3rd Generation Device Design

1
3rd Generation Device Design
60 mm, 2 beam Device

• Driving/sensing setup allows for separate driving
  and sensing signal comb drives
• However, amplitude of the outer edge of the comb
  drive is limited by the comb fingers touching
  the spoke of the comb drive bends and reduces the
  spacing between the fingers
• The ratio of the rotation of the specimen at the
  ring to the outer edge of the comb drive ranges
  from 12 to 14, depending on the device

2
3rd Generation Maximum Stress

• These values for stress are based on the maximum
  deflection obtainable in vacuum estimating an
  amplitude of 2 mm at the end of the specimen
• The devices were run for gt1010 cycles and no
  fatigue damage was observed
• To increase the maximum stress and produce
  failure, an notch was introduced by FIB
• The stress concentration factor ranged from 3 - 4
• Stresses ranged from 1 to 4 GPa

• The introduction of the notch reduced the
  stiffness and therefore resonance frequency of
  the device

Area notched with FIB
MUMPS 48 Chip 5 60-mm Beam Device
3
4th Generation Device Design

• Design now has a stiffer comb drive-ring
  structure
• The ratio of the rotation of the specimen at the
  ring to the outer edge of the comb drive is a
  little less than 1

• More linear amplitude of comb drive along the
  spoke
• Allows for a 2 mm displacement at the end of the
  specimen beam
• Can therefore reach stress levels high enough to
  cause failure