The field of robotics has witnessed a remarkable transformation in recent years, with the integration of advanced materials and technologies enabling the development of more capable and sophisticated robots. Nanotube thin films offer exceptional mechanical, electrical, and optical properties, making them ideal for manufacturing various robotic components.
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Nanotube Thin Films: An Overview
Nanotube thin films are 2D networks of semiconducting and metallic nanotubes with exceptional electrical, mechanical, and optical properties. These films exhibit the collective behavior of the individual nanotubes and additional properties resulting from tube-tube interactions.
Nanotube thin films are highly suitable for a wide range of applications that demand exceptional strength, durability, electrical and thermal conductivity, and lightweight characteristics surpassing those of conventional materials.
What Makes Nanotube Thin Films Ideal for Manufacturing Robotic Components?
In robotics, nanotube thin films offer enhanced mobility, improved strength, increased efficiency, and better sensing capabilities due to their high strength-to-weight ratio.
As a result, they can be used to develop lightweight and high-strength actuators, sensors, and exoskeletons that enable robots to perform a wider range of tasks with greater ease and efficiency.
Enhanced Mechanical Properties
Nanotube thin films possess high mechanical flexibility, stretchability, and foldability due to the individual nanotubes' superior mechanical properties and strong interactions with substrates.
They have exceptional bending ability and can be bent down to a radius of 2 mm without failure. In addition, they maintain stable electrical conductivity up to 700% strain, making them suitable for flexible and stretchable electronic devices.
Nanotube films are often combined with polymers to enhance their integrity to form interpenetrated networks.
High Chemical, Ultraviolet, and Heat Stability
Nanotube thin films are robust and have been extensively researched for chemical and biological sensing applications due to their high sensitivity. In addition, they exhibit a conductance response to chemicals through charge transfer or potential energy barrier creation.
Nanotube thin films are heat-stable but have varying UV stability depending on the nanotubes' quality. Due to their network structure, these films are often employed as thermal interface layers for heat dissipation in electronic packaging.
Superior Electrical Properties
Nanotube thin films are good conductors of electricity, but their conductivity depends on their diameter, curvature, defect, chirality, and local environment.
When nanotubes are made into films, their conductivity is lower due to barriers at intertube junctions and resistances introduced during the fabrication process. However, their sheet resistance can be improved after a multi-step purification process.
The electrical conductivity of nanotube films can be further improved by treatment with acids, which removes residual surfactant molecules and densifies the films.
Nanotube thin films have good electronic conductance and electrocatalytic activity, making them useful for energy conversion devices and biosensors. In addition, they can serve as ultrasensitive transducers in biosensors and be chemically functionalized to achieve specific detection.
These unique properties make nanotube thin films ideal for use in robotics.
Which Robotic Components Can Be Manufactured Using Nanotube Thin Films?
Sensors
Sensors play a critical role in robotic systems by providing essential sensory data such as position, velocity, orientation, temperature, force, and weight, enabling robots to perceive their surroundings and perform various tasks.
Nanotube film-based sensors provide advantages such as improved sensitivity, adjustable measurement range, and easy integration into large surfaces, including buried layers in material systems. This novel technology opens up possibilities for developing highly effective strain sensors.
In a study published in Proceedings of the National Academy of Sciences, researchers developed highly sensitive tactile sensors, e-whiskers, for robotics using carbon nanotube films that mimic the functionality of animal whiskers. The e-whiskers can detect pressure as slightly as a single Pascal, making them ten times more sensitive than previous pressure sensors.
They can be incorporated with various user-interactive systems, allowing for various applications in advanced robotics, biological applications, and human-machine user interfaces. For example, these sensors allow robots to "see" and "feel" their surroundings and facilitate tactile sensing for spatially mapping surrounding objects.
Actuators
Actuators are vital for robot movement as they convert stored energy into mechanical work, supplying the necessary force for motion.
Graphene and carbon nanotubes have emerged as promising candidates for robotic actuators due to their superior properties, such as softness, light absorption, and thermal conductivity.
In a study published in Nanotechnology, researchers developed a high-performance advanced robotic actuator using a highly-oriented carbon nanotube film. The actuator takes only 0.9 seconds to deform large-angle and can manipulate small objects.
The carbon nanotube film exhibits anisotropic properties, displaying varying physical characteristics along different directions. This enabled precise control over the deformation of the actuator.
Exoskeleton/Frame of the Robot
A nanotube thin film exoskeleton provides enhanced mobility, increased efficiency, improved strength, and better sensing capabilities than conventional material. In addition, its high strength-to-weight ratio reduces energy requirements and enables feedback on position, movement, and force.
A study published in Nano Letters introduced a novel approach to fabricating durable carbon nanotube films suitable for constructing robust frames or bodies. The method involves generating a hollow cylindrical assembly of carbon nanotubes and condensing it onto a winding drum.
By arranging the nanotubes parallel, researchers developed a carbon nanotube-based film that is five times stronger and 8% more pliable than any previous material. This new film has an average strength of 9.6 gigapascals, which is much higher than the strength of Kevlar (3.7 GPa) and carbon fiber (7 GPa).
Future Prospects
Nanotube thin films provide several benefits for robots, including lightweight design for improved agility, durability in harsh environments, and conductivity for electronic components. However, these films' high cost and manufacturing scalability challenge their widespread use in larger-scale applications.
As technology advances, it is anticipated that the cost of nanotube thin films will decrease, and manufacturing processes will become more efficient. This will enhance affordability and accessibility, driving the widespread adoption of nanotube thin films in robotics.
References and Further Reading
Takei, K., Yu, Z., Zheng, M., Ota, H., Takahashi, T., & Javey, A. (2014). Highly sensitive electronic whiskers based on patterned carbon nanotube and silver nanoparticle composite films. Proceedings of the National Academy of Sciences, 111(5), pp. 1703-1707. https://doi.org/10.1073/pnas.1317920111
Li, Q., & Liu, C. (2019). Fast-response, agile, and functional soft actuators based on highly-oriented carbon nanotube thin films. Nanotechnology, 31(8), p. 085501. https://doi.org/10.1088/1361-6528/ab4f2b
Xu, W., Chen, Y., Zhan, H., & Wang, J. N. (2016). High-strength carbon nanotube film from improving alignment and densification. Nano letters, 16(2), pp. 946-952. https://doi.org/10.1021/acs.nanolett.5b03863
Huang, Y., Su, C., Yu, Q., Jiang, J., Chen, N., & Shao, H. (2022). Carbon-based photo-thermal responsive film actuators with a sandwich structure for soft robots. Journal of Science: Advanced Materials and Devices, 7(1), p. 100412. https://doi.org/10.1016/j.jsamd.2021.100412
Wang, Q., & Moriyam, H. (2011). Carbon Nanotube-Based Thin Films: Synthesis and Properties. InTech. doi.org/10.5772/22021
Hu, L., Hecht, D. S., & Gruner, G. (2010). Carbon nanotube thin films: fabrication, properties, and applications. Chemical Reviews, 110(10), pp. 5790-5844. https://doi.org/10.1021/cr9002962
Hirotani, J., & Ohno, Y. (2019). Carbon nanotube thin films for high-performance flexible electronics applications. Single-Walled Carbon Nanotubes: Preparation, Properties and Applications, pp. 257-270. https://doi.org/10.1007/s41061-018-0227-y
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