# Review of the Research Progress in Soft Robots
## 1 Introduction  
Due to the disadvantages of traditional robots, such as large rigidity, complex structure, and poor flexibility [1], the researchers are prompted to draw inspiration from nature and conduct in-depth research on the bionic mechanism, and develop different types of soft robots [2]. The soft robot is a new type of robot made of flexible materials, which can adapt to various unstructured environments and can also form any desired shape by bending, twisting, and stretching to a certain extent [3]. This makes up for the shortcomings of traditional robots in terms of freedom and flexibility. The use of flexible materials also makes soft robots lighter than ever. The application of soft robots also provides a good foundation for maintaining security and flexibility in the current human-computer interaction and complex situations. Today, soft robots are used in a wide range of applications in bioengineering, disaster relief and rescue, industrial production, medical services, exploration, and surveying. For example, [PERSON] et al. from the University of Science and Technology of China [4] designed a frog swimming, which was soft driven with the pneumatic articulated soft driven for joints based on the motion of the frog jumping, thus miniaturizing the frog swimming robot and effectively reducing the mass and volume of the underwater soft robot, enabling it to travel freely between multiple obstacles in the underwater environment. [PERSON] et al. [5] from Shanghai Jiaotong University designed a soft robot for minimally invasive cardiac surgery, which was inspired by the physiological structure of an elephant's trunk and made of a non-toxic and non-polluting medical silicone material that can be safely integrated into the patient's body. The reference [6] presents a scalable continuum of robots inspired by natural lianas, whose ability to bend significantly allowsthem to adapt to environmental features by curling around them to facilitate navigation and manipulation. Research on digital models based on the principles of bionic motion for soft robots is also underway [7; 8; 9]. In addition, due to the advantages of 3D printing with methods and materials, 3D printing is playing an important role in the field of soft robots [10; 11; 12]. Soft robot 3D printing manufacturing technology avoids manual errors, simplifies manufacturing steps, and achieves low-cost personalized manufacturing of soft robots. Currently, 3D printing processes that can be used for soft robots include fused deposition modelling (FDM), direct ink writing (DIW), inkjet printing (IP), stereo lithography (SLA), digital light processing (DLP), selective laser sintering (SLS), and other technologies. In the future, with the continuous development of the 3D printing process, high-quality integrated manufacturing of soft robots becomes possible [13; 14]. In this article, firstly, the principles, characteristics, materials, and research results of several typical driven methods for soft robots are described. Secondly, the process, practical applications, and advantages and disadvantages of the different technologies in 3D printing for soft robots are dedicated. Thirdly, the application status and latest progress for soft robots in the fields of bionic structure, grasping operation, and medical rehabilitation are expounded. Finally, the problems and difficulties in the research of soft robot technology are discussed.