Hey. I would use an adhesion layer of a metal that sticks to glass and gold well, something like titanium or chromium--this layer can just be 5-10 nm. Layer both on to really clean glass (piranha clean if you like + oxygen plasma), and don't break vacuum in between metallic layers. Hope that helps !

Hey. I would use an adhesion layer of a metal that sticks to glass and gold well, something like titanium or chromium--this layer can just be 5-10 nm. Layer both on to really clean glass (piranha clean if you like + oxygen plasma), and don't break vacuum in between metallic layers. Hope that helps !

Platinum is also a suitable adhesion layer - Good luck!

Dear Marcin - How do you plan to detach the PDMS films from the gold? From my experience, even if you make use of an interlayer to promote the adhesion of gold to the glass, the mechanical contact will not be very strong. But infact, as mentioned above, Cr or Ti interlayers of 5-10 nm help substantially to improve the adhesion! Good luck, Dirk

First of all - thank you all for the answers! :)

@Richie - I'll try sputtering Ti or Cr first and then Au. Piranha and oxygen plasma you say? I'll have to try that as well!

@Silvio - unfortunately we don't have Pt target in our lab ;) so for the first tests I'll try other metals :)

@Dirk - I understand your concern - most people stick glass to PDMS after activation of the surfaces with plasma - I'm not doing that, I just put the PDMS on the glass and press it with a special holder; I'm using little volume flows, so it doesn't leak :)

Well, I've done almost exactly the same thing before and I fail to find a way to make it stay on glass. PDMS will peel the gold film straight off. It is just a one-shot device...And yes I've tried Cr and Ti adhesion layer, and plasma treatment. Sorry...

But maybe you can try ITO glass, it is far more stable on glass than Au does.

I have done that before and it worked. There is a problem in adhesion if the gold electrodes are above the glass, but if they are small and gold layer is very thin (100 nm), while PDMS have a much larger area to attach it can work. A seed layer is a necessity, chromium or titanium are normally used. Also, the quality of sputtered gold will depend on the environment: I recall electrodes had worse adhesion in summer than in other times of the year because of humidity, despite using laminar flow and controlled conditions in the clean room during sputtering. 

Good luck. 

Thanks guys, you're all awesome! :)

@Ye - actually, I etch ITO (after masking) to make band ITO electrodes and then I mask the surface again to sputter gold band electrodes, so I can have band gold counter electrode and band gold/silver (after electrodeposition of Ag) pseudoreference electrode :)

@Anna - I'm trying 10 nm of Cr and 100 nm of Au. I'm using a vacuum sputtering, so I don't think humidity could have any effect on the sputtering, couldn't it? I'm not an expert though, so correct me if I'm wrong :)

We have the gold sputtered commercially so far and it worked very well for a couple of months, but since it's kind of expensive service and we do have the equipment for sputtering at our institute, I've decided to do it on my own :) So there is a way to do it properly! I've read that annealing of the gold enhance its durability, but I haven't found exactly the right conditions... Do you have any idea about annealing sputtered gold?

Hallo Marcin, Some hints to the adhesion metal: If your fluidic system interacts with chromium you get a problem with corrosion. In that case you are forced to use titanium or platin. The lack of titanium is, that you must etch it with HF, the alternative way is a Lift-off process. With chromium you are more flexible

Hi, to get the best adhesion the glass substrate should be ideally clean. Sometimes it helps to heat the substrate in the vacuum at 300 C for several hours. From our experience the gold film adhesion improves significantly. The heat pretreatment removes water and degas the substrate, reducing the number of substrate surface defects.

The flame annealing usually done to achieve smoother surface. You could do annealing at moderate temperature of 300 C for 12 hours in vacuum, it gives also good smoothing effect and it is less aggressive, as you are not at risk to loose your sample.

gold have some adhesion

problem on glass and silicon substrate . so try coating chromium and then gold