Following the steps of the iterative engineering design process, student teams use what they learned in the previous lessons and activity in this unit to research and choose materials for their model heart valves and test those materials to compare their properties to known properties of real heart valve tissues. Once testing is complete, they choose final materials and design and construct prototype valve models, then test them and evaluate their data. Based on their evaluations, students consider how they might redesign their models for improvement and then change some aspect of their models and retest aiming to design optimal heart valve models as solutions to the unit's overarching design challenge. They conclude by presenting for client review, in both verbal and written portfolio/report formats, summaries and descriptions of their final products with supporting data.
As part of the engineering design process to create testable model heart valves, students learn about the forces at play in the human body to open and close aortic valves. They learn about blood flow forces, elasticity, stress, strain, valve structure and tissue properties, and Young's modulus, including laminar and oscillatory flow, stress vs. strain relationship and how to calculate Young's modulus. They complete some practice problems that use the equations learned in the lesson mathematical functions that relate to the functioning of the human heart. With this understanding, students are ready for the associated activity, during which they research and test materials and incorporate the most suitable to design, build and test their own prototype model heart valves.
Students are presented with an engineering challenge that asks them to develop a material and model that can be used to test the properties of aortic valves without using real specimens. Developing material that is similar to human heart valves makes testing easier for biomedical engineers because they can test new devices or ideas on the model valve instead of real heart valves, which can be difficult to obtain for research. To meet the challenge, students are presented with a variety of background information, are asked to research the topic to learn more specific information pertaining to the challenge, and design and build a (prototype) product. After students test their products and make modifications as needed, they convey background and product information in the form of portfolios and presentations to the potential buyer.
Students are presented with the unit's grand challenge problem: You are the lead engineer for a biomaterials company that has a cardiovascular systems client who wants you to develop a model that can be used to test the properties of heart valves without using real specimens. How might you go about accomplishing this task? What information do you need to create an accurate model? How could your materials be tested? Students brainstorm as a class, then learn some basic information relevant to the problem (by reading the transcript of an interview with a biomedical engineer), and then learn more specific information on how heart tissues work their structure and composition (lecture information presented by the teacher). This prepares them for the associated activity, during which students cement their understanding of the heart and its function by dissecting sheep hearts to explore heart anatomy.