You can express the electrostatic force as a pressure.

You can calculate the pressure required to displace your membrane a
given amount.

These numbers must balance.

When you do this, what do you get?

-----Original Message-----
From: dyqiao@nwpu.edu.cn [mailto:dyqiao@nwpu.edu.cn]
Sent: Sunday, June 27, 2010 8:08 PM
To: mems-talk@memsnet.org
Subject: [mems-talk] About electrostatic actuation of Si membrane

Hi all,
    I'm working on a membrane mirror research, the mirror was fabricated
by anodic bonding of Pyrex 7740 glass to Si wafer.  My idea is, by
applying voltage between the Al electrodes patterned on glasss wafer and
the Silicon membrane , the membrane will deform through the air gap
under the electrostatic force. But, terriblly, obviously no deformation
was observed when even a 300 V voltage is applied and the air gap is
only 20 microns. I have tested the whole structure and I'm sure that
there is no short circuit between the membrane and the Al electrode,
now, I'm desperate and I hope anyone can save me.

 Joe