I apply low AC voltages and frequencies at kHz levels on planar gold electrodes which are directly in contact with a sucrose-dextrose medium (These gold electrodes are attached to the glass substrate via 30 nm thick Ti layer and I believe that electrolysis occurs because of Ti existence).
What do you mean low voltages? For pH 7 at 25 degrees Celsius aqueous solution, the minimum voltage for hydrolysis is about 1.48 V. Check if the problem is solved if you apply lower voltage :)
This is a problem we used to have as well with Platinum/Titanium electrodes in microfluidic channels. We solved the problem by depositing a layer of SiO2 by PECVD on the surface of the electrodes (and using kapton tape to "mask" the edges for proper electrical contact). Since I am not sure of your application, this is the best advice I can offer you.
Have you also tried using Chromium as the adhesion layer instead of Titanium?
Thanks for the answers.
Applied voltage is about 20Vpp and when I decrease the voltage to 3Vpp (as you suggest), I cannot get proper electric field gradient, so I need a solution for 10Vpp-20Vpp levels.
I will try to deposit SiO2 layer on electrodes by PECVD. Besides, I guess Chromium can cause the same effect on electrodes. Can you please explain the differences btw Ti and Cr on electrolysis effect more?
Hi Gurhan
Apologies. I was not suggesting that the use of Cr would eliminate the issue, rather that Cr is often used along with Au as an adhesion layer on glass substrates. The reason for this is that I had never tried using a Ti/Au combination before.
As you suggested, electrolysis would most likely occur using either material. Passivating your electrodes would surely help the issue.
For the SiO2 layers deposited, you will need to ensure the quality of deposition with PECVD since any pinholes in the SiO2 layer will still subject your electrodes to electrolysis.
Should the PECVD layer not be suitable, we had also tried either spin-coating or bonding thin PDMS membranes on the electrodes. Both method were highly successful in isolating the electrodes from the solution.
Cheers
Eric
Hi,
an other solution consists in increasing the frequency above 50kHz... depending on the dielectrophoresis effect you need (you mention electric field gradient), you will have to adjust frequency...
regards
O.F.
- Badges
- Science topic
- Similar topics
- Engineering
- Electrical Engineering
- Electrodes