Sagar Nadimpalli NSF REU 2010 - 7.29.2010 Bioengineering University of Illinois at Chicago

1. Modeling and Designing of a Drift-free Biocompatible Pressure Sensor for use in Long Term In-Vivo Testing Sagar Nadimpalli NSF REU 2010 - 7.29.2010 Bioengineering University of Illinois at Chicago

2. Acknowledgments • NSF (EEC-NSF Grant # 0755115) • US D.O.D. ASSURE • Directors • Dr. Christos G. Takoudis • Dr. Gregory Jursich • Advisor • Dr. Alan Feinerman • Graduate Student Advisee • Kasun Punchihewa Sagar Nadimpalli REU 2010

3. Introduction / Background • Pressure build-ups or drops in our bodies can influence the blood flow going through the body • Specific delicate situations / regions are: • CSF [Brain] • Glaucoma [Eye (build-up of pressure in this region)] • It has been known through various research and modeling with blood mechanics that pressure drops are directly proportional with blood flow4 • If pressure is not detected and monitored carefully • Blood flow to that region would be reduced • With this in mind, a pressure drop of about 10 Torr for any patient can be means for dealing with a medical situation as a result of this change Images Courtesy of: • http://en.wikipedia.org/wiki/Brain_hemorrhage • http://biomed.brown.edu/Courses/BI108/2006-108websites/group02glaucoma/glaucoma.html Sagar Nadimpalli REU 2010

4. Introduction/Background [Continued] Images Courtesy of: http://en.wikipedia.org/wiki/Brain_hemorrhage http://biomed.brown.edu/Courses/BI108/2006-108websites/group02glaucoma/glaucoma.html Sagar Nadimpalli REU 2010

5. Objectives • To design and test a drift-free biocompatible pressure sensor which measures small variations in applied pressure • Can be used for further experimentation as pressure monitoring in various parts of the body (eye for example) • Potential for monitoring the CSF variations through pressure monitoring at the brain • Three specific tests were performed so far to understand the pressure sensor’s abilities for the body • Impedance variations during pressure change and change of salt concentrations • Conductivity variations during pressure change • Modeling/Simulation of the pressure sensor design and materials through COMSOL Sagar Nadimpalli REU 2010

6. Design of the Pressure Sensor Prototype: Materials • Mylar film to create the sensor region • Two electrodes • Composed of primarily titanium and having a mixture of the following • Aluminum (6%) • Vanadium (4%) • LDPE (low density polyethylene) tubes • 30 cm in length for the center tube • 4 cm in length for the part covering each electrode • Injected with approx. 0.135 mL of BSS (Balanced Salt Solution) when sensor is ready Sagar Nadimpalli REU 2010

7. Design of the Pressure Sensor Prototype: Materials • All these materials are considered biocompatible for use2 Sagar Nadimpalli REU 2010

8. Experimental Setup Design • Pressure Chamber • Impedance Analyzer • Pressure Gauge • Container • Aquarium Pump • Pressure flow switch Sagar Nadimpalli REU 2010

9. Experimental Setup Design Container Aquarium Pump Pressure Flow Switch Pressure Gauge Impedance Analyzer Pressure Chamber Sagar Nadimpalli REU 2010

10. COMSOL – Pressure sensor 2D Sagar Nadimpalli REU 2010

11. COMSOL – Pressure sensor 3D Sagar Nadimpalli REU 2010

12. Experimental Testing – Part I Sagar Nadimpalli REU 2010

13. Experimental Testing – Part II Sagar Nadimpalli REU 2010

14. Experimental Testing – Part III (Volume = 400 mL*) Sagar Nadimpalli REU 2010

15. Future Goals • Run additional simulations regarding the mechanical properties of the biocompatible materials being considered for the upcoming prototypes through COMSOL • Make further data runs to better support the current and potential future prototypes of pressure sensor implants • Prepare a batch that after having successfully accomplished the safety guidelines for both the properties on an engineered design level and for medical use (research studies through in-vivo usage) Sagar Nadimpalli REU 2010

16. References • N. Paya, Tatjana Dankovic, and A. Feinerman, “A Microfluidic Mixer Fabricated From Compliant Thermoplastic Films,” Journal of Undergraduate Research 2, pp. 1-5 (2008). http://jur.phy.uic.edu/issue2/JUR-REU0801005.pdf • Beanger MC, Marois Y. Hemocompatibility, biocompatibility, inflammatory and in vivo studies of primary reference materials low-density polyethylene and polydimethylsiloxane: a review. J Biomed Mater Res. 2001;58(5):467-77. Review. • A. Duffy, Kasun Punchihewa, and A. Feinerman, “Development of a Meso-scale Drift-free Pressure-sensor for Glaucoma Patients” Journal of Undergraduate Research – NSF REU 2009 <http://www.uic.edu/labs/AMReL/NSFREU2009/reports/JUR_REU_Final_Report_Andrew.pdf>. • Paul, A., Nadimpalli, S., Lin, A., Hsu, Y., "Detailed Model of Blood Flow in the Arms and Legs Using Circuit Analysis." UIC-LPPD-112009, Nov., 2009. Sagar Nadimpalli REU 2010