Design and Development of a Progressive Cavity Pump for Extrusion Based Bioprinting

Abstract

Bioprinting is an emerging technology with the ability to fabricate customised tissue con structs. Extrusion-based bioprinting (EBB) attracts considerable attention due to its ability to continuously extrude high-viscous materials with the necessary precision. While cur rently available EBB methods, mechanical or pneumatic driven syringes-based systems, provide an acceptable extrusion, several limitations remain, such as low accuracy, the abil ity to retract material from the nozzle and cartridge volume restriction. Recently, progressive cavity pumps (PCPs) have started to be used in the field of bioprinting as an advanced dis pensing unit and have shown promising results. However, they require an adaptation for bioprinting needs in terms of easy cleaning, low cost and low dead volume. This study aimed to develop a low-cost, scalable, easy-to-clean extrusion system based on the PCP principle to overcome the mentioned limitations. PCPs have a long history; however, the working mechanism of the first design and core com ponents have almost never changed. Developing a new product requires extensive research on problem definition and many iterations of possible solutions. Recent developments in the field of additive manufacturing (AM) have led to a renewed interest in the spiral product development process. The spiral development model allows the generation of various con cepts quickly with AM’s help. Therefore, it was more likely to find an innovative solution for the current drawbacks of dispensing PCPs by obtaining insight from each concept. Con sequently, a spiral development model was established in this research. The development process consists of three main phases: initials, concept development and product develop ment. The initials phase begins with the problem definition: the high cost of PCP and control unit, cleaning difficulty, and scalability of PCPs. Based on the problem definition, background research was conducted, including literature research, user questionnaire and user inter view. Subsequently, a commercial syringe pump was evaluated to highlight the limitations of current technology. The syringe pump evaluation step aimed to explore the relationship between extrusion accuracy and syringe features, including plunger rubber compressibility and the amount of volume inside the syringe. The weighing scale and the flow rate sensor were used to assess the extrusion accuracy. Results showed that the plunger rubber has a neg ative impact on extrusion accuracy due to its compressibility. Likewise, when the amount of compressed volume inside the syringe increases, the start and stop accuracy of the extrusion decreases. Finally, a conventional PCP design was reverse-engineered to understand better the fundamentals of PCPs, including the design’s working principle and essential features. To conclude the initials phase, the collected information was expressed as technical terms and specifications to develop the requirements of the concept development phase. The key research question of this study was whether or not there is a better unknown PCP mechanism for EBB. Due to the nature of the spiral development process, the concept devel opment phase requires many iterations of PCP designs. Therefore, an application program ming interface (API) was developed to enable rapid design iterations of PCP components. Subsequently, various concepts were developed by collecting information from the reverse engineering phase and previous concepts. These concepts were evaluated to produce a bet ter PCP design, either changing the working mechanism or cross-sectional geometry design of the rotor and stator. Consequently, three PCP concepts were designed, prototyped and evaluated to meet the EBB requirements, and the product development phase began with a selected concept. The selected concept was redesigned and prototyped for validation tests in the product de velopment phase. A previously developed open-source and commercial syringe pumps were used to validate the novel PCP concept. The developed PCP showed better performance than syringe pumps for highly viscous materials. In addition, the aim of the low-cost, scalable and easy-to-clean PCP was successfully developed. The proposed spiral development model has the potential to offer a quick product development methodology. In addition, the devel oped PCP has excellent potential as an advanced dispensing unit for highly viscous fluids and pastes.