CDTL TEG Talk

Applying Kirigami Models in Teaching

Micro-electro-mechanical Systems

Yung C. Liang

Liang 2014

� The Teaching Approach

� Classroom Case Example

� Paper Model Structure

� Considerations in Material Parameters

� Laboratory Measurement

� Analyses and Verification

� Conclusion

Outlines

The Module

EE4509 Introduction to Silicon Microsystems

• Class Lectures and Tutorials

• One Laboratory Session (2 persons in a team)

• Paper Structure Heavy-Duty Challenge

• Two Take-home Quizzes

• Paper Model Project (2 persons in a team)

Assessment

• Laboratory Work

(Understanding Comb Actuator) 10%

• Take-Home Quizzes 20%

• Paper Structure Heavy-Duty Challenge 5%

• Paper Model Project 25%

• Final Examination 40%

Comb Actuators

MEMS Structures

The Micro-Electro-Mechanical Systems (MEMS), such as micro-resonators, micro-

mirrors, accelerometers and micro-gyroscope, are formed with the integration of

micro-mechanical sensing and actuation elements on a common silicon substrate.

Such kind of hybrid microsystems can be practically fabricated by modern

microelectronic foundry technology through the micromachining processes.

They can Move

Paper Model Project

The kirigami approach can be used in the learning of

EE4509 Silicon Microsystems by the creation of

precisely proportioned model of micro-mechanical

structures by using paper material.

The aim of working on the paper model project is to

achieve the objectives of having easy structural

visualisation on how the structure works and what the

interaction is among different parts within the structure,

and for the validation of its micro-mechanical

properties through laboratory measurement.

• The material Young’s modulus: Paper material

has a different Young’s modulus from silicon

material;

• The material density: Paper has a different

material density from that of silicon;

• The strain limit: Paper has a different breaking

strain limit from that of silicon.

These rules need to be followed in order to correctly validate

the properties of the paper kirigami micro-mechanical

structure to map to those of an actual silicon micro-

mechanical structure.

The Three Important Rules

Recommended Working Steps for the paper project

• Form a two-member team

• Find a suitable MEMS structure from technical papers

• Plan on how to create the paper model

• Plan on how to validate (test) its performance

• Plan detailed working schedule

• Construct the paper model and do measurements

• Report writing

• Presentation

Some Prior Exercises

Making a Silicon Orientation Cube

• Download the PDF file;

• Print on transparency;

• Assemble it

Judy (UCLA) and Pister (UCB)

The Paper Structure Heavy-Duty ChallengeGiven a single sheet of A4 Xerox copier paper and a Scotch tape of

15 cm, design a structure to support as much weight as possible at a

height of at least 20 cm above the surface of a flat level table top.

MEMS Structures

Paper Model Example

This design case is on the micromachined RF MEMS (Radio

Frequency Micro Electro Mechanical System) switch and to

replicate this structure in the macro world using paper model. At

the macro level, the design parameters are up-scaled and the

paper structure is constructed by the proper scaling factor.

Consequently, experiments are performed to verify the paper

model with theoretical calculations.

128Total width of the structure = 160

256Total length of the structure = 320

80Length and width of movable plate = 100

16H = 20

8W = 10

8L = 10

0.8*Spring hinge thickness = 1

Scaled Dimension

(in mm)

Original Dimensions of Micro-Structure

(in µm)

Original and scaled dimensions of the RF MEMS switch

*: actual thickness may vary due to glue lamination

Paper Model on RF MEMS Switch

Working Steps

1. Construct a cantilever beam to obtain the laminated paper’s

Young’s Modulus experimentally.

2. Calculate the suspension spring constant.

3. Calculate the resonant frequency of the moveable plate

4. Conduct laboratory measurement

5. Bench-mark with the data from published technical paper

Laboratory Measurement

Variable frequency shaker

Signal generator to control frequency

Frequency and

oscillation

magnitude of the

shaker

The paper

structure under

test

0

1

2

3

4

5

6

6 9 12 15 18 21

Frequancy (Hz)

Ma

gn

itu

de

(m

m)

12.14 Hz as calculated

resonant frequency

11.5 Hz as the measured

resonant frequency

Frequency (Hz)

The resonant frequency of the paper structure is translated into

micro-world to be at 78 kHz, to bench mark with the frequency of 58

kHz in the published paper

Classroom Presentation

Students doing a

presentation on a 2-D

micro-mirror with micro-

mechanical spring and

hinge structures

A student doing her presentation on

the micro-mechanical knife for

surgery purpose

Learning Outcomes

Students are able to touch and manipulate the scaled-up MEMS

structure to visualise the movement and interaction, in helping

them understand the complicated micromechanics.

Students are able to construct a scaled-up MEMS structure

without going through the tedious microfabrication process;

Students have learned on how to calculate the static and dynamic

performance of the built structure, and verified with laboratory

measurement;

Students have learned on how to scale up the structure, how to

adopt different material properties in the performance

calculations, and how to design and build those structures;

Conclusions

An innovative teaching methodology using the precisely scaled

paper model construction is proposed in the teaching of micro-

electro-mechanical devices

The paper model is able to provide a clear and reasonable

representation to predict the static and dynamic performance

of the counterpart micro-scaled device.

This approach is able to achieve an effective learning outcome

for students to quickly understand the micro-mechanical system

interaction and its performance by real observation and

measurement, without using any complicated finite-element

computer simulation tools or going through high-cost silicon

wafer fabrication processes.

Liang 2012

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