Soft-rigid origami robots move silently with heat actuators

An engineering team from Princeton University has developed soft-rigid hybrid robots made of a liquid elastomer that are set in motion by heating and an origami folding technique. The robots thus operate without motors or pneumatic systems and are subject to hardly any wear.

The scientists at Princeton University combined a special liquid crystal polymer with the Japanese origami folding technique to form movable robots, as shown in the study “Digital Actuation Control of Soft Robotic Origami With Self-Folding Liquid Crystal Elastomer Hinges”, which was published in Advanced Functional Materials.

Robot joints embedded in the material

Using a specially designed 3D printer, the researchers printed a robot structure from the polymer, considering the internal orientation of the polymer's molecular structure. This allowed the scientists to print structured zones with a consistent molecular orientation within the printed material. By stacking and connecting these zones, they succeeded in creating joints within the material itself that deform in a predetermined way when the material is heated.

During the printing process, the scientists integrated flexible electronic circuit boards in the joint area into the material to better control the heat actuators. The direct integration into the joints has the advantage that the electronics do not have to be applied in a separate step, which would complicate and increase the cost of manufacturing. Furthermore, control can be implemented more easily and functionally.

Via the flexible circuit boards, the scientists controlled the heat actuators, which were also embedded in the joints, with integrated temperature sensors. By selectively heating specific areas, the material contracts in the way predetermined by the researchers through printing. The researchers utilize the precise structure of the polymer for this.

Perfect movement through origami folding

The bending of the material is used to trigger specific movements via origami folds along hinges. To achieve this, the researchers inserted lightweight fiberglass plates between the flexible circuit boards and the polymer hinges to ensure the desired movement sequences. The embedded temperature sensors are used to control the heat actuators in such a way that minor inaccuracies can be compensated for during repeated shape changes. The scientists had previously derived the necessary origami folding patterns using mathematical calculations.

Using this technique, the researchers created, among other things, a crane-like robot that can move its body and flap its wings. However, the movements are quite slow. To make it easier to create more robots, the researchers have developed a software tool called OriCadLCE. This allows origami robots that work with heat actuators to be designed more quickly.

(olb)