An international team of researchers led by Professor Sang Ok Kim of the Korea Advanced Institute of Science and Technology (KAIST) has developed a soft robot called BeetleBot, inspired by a beetle. It can be controlled by bending and straightening a finger. The robot is able to move, grasp objects and transmit images and contact information to the user. The work was published in the journal Science Advances.
Soft robots are made from flexible materials, but their actuators (the mechanisms that make the robot move), sensors and control system are often built as separate units. This makes it difficult to assemble a compact robot that can move, sense and obey commands. The new development combines all of this in a single small device.
BeetleBot's artificial muscles are 3D-printed from a liquid crystal elastomer, a polymer that contracts when heated. Heating is provided by an electrical module. The muscles in different parts of the robot work independently, and the order in which they are activated can be changed, so the robot walks forward and turns.
The gripper mimics a beetle's mandibles. It combines artificial muscles with a capacitive pressure sensor. When the muscles contract, the gripper closes, and the sensor records the contact force: when pressed, the distance between the electrodes inside the sensor changes, and therefore so does its capacitance (its ability to store charge). This change is used to determine whether an object has been grasped.
Commands are given through a stretchable pad on the finger. When it is bent, its electrical resistance changes: carbon nanotubes inside form conductive paths that reconfigure under deformation. The signals are divided into four commands: forward, left, right and grasp. They are transmitted to the robot via Bluetooth Low Energy (an energy-efficient wireless protocol).
The user sees the surroundings through a miniature camera on the robot and assesses contact with an object using data from the pressure sensor. On the basis of this information, the user chooses the next action and again gives a command with a finger movement. This is how two-way feedback works: commands go from the person to the robot, and sensor data comes back.
In experiments, BeetleBot went around obstacles, approached a target, and grasped and carried objects. The authors note that before widespread use, for example for inspecting hard-to-reach places or industrial equipment, it is necessary to increase the speed of the muscles' response and their energy efficiency and to improve power supply. In addition, the tests were conducted in laboratory conditions, and the robot's operation still needs to be tested in a real environment.
"This study expands the capabilities of soft robots by combining artificial muscle movement, sensing and user control in a single system," a press release quotes Kim as saying. The first author of the work, Professor Inho Kim of Sungkyunkwan University, emphasizes the key feature: two-way feedback linking the data received by the robot to the person's next action.