Page 116 - Mechanics of Microelectromechanical Systems

2. Microcantilevers, microhinges, microbridges 103
can be determined. The bending-related stiffnesses can be found by inversion
of the compliance sub-matrix, namely:

Example 2.11
A right circular microhinge is designed to produce a tip slope of
under a force Determine the thickness t when l = 150
and E = 135 GPa and when the tip deflection is not taken into
account.

Solution:
The tip force can be approximated to:

in the case where no other experimental data, such as the tip deflection is
available. The cross-bending stiffness is given in Eq. (2.124). By substituting
it into Eq. (2.136), the thickness can be determined as:

and its numerical value is

4. COMPOUND MICROCANTILEVERS

The solid microcantilevers that have been analyzed thus far were
constructed as single members, but designs do also exist with several
compliant members of different geometries making up together compound
devices that overall function as regular microcantilevers. Two cases will be
analyzed here, namely the notched microcantilever and the folded one.

4.1 Notched Microcantilevers

Applications such as mass addition detection by means of monitoring the
tip slope of a microcantilever might require stiffnesses that have specific
values, enabling thus capturing of discrete environmental changes such as
mass deposition. For a pre-specified geometric envelope of the
microcantilever (such as a rectangle), the only way of altering the stiffness is