Dielectric Spectroscopy of Molecular Interaction

 

Prashant Patil, Center for Bits and Atoms

 

What is the Goal?

 

Dielectric spectroscopy of molecular interaction. Materials dielectric properties are determined by its molecular structure. If the molecular structure changes it dielectric properties changes.

 

To accomplish this, what question(s) will you answer?

 

1 - Bridge circuit to directly determine the change in dielectric propery after molecular interaction (for example water and water+salt)

2 - Electrode geometery and measurement techniques (ex: coaxial probes, resonant cavity or parallel electrodes)

 

 

What technique(s) will you use to answer them?

 

Balanced Wheatstone bridge with Precise Resistors

 

Circuit Schematic Diagram

 

 

Circuit Board Layout

 

 

Circuit Board

 

 

Conclussion

 

- The observed permittivity was dominated by resistors only not by H2O/water interaction.

- Freespace geometry is not suitalbe for this application.

 

 

Balanced Wheatstone bridge

 

Circuit Diagram

 

 

 

Circuit Board

 

 

FWD Reflectance (S11)

 

FWD Transmission (S21)

 

 

How will you evaluate the results?

 

- Compare with standard H2O and H2O/Salt dielectric spectroscopy in time domain and frequency domain.

 

 

Differential FWD Tranismission response of slat water at 3 differenet concentration

 

Pure Water

 

50mM Salt Water

 

 

500mM Salt Water

 

 

1M Salt Water

 

 

 

Conclussion and Future Work

 

1- Frquency range/ high frequency probes

 

 

We limited ourself to 10MHz because of impedance matching problem.

 

2 - Reflection and Transmission coefficients to dielectric properties

 

Reference

 

http://www.home.agilent.com/upload/cmc_upload/All/MWDielectricSpectroscopyWS.pdf?&cc=US&lc=eng

http://apl.aip.org/resource/1/applab/v90/i24/p243901_s1