Everything I Know About PEDOT:PSS

Published August 5, 2021


I've been reading about PEDOT, which is a conductive polymer.

I first heard about its use in making flexible, tissue-conforming electrodes for EMG and EEG, but it is apparently good for making electro-osmotic devices as well (as well as a whole host of other things).

Conductivity

The conductivity is quite good relative to other organic polymers, with several papers reaching a sheet resistance of 20Ω/sq [1][2]. Compare this to a 1oz sheet of copper's sheet resistance of 0.5Ω/sq, and it's about the resistivity of titanium or lead. Raw PEDOT:PSS is something like 100kΩ/sq, so the dopants are really necessary.

Usual forms

Usually aqeous solutions are around 1-4% PEDOT:PSS by weight, with some adding 5% diethylene glycol to increase the conductivity. The PSS is needed for enhanced solubility, though it negatively impacts the conductivity. The reference [1] above adds a graphene oxide solution as well, also to increase conductivity. It's sometimes confusing because they give the conductivity instead of the resistance, but I'm sure it's convertible.

Sigma-Aldrich sells it in dried pellets as well. Some guy on the cyan site said dissolving it in water will destroy its conductivity, but that's what this paper did with no problem. About a gram of this stuff costs $50, and people on ebay are no kinder ($50 for 30g of 1.1%)

Working with it

Sheets of this stuff are made by pouring out a solution and letting it dry. Some people will fire it in an oven at 60C for a few hours to get all the water out. In the end, you get a flexible sheet of it. Kinda cool!

You can also remove the PSS after drying to increase conductivity. Dipping it in a solvent does the trick here

You can add PDMS to make it stretchier (up to 80%!), but you'll need to add this surfactant with the dope name Triton X-100. Reference

What I want to do with it

  1. I want to deposit some and do a sheet resistance test, maybe with diethylene glycol or ethylene glycol
  2. Since ethylene glycol does approximately the same thing as the much more poisonous diethylene glycol, maybe do a test with that instead [paper]
  3. Maybe since propylene glycol is even less poisonous than that, use it instead? It seems to work for conductvity if you soak PEDOT in it after drying it.

Ethylene Glycol > Diethylene Glycol

Ethylene Glycol > Diethylene Glycol

Conclusions

Ok so it's not much, but I hope it gives you some good leads.


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