Title: MEMS Endovascular Pressure Sensors
1MEMS Endovascular Pressure Sensors
- Jonathan Brickey, Niels Black, Charles Wang
December 14, 2007
2Anatomy of the Heart
http//www.nhlbi.nih.gov/health/dci/Diseases/pda/p
da_heartworks.html
3Abdominal Aorta Aneurysm
Healthy Blood Pressure Diastole lt80 mmHg (11
kPa) Systole lt120 mmHg (16 kPa) Hypertension
Stage 2 Diastole gt100 mmHg (13 kPa) Systole
gt160 mmHg (21 kPa)
http//www.ultrasoundspecialists.com/screenings.ht
ml
4Prevalence of AAA
- 10th leading cause of death 65-74 years old
- 5-7 men over 60 diagnosed with AAA
- 1-3 men over 65 experience aortic rupture
- 75-90 mortality rate from rupture
- 111 malefemale ratio 60-64 years old
5Methods of Treatment
http//www.nhlbi.nih.gov/health/dci/Diseases/arm/a
rm_treatments.html
http//www.vascularweb.org/_CONTRIBUTION_PAGES/Pat
ient_Information/NorthPoint/Abdominal_Aortic_Aneur
ysm.html
6EndoSure by CardioMEMS
- EndoSure Wireless AAA Pressure Measurement System
- Permanently implanted
- Radio frequency transmission
- Radio frequency powered
- Size of a paper clip
- Biocompatible
http//www.physorg.com/news10533.html
http//www.cardiomems.com/content.asp?displaymedi
calmbexpandess
7Design Record
- Jay S. Yadav, M.D and Mark G. Allen
- 1995 cofound CardioMEMS
- 2005 EndoSure sensor invented
- April, 2007 granted FDA approval
http//www.physorg.com/news10533.html
8- 1967 C. C. Collins Miniature Passive Pressure
Transensor for Implanting in the Eye
91995, William N.Carr, NJIT Hartley Oscillator
101999-2002 Mark Allen, GA Tech
Wireless micromachined ceramic pressure sensors
High temperature self packaged wireless ceramic
pressure sensor
112006 Mark Allen, GA Tech
- Flexible Wireless Passive Pressure Sensors for
Biomedical Applications
12Flexible Substrates Types
- Liquid Crystal Polymers (LCP)
- Almost as ordered as fully crystalline solids
- Chemically inert
- Easy to fabricate
- Polyamide Films
- Kapton-E (DuPont)
- thermal expansion coefficient same as Cu
- 13-50 micron thickness
13Flexible Substrates Advantages
- For machining application
- Very high dimensional stability
- High etchability heavily isotropic
- For biomedical applications
- Flexibility allows less invasive implantation
- High levels of chemical inertness
14MEMS Screenprinting
- Additive process
- Mesh overlay polyester or steel
- Places where material does not go are painted
over - Mesh screen placed on substrate, liquid poured
over
15MEMS Screenprinting
- Advantages/Disadvantages
- Cheap!
- Does not require pressurization or extremely
expensive equipment, like lithography - Mesh can be reused
- Not particularly precise
- Features can be no smaller than mesh spacing (50
µm)
16Lithography
Lithography mask for Inductor-Capacitor setup
Cross-section of Cu application
(Fonseca 2006)
17Capacitance vs. Pressure
18Power and Signal Transmission
19Final Output
20Problems in Simplification
- Actual capacitor shape not circular
- tapered in the center to reduce deflection and
avoid shorting out the capacitor (Fonseca 2006) - Circular model shorts out just before 13 kPa
- Inductance
- Very simplified
- Most MEMS inductors use complicated programs
21Future Improvements
- Major limitations Size, Sensitivity,
Transmission Distance - MEMS fabrication results in increased sensitivity
- Size and Transmission Distance invariably linked
22Other Possible Design Improvements
- Finite element analysis of coil design inductance
- Substrates with low dielectric constants
- Hartley oscillators or other more complex CMOS
for improving sensitivity or transmission distance
23References
- Wiemer, M., Frömel, J., Jia, C., Geßner, T.,
Bonding and contacting of MEMS-structures on
wafer level. The Electrochemical Society - 203rd
meeting, Paris (France), 2003 April 27- May 2 - Fonseca, M.A. English, J.M. von Arx, M. and
Allen, M.G., "Wireless Micromachined Ceramic
Pressure Sensor for High Temperature
Applications," IEEE J. Microelectromechanical
Systems, vol. 11, no.4, p. 337-43 (2002) - Fonseca, M.A., Kroh, J., White, J., and Allen,
M.G., Flexible Wireless Passive Pressure Sensors
for Biomedical Applications, Tech. Dig.
Solid-State Sensor, Actuator, and Microsystems
Workshop (Hilton Head 2006), June 2006
24References (continued)
- New Medical Device Combines Wireless and MEMS
Technology, Physorg.com, February 03, 2006,
December 08, 2007, lthttp//www.physorg.com/news105
33.htmlgt - Rosengren, L., Backlund, Y., Sjostrom, T., Hok,
E., and Svedbergh, B., A System for Wireless
Intra-Ocular Pressure Measurements Using a
Silicon Micromachined Sensor, (1992) - Collins, C.C., Miniature Passive Pressure
Transensor for Implanting in the Eye, IEEE
Transactions on Biomedical Engineering, vol.
BME-14, no. 2, April, 1967 - Allen, M.G., Implantable micromachined wireless
pressure sensors approach and clinical
demonstration, 2nd International Workshop on BSN
2005 Wearable and Implantable Body Sensor
Networks, 2005, p 40-1.