This is an example of a HTML caption with a link.

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





- 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