MEMS: basic characteristics and salient features

Definition: MEMS (Micro-Electro-Mechanical Systems) are miniaturised devices, typically 1 µm to 1 mm in size, that combine mechanical elements, sensors, actuators and electronics on a common substrate (usually silicon) using micro-fabrication.

Basic characteristics

• Microscale size: moving parts range from a few microns to a few hundred microns.
• Multi-domain: couples mechanical, electrical, thermal, fluidic and optical effects.
• Batch fabrication: many devices are made on one wafer using IC-style processes.
• Surface forces dominate: the surface-to-volume ratio is large, so stiction, surface tension and electrostatic forces matter more than gravity or inertia.

Salient features

Feature	Benefit
Miniaturisation	Small, light, easy to embed (implants, wearables)
Low power	Small masses need little energy
Batch production	Low cost per device at high volume
Integration with ICs	Sensing, signal conditioning and actuation on one chip
High sensitivity and fast response	Low mass gives a high resonant frequency
Reliability	Few wearing parts; repeatable fabrication

Typical materials

Silicon, silicon dioxide, silicon nitride, polysilicon, polymers (PDMS, SU-8), glass, piezoelectric films (PZT, ZnO).

Exam tip

Write the definition first, then 4 to 5 features with a one-line reason each. A block diagram earns presentation marks.