Just Like Kidneys: Semipermeable Membrane Prototypes Stacey Simons Markley Bridgeport High School Abstract Project Description Assessment of Project “Using household materials, student teams design prototype models that demonstrate semi-permeability under the hypothetical scenario that they are creating a teaching tool for medical students. Working within material constraints, each model consists of two layers of a medium separated by material acting as the membrane. The competing groups must each demonstrate how water passes through all three layers of the model. After a few test/evaluate/redesign cycles, teams present their best prototypes to the class. Then student teams collaborate as a class to create one optimal design that reflects what they learned from the group design successes and failures. A pre/post-quiz, worksheet and rubric are provided.” https://www.teachengineering.org/activities/view/nds-1731-semipermeable-membrane-prototypes-kidney-dialysis In groups of two, students discussed possible solutions for building a model of a semi-permeable membrane. After choosing a prototype design, students tested it by securing it to a ring stand using clothespins. Water tinted with food coloring was dropped steadily on the model. Students recorded how many drops and how long it took for the water to reach the other side. Each group had the opportunity to redesign, build and test a second prototype. Finally, after discussing their results and what they learned from their individual experiences , each class created a final prototype that was tested. WV NxGen Standards purpose Engineering Design Products S.HS.ETS.2 design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering S.6-8.ETS.2 evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraint of the problem. S.6-8.ETS.4 develop a model to generate data for iterative testing and modification of a proposed object, tool, or process such that an optimal design can be achieved Material Choices: paper plates, copy paper, newspaper, magazine paper, cardboard, fabric, sugar cubes, paper towels Final Classroom Protoypes: Paper towel Fabric Newspaper Source: Revised from PBS Design Squad, 2009 http://www-tc.pbskids.org/designsquad/ pdf/parentseducators/DS_TG_ImplementResources.pdf Evaluate/Reflect Project Timeline Overall, this is a great alternative activity to do with cell transport. There are very few engineering projects out there for biology classes and I appreciate the effort that was made in designing this activity. Many students enjoyed this activity and it received four out of five stars on a survey I generated on surveymonkey.com. The survey data also showed that roughly 19% of students were successful with both designs, 62% of students were only successful with the second design, 3% were successful only with the first design, and 16% were unsuccessful with both designs. Next time, I would like to plan more time for the introduction and have students bring in alternative materials for their redesign. This activity could also be altered to make it more appropriate for the high school level. Day1 Students complete a pre-quiz to test prior knowledge Introduction: Identify the needs and constraints of the problem. Discuss the need for semipermeable membranes in dialysis Research the problem. Develop possible solutions. Choose one promising solution. Build prototype 1. Test and evaluate prototype 1. Redesign the prototype to improve its results Day 2 Build prototype 2 Test prototype 2 Analyze the results. Compare with other groups Day 3 Discuss results Build Classroom prototype Test Classroom prototype Students complete a post quiz. Student survey. Students created their original prototypes and tested them for at least two trials to determine the success of their prototype. If the design was successful, four trials were conducted to get enough data to analyze before deciding how to improve their designs. Their second prototype design was more developed because of their original experiences with the first prototype. Some students changed materials, while others simply changed the order of the materials. Acknowledgements Contributed by: RET Program, College of Engineering, North Dakota State University Fargo and provided by teachenginneering.org The final classroom prototypes were constructed after a brief discussion about their lab results. Students eliminated materials that they felt were completely not viable. The other materials were discussed and evaluated based on their results. Students voted on the materials and their order in the prototype.