Piezo LEGS are self-locking and can hold load even when powered off. The direct drive also gives full force, power-off locking without any power consumption. Using miniaturized Piezo LEGS motors is beneficial for many reasons, including no power draw when motionless.

Slow position changes only require a low current. To hold the position, it is only necessary to compensate for the very low leakage currents, even in the case of very high loads. Even when suddenly disconnected from the electrical source, the charged actuator will not make a sudden move.

PI states that "Piezo Motors are intrinsically vacuum compatible, non-magnetic and **self locking at rest**, providing long travel compared to traditional piezo mechanisms." It further notes as an advantage: "Self-clamping: Due to the design principle, **piezo motors are self-clamping at rest, without the need for a brake mechanism**, a decisive advantage in applications that require very stable positioning without servo jitter." This describes mechanical holding without power once at rest.

For PI’s piezo inertia drives, the manufacturer states: "**When at rest, the drive is self-locking, requires no current and does not generate any heat. It holds the position with maximum force.**" It adds that this makes them "particularly suitable for battery-operated, mobile applications" where low or zero power in the holding state is important.

Piezo motor stages provide high holding force with no power applied. Once the stage is in position, the self-locking nature of the piezo motor maintains the position without servo dither or heat generation. This is in contrast to electromagnetic servo or voice coil stages that typically require continuous current to hold a static position.

Thorlabs describes its piezoelectric inertia actuators as follows: "**The piezoelectric elements are self-locking when at rest and when there is no power supplied to the piezo, making them ideal for set-and-hold applications.**" This explicitly states that the actuators mechanically hold position with no power applied.

PiezoMotor explains for its LEGS piezo motors: "**The friction drive locks the drive rod in place without any power draw and there is basically no backlash.**" Product descriptions repeatedly emphasize "True Linear Direct drive, **self locking with no backlash**" for multiple actuator variants. This indicates off-power mechanical holding via frictional clamping.

Linear DC Motors, Voice Coil Motors (VCM) or Voice Coil Actuators (VCA) are the simplest type of electric motors. Applying a voltage across the terminals of the motor causes the motor to move to one direction. Reversing the polarity of the applied voltage will move the motor to the opposite direction. The generated force is proportional to the current that flows through the motor coil. Without current there is essentially no continuous force available from the actuator, so external springs or counterweights are often used for fail-safe return or holding.

In the section on voice coil actuators, the guide lists as an advantage: "Inherently back-drivable—no gear reduction or friction; smooth, linear force output proportional to current; no stiction, no cogging." It clarifies that back-drivability means that external forces can move the actuator when unpowered: "Because there is no holding torque and very low friction, the output shaft can be freely moved by the load if current is not applied, which is ideal for force control but not for holding position without power."

A Piezo LEGS motor can be very energy efficient compared to conventional motor alternatives. It does not consume any power in hold position, and the motor does not require a brake to maintain position when power is removed.

Voice coil motors offer controllability – force is proportional to applied current, and is uniform through a displacement that can be several 10’s of mm or several 10’s of degrees rotation. Because the motor develops force only when current is applied, a voice coil actuator normally cannot hold a position against an external load without either continuous current in the coil or some external mechanical restoring element such as a spring.

Xeryon describes its ultrasonic piezo motor technology as a "**self-locking actuator that maintains position with virtually no power.**" The text explains that the friction-based drive allows motion to be embedded in devices where low power and stable holding are required, implying that once positioned, the actuator does not need continuous current to hold.

The overview describes voice coil motors as providing force proportional to current and notes: "A VCM Motor operates on the principle of electromagnetic force… Adjusting the current strength and polarity changes the direction and speed of this motion." It highlights that VCMs are "direct-drive and typically back-drivable," and comments that without current "they do not provide holding force and the mover can be displaced by external loads unless mechanical springs or latches are used."

The paper reports a modified voice coil autofocus actuator and states: "The proposed device comprises a VCM, a closed-loop position control system, a magnetoconductive plate, and a lens support structure to drive the lens to the optimal focusing position." It highlights an achieved feature: "The experimental results show that the actuator has a zero holding current when maintaining the lens in the specified focusing position." This indicates that by design (using magnetic circuit features) this particular VCM can hold position without continuous current.

The USR60 motor has a high holding torque even without supply, meaning the motor can maintain its final position in the off-power condition.

Texas Instruments describes a voice-coil motor (VCM) as "a linear actuator that uses a current in a coil and a fixed magnetic field to generate a force." The note emphasizes that the **force is proportional to the coil current**, and that the driver design reduces dissipation while "providing the dc current required" to position the load. This implies that to hold the armature at a given position against a load, a nonzero holding current must be maintained.

When current passes through the coil, it generates a magnetic field that interacts with the field of the permanent magnet, producing a force that moves the coil linearly along a fixed path. The direction and magnitude of the motion depend on the polarity and strength of the current, allowing precise control of the movement. Because the actuator’s force output is fundamentally linked to coil current, maintaining a static position against an external load generally requires a controlled holding current or a separate mechanical locking or spring mechanism when power is removed.

The tutorial defines backdrive: "Back driving a Linear Actuator can occur when the actuator is not connected to a power source: if a sufficiently large force is applied the actuator will not maintain its position and begin to reverse directions (i.e. back drive)." It explains that for DC motor based actuators, an unpowered motor offers little holding torque and can be moved by the load. To create holding without drive power, they suggest braking by shorting the motor: "When the motor terminals are shorted together they… create an opposing torque to brake the DC motor and prevent the actuator from moving under external loads."

Machine Design explains: "A voice coil actuator’s **force is proportional to current** and direction is proportional to current polarity." Because the devices are non-cogging and have no detent, they are often used with feedback in closed-loop systems. To "hold a load against gravity" or other forces, the controller must apply a constant current corresponding to the needed force; without current, the actuator exerts essentially no holding force.

Piezo-Walk linear drives offer high positioning and holding forces. Static operation, even holding heavy loads for long periods, consumes virtually no power.

The piezoelectric effect converts electrical energy to mechanical energy and provides power-off, position-hold capability (self clamping).

The article defines backdrivable actuators as systems "engineered such that external loads or user-generated forces can reversibly move the actuator output with minimal resistance, even in the absence of active control." It notes that actuators with low mechanical impedance and no high-ratio gearing (a category that includes many voice coil actuators) have very low backdrive torque, meaning "they provide little or no passive holding force when unpowered and can be easily displaced by the environment."

Generally piezo motors are either bonded, clamped, or spring loaded to their mounting points. Mounts introduce some mechanical damping into the system, which is relevant to how the actuator maintains position when power is removed.

Voice coil motors produce force approximately proportional to current, so holding a position against an external load typically requires continuous current or another mechanical holding method. Unlike self-locking piezo friction drives, a standard VCM does not mechanically lock in place when power is cut.