MEMS Principles and Scaling Law

Prof. Tianhong Cui, Mechanical Engineering

ME 8254

Overview of Class

Electrical basics

Thermal basics

Scaling Laws

Scaling Laws Time L0

Distance / Velocity L1

Surface tension L2

Electrostatic force L2

Friction L2

Thermal losses L2

Mass L3

Gravity L3

Magnetics L3

Power L3

Scaling Laws Vertical bracket notation

Determine scaling for eachcomponent in equation

Change “input” by desired orderof magnitude

Derive change in outputparameter

F=ma a linked by mass

Scaling in Microfluidics

Reynolds number– Laminar flow

– Friction factor

Pressure drop

Breakdown in continuum theory– Mean free path

Sample sizes / concentrations

Microfluidic Scaling All flow is laminar (no turbulent mixing)

Surface tension becomes significant

No inertia effects

Apparent viscosity increases