Folks,

I'm currently working on a bioelectronics application wherein we're
planning to use microelectrode arrays supplied by an outside vendor. The
vendor's stock electrodes are Au pads with an electrodeposited coating of
fine-grained platinum (Pt black). Our process involves alkanethiol-based
self-assembled monolayers, which as far as I know can be formed on the gold
surface but not on the Pt.

The manufacturer is willing to provide probes without the Pt, but doing so
will double our costs because they bill this as a custom order. We've
considered buying the stock probes and etching off the Pt, but the only
solution I know that etches Pt is aqua regia, which will also attack Au.
Does anyone know of an etchant for Pt that either does not attack Au or is
fairly selective for Pt over Au?

Alik Widge
MEMS Laboratory
Carnegie Mellon University