Lecture Notes

L1 Introduction: From Tissue Biomechanics to Molecular Nanomechanics (PDF - 1.1 MB)  
Molecular Mechanics

Length, Time and Forces in Biology

Molecules of Interest: DNA, Proteins, Actin, Peptides, Lipids

Molecular Forces: Charges, Dipole, Van der Waals, Hydrogen Bonding

kT as Ruler of Molecular Forces

Thermal Forces and Brownian Motion

Life at Low Reynolds Number


Thermodynamics and Elementary Statistical Mechanics

Review of Classical Thermodynamics: Entropy, Equilibrium, Open Systems, Ensembles, Boltzmann Distribution, Entropic Forces

Tutorial on Statistical Mechanics




Ideal Polymer Chains and Entropic Elasticity

Statistics of Random Walks - Freely Jointed Chain - Origins of Elastic Forces

Extreme Extension of a FJC and Modeling Force as an Effective Potential Field


Persistent Chain Model and Cooperativity

The Worm-like Chain Model - Persistence Length as a Measure of Rigidity - Cooperativity Modeled using Ising Models

Examples: Actin Length Fluctuations, Pulling on DNA and Synthetic Polymers



Reactions and Chemical Equilibrium - Kramers/Eyring Rate Theories - Effect of Forces on Chemical Equilibrium

Examples: Pulling on Titin, Bond Rupture Experiments


Motility at the Macromolecular Level

Forces by Polymerization - Concept of Equilibrium Force - Motor Proteins - Molecular Springs

Examples: Listeria, Acto-myosin Motors, Kinesin, Vorticellid


Linear Elasticity

Continuum Mechanics - Basis of Linear Elasticity: Stress, Strain vs. Strain-rate, Hooke’s Law, Experiments to Measure the Moduli

(PDF - 1.5 MB)  
Tissue Mechanics

Composition and Structure of the Extracellular Matrix (ECM)

Collagens, Proteoglycans, Elastin - Cellular Synthesis and Secretion of ECM Macromolecules - Cell-mediated Assembly of ECM


Pushing and Pulling on Molecules

Guest Lecturer: Prof. Matt Lang


Elastic (Time-Independent) Behavior of Tissues

Stress and Strain in Tissues Modeled via Hookian Constitutive Law - Homogeneous/NonHomogeneous - Isotropic/Anisotropic - Linear/Nonlinear Behavior of Tissues and Relation to the ECM - Relation between Molecular Constituents and Macroscopic Tensile, Compressive, and Shear Properties of Connective Tissues



Isotropic Cross-linked Gels Compared to Fibrous Tissues such as Arterial Wall, Cornea (Relevant to Corneal Dystrophy), Tendon, Ligament, Cartilage, Bone, Lung


Viscoelastic (Time-Dependent) Behavior of Tissues

Time-dependent Viscoelastic Behavior of Tissues as Single-phase Materials - Transient Behavior (Creep and Stress Relaxation) - Dynamic Behavior (Storage and Loss Moduli) - Lumped Parameter Models (Advantages and Limitations)


L14 Viscoelastic (Time-Dependent) Behavior of Tissues (cont.)   (PDF)

Poroelastic (Time-Dependent) Behavior of Tissues

The Role of Fluid/Matrix Interactions in Tissue Biomechanics - Darcy’s Law and Hydraulic Permeability, Continuity, Conservation of Momentum - Creep, Stress Relaxation, Dynamic Moduli Revisited - Poro-viscoelastic Behavior

Examples: Muscle and Soft Tissues in Health and Disease - e.g., Arthritis and Joint Degeneration

E1 Midterm Quiz    
L16 Poroelastic (Time-Dependent) Behavior of Tissues (cont.)   (PDF)

Electromechanical and Physicochemical Properties of Tissues

Role of Electrical and Chemical Phenomena in Determining Tissue Biomechanical Behavior - Fluid Convection of Ions During Tissue Deformation and the Resulting “Electrokinetic” Phenomena - Electrostatic Interactions between Charged ECM

Molecules: Tissue Swelling and Donnan Osmotic Swelling Pressure

Examples: Bone, Muscle, Soft Connective Tissues - Streaming Potentials and Electro-osmosis - Tissue Swelling and Molecular Electromechanical Forces


Muscle Constriction From the Molecular to Macro Scale

Characteristics of Contracting Muscle - Hill’s Equation - Force-velocity Curves - Muscle Energetics, Activation - Cross-bridge Dynamics - Models for Muscle Behavior

Cell Mechanics

Structure of the Cell

Cellular Anatomy, Cytoskeleton, Membrane, Types of Attachment to Neighboring Cells or the ECM, Receptors, Different Cell Types, Experimental Measurements of Mechanical Behavior



Stiffness and Role of Transmembrane Proteins - Equations for a 2-D Elastic Plate - Patch-clamp Experiments - Membrane Cortex - Vesicles: Model Systems


The Cytoskeleton

Fiber Microstructure - Actin and Microtubule Dynamics, Methods of Visualizing Actin Diffusion and Polymerization - Rheology of the Cytoskeleton - Active and Passive Measures of Deformation - Storage and Loss Moduli and their Measurements - Models of the Cytoskeleton: Continuum, Microstructural - Tensegrity, Cellular Solids, Polymer Solution


Cell Peeking and Poking

Guest Lecturer: Prof. Peter So

L23 The Cytoskeleton (cont.)   (PDF)

Cell Adhesion and Aggregation

Cell Adhesion Assays, Cell-free Adhesion Assays - Receptor-ligand Interactions Mediated by the Cytoskeleton and the Cell Membrane - Focal Adhesions




Cell Migration and Mechanotransduction

Measurement of Cell Motility (Speed, Persistence, “Diffusivity”) - Simple Models for Cell Migration - Actin Filament Assembly/Crosslinking and Disassembly - Intracellular Signaling Relating to Physical Force - Molecular Mechanisms of Force Transduction - Force Estimates and Distribution within the Cell


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