We can easily make circular membranes of silicon nitride, for example. We have previously made such parts for valve research. We would be happy to quote on this job if you can send us specifications for what you need. Christopher Bang Manager, Sensors and Actuators Advanced MicroMachines Inc. 11000 Cedar Avenue Cleveland, OH 44106 tel: 216-229-4636 x207 fax: 216-229-4774 bang@memslink.com http://www.memslink.com