micromotor

A micromotor is a small electric motor designed to produce rotational motion at miniature scales. The term covers motors with outer diameters from about 0.5 mm to several millimeters, up to a few centimeters in length. Micromotors are used where space, weight, or energy efficiency is critical, such as in MEMS, miniature robots, optical devices, and medical instruments. Operating speeds typically range from thousands to hundreds of thousands of rpm, with torques in the micro- to milli-newton-centimeter range.

Principles: Most micromotors convert electrical energy into rotation through electromagnetic transduction or piezoelectric actuation. Brushed and brushless DC micromotors use magnets and stator windings; speed rises with voltage and falls with load, while torque grows with current. Piezoelectric ultrasonic motors use high-frequency actuators to create traveling waves that drive a rotor by friction, allowing compact size and smooth torque at low voltages.

Common types: brushed DC micro motors, brushless DC micro motors (BLDC), micro stepper motors, piezoelectric ultrasonic motors, and electrostatic MEMS motors. Tradeoffs include control complexity, efficiency, noise, lifetime, and the ability to scale to very small sizes.

Applications: micromotors are used in MEMS devices, medical tools such as microsurgical actuators and endoscopes, microfluidic pumps, laboratory automation, micro-robotics, camera autofocus mechanisms, and tactile actuators for haptics.

Advantages and challenges: micromotors offer high power density and precise control at small scales but require careful heat management and bearing wear in brushed designs. Integration costs and manufacturing tolerances can be an issue for sub-millimeter devices. Ongoing developments in MEMS fabrication, BLDC control, and novel transduction methods continue to expand their use.