South Korean engineers have developed a flexible robotic sheet which can grasp objects and move across surfaces – useful skills for applications in healthcare, exploration and haptic displays where users can “feel” virtual stimuli.
The design is detailed in a paper published in Nature Communications.
Engineers have been developing flexible robots that can change shape for years. These robots, however, tend to require fixed hinge-like structures which restrict their range of movement.
The new robotic folding sheet is made with heat-sensitive electrical elements which are distributed across a flexible, layered square of material with 6.3cm sides. The flexible layers are the high-performance polymers polyimide and polydimethylsiloxane.
A total of 308 resistors placed on the square act as heaters and sensors allowing for both precise movement control and continuous adjustment based on feedback from the sensors.
When the resistors embedded in the material heat up, the material undergoes thermal expansion causing it to transform its shape. This shape-shifting can be programmed to fulfill different functions such as locomotion or gripping.
Folding angles range from -87° to 109° – more than 180° of motion. The system performed consistently across a range of temperatures even as high as 170°C.
The researchers demonstrated their flexible robotic sheet’s dexterity in crawling across a surface and grasping and lifting various objects.
This locomotion could see the robotic sheet deployed in exploratory applications.
“Robotic exploration in challenging terrains (rugged and obscured) may require a compact system design and the ability to perform dexterous locomotion that can benefit from robotic designs with structural compliance,” they write.
“The field-programmability presented here expands the available modes of locomotive strategies. For instance, when the robotic sheet is deployed on the ground, the robotic sheet can imitate various bio-inspired movements such as crawling, waving, walking, and dragging.
“The integration of advances in materials, computation, and electronics facilitates the delicate manoeuvring of numerous shape configurations that alleviate the use of fixed hinges as in previous attempts,” they add.
“Despite these promising features, several concerns should be addressed to further mature our technology,” the authors caution. “First, the mechanical performance should be improved to enhance both shape responsiveness and load-bearing capacity.”
They suggest that other materials, which may be even more responsive to changes in heat, should be investigated. The authors also say that other applications not tested in their study should also be considered in future work. This may include light modulators – devices which can control the intensity, phase or polarisation of a light source.