1. Measuring Impedance Across the Channel of a Biodevice Presented by: Kaidi He August 24, 2007 Mentors: Prof. Reginald Penner Li-Mei Yang

2. Outline I. Project Overview II. Methods a.Device Fabrication b.Experimental Setup c.Procedures III. Data and Analysis IV. Conclusion

3. I. Project Overview Measure impedance across the channel of a biodevice for different channel widths exposed to various concentrations Measure impedance across the channel of a biodevice for different channel widths exposed to various concentrations Construct a calibration curve Construct a calibration curve Courtesy of Prof. Penner

4. SU8 Glass Au SU8 Au Exposure Development Au etch II. Methods, (a) Device Fabrication A. B. A. B. Courtesy of Li-Mei Yang SU-8 Au glass Au SU-8

5. Original: Original: NickelNickel Wire attachmentsWire attachments Silver contactsSilver contacts Final: Final: Gold with silver contactsGold with silver contacts S

6. b. Experimental Setup electrochemical cell reference working

7. 5.00e-6 E-1 Nyquist Plot: Zim vs. Zre

8. Bode Plot: Zre, Zim, phase angle vs. Frequency

9. 5E-4M NaCl 5E-1M NaCl EIS x3 H2O 5E-4M NaCl EIS x3 0.1 – 5e-6 M NaCl EIS (3) Procedures Courtesy of Li-Mei

10. III. Data and Analysis, (1) Stability of Device 1st 2nd 3rd

11. 5E-4M NaCl 5E-1M NaCl EIS x3 H2O 5E-4M NaCl EIS x3 5E-1-5E-6M NaCl EIS Courtesy of Li-Mei

12. 5E-4 M 5E-1 M (2) Alternating, ZRe, Low and High Concentrations

13. 5E-4 M 5E-1 M

14. 1.Low concentration, more noise 2.Low frequency, more noise

15. 5E-4M NaCl 5E-1M NaCl EIS x3 H2O 5E-4M NaCl EIS x3 5E-1~5E-6M NaCl EIS Courtesy of Li-Mei

16. (3) Random Sampling As expected, increasing concentration results in decreasing resistance

18. Λ = Λº - (A+B Λº)c 1/2 for c< 0.001 mol/L Λ = equivalent molar conductivity Λ º = equivalent molar conductivity at infinite dilution A = 60.20 B = 0.229 C = electrolyte concentration Λ = κ/c eq C eq = c|z| Plotting Λ against c 1/2 will be linear…

19. Sample Data Set, 500 micron

20. Sample Data Set, 1 mm device

21. Sample Data Set, 3.5 mm device

22. IV. Conclusion We have achieved our goal of constructing a calibration curve which will allow us to know concentration with a device of given channel width and impedance across the channel We have achieved our goal of constructing a calibration curve which will allow us to know concentration with a device of given channel width and impedance across the channel With photolithography, we are able to construct miniaturized conductivity cells quantitatively follow the Debye-Huckel-Onsanger Equation and operate best at large interelectrode spacings With photolithography, we are able to construct miniaturized conductivity cells quantitatively follow the Debye-Huckel-Onsanger Equation and operate best at large interelectrode spacings This most likely will lead to their functioning as biosensor transducers in the future This most likely will lead to their functioning as biosensor transducers in the future

23. Acknowledgments Thank you to Prof. Penner, Li-Mei Yang, Keith Donovan, Travis Kruse, Dat Hoang, Said Shokair, IM-SURE, and NSF for their guidance and support Thank you to Prof. Penner, Li-Mei Yang, Keith Donovan, Travis Kruse, Dat Hoang, Said Shokair, IM-SURE, and NSF for their guidance and support