I would like to know how to make electrical conductive paint electrode for PDMS/nanoparticle composites.
Developing a conductive paint would be far more involved that would be appropriate for this forum. I suspect you are looking for a way to form a contact between your composite and a power source. Have you tried silver paste? It seems to be the sort of thing you're describing you need. Have you looked at silver filled epoxy from Masterbond, part # EP77M-F ? http://www.masterbond.com/tds/ep77m-f
Thank you Dr. Douglas. I need the composite keep flexible to test a mechanical vibration while silver filled epoxy make the composite not flexible.
Any polymer can be filled with conductive fillers to achieve conductivity. The question is how much conductivity you require. Possible fillers: metallic particles or flakes, carbon black, graphite.
When one adds filler to a polymer, there are two critical points of interest: percolation threshold and maximum filler loading (also known as critical filler volume concentration).
All fillers form random clusters in the continuous medium housing them. This is a product of randomness, even for properly-dispersed and stabilized pigments. Those clusters grow as their concentration increases until one reaches the point where the first random cluster spans the dimensions of the film. That is known as the percolation threshold. Typical levels: 15 to 30 % by volume. (density is irrelevant -- only volume relationships count)
As one continues to increase the filler loading, the clusters increase in both size but decrease in concentration as each added particle increasingly bridges adjacent clusters instead of starting new ones. At some point, those clusters approach unity, where one has two continuous phases: a single particulate phase and a single binder phase. This critical volume loading is the point beyond which air voids are increasingly introduced into the final film because there is insufficient binder (polymer) to encapsulate all the filler particles and fill residual voids in the packing structure. Typical level: 50 to 70 % by volume.
The significance is that beyond the percolation threshold, one will have a semi-conducting paint, while beyond the critical loading, one will have a highly conductive paint. Thus, it is important to know how much conductivity you desire.
By using a flexible polymer, one can achieve the mechanical properties you desire, although filler will stiffen the polymer somewhat.
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