For students interested in studying biomechanical engineering, especially in the field of surgery, this lesson serves as an anatomy and physiology primer of the abdominopelvic cavity. Students are introduced to the abdominopelvic cavity—a region of the body that is the focus of laparoscopic surgery—as well as the benefits and drawbacks of laparoscopic surgery. Understanding the abdominopelvic environment and laparoscopic surgery is critical for biomechanical engineers who design laparoscopic surgical tools.

Students teams use a laparoscopic surgical trainer to perform simple laparoscopic surgery tasks (dissections, sutures) using laparoscopic tools. Just like in the operating room, where the purpose is to perform surgery carefully and quickly to minimize patient trauma, students' surgery time and mistakes are observed and recorded to quantify their performances. They learn about the engineering component of surgery.

Students learn about viscoelastic material behavior, such as strain rate dependence and creep, by using silly putty, an easy-to-make polymer material. They learn how to make silly putty, observe its behavior with different strain rates, and then measure the creep time of different formulations of silly putty. By seeing the viscoelastic behavior of silly putty, students start to gain an understanding of how biological materials function. Students gain experience in data collection, graph interpretation, and comparison of material properties to elucidate material behavior. It is recommended that students perform Part 1of the activity first (making and playing with silly putty), then receive the content and concept information in the associated lesson, and then complete Part 2 of the activity (experimenting and making measurements with silly putty).

Student teams create laparoscopic surgical robots designed to reduce the invasiveness of diagnosing endometriosis and investigate how the disease forms and spreads. Using a synthetic abdominal cavity simulator, students test and iterate their remotely controlled, camera-toting prototype devices, which must fit through small incisions, inspect the organs and tissue for disease, obtain biopsies, and monitor via ongoing wireless image-taking. Note: This activity is the core design project for a semester-long, three-credit high school engineering course. Refer to the associated curricular unit for preparatory lessons and activities.

After conducting the associated activity, students are introduced to the material behavior of elastic solids. Engineering stress and strain are defined and their importance in designing devices and systems is explained. How engineers measure, calculate and interpret properties of elastic materials is addressed. Students calculate stress, strain and modulus of elasticity, and learn about the typical engineering stress-strain diagram (graph) of an elastic material.

Students use balloons (a polymer) to explore preconditioning a viscoelastic material behavior that is important to understand when designing biomedical devices. They improve their understanding of preconditioning by measuring the force needed to stretch a balloon to the same displacement multiple times. Students gain experience in data collection and graph interpretation.

Students reflect on their experiences making silly putty (the previous hands-on activity in the unit), especially why changing the borax concentration alters the mechanical properties of silly putty and how this pertains to tissue mechanics. Students learn why engineers must understand tissue mechanics in order to design devices that will be implanted or used inside bodies, to study pathologies of tissues and how this alters tissue function, and to design prosthetics. Finally, students learn about collagen, elastin and proteoglycans and their roles in giving body tissues their unique functions. This prepares them for the culminating design-build-test activity of the unit.

Students explore the response of springs to forces as a way to begin to understand elastic solid behavior. They gain experience in data collection, spring constant calculation, and comparison and interpretation of graphs and material properties to elucidate material behavior. Conduct this activity before proceeding to the associated lesson.

Students are introduced to the concept of viscoelasticity and some of the material behaviors of viscoelastic materials, including strain rate dependence, stress relaxation, creep, hysteresis and preconditioning. Viscoelastic material behavior is compared to elastic solids and viscous fluids. Students learn about materials that have viscoelastic behavior along with the importance of engineers understanding viscoelasticity. To best engage the students, conduct the first half of the associated Creepy Silly Putty activity before conducting this lesson.

Students are introduced to the similarities and differences in the behaviors of elastic solids and viscous fluids. Several types of fluid behaviors are described Bingham plastic, Newtonian, shear thinning and shear thickening along with their respective shear stress vs. rate of shearing strain diagrams. In addition, fluid material properties such as viscosity are introduced, along with the methods that engineers use to determine those physical properties.