Soft Robots: Why Engineers Are Building Robots Without Hard Metal Frames

Most robots are built from rigid metal links, motors, and joints. This structure gives them strength and precision, but it also makes them less suitable for handling fragile objects, moving through narrow spaces, or working safely next to people. Soft robots take a different approach by using flexible materials that can bend, stretch, and change shape.

Soft robots are often made from silicone, rubber-like elastomers, flexible polymers, or hydrogels. Instead of moving through traditional hinges, many use soft actuators that expand or contract when filled with air or liquid, heated, electrically stimulated, or exposed to a magnetic field. A 2024 review published in Nature Communications grouped untethered soft actuators into pneumatic, magnetic, heat-driven, and electrically driven systems.

The main advantage of softness is adaptability. A rigid robotic gripper needs to calculate the exact position and shape of an object before picking it up. A soft gripper can bend around the object and distribute pressure across its surface. This makes it useful for handling items that are easily damaged, such as fruit, laboratory samples, or delicate components.

Flexible bodies can also move through environments that would be difficult for conventional machines. The same 2024 Nature Communications review noted that soft robots may be especially useful for navigating twisting spaces, operating under deep-sea pressure, and performing minimally invasive medical procedures. Their ability to deform allows them to squeeze through openings or move around obstacles without requiring a complicated system of rigid joints.

Medicine is one of the most promising areas for soft robotics because a flexible machine can interact more gently with the body. A 2024 study in Nature Communications introduced a multilayer magnetic soft robot that could change its movement patterns and carry out targeted adhesion. The researchers described potential uses in minimally invasive procedures and delivering medical materials to specific areas of the body.

However, removing the hard frame also creates new problems. Rigid robots are easier to model because their joints move along predictable paths. A soft robot can deform in many directions at once, making its exact position and shape harder to measure and control. Researchers must also integrate sensors, power sources, and electronic controllers without making the robot too stiff. MIT researchers have noted that conventional rigid sensors can interfere with a soft robot’s flexibility and may create additional points of mechanical failure.

Soft robots are also usually weaker and less precise than rigid machines. For this reason, some engineers are developing hybrid robots that can switch between soft and stiff states. MIT researchers proposed a design that could become rigid when strength and accuracy were needed, then return to a flexible form for safer or more adaptable movement. This approach aims to combine the advantages of both types of robot rather than replacing rigid machines completely.

Soft robots show that machines do not always need hard metal skeletons to be useful. Their flexibility can help them handle fragile objects, enter confined spaces, and interact more safely with people and the human body. The technology still faces challenges in strength, sensing, and control, but it could give robots access to tasks that traditional rigid designs cannot perform.