Compared with traditional rigid robots, the design of soft robots is inspired by biological systems in nature, such as worms, octopuses, geckos and frogs. These bio-based materials are soft, resilient and exhibit superior athleticism in complex environments. However, in practical applications, soft robots rely on external power or drive power sources and are connected by physical tethers, resulting in limited range of movement. In addition, the weight of traditional soft actuators, such as pneumatic network actuators (PNEU-NETS), has also become a key factor restricting the untethered operation of soft robots. To solve this problem, the FiBa (thin film balloon) soft actuator developed by Ching et al. has brought a new breakthrough to the field of soft robotics, and the research results have been published in the journal Science Robotics, with members from the Singapore University of Technology and Design (SUTD), the National University of Singapore (NUS) and the Queensland University of Technology (QUT).
▍FiBa soft actuator is designed with Dragon Skin 30 silicone and polymer film with transverse curvature
The FiBa soft actuator features a unique structural design that combines a 3D printed pneumatic balloon with a polymer film with transverse curvature. The advantage of this design is that it effectively reduces the weight of the actuator while retaining its versatile features, allowing for tetherless operation.
Compared to conventional silicone rubber materials, FiBa actuators use Dragon Skin 30 silicone, which has a higher modulus of elasticity (about 593 kPa) and is able to provide more powerful driving power without adding too much weight. The high modulus of elasticity means that Dragon Skin 30 silicone is able to generate greater internal pressure for the same volume, which enhances the bending and actuation of the actuator.
Another key component of the FiBa actuator is a polymer film with transverse curvature. This film material is not only lightweight, but also has good flexibility and plasticity. By introducing a transverse curvature design, the local stiffness of the film is enhanced, enabling a directional bend when inflated and quickly returning to its original shape after deflation. According to the researchers, by designing the transverse curvature, the bending characteristics of the polymer film are significantly improved, which improves the overall performance and reliability of the actuator.
It is worth mentioning that traditional flat film materials are prone to irregular twisting and bending when subjected to external forces. By introducing a transverse curvature design, the bending characteristics of the film are directionally enhanced. When the balloon is inflated, the film bends in a preset direction of curvature, creating a steady driving force. This directional bending feature not only improves the control accuracy of the actuator, but also extends its service life.
The transverse curvature design also helps to improve the structural reliability and durability of the actuator. During the outgassing process, the film quickly recovers to its original shape, avoiding performance degradation and structural damage due to long-term deformation. In addition, by optimizing the curvature parameters and film thickness, the bending angle and driving force of the actuator can be further adjusted to meet the needs of different application scenarios.
Schematic diagram of the FiBa module
In terms of design, the FiBa actuator adopts a modular design approach, including the FiBa bending module and the FiBa variable stiffness beam module. With the modular design, researchers can quickly prototype and iteratively optimize actuators. Different modules can be combined into actuators of various shapes and functions to meet the needs of different application scenarios. This rapid prototyping capability not only accelerates the product development cycle, but also reduces cost risk.
Features of curved construction and modular balloons
The modular structure of FiBa actuators is also highly customizable, allowing researchers to customize actuators to suit different environments and tasks by adjusting the number, arrangement, and size parameters of the modules. For example, in a climbing robot, the robot's climbing ability and stability can be improved by increasing the number and layout of grasping and bending modules.
For untethered operation, FiBa actuators also integrate electronic components such as pneumatic pumps, valves, batteries, and control panels. When selecting electronic components, researchers focus on their lightweight and high performance. For example, the use of miniature pneumatic pumps and valves can reduce the overall weight of the system, and the use of high-performance batteries and control boards can improve the energy efficiency and stability of the system. The lightweight electronics enable FiBa actuators to operate stably for a long time in an untethered environment.
In terms of integration, the researchers optimized the layout and connection of electronic components to reduce signal interference and energy loss, while improving the reliability and safety of the system by adding redundant design and troubleshooting functions.
▍Discussion of the four forms of FiBa soft robots and landing scenarios
To verify the performance and versatility of the FiBa actuator, the research team successfully demonstrated four untethered bionic movement modes, namely turtle-inspired crawling, inchworm-inspired climbing, bat-inspired perching, and ladybug-inspired flight.
Crawling robots inspired by sea turtles
The turtle-inspired crawling robot uses four FiBa bending modules as "fins" to simulate the forelimbs of a sea turtle to propel the robot forward by simulating the way a sea turtle moves on land. The modules are combined with a 3D printed pneumatic balloon by a transversely curved polymer film to achieve a lightweight and efficient bending motion. The robot is also equipped with a lifting actuator module to adjust the height of the fuselage when needed to adapt to different terrain conditions.
In terms of application scenarios, after natural disasters such as earthquakes and tsunamis, there are often a large number of narrow gaps in the ruins, which are difficult for traditional rigid robots to enter. This crawling robot can easily pass through these gaps, carry equipment such as life detectors, search for trapped people, and transmit the scene situation to rescuers in real time through wireless communication, which greatly improves rescue efficiency.
Inchworm-inspired climbing robots
The inchworm-inspired climbing robot uses the FiBa bending module and grasping module to achieve vertical climbing by simulating the wriggling mode of the inchworm. The gripping module is tightly wrapped around the climbing surface by an inflated silicone balloon to provide adequate support. At the same time, the FiBa bending module drives the robot to move along the climbing surface to achieve stable climbing.
In the industrial field, this climbing robot can be applied to the inspection and maintenance of vertical pipes, bridges, and façades of high-rise buildings. The robot is equipped with high-definition cameras, infrared thermal imagers and other equipment to carry out detailed inspection of the surface of the structure, find potential safety hazards in time, and reduce the risk and cost of manual inspection. In the inspection of infrastructure such as power lines and communication towers, this climbing robot also performs well. It can quickly rise along the pole or communication tower, inspect the line insulator, tower connector, etc., and improve the efficiency and accuracy of inspection.
Bat-inspired roosting robots
The bat-inspired roosting robot built a lightweight four-finger gripper with the FiBa module that mimics how bats hang upside down on tree branches. The pneumatic structure inside the gripper creates a strong grip when inflated, allowing the robot to stably perch on supports such as tree branches and utility poles.
In terms of application landing, installing this perching robot on the drone can greatly extend the flight time of the drone. During the mission, the drone can perch on the support to save energy, and then take off again when the mission continues, thereby reducing energy costs and broadening the application field. In field operations such as geological exploration and forestry survey, the perching robot can be used as a temporary support platform. After completing the task, the drone can roost nearby to recharge or wait for further instructions, improving operational efficiency and safety.
Ladybug-inspired wings
The ladybug-inspired flying robot uses the FiBa variable stiffness beam module as the main structural component of the wing. These modules produce enough stiffness and strength to support flight when inflated, while they can be easily folded and rolled up in an uninflated state for easy transport and storage. The robot is also equipped with a thrust device and a control system for autonomous flight and attitude adjustment. In the event of an emergency such as a natural disaster, this flying robot can respond quickly and deliver urgently needed supplies such as food and medicine to the affected areas with precision. Its foldable wing design allows the robot to occupy less space during transportation, which is convenient for large-scale deployment; The ability to fly autonomously ensures the accuracy and timeliness of material delivery. In the field of environmental monitoring, flying robots can carry a variety of sensors and equipment to comprehensively monitor and collect data on air quality and water quality. Its flexible flight capability and wide monitoring range allow the robot to quickly cover large areas and provide accurate data support. In addition, it can also be used in the agricultural field for pest and disease monitoring and crop growth assessment.
▍Conclusion and Future:
The advent of the FiBa soft actuator marks a major breakthrough in soft robotics. Through the selection of lightweight materials and the application of modular design, the FiBa actuator has the characteristics of lightweight and multi-function, which not only solves the weight problem of traditional soft robots, but also has a high generalization in practical scenarios. In the future, researchers will continue to optimize the design and technical solutions of FiBa actuators to improve their performance and reliability, and with the development of intelligent control and autonomous navigation technology, FiBa soft robots are expected to behave more intelligently in the future.