Soft robot

An octopus has no skeleton. Every one of its eight arms is entirely soft tissue, yet it can squeeze through a hole barely larger than its beak, grip a crab with the exact pressure required to hold without crushing it, and change the stiffness of its arm in milliseconds — from floppy to rigid and back — purely by tensing its muscles. It navigates, manipulates, and explores with capabilities that no rigid robot can match.

Soft robotics is the field that looks at biology's softest creatures and asks: what if we built machines that way?

What makes a robot "soft"

A conventional robot arm is made of aluminium alloy, steel shafts, and hard plastic. It is precise and powerful, but it is also rigid — it cannot reshape itself, it cannot absorb an unexpected collision by deforming, and if it grabs a delicate object with the wrong amount of force, that object is destroyed.

A soft robot is made predominantly from compliant materials — silicone, latex, fabric, hydrogels, even living tissue in experimental work. It deforms continuously in response to its environment. It has no sharp edges. It can squeeze into confined spaces. And crucially, it is inherently safe around humans and delicate objects, because a collision simply causes the robot to flex rather than break or bruise.

How soft robots move

Without rigid joints and motors, soft robots need different actuation mechanisms:

• Pneumatic inflation — chambers of silicone are inflated with air to bend, extend, or grip. Most commercial soft grippers work this way.
• Tendon-driven — flexible cables threaded through a soft body pull sections into a curl or extend them.
• Shape-memory materials — materials that change shape when heated, then return to their original form when cooled.
• Electroactive polymers — materials that deform in response to an electric field, allowing actuation without air or cables.

A real example

Soft Robotics Inc. (Cambridge, Massachusetts) makes pneumatic soft grippers used in food packaging lines — handling delicate items like croissants, tomatoes, and chicken breasts that would be crushed or deformed by a conventional gripper. The gripper's silicone fingers conform to the object's irregular shape, applying gentle distributed pressure. The same gripper that picks a strawberry can pick a lemon without any adjustment — a flexibility that rigid grippers cannot match.

The challenges ahead

Soft robots are slower and less precise than rigid robots. Measuring their exact position is harder because they deform continuously. Pneumatic systems require air supply infrastructure. And designing control software for a robot with infinite degrees of deformation — rather than a fixed number of joints — is mathematically challenging. For many applications, a hybrid approach is emerging: rigid structure where precision and force are needed, soft elements where compliance and safety matter.

The first entirely soft autonomous robot — powered by chemical reactions rather than a motor or battery — crawled its first steps at Harvard in 2016, and nobody is entirely sure what the ceiling of that idea is.