The challenge of creating materials and devices that mirror the powers and flexibility of biological organisms is often driven by an interest in natural structures. Nature has always inspired and motivated scientists to create devices that emulate life-like mobility, especially within robotic systems.
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Robots are defined as machines that can automatically perform a series of complex or simple tasks. Robots have revolutionized the world in many aspects.
The study of the versatility of motions of different living creatures has led scientists to develop soft robots. Unlike hard robots, which have rigid body segments that inhibit the adaptability and versatility of these devices, soft robots are made entirely of flexible polymers and closely resemble living creatures.
What are Soft Robots?
Soft robots are systems made up of flexible polymers with mechanical properties like biological tissues. The design and manufacturing process of these robots is unique, unlike rigid body robots, which are usually assembled in serial or parallel arrangements of blocks.
The flexibility in joints and body of soft robots can efficiently handle delicate and soft objects which do not require hard interaction and complex handling algorithms. These systems are free to deform their shapes to absorb the impact energy, avoiding damage to themselves.
According to recent research, stimuli-sensitive soft polymers are good candidates for constructing soft robotics because they have a lot of promise for integrating sensors, actuators, and control systems into micro-meter soft supporting structures.
Liquid Crystal Polymers in Soft Robots
The promise of liquid crystal polymers (LCPs) in soft robotics has been emphasized by their unique properties such as anisotropic deformation, exceptional elasticity and flexibility, and order-disorder phase-transition-induced changes in shape. This article will explore liquid crystal polymers based soft robots.
The team of researchers at Université de Sherbrooke published an article in the journal Advanced Intelligent Systems that explores the use of LCPs in soft robots, their design, and development.
The LCPs have high molecular mass, and they behave a mesomorphic behavior between regular liquids and crystalline materials. They have the anisotropic characteristics of crystalline solids and liquid-like fluidity.
The LCPs can respond to stimuli of heat, light, humidity, electricity, etc. When LCPs are subjected to these impulses, they change their shape. This deformation in LCPs is reversible, even for diverse stimuli. This behavior can be used for conducting mechanical work in multiple ways, such as transporting, translating, grasping, and handling objects.
LCP Soft Robots Applications in Mechanical Work
The most important part of robots is their actuators. The LCP actuators can be served as artificial muscles, grippers, walkers, rollers, jumpers, swimmers, and self-sustained motion devices.
The LCP soft robots with uniaxial liquid crystal orientation can execute muscle-like contraction with high strains and actuation stress. These soft robots have multiple advantages over rigid body robotics grippers, including the capability to handle delicate and sensitive objects carefully and provide shape versatility.
The LCP soft robots can achieve flexible control with high degrees of freedom through simple stimuli and deform their bodies to adapt to the environment, such as contracting their bodies to a scale of micrometers while going through a narrow space.
These robots can also do swimming like aquatic animals. The most important trait in aquatic animals is that they undergo periodic deformations such as reversible bending or unbending, which are typical in LCP-based swimmers.
Using a basic untethered liquid crystal polymer, it is relatively straightforward to temporally and spatially manipulate the body curvature to mimic intricate swimming motion.
All these traits of liquid crystal polymer soft robots make them costly and structurally efficient.
Challenges and Future of Soft Robots
LCP soft robots have a promising future owing to their good mechanical and actuation performance, high degree of freedom motion flexibility, and versatility in their response.
The rapid development and advances in biological and materials sciences have made LCP soft robots operational. However, these soft robots must be improved to fulfill the growing demands of actuation performance as they lack availability and intelligence in their actuation behaviors for practical applications.
Living organisms sense stimuli and adapt to environmental changes, while soft robots lack biological sensing and intelligence. It is a great challenge to design an intelligent soft robot that can autonomously analyze the surroundings and respond to the stimuli.
Organisms can also change their motion behaviors for different conditions. However, LCP soft robots can display only one actuation mode once they are fabricated. This is because the liquid crystal polymers are permanently cross-linked networks.
The problem of low actuation, structural design, and engineering of LCP soft robots owing to their soft nature is also a great challenge.
Even though LCP soft robots have already achieved multimode motion, multidirectional locomotion, and multifunctionality, integrating all of these characteristics in a single system is still required for advanced soft robots in the future.
The current dependence of researchers on stimuli control to control the actions of a specific structure may complicate the operation and results in interference in actuation behaviors.
Therefore, cooperation in stimulus modulation, reconstruction, and network reprogramming is needed to improve the agility and adaptability of robotic mobility.
The application of LCP soft robots in industries demands the ease of programming, processing, and fabrication; therefore, reprogrammable, processable soft robots and their 3D printing might be highly useful research areas for the future.
References and Further Reading
Pilz Da Cunha, M., Debije, M. G. and Schenning, A. P. H. J. (2020) ‘Bioinspired light-driven soft robots based on liquid crystal polymers, Chemical Society Reviews, 49(18), pp. 6568–6578. Available at: https://doi.org/10.1039/d0cs00363h.
Schmitt, F. et al. (2018) ‘Soft robots manufacturing: A review’, Frontiers Robotics AI, 5(JUN). doi: 10.3389/frobt.2018.00084. Available at: https://doi.org/10.3389/frobt.2018.00084.
Xiao, Y.-Y., Jiang, Z.-C. and Zhao, Y. (2020) ‘Liquid Crystal Polymer‐Based Soft Robots’, Advanced Intelligent Systems, 2(12), p. 2000148. Available at: https://doi.org/10.1002/aisy.202000148.