Page 142 - Mechanics of Microelectromechanical Systems
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2. Microcantilevers, microhinges, microbridges 129
minimum width as the original design in order to increase the axial stiffness
by 50%. Determine the fillet radius which will produce this stiffness.
Answer:
The axial stiffness of the circularly-filleted microhinge is 1.5 times the
axial stiffness of the rectangular configuration. The fillet radius is
Problem 2.10
A circularly-notched microcantilever is used as a torsional balance in a
mass deposition detection application. The constant rectangular segment is
defined by and The notch width is and
the shear modulus is G = 80 GPa. If the notch radius is what is the
thickness t which will produce an overall torsional stiffness of
Nm?
Answer:
Problem 2.11
A folded microcantilever has a fixed length of the longer, identical legs
and the same cross-section for all three legs. Determine the length of the
middle leg that would minimize the out-of-the-plane bending stiffness of
this design.
Answer:
If the relationship exists between the two lengths: then the linear
bending stiffness is minimum when c = 1 (the legs have identical lengths).
Problem 2.12
Design a constant rectangular cross-section microbridge whose torsional-
to-bending stiffness ratio is maximum.
Answer:
The stiffness ratio is:
and therefore the length of the microbridge has to be maximum whereas the
material has to have a minimum Poisson’s ratio.
Problem 2.13
A microbridge consists of two end corner-filleted microhinges defined
by and a middle plate of constant
rectangular cross-section defined by and
