# Acuators in MEMS.pptx

29. May 2023
1 von 16

### Acuators in MEMS.pptx

• 2.  It statnds for micro electro mechanical systems.  It is the integration of elements sensors actuators and electronics on a common silicon substrate.  Micro fabrication technology for making microscopic devices.
• 3.  The actuator is an element which applies a force to some object through a distance  Various actuation mechanisms : 1. Electrostatic actuation. 2. Thermal actuation. 3. Piezoelectric actuation. 4. Magnetic actuation.
• 5.  A voltage is applied between metal plates to induce opposite charges and coulomb attraction.
• 6.  Electrostatic micro-actuator consist of many fingers that ate actuated by applying a voltage.  The thickness of the fingers is small in comparison to their length and width.  The attractive forces are mainly due to the fringing fields rather than the parallel plate fields. Firing Curves
• 7.  Electrostatic energy :  Electrostatic Force : ◦ Coulomb’s Law: Force between two point charges
• 8.  Low power dissipation.  Can be designed to dissipate no power while exerting a force.  High power density at micro scale.  Easy to fabricated
• 9.  Scaling  Noise & efficiency  Range of force, motion and frequency  Repeatability  Nonlinearity
• 11.  Assume that the electrical field is uniform between the plates of the capacitor and zero outside.  Uniform electric field between the plates has the magnitude.  Voltage across the capacitor is the product of E-field and the gap.  The capacitance is the ratio of the charge and the voltage
• 12.  When the capacitor plates are fixed the stored energy is given by :  Fixed gap – increasing charge
• 13.  At zero gap, the electrical energy is zero.  The force between two plates with opposite charges +Q and –Q depends on electric fields setup by charges  The field is : ɛ=Q/ɛA  The corresponding force is :  F=(Q/2) ɛ=Q²/2ɛA  Now we pull upper plate by distance g  W(g)=F*g=Q²g/2ɛA  Charge fixed – increasing gap
• 14.  Micromotor, Microshutter, Micromirror, Microrelay, Micropump
• 15.  Micro pumps play a significant role in micro fluid systems of MEMS.  Micro pumps were started in middle 1980s.  Before 1990s, mechanical pumps were mainly studied. After 1990s, non-mechanical pumps were introduced.  Presently most micro pumps aim to fluid pumping.
• 16. Goodness: Low power, good control of actuation and short response time. Weakness: High actuation voltage, small stroke.