Introduction

Soft robotics is a rapidly growing subdomain of robotics that has come into the spotlight due to several advancements made in the past few years. Soft robotics deals with the creation and study of robots constructed with flexible bodies and electronics. Soft robotics is a novel approach for improving the adaptability and flexibility of traditional robotic systems in order to allow for increased effectiveness in a wide range of environments. In particular, soft robotics is particularly useful in the fields of medicinal technologies and manufacturing, where adaptability is a critical component that robots being developed for these domains must-have (The University of California – San Diego). Soft robotics is especially disruptive in the field of medical technologies. The human body is incredibly complex and, because of this, robots are required to be flexible and be able to orient themselves into various shapes and positions (Trivedi, D. et al.). This task is simply impractical for traditional robots but it is trivial for complex soft robots. Soft robots have tremendous potential. One recent development in the field of soft robotics was the creation of a four-legged soft robot that was dependent on no control circuitry and was solely reliant on a constant source of pressurized air. This advancement was made by the University of California San Diego with the hopes of developing an efficient low-cost soft robot for use in environments where the use of electrical systems is impossible. This robot represents a major step forward towards the development of fully autonomous cost-effective robots and hopefully will inspire other researchers to continue research into this exciting subfield. 

Development of Soft Robots

Although it may appear otherwise, soft robots have several disadvantages that are currently limiting the accessibility of this technology. The manufacture of soft robots is incredibly complex and currently is not very cost-effective. Typical manufacturing processes, such as milling and drilling, are not useful in the creation of soft robots. Instead, advanced manufacturing strategies are currently involved in continuous development to facilitate the creation of these complex bodies. Currently, the most popular methods for the manufacture of soft robots are Shape Deposition Manufacturing and 3D multi-material printing. Functionally, the techniques utilized in soft robots to generate movement vary greatly, but certain strategies are much more widespread than others. Once the soft robot is built, researchers have a wide range of techniques for generating movement to choose from, but bio-mimicry is the preferred method for generating movement in soft robots that mimics certain processes found in plant cells. Plant cells produce hydrostatic pressure as a result of a solute concentration gradient between the cytoplasm of the cell and external surroundings. Furthermore, plant cells can adjust the concentration of the solute gradient through the movement of ions across the plant cell membrane (Kim, Sangbae, et al.). This process ultimately modifies the shape of the plant due to a change in hydrostatic pressure (Kim, Sangbae, et al.). Many soft robots rely on similar principles for generating movement and they often utilize macro-scale substitutes for the components responsible for movement found in microscopic plant cells. 

Another challenge currently plaguing the efficacy of soft robots is the means by which control is expressed over the movements joints within a soft robot (Trivedi, D. et al.). All soft robots require some form of actuation system to generate controlled movement. Soft actuation systems are incredibly complex to design because they must be able to work without the use of any rigid materials that would interfere with the movement of the soft robot. These materials, including circuit boards, are relatively limited in their potential for future improvements targeted at increasing functionality in soft robots, and other alternative solutions for actuation control should be pursued to overcome these constraints. 

Importance of Advancements Made by the University of California

The current limitations posed by the use of electrical components for actuation control greatly limit the potential applications of soft robotics. The University of California’s recent quadruped soft robot is a great advancement in the field of soft robotics because it requires no electrical control system and instead uses an inexpensive system of pneumatic circuits (The University of California – San Diego). Essentially, the soft robot is reliant on three valves in the central section of the robot, each of which delays the spread of pressurized air to the leg joints (The University of California – San Diego). The leg joints are constructed using three pneumatic cylindrical chambers which, once filled with pressurized air, generate linear motion which creates movement in that joint (The University of California – San Diego). Essentially, the soft robot is made of a system of valves that oscillate repeatedly in order to let compressed air into the robot’s joints which engender movement. Furthermore, the team was able to create sensors without the use of any electronics. Traditional soft robots make use of rigid electrical components for sensors that, when implemented in a soft robot, severely diminishes body flexibility and adjustability. In contrast, the sensors developed by the team at the University of California developed a novel solution to this problem that would pose no hindrance to the effectiveness of the soft robot. These sensors were small bubbles attached to small tentacle-like structures extending from the robot’s body (The University of California – San Diego). Once the bubbles are depressed in the event of a collision with a foreign object, the fluid created from that collision causes a reversal of one of the valves in the soft robot which causes it to reverse its direction. 

Conclusion

Traditional soft robots are significantly hindered by the use of rigid electrical components that degrade both the flexibility and adaptability of said robot. The recent advancements made by the University of California at San Diego demonstrate alternative options for the creation of autonomous soft robots in an inexpensive manner without compromising the adaptability of the soft robot as a whole. The University of California at San Diego has made several important improvements to critical components of soft robotic systems and, hopefully, these developments will prompt other researchers to continue studying this rapidly growing subfield. 

Citations

The University of California – San Diego. (2021, February 17). This robot doesn’t need any electronics: Walking quadruped is controlled and powered by pressurized air. ScienceDaily. Retrieved February 24, 2021 from www.sciencedaily.com/releases/2021/02/210217151054.htm

Thuruthel, T., Shih, B., Laschi, C., & Tolley, M. (2019, January 30). Soft robot perception using embedded soft sensors and recurrent neural networks. Retrieved February 21, 2021, from https://robotics.sciencemag.org/content/4/26/eaav1488

Kim, Sangbae; Laschi, Cecilia; Trimmer, Barry (2013). “Soft robotics: a bioinspired evolution in robotics”. Trends in Biotechnology. 31 (5): 287–94. doi:10.1016/j.tibtech.2013.03.002. PMID 23582470.

 Trivedi, D., Rahn, C. D., Kier, W. M., & Walker, I. D. (2008). Soft robotics: Biological inspiration, state of the art, and future research. Applied Bionics and Biomechanics, 5(3), 99-117.

Li, Suyi; Wang, K. W. (1 January 2017). “Plant-inspired adaptive structures and materials for morphing and actuation: a review”. Bioinspiration & Biomimetics. 12 (1): 011001. Bibcode:2017BiBi…12a1001L. doi:10.1088/1748-3190/12/1/011001. ISSN 1748-3190. PMID 27995902.

Cho, Kyu-Jin; Koh, Je-Sung; Kim, Sangwoo; Chu, Won-Shik; Hong, Yongtaek; Ahn, Sung-Hoon (11 October 2009). “Review of manufacturing processes for soft biomimetic robots”. International Journal of Precision Engineering and Manufacturing. 10 (3): 171–181. doi:10.1007/s12541-009-0064-6.