Esther Johnson
Physics, Del Rio High School
Dr. Alvin Yeh, Associate Professor of Biomedical
Engineering
Dr. Arne Lekven, Associate Professor of Biology
Setup
Noninvasive
High resolution
3D Images
Two Photon
Fluorescence
 Second Harmonic
Generation (SHG)




 Embryos
are large,
robust and
transparent
 Easily observed
 Embryonic
development
occurs rapidly
 Embryos are easily
manipulated



Yuqiang Bai - Biomechanics
Macroscopic Properties of Engineered
Tissue
Microscopic Properties of Extracellular
Matrix
1.0:1.0
1.1:1.0
1.1:1.1
1.2:1.1
1.2:1.2
Various stretch ratio
Photos courtesy of Yuqiang Bai
Photos courtesy of Yuqiang Bai
 Connecting
molecular
and cellular biology
 Biomechanics
 Engineered Tissues
 Stem cell replacement
therapy
 Cancer research
 Various other
biomedical arenas
 TAKS
Science Objective 5
 Physics TEKS
• c.3.E, F
• c.6.B,E
 Research: focus
on biomechanics
 Correlation
Elasticity
Hooke’s law
 Test
the biomechanical properties of
“engineered skin tissue”
Photo courtesy of http://hyperphysics.phy-astr.gsu.edu/hbase/permot2.html
Memory metal spring.wmv
 Hook
Activity:
• Demonstration of Nitinol Spring vs. Regular
Spring
• Ask students why there was a difference
 Notes
on Elasticity and Hooke’s Law
 Homework (research assignment)
• Students must go home and research Nitinol
springs
 Elasticity: the
property of a substance that
enables it to change its length, volume, or
shape in direct response to a force effecting
such a change and to recover its original
form upon the removal of the force
(dictionary.com)
 Hooke’s Law or Elasticity
• F = -kx
 F = restoring force exerted by the spring
 k = spring constant
 x = displacement of the spring end from its equilibrium position
 Hooke’s
Law
computer simulation
 Homework: Hooke’s
Law practice
problems
http://phet.colorado.edu/sims/mass-spring-lab/mass-spring-lab_en.html
 Hooke’s
Law Lab
 PowerPoint on my summer research
experience
Photo courtesy of Wikipedia
Photo courtesy of JL Stanbrough
http://www.batesville.k12.in.us/physics/phynet/mechanics/newt
on3/Labs/SpringScale.html
Stretchiest skin - Guinness World Record2.wmv
 Engineering
Challenge:
• design a mechanism to test the stretch vs. strain
on skin-like materials
• compare the graphs from engineering challenge
with graphs from the Hooke’s Law lab
 Background: Human
 Must be elastic
 If not, it would tear
Skin
Photo courtesy of exorgroup inc.
 Can
synthetic skin handle the same kinds
of stressors as its biological
counterparts?
Human skin is considered
“viscoelastic” meaning it
demonstrates both
viscous and elastic
properties while it is
deformed
Graph courtesy of http://www.engin.umich.edu/class/bme456/ligten/ligten.htm
 Students
must design a mechanism to
compare the various “skins” to identify
which most closely resembles human
skin
Photos courtesy of http://www.purdue.edu/uns/html4ever/0002.Badylak.SIS.html and
http://childrenshospital.org/newsroom/Site1339/mainpageS1339P223.html
 The
stress/pull on the fabric must be
equally distributed over a cross-section
 Material must be immobilized on the
other side
 Material cannot be torn or the test has
failed
 Students must decide which material
presents a stress-strain graph which most
closely resembles human skin’s stressstrain graph.
 Various
material squares (wool, spandex,
cotton, rubber, leather, etc)
 Ruler
 Hanging Mass Set
 Wood blocks
 Pulley apparatus
 Cardboard
 Masking tape
 Wire hangers
 Paper clips
 Post-Test
(identical
to pretest)
 Closure/
Discussion
 Students
will
• Be able to manipulate the Hooke’s Law equation.
• Analyze and verify Hooke’s Law.
• Explore the field of Biomedical Engineering
• Identify practical applications of physics in
engineering
• Design a Biomechanical testing device
• Evaluate and rank the biomechanical properties
of various materials
Yuqiang Bai
Kirsten Brink