potential enhancements must consider the design intent and simplicity. The design of this sterile incubator volume system is an important step in improving tissue engineering technology and the types of tissues that can be engineered.

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