The growing interest in soft robotics results from the innovative solutions these systems can provide for robotics problems that rigid body robots cannot solve. The rigid robots can conduct complicated and precise motion control through rigid link joints. However, the benefits of traditional rigid robots also bring drawbacks. They usually need many rigid link joints, which means rigid robots typically need accurate motion control so that they will not damage target objects, hurt the human body or even damage the robots themselves. The rigid components are mostly made of metal. A simple rigid robotic gripper will easily weigh higher than a human hand to achieve the same functionality and thus make it hard to deploy on smaller-scale robotic systems. Because of these issues, researchers in...[ Read more ]

The growing interest in soft robotics results from the innovative solutions these systems can provide for robotics problems that rigid body robots cannot solve. The rigid robots can conduct complicated and precise motion control through rigid link joints. However, the benefits of traditional rigid robots also bring drawbacks. They usually need many rigid link joints, which means rigid robots typically need accurate motion control so that they will not damage target objects, hurt the human body or even damage the robots themselves. The rigid components are mostly made of metal. A simple rigid robotic gripper will easily weigh higher than a human hand to achieve the same functionality and thus make it hard to deploy on smaller-scale robotic systems. Because of these issues, researchers innovated soft robots to replace rigid robots in specific scenarios. Soft robots contain components that are made of soft materials. It utilizes elastic deformation of the soft materials and converts it into various motions like rotation, compression, twisting, and stretch. The actuation of soft robots also varies: hydraulic, cable-driven, and some soft robots use smart materials like dielectric elastomer and shape memory alloy. Compared with traditional rigid robots, soft robots perfectly compensate for the drawbacks of rigid robots. Because of the continuum of soft materials, they usually have infinite degrees of freedom (DOF). Thus soft robots can passively deform when they interact with the environment. This feature makes the soft robotic system much safer than rigid ones. The compliance and durability of soft materials also enable soft robots to work in extreme conditions such as underwater and in an acidic environment. As researchers and engineers are now keeping expanding the applications of soft robots, soft robotics has been a hot topic in robotic research.

With all the benefits that soft robots can offer, the challenges come together with them. Currently, most soft robots are fabricated through silicone molding. Every soft robot in a new scenario needs a new mold design. Because of the principle of molding that materials need to fill the mold chamber, soft robots that are fabricated by this method cannot have complex inner structures. This limitation highly decreased the performance of soft robots. With the development of the fast prototyping industry, 3D printing is now becoming the potential replacement for silicone molding. Although there are limited numbers of 3D printing soft materials that have similar mechanical properties as cast silicone, it is foreseeable that in the near future, soft material 3D printing could provide enough strength that soft robotic systems need. In this thesis I took advantage of 3D printing to fabricate a series of novel pneumatic soft actuators that provides basic motions for robotic application.

Soft robots and rigid robots never go oppositely. They cooperate with each other and become more robust and dexterous when combined together. The human body is the best example. The rigid bones shape our bodies and make us stand up straight. The muscles attached to the bones help us move and smile. The dexterity that the human body can achieve is still pursued by many researchers and engineers. Inspired by this nature, integrating rigid components with soft materials to enhance the stiffness of the whole system is a great method to improve the performance of soft robots. With this concept I designed two compliant mechanisms that can work as the bone structure for soft actuators to adhere.

Sensing is also one of the features that we can learn from ourselves. Our hands overwhelm any smart robotic hands in the current industry. We could sense the shape, temperature, and texture of objects through touch. The skin, nerves, and muscles underneath make it happen. By mimicking the principle of our hand, we developed tactile sensors for robots to get real-time information from the environment.

In a sum, this thesis reported three main parts that utilized the innovations mentioned above: A systematic method from designing to fabrication of a family of scaleable 3D-printable and programmable hydraulic soft actuators, an exploratory work on compliant mechanisms combined with soft actuators, and a vision-based soft tactile sensor. The designing principles of the soft actuators are explored theoretically and the printed parts are implemented into several different robotic systems for practical tests. The tactile sensor involves illumination optimization to get the precise image in a large sensing area. Those prototypes can help researchers to further develop and explore the potential of soft robotic systems.