Floppy Heart Valves

This "legacy cycle" unit is structured with a contextually based Grand Challenge followed by a sequence of instruction in which students first offer initial predictions (Generate Ideas) and then gather information from multiple sources (Multiple Perspectives). This is followed by a Research and Revise phase as students integrate and extend their knowledge through a variety of learning activities. The cycle concludes with formative (Test Your Mettle) and summative (Go Public) assessments that lead students towards answering the Challenge question. See below for the progression of the legacy cycle through the unit. Research and ideas behind this way of learning may be found in How People Learn: Brain, Mind, Experience and School (Bransford, Brown & Cocking, National Academy Press, 2000); see the entire text at https://www.nap.edu/read/9853/chapter/1.

The legacy cycle is similar to the engineering design process in that they both involve identifying an existing societal need, applying science and math to develop solutions and using the research conclusions to design a clear, conceived solution to the challenge. Though the engineering design process and the legacy cycle both result in viable solutions, each focuses differently on how the solution is devised and presented. See an overview of the engineering design process in the engineering design handout in the final activity, or at https://www.teachengineering.org/populartopics/designprocess.

In What Do I Need to Know about Heart Valves?(lesson 1), students are introduced to the challenge question and exposed to some basic information relevant to the topic of heart valve tissue. This supplies the Challenge, Generate Ideas, and Multiple Perspective portions of the legacy cycle. Students wrap up the lesson by researching heart valve mechanics and valve tissue anatomy and details. These activities represent the Research and Revise portion of the legacy cycle. In The Mighty Heart associated activity, student groups dissect sheep hearts to see and feel its structure, including valves, and learn more in-depth information about valves.

In Elasticity & Young's Modulus for Tissue Analysis (lesson 2), students learn about the forces that act on heart valve tissue, as well as elasticity, stress, strain, Young's modulus and how to calculate Young's modulus for materials. They complete some practice problems to solidify their understanding. In the Does My Model Valve Stack up to the Real Thing? associated activity, students research materials suitable for their model valves. They test possible materials to evaluate them for similarities to real heart valves. Then they design and test their prototype heart valve models. Students refine their models after testing and before presenting the information to the teacher and class as an information packet. The work accomplished in this activity represents the Test Your Mettle and the Go Public portions of the legacy cycle.

Engineers look into ways to improve problems that humans face by developing solutions, and then researching, building, testing and redesigning those solutions to improve upon the initial design. Often what is needed does not exist, so it is up to engineers to develop novel materials, structures or procedures to solve the problems. Bioengineers perform all of these tasks, but with a focus on biological materials, processes or chemicals. In this case, student groups are challenged to develop a material that mimics the behavior and mechanical properties of aortic valves. To do this, students study the problem, learn as much about heart valves as they can, and apply their knowledge towards the design, building and testing of a material and model that meets the buyer's needs.