Course: BIOEN 326 – Solid and Gel Biomechanics

Credits: 3; Three 50-minute lecture periods per week.

Instructor: Wendy Thomas

Texts and Supplemental Materials:

Mechanics of Materials, Brief Edition, by James M. Gere. (c) 2011. Other editions of this text will also suffice, but other texts by the same name by other authors will not.

Course Pack, provided by UW Copy Services is required and includes material from.

  • Biomaterials; the Intersection of Biology and Materials Science, by J. S. Temenoff and A. G. Mikos, © 2008 by Pearson Prentice Hall, ISBN 978-0-13-009710-1
  • Physiological Control Systems: Analysis, Simulation, and Estimation, by Michael C.K. Khoo, © 2000 by Wiley-IEEE Press, ISBN/ISSN: 9780470545515
  • Mechanics of Motor Proteins and the Cytoskeleton, by Jonathon Howard, © 2001 by Sinauer Associates ISBN 0-87893-334-4

UW Catalog Description: Solid mechanics and interactions of biological structures and medical materials. Emphasis on the relationships between composition, structure, properties and performance of metals and ceramics, synthetic and natural macromolecules, cells, tissues and self-assembling systems.

Instructor Overview: This course introduces the mechanical behavior of biological and medical structures and materials, from the continuum description of properties to the atomistic and molecular mechanisms that confer those properties.  Subjects include elastic and viscoelastic deformation, failure and adhesion of metals, ceramics, polymers and biological structures. Measurement methods and quantitative analytic and numerical models will be applied to these topics. This course will also introduce principles of how biological and nonbiological materials interact, such as protein adsorption to surfaces and mechanical sensing of material stiffness.

Prerequisites by Course: CHEM 142; 152; 162; PHYS 122; BIOEN 315

Prerequisites by Topic: Biochemical Molecular Engineering, Physics (Mechanics and Oscillatory Motion), General Chemistry

Required or Elective: Required

Course Grading:

  • Homework 40%
  • Final Exam 40%
  • Midterms 20%

Course Outcomes and Assessment: Students will learn skills in lecture, practice skills in weekly homeworks, verify their ability in quizzes, and be assessed in the final exam.

Specific Outcomes: By the end of the course, students should be able to:

  1. Identify the biomolecular basis of linear and nonlinear viscoelastic material properties of cells, tissues, and biomaterials.
  2. Use engineering formulae to relate experimental results to models and theoretical calculations for elastic and viscoelastic materials.
  3. Develop and solve ODE models of static and dynamic viscoelastic materials to solve biological problems.
  4. Develop a basic understanding of mechanotransduction, including the integrin biology of cell adhesion
  5. Understand principle of adhesion between biological materials.
  6. Learn and apply skills for independently evaluating scholarly work

Outcomes Addressed by this Course:

E. An ability to identify, formulate, and solve engineering problems.

  • Develop and solve ODE models of static and dynamic biomechanical systems

Students will learn to formulate models, solve, and interpret ODE models for viscoelastic materials in dynamic conditions. Students will be taught basic viscoelastic models such as Kelvin, Voigt and Maxwell models in lecture, and will be taught solution techniques to investigate the dynamic behaviors of some of these models, to explain creep, relaxation and hysteresis. Students will apply this knowledge in homework by building a model for muscle viscoelasticity and determining whether the dynamic behavior of their model fits an experimental observation. Student competency in this area will be assessed in a question on the final exam which will require a quantitative answer that requires students to build a model from a written description, and determine how it would respond to a dynamic response.

I. A recognition of the need for, and an ability to engage in life-long learning.

  • Learn and apply skills for independently evaluating scholarly work.

In lecture, students will learn how to identify the major conclusions of original research articles, and to assess the level of certainty for each conclusion based on the strengths and weaknesses of the experiments and arguments presented in the paper, and to use precise terms to describe the level of certainty. Students will then practice this skill by reading seminal articles about the role of mechanobiology in tissue engineering. Student competency in this area will be assessed in a question on the final exam, which will require students to read a passage and identify and justify the level of certainty for several conclusions.

L. An understanding of biology and physiology.

  • A. Identify the biomolecular basis of linear and nonlinear viscoelastic material properties.

In lectures, students will learn the structural basis of different biological and nonbiological materials. In homeworks, they will apply this knowledge to predict the classification of the mechanical properties of a material given a description of the molecular structure, such as viscoelastic vs elastic, linear vs nonlinear, whether the  nonlinear region is plastic vs reversible, etc. Student competency in this area will be assessed through a similar question on the final exam.

  • B. Develop a basic understanding of mechanotransduction, including the integrin biology of cell adhesion.

Students will learn about mechanotransduction in lectures. They will practice this in homework by describing how force might be applied to molecules in a system described in an original research article chosen by the instructor, and assessing whether the amount of force could induce a chemical change. Student ability to identify key elements and outcomes of mechanotransduction will be assessed on the final exam.

M. The capability to apply advanced mathematics (including differential equations and statistics), science, and engineering.

  • Calculate normal and shear forces and stresses in isotropic linear solids.

Students will learn how to calculate normal and shear forces and stresses in lectures, and will apply this skill in a homework in order to determine intrinsic properties of a material from measurement data, or to predict the behaviors of an element from the intrinsic properties. This skill will be applied to linear elastic systems, including linearized systems derived from nonlinear mechanical properties. This skill will encompass many topics over a third of the course. Student competency in this area will be assessed through one or more questions on the final exam that require students to formulate a problem involving either predicting behavior from materials properties or vice versa. The students will be tested on their ability to write all the equations needed for the solution, and to describe how the result would be interpreted.

Topics Covered:

  1. Molecular basis of materials properties.
  2. Stress, strain, and concepts of intrinsic properties.
  3. Mechanical properties of linear elastic materials.
  4. Measurement methods
  5. Plasticity, failure, and strength
  6. Viscoelastic materials
  7. Stress analysis: analytical and numerical approaches

Relationship of course to program educational objectives:

Bioen 326 is a primarily technical course, teaching fundamental engineering skills. These technical skills help students obtain and succeed in educational opportunities and/or employment in bioengineering-related fields. Students may also apply these skills in their jobs to develop new technologies or technical knowledge.  Bioen 326 also teaches critical literature analysis, which is a fundamental skill necessary for independent learning in their fields, and thus can contribute to professional growth and development. Thus, Bioen 326 contributes to the following program educational objectives:

  •  Earn advanced degrees and/or obtain employment in bioengineering-related fields such as medicine, device development, and biotechnology
  • Advance their careers by obtaining appropriate educational and professional qualifications.
  • Contribute to responsible development of new technical knowledge.

Course Schedule:

Week Lecture Topics
1 Linear Elasticity: Elastic materials, Normal and Shear Stress and Strain, Young’s modulus, Shear Modulus, Poisson ratio, plasticity, failure and strength, Hook’s Law; Molecular structure and strength of linear elastic materials (covalent, ionic, van der waals).
2 Nonlinear Elasticity: Yielding and strain hardening. Molecular structure of nonlinear materials. Mechanical properties of polymers, including biological polymers that undergo phase transitions.
3 Viscoelasticity: Time dependent mechanical properties: Hysteresis, creep, and stress relaxation. Linear viscoelastic (Maxwell, Voigt, and Kelvin) models. Molecular structure of viscoelastic materials.
4 Mechanically Active Materials. Biological significance of Mechanotransduction to hearing, bone physiology and tissue engineering. Molecular basis of mechanotransduction, including cilia, ion channels, and focal adhesion complexes. Force generation by cytoskeletal filaments.
5 Stress analysis: Cauchy stress sensor, Mohr’s circle, Maximum stresses
6 Free body diagrams: support reactions, equilibrium equations, model building.
7 Rods. Stresses and strains from pure axial and pure torsional loads.
8 Beams. shear forces and bending moments in beams. Normal and shear stress in beams
9 Deformations. Spherical and Cylindrical vessels with linear and nonlinear materials, aneurisms. Deflections of Beams. Columns and Euler’s formula.
10 Integration I; Cell adhesion.
11 Review and more integration

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