ME416
Intro to MEMS: Fabr & Appl

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Catalog Description: (Prerequisities - Junior class standing) Properties of silicon wafers, wafer-level processes, surface and bulk micromachining, thin-film deposition, dry and wet etching, photolithography, process integration, simple actuators. Introduction to microfluidic systems. MEMS applications: capacitive accelerometer, cantilever and pressure sensor.

 

 
Topics
Homework
Other Stuff
 
 
 
 

Other Stuff

Si as a Mechanical Element:

You should be able to answer each of the following questions.
  • What is the definition of strain? of stress?
  • What is meant be yield stress?
  • What is Poisson contraction? What does the upper limit of ν = 0.5 correspond to?
  • There are many moduli in solid mechanics: Young's modulus, the biaxial modulus, the shear modulus, etc. What do all of them have in common?
  • Crystalline Si is a cubic material. How does this complicate the stress/strain relationship? What does this relationship look like?
  • We often approximate strain as dux/dx = DL/L or something like that. (I.e., no derivitives, but simply changes.) When is this not an approximation at all, but the truth, the whole truth and nothing but the truth?

Mechanical Properties of Thin Films:

You should be able to answer each of the following questions.
  • What are a couple of ways to ensure good adhesion of a film to a substrate?
  • What is the difference between intrinsic stress and extrinsic stress? Give an example of each.
  • We often assume stress in thin films is biaxial. What is meant by biaxial?
  • Why is the assumption of a biaxial stress a good one in the case of thermal stress?
  • What is responsible for the peel forces near the edges of thin films?
  • Describe in general terms how the disk method of estimating stress works.
  • In the disk method for measuring thin film stress, the biaxial modulus relating stress to strain is that of the substrate material, not the film. Why? (Hint: Think about how we related the strains of the two materials and why.)


Basic Heat Transfer and Thermal Actuation:

You should be able to answer each of the following questions.
  • What are the three modes of heat transfer?
  • List three ways radiation is different from the other modes of heat transfer.
  • Consider a thin slab of aluminum subject to 1-D conduction as shown in the figure. The left face of the slab is maintained at T1 and the right is maintained at T2 < T1. Explain the effect of each parameter variation below on the thermal resistance and conduction heat transfer rate through the slab.

    slab

    • Changing the slab material from aluminum to wood
    • Doubling the surface area A
    • Doubling the temperature difference (T1 - T2)
    • Reducing the both the surface area A and thickness d by 1/2
    • Decreasing T2
  • Consider 1-D conduction in the radial direction of a hollow cylinder as shown in the figure. The inside of the cylinder is maintained at T1 and the outside is maintained at T2 < T1.

    cylinder

    Would you expect the themal resistance to be Rth = d/(kA) in this case? If not, what's the problem?
  • In general, which mode of heat transfer is more efficient, convection or conduction? Why?
  • List three advantages of small scale heat transfer.
  • Explain in general terms how each of the following thermal actuators work.
    • Hot arm actuators
    • Thermopneumatic actuators
    • Bimetallic actuators
    • Shape memory alloy actuators