Actuators & motors

In one line

An actuator turns electrical energy into motion or force. Sensors let a device sense; actuators let it act on the world — pushing a plunger, turning a joint, opening a valve.

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The common types

• DC motor — simple, spins fast; pair with a gearbox for torque.
• Stepper motor — moves in exact, countable steps. Drives the lead-screw of an infusion or syringe pump, so every step delivers a precise micro-dose.
• Servo — a motor plus a position sensor and controller, so you command an angle and it holds it. Robot joints, prosthetic fingers.
• Solenoid / valve — an electromagnet that snaps open or shut. Gas and fluid control in ventilators.

A controller pin can't move a motor directly, so it switches a transistor / MOSFET (often an H-bridge) that powers the motor.

Where it shows up in digital health

• Infusion & syringe pumps — a stepper turning a lead-screw; step count = volume delivered.
• Surgical & assistive robots — servos at each joint, commanded by the control loop.
• Prosthetics & exoskeletons — motors driven by muscle (EMG) signals.

Watch for

Anything that moves can harm. Medical actuators pair with sensors that close the loop and hard limits so a runaway motor is caught — a pump must know it delivered the dose, not assume it.