The Art and Signs of a Few Good Mechanical Designs in MEMS
49
9 Modularity in a Compliant xy-Stage
Many designs illustrated so far have modular construction: a building block repeated
in different ways in a specific arrangement to serve a function that is beyond what the
building block does. The two-axis gimbal mechanism, comb drive actuator, polychromator, cell stretcher, concentric ring gyroscope, bent-beam actuator, and expanding
and contracting heatuator blocks—all of them used building blocks. Modularity is
thus a feature of a good design. It makes design and fabrication easy. The modules
need not be identical. Even when they are identical, their interesting arrangements
can lead to novel functionality. We illustrate novel arrangements of identical and
non-identical building blocks, in this section.
Consider the compliant slider (or, the folded-beam suspension) once again. The
slider and its schematic are shown in Fig. 26a, b. Shown in Fig. 26c is an arrangement
of eight sliding joints connected in a specific arrangement to give the platform at the
center two translational degrees of freedom. The platform of this kind cannot rotate.
It is an xy-stage. By examining the motion of the platform in the x- and y-directions,
one at a time, it can be seen that there is perfect decoupling of the two translatory
motions in the plane. That is, when the platform moves in the x-direction, four sliders
oriented in the x-direction move without disturbing the other four. The same is true
Fig. 26 A single-layer compliant stage with independent motion in x- and y-directions: a a
compliant slider; b schematic of a compliant slider as a sliding joint; c an arrangement that illustrated how independent in x- and y-movements can be conceived; and d compliant version of the
scheme in c
49
9 Modularity in a Compliant xy-Stage
Many designs illustrated so far have modular construction: a building block repeated
in different ways in a specific arrangement to serve a function that is beyond what the
building block does. The two-axis gimbal mechanism, comb drive actuator, polychromator, cell stretcher, concentric ring gyroscope, bent-beam actuator, and expanding
and contracting heatuator blocks—all of them used building blocks. Modularity is
thus a feature of a good design. It makes design and fabrication easy. The modules
need not be identical. Even when they are identical, their interesting arrangements
can lead to novel functionality. We illustrate novel arrangements of identical and
non-identical building blocks, in this section.
Consider the compliant slider (or, the folded-beam suspension) once again. The
slider and its schematic are shown in Fig. 26a, b. Shown in Fig. 26c is an arrangement
of eight sliding joints connected in a specific arrangement to give the platform at the
center two translational degrees of freedom. The platform of this kind cannot rotate.
It is an xy-stage. By examining the motion of the platform in the x- and y-directions,
one at a time, it can be seen that there is perfect decoupling of the two translatory
motions in the plane. That is, when the platform moves in the x-direction, four sliders
oriented in the x-direction move without disturbing the other four. The same is true
Fig. 26 A single-layer compliant stage with independent motion in x- and y-directions: a a
compliant slider; b schematic of a compliant slider as a sliding joint; c an arrangement that illustrated how independent in x- and y-movements can be conceived; and d compliant version of the
scheme in c