1. Time Dependent Roughness Change of PPy(DBS) from Reduced to Oxidized State
A. Palumbo, C. Cupo, R. Zhang, J. Xu, W. Xu, and E. H. Yang Department of Mechanical Engineering
1. Motivation
4. Experimental Setup
a) Reduction Setup:
b) MV1000 AFM & Microscope:
Dodecylbenzenesulfonate Doped polypyrrole, PPy(DBS):
- Biocompatible conjugated polymer
- Oxidation/Reduction at ultra-low voltages (< 1 V)
- Smart material: Switchable adhesion to liquid droplets
Dry PPy(DBS)
Polypyrrole, conjugated polymer
Sodium dodecylbenzenesulfonate, surfactant dopant +
*Initiate AFM scans at 10 min intervals (immediately following reduction)
5. Roughness (Overtime) after Reduction
a) Dried until no visible water droplets (~15 sec):
Surface Roughness of PPy(DBS) may influence:
Contact angle and pinning (i.e., hydrophobicity)
Surface area/interactions for sensing applications
Initial surface microbial colonization, with potential use as an active antimicrobial surface
Not shown:
Roughness measured several days later: nm
Hypothesis: due to drying/settling after removal from electrolyte
Conventional knowledge from literature agrees to no reliable change in roughness of PPy(DBS) between oxidized and reduced states. However, the change in roughness as a function of time has yet to be reported.
2. PPy(DBS) Fabrication
PPy(DBS) Electropolymerization:
DBS- Dopant
Practical RMS range: nm (3.89 nm nm)
Electropolymerization
b) Controlled drying for 60 sec:
Three electrodes setup
PPy chain
3. Initial Results (Disregarding Time)
Pre-redox
Reduced
Oxidized
Not shown:
Roughness measured several days later: nm
Practical RMS range: nm (3.44 nm – 4.08 nm)
6. Future Work
As control group, submerge PPy(DBS) sample in electrolyte, under same conditions as above, with the exception of applying voltage, and measure RMS overtime to determine apparent statistical/equipment error
Determine conditions that will result in maximum and minimum range of roughness change overtime, systematically varying one parameter at a time
Measure contact angle (water in air) under same conditions to determine correlation between change in nanoroughness and change in contact angle as functions of time.
*Scans shown for PPy(DBS) sample fabricated at 0.6V (100 mC/cm2)
7. Conclusions
We fabricated PPy(DBS) and observed the changes in roughness (RMS) as a function of time after completion of reduction; average roughness gradually increases to RMS values similar to the expected oxidized state of the sample (within 24 hours)
Initial roughness is affected by the amount of drying after being removed from the electrolyte (before scanning)
PPy(DBS) conditions may affect the range of roughness change from reduced to oxidized state; 0.8V sample displayed RMS range of 0.64 nm, and 0.7V sample displayed RMS range of 1.55 nm