Octopus-Inspired Muscle Design Simplifies Dexterous Soft Robots

SINGAPORE — Researchers at the National University of Singapore have built a soft robotic arm inspired by octopus muscles that can produce multiple controlled bends using a single continuous artificial muscle, reducing the number of separate actuators needed for complex motion.

Instead of installing an actuator at each controllable section, the researchers placed a single shape‑memory‑alloy spring with electrical contact points. It lets different segments contract independently and reduces the number of actuators and simplifying control, according to a report, published in Science Advances.
The research was led by Cecilia Laschi, a professor of mechanical engineering at NUS and director of the NUS Advanced Robotics Centre and Soft Robotics Lab. Laschi and Wenci Xin, a former doctoral student at the lab and the paper's first author, are pictured with the robotic arm in the accompanying photo.
The researchers took inspiration from the neural pathways that stimulate specific areas within an octopus's arms. An octopus can bend one part of an arm around an obstacle while using another section to reach for an object without the rigid joints found in many robots.

In one prototype, four continuous actuators controlled six sections of the arm. Xin estimated the conventional design would need about 24 motors; this is an approximation, not based on a 24-motor comparison.

In tests on two 10‑cm arms, the continuous design bent 91° while the stacked design bent 46° under the same driving conditions. Computer modeling estimated its tip could extend to almost three times the space the conventional arm could reach.
The architecture also lets researchers exchange movement complexity for energy use.  Controlling the full length as a single section consumed 40% less energy than controlling four segments independently, while separate activation allowed more bends to navigate around obstacles.

The researchers also built a 0.6-meter arm-and-gripper system that could be carried beneath a drone. Different sections of the actuators bent the arm, operated its gripper and moved a syringe plunger for liquid sampling.

With its supporting equipment included, the robotic attachment weighed about 450 grams. In demonstrations at a simulated hard-to-access location, it collected liquid and solid samples through a 2-centimeter-high opening and retrieved objects while suspended beneath the drone.

The system is still research hardware, not yet a deployed robot. The team plans to study different spring geometries and heat-responsive materials. They will also add built-in air cooling to increase force and shorten cooling time between movements.