Transcript Slide 1

Simulation and
Experimental Studies of
Biomechanics at the
Micro-Scale
Elizabeth Nettleton, Undergraduate:
Chemistry, University of South Dakota
IM SURE Fellow, 2006
Dr. William C. Tang, Professor and Mentor:
Biomedical Engineering,
University of California, Irvine
Gloria Yang, Graduate Student:
Electrical Engineering,
University of California, Irvine
Outline
•
•
•
•
•
•
The Work of the Tang Lab
My Role in the Project
My Work
Results
Conclusion
Acknowledgements
The Big Picture—
My Lab’s Goals
• Heart Valve
– Prosthetic valves weaken over time
– Use a sensor to provide measurements
of strain within a valve
• Bone Strain
– Bone tumors and osteoporosis lead to
a decrease in skeletal density
– Monitoring bone strain could track
skeletal remodeling and disease
progression
Device Designs
Cantilever Beam: Heart Valve
Strain Gauge: Bone
Photos Courtesy of Gloria Yang
My Role in the Project
• Heart Valve Investigation
– Use COMSOL to find the values of the
spring constant, k, and resonant frequency,
ω, of our device
– Use a probe station to characterize the
device
– Characterize the effects of adhesives on
heart valves
– Use our device to find the compliance over
the surface of the heart valve tissue
My Role, Cont.
• Bone Investigation
– Use COMSOL to model heat transfer of a
device to surrounding tissue
• Work Applicable to Both Projects
– Research adhesives
• Biocompatibility, faithful transmission of
surface tension to sensor, etc
• Ethicon: Johnson & Johnson
Microval
BD Healthsciences
Cryolife
Edwards Lifesciences
Carpentier-Edwards PERIMOUNT
Pericardial Bioprosthesis Aortic Model 2700
• Learned about
prosthetics
• Use their
bovine
pericardium
valves
• Use their
equipment to
test adhesion
effects
Example of COMSOL
Simulation—Cantilever
Example of Physical Data
B4-Delta R (MM)
0.07
0.06
y = 2.417E-04x
0.05
y = 2.333E-04x
Delta R (ohms)
y = 2.263E-04x
y = 2.160E-04x
0.04
y = 2.149E-04x
y = 2.210E-04x
0.03
y = 2.196E-04x
y = 2.005E-04x
0.02
0.01
0
0
50
100
150
200
250
Displacement (micrometers)
Linear (Trial One)
Linear (Trial Two)
Linear (Trial Three)
Linear (Trial Four)
Linear (Trial Five)
Linear (Trial Six)
Linear (Trial Seven)
Linear (Trial Eight)
300
Example of COMSOL
Simulation—Heat Transfer
Dermabond—Adhesive
• Manufactured by
Ethicon, a Johnson
& Johnson Company
• Attached sensor
prototype to a
foam block
simulating the
skin’s surface
• In the process of
monitoring
adhesive
properties for
seven days
Results
• Cantilever Modeling
– Spring Constants
• COMSOL vs. Theoretical Values:
Percent Difference for each length <1.32%
– Resonant Frequencies: forthcoming?
– As of yet, our simulations have not been
successful. We have no data to compare to
the theoretical values.
Results, Cont.
• Probe Station—Device Characterization
– Multimeter vs. Wheatstone Bridge
• Graphed resistance changes vs. probe
displacement
• Results similar for both
• Data best when lines of best fit forced
through zero
• Multimeter-lower standard deviation
• Repeating Wheatstone bridge measurements,
changing technique
Results, Cont.
– Heat Transfer Modeling
– Have the model completed, working
to apply boundary conditions
– Adhesive Testing
– Currently monitoring Dermabond on
foam block
Conclusions
• What I’ve achieved:
– Providing theoretical data for the
spring constant of our device
– Characterizing the device—its changing
resistance with changing deflection
• I’ve also provided initial data on:
– Modeling the resonant frequency of our
device
– Modeling the heat transfer in an
implanted device
– Monitoring the adhesion of Dermabond
Conclusions, Cont.
• Future Work
– Currently the heart valve project is
focused on prosthetic valves
– Eventually, apply research to living
heart valves, in vivo
• Real-Time measurements
• Wireless Communication System
Acknowledgements
• I would like to thank the following
people and organizations for making
this experience possible:
–
–
–
–
–
My mentor, William C. Tang
My graduate student, Gloria Yang
The Tang Lab, as a whole
UROP and the IM-SURE Program
National Science Foundation