Thermal Actuators

Question 1

Thermal Energy can cause physical changes to materials such as

Answer 1

• Thermal expansion . contraction
• Electrical resistance
• Optical Radiation emission
• Phase changes

Question 2

MEMs devices can transduce thermal energy to create

Answer 2

Microactuators and microsensors

Question 3

Two types of microactuators

Answer 3

Thermal bimorph
Fluid dispensers

Question 4

Three types of micro sensors are

Answer 4

• Thermal bimorph
• micro thermocouples
• Thermo resistive sensors

Question 5

What do inkjet printers use?

Answer 5

The phase change aspect of microthermal actuation

Question 6

What principle for bimorph actuators operate on?

Answer 6

Differential thermal expansion produces motion
> Width differential in two different arms creates one arm with a large heat sink and a temp differential. This causes one side to heat up and expand. Bending at the thin flexure

Question 7

Four modes of heat transfer

Answer 7

• conduction (through solid matter)
• natural thermal convection (from surface into stationary fluid)
• Forced convection ( from surface into a moving fluid)
• Radiation ( electromagnetic radiation through air or vacuum from a surface)

Question 8

Thermal heat capacity is analogous to

Answer 8

electrical capacitance

Question 9

Thermocouples work by ___

Answer 9

• two wires of dissimilar materials joined at one point
• transduces, and coverts thermal energy into electrical energy

Question 10

The seebeck coefficient describes__

Answer 10

The voltage difference developed for a given temperature difference

Question 11

What is a thermister?

Answer 11

A thermal resistor with significant temp sensitivity

Question 12

4 point probe measurement

Answer 12

• Uses voltmeter and ammeter.
• No v drops across the probes
• ## The current through the ammeter is the current under test

Question 13

How does a pirani gauge work?

Answer 13

• thermal conduction across a gap is related to the mean free path of the gas in the gap
• thermal conduction can then be related to gas pressure

Question 14

How does a MEMs thermal accelerometer work?

Answer 14

A bubble of hot air is created between two temp sensors.
- under acceleration, the bubble will move in the opposite direction of acceleration (buoyancy), setting off one of the temp sensors

Question 15

Hot wire anemometry is used for

Answer 15

Measuring fluid velocity

Question 16

Thermal bubble anemometer

Answer 16

Uses the same structure as a thermal accelerometer, using forced convection rather than acceleration to move thermal bubble