PowerPoint 프레젠테이션 - KOCw

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Seong J. Cho Research

초소형 기전공학 설계 #2

Micro Electro Mechaical System & Future Technology

조성진

Office: 042-821-5648 [email protected]

mems.cnu.ac.kr

기계공학부 충남대학교

2016/1

PowerPoints organized by Prof. J. Kim, G. Lim, POSTECH and Prof. Seong J. Cho, CNU

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Current Technology

※ Electronic systems

→ Computers (chips, circuit boards, software)

→ Communications (networks, smartphones)

※ Mechanical systems

→ Automobiles, Space vehicles

※ Electronic systems

→ Chemical analysis

→ DNA manipulation

※ Medical systems

→ Pharmaceutical development

→ Artificial organs

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Design Consideration



Overall dimensions of the parts/products



Diameter, width, length, thickness



Maximum & minimum dimension



Complexity around dimensional scale issues



Part/component local features



Aspect ratio, wall thickness, local feature density



Tool geometry



Stiffness, rigidity of the part/product structures



Tolerance and surface quality capability



Most of the data is “in-house”



Consult with the manufacturing engineers

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Design Consideration



Material capability



Size effect



Grain sizes



Part/component material properties after processing



Chemical and high temperature process



Characteristics of volume production



Manufacturing cost



Synthesis factor

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Intro

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Insects vs. Human

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How do things behave in microscale ?

• Attack of gigantic (e.g. elephant size) Ants….. What do you think ? Insects vs. Human

Insects

lift 10 times of own weight.

do not get injured from falling.

some can fly or walk on the walls.

(even though they were smart) (dead near fire)

(dry clean, avoid liquids)

Human

(barely lift own weight.) (do get easily injured.)

(we wish .. just horizontal walking.) Use tools.

Use fire.

take showers, enjoy swimming.

•Observation: Different physical phenomena dominate at different physical scales.

•Problem with proportional miniaturization: for example – Miniature Book

hard to open the book (intermolecular force)

•Our intuition of macroscale phenomena does NOT directly transfer to the microscale.

Therefore,different designs and types of operation are required.

Dimensional analysis (extended from classical physics)



can reveal “how things behave” in micro world without full scale mat

hematical analysis.

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Scaling

• Most physical quantities (e.g. force, volume,etc.) scale differently with dimension L.

•Assumption: Isometric scaling ( i.e., isometry, geometric similarity)

•Line force (surface tension)

•Heat transfer

•Diffusion

•Muscle strength

•Bone strength

•Mass

∝ ^Size _a _ _{1/4 a}

∝ Ârea â² ^ ^1/16â²

∝ ^Volume ^a³ ^ ^1/64^a³

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Scaling Example 1 : Weight-Lifting

World weight-lifting records agree well !

(Lietzke, Science 1956)

•Observation: Different-sized individuals of same species generally keep a reasonably faithful pr oportion -- Isometry

Therefore, W

_lift

∝ [W

_body

]

^2/3

• Assumption: Muscle stress is

Invariant of body size (σ= F/A=constant)

• Prediction of the lifting ability of a person based on weight (Comparing individuals who are very fit)

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Scaling Example 2

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Scaling Example 3

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The actual data with common nails agree.

(On size and Life by McMahon and Bonner)

• Observation: For living things of greatly different sizes (different species), proportions change with size -- Allometry

•Assumption: comparing nails of the same material (σ= F/A=constant) and P_min < F < P_crit

•Explanation for non-isometry of common nail production

d ∝ L^x

?

Bucking consideration P

_crit ∝ EI/L²

(where E:Young’s Modulus, I: moment of inertia) Since, I ∝d⁴,

P

_crit ∝ d⁴

/ L

²

Friction consideration

Minimum load

, P

_min ∝ πd

So, when P_min= P_crit

d ∝ d⁴

/ L

²,

 d ∝ L

^2/3

d L

F

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Scaling Example 4

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Moment of inertia

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Scaling in Rigid-Body Dynamics

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Scaling in Fluid Mechanics

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하겐 푸아죄유 법칙

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Scaling in Heat Conduction

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Scaling in Heat Conduction

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Scaling of Mechanical Systems (Trimmer 1989)

• A simple format (a matrix form) shows dependence on length scale [s] for various systems.

Electrostatic②, Pressure force, Magnetic①…

Surface tension,electrostatic①..

Inertial,Magnetic②… Magnetic③…

Response time 

Power 

Accelerations

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Scaling in Electrostatic Force

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Scaling in Electrostatic Forces

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Scaling in Electromagnetic Forces

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Scaling in Electricity

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Scaling in Electricity

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