Domain

Explanation

MUM?

• MEMS or microelectromechanical systems

What's that?

• From the name, we know that MEMS are working assemblies of electrical & mechanical components of very small size
• MEMS are then purpose-built miniature devices or systems using micro- and nanotechnology

Micro? Nano?

• In engineering terms, the SI unit for length is metre (m)
• Micro refers to micrometre (m m) and Nano refers to nanometre (nm)
• The term " micro- and nanotechnology" is broadly defined to encompass the synthesis & integration of materials, processes and devices of submicron size (<m m)

What's the catch?

• Although MEMS sound like space-age science-fiction (like mini-robots swimming in our blood vessels & clearing up & detecting diseases), it is scotching hot technology domain with active research & development
• The impact on our present & future can be far-reaching

Why so?

• There exists tremendous potential & inherent benefits as listed below:

1. Dramatic payload downsizing
2. Reduced development & test costs: at a fraction of the costs of a mega-project, each microinstrument can reduce costs of production & failure as well as expanding test width & depth
3. Lower volume: less scarce resources & materials needed (though just like anything free, this might induce unwarranted over-production & excess-capacity); ability to penetrate into voids that are not accessible with bulky devices
4. Lower weight with lower power & thermal demands: with distributed micromachinery, less cumulative power is consumed with consequent higher efficiency
5. Less susceptibility to shock: catastrophic failures of large equipment occur mostly due to loosening parts during shock & vibration; with smaller size & better design & fabrication, microinstruments are more robust
6. Improved reliability through redundancy: more tolerant of imperfections, uncertainties and indeterminacy
7. Enhanced data acquisition & awareness through distributed sensor networks: with more sensors spread over larger domain
8. Integration of microsensors with electronics: to produce complete, stand-alone, application-specific microinstruments

All good news?

• Not necessarily
• MEMS is still an emerging science & engineering
• New materials have to be synthesized and new technologies from concept & design to fabrication & usage are still in the green phase of R&D
• Already microdevices increase complexity, require more stringent controls during materials processing & impose stricter demands on materials compatibility

What's the vision for MUM?

• MEMS
• It is a natural step in the electronics revolution from bungalow-big computer to transistors to integrated circuit (IC) to integrated microcircuit (IMC)
• Design philosophy based on distribution & divisions - the parts make the whole

Industry trend?

• Historically, American high technology serves first, the needs of government agencies & then, the civilian sector
• In the case of microengineering, it is the opposite where the majority of applications are directed at the civilian sector & less to government ones
• Investments by some commercial entities:

1. GM, Ford
2. IBM, HP, Motorola
3. Lucas Novasensor
4. DARPA (Defense Advanced Research Projects Agency)

• R&D by American national microengineering facilities:

1. Sandia National Labs
2. Lawrence Livermore National Lab
3. Naval Research Lab
4. Jet Propulsion Lab

• Joint industry-university consortia like those involving Cornell, Stanford, UC Berkeley & commercial foundry networks like MOSIS & launched at a fraction of today's costs
• Other countries include the EC & Singapore

Likely uses?

• As microsensors & microinstruments for guidance, navigation & control: temperature, pressure, chemicals, optics, tribologics
• Spacecraft technologies: nanosatellites, communications, thermal control, power systems & ordnance
• Electronic packaging with multichip modules
• Microfabrication & microelectronics
• Cost reduction with widespread miniaturization: after critical mass reached

Apply to structural mechanics?

• The design concept:

1. Understanding of mechnical behaviour of microdevices
2. R&D of micromechanics
3. Exploration into & exploitation for structural use

• The scope of nanotechnology for structural mechanics:

1. Adaptive structures: by increasing damping, reducing vibration & weights
2. Fabrication of nanodevices such as sensors & actuators
3. Microelectronic machining
4. Materials synthesis
5. Concepts for revolutionary structural design, components & foundation-control-structure-environment interaction

• Emphasis is on:

1. Performance improvement of structural components & systems by means of miniature patch devices
2. To improve guidance & control systems
3. For miniature devices to replace current marginal ones

• Examples of research efforts:

1. Embedding microdevices & control elements directly into structural elements like truss, beams, slabs & columns
2. SMA wires embedded to control stiffness or actuation
3. Guidance controls for optics
4. Replace ball bearings (limiting factor of service life) with special lubricants & electrostatically or -magnetically driven devices to eliminate friction
5. Fracture mechanics & control

Any useful terms to keep note?

• MEMS
• ASIM: application-specific integrated microinstrument
• ASIC: application-specific integrated circuit
• Micromachined gyros, accelerometers, magnetometers, sensors (star, sun & earth) & actuators (piezo: vehicle attitude control, optical wavefront & pointing control, deformable mirrors, shape & vibration control)
• Mini- (10kg~500kg), micro- (0.1kg~10kg) & nanosatellite (<0.1kg)