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Table 5 Description of safety mechanisms with relative advantages and disadvantages

From: Soft robotic devices for hand rehabilitation and assistance: a narrative review

Safety Mechanism Description Advantages Disadvantages
Spool rotational limit Spools which guide the cables are limited in rotation, thereby preventing hyper-flexion/ extension Intrinsically built into the system to avoid over-actuation of the digits. Possibility of failure if patient initiates device mode incorrectly
Pressure sensor Pressure sensor shuts off actuation when threshold pressure is exceeded Sensor can be easily incorporated into control unit Pressure thresholds may not be the same among patients with differing degrees of impairment
Emergency button A button is available on the control unit to provide immediate cessation of actuation Patient has ability to override the device when they sense discomfort Patients with impairments may not react quickly to prevent damage from severe malfunction
Bend sensors / Strain sensors Sensors placed along the joints can detect and control the degree of bending Can more directly measure the degree of joint bending May be more difficult to implement and must be cautious when adding them to the hand orthosis
Unactuated digit detection Monitors the movement of a digit that is not actuated so that the patient’s voluntary movement of that digit sends a signal to the device to turn off Patient has ability to determine when to shut off the device Requires residual function in a digit, forces device to leave at least one digit unactuated
Magnetic coupling The actuator cables are magnetically coupled to the robotic tendons and detach when the tension is too high Patient does not need to alert for termination May be difficult to customize for varying levels of hand dysfunction
Verbal command The user says a verbal command, such as “stop” Patient can quickly terminate device Voice recognition failure
Multi-modal feedback Sensors for temperature, motor current, battery levels, and loss of sensor feedback all have the ability to cease operation Many layers of security to greater ensure protection from electrical components of device Only motor current to the actuators is vaguely correlated to degree of finger movement