Self-organisation of artificial muscles based on the cilia and flagella

This project falls within the EPSRC Engineering and Mathematical sciences.

Artificial muscles are materials characterised by their ability to contract, expand or rotate in response to external stimuli. Capable of large power-to-weight ratios and large ranges of motion, artificial muscles hold great promise for pushing forward various robotic applications, from robotic prosthetics and exoskeletons to medical robots [1]. There exist several actuators in this category, including piezoelectric actuators, shape-memory alloys and electroactive polymer actuators, each with their own advantages and limitations. A common problem with existing artificial muscles is the difficulty incorporating sensors that allow for actuation in response to their environment. These artificial muscles are disconnected from the behaviour of real muscular fibres, in which contraction is caused by the sliding of protein filaments relative to one another, driven by molecular motors [2]. The same mechanism is responsible for the movement of cilia and flagella, which are hair-like structures in cells that act as a fundamental unit of motion by converting chemical energy into mechanical work [3].

The aim of the PhD project is to develop new artificial muscle cells based on the cilia and flagella. Responsible for a wide array of functions, from swimming algae to pumping fluid in the brains of mammals [4], cilia and flagella are a sensible starting point for the development of new artificial muscle cells. Recent research into the flagella beating in sperm [5] highlights the importance of additional structures present in sperm's flagella. By modelling the flagella as an elastic filament, I will use a coarse-grained approach [6] to develop a 3-dimensional model of sperm which allows for efficient simulation. This will allow me to model different structures in the flagella and highlight their importance for sperm movement in high-viscosity environments. I will also investigate the self-organisation of molecular motors which drive the flagllum beat, and once I have a suitable model I will use soft robotics to scale up the system to create robotics based on the flagella. The purpose here is to find the minimal set of interactions that give rise to artificial muscles capable of carrying out tasks. This PhD will not only contribute to our understanding of flagella motion and sperm function, but provide insight into a wide array of robotics applications. Self-organisation is also a universal property observered in numerous natural systems, including swimming bacteria and flocks of birds; this ensures that the PhD has potential to impact a wide array of fields

1] Zhang, Jet al., Robotic Artificial Muscles: Current Progress and Future Perspectives, IEEE Transactions on Robotics, vol. 35, pp. 761-781 (2019)
[2] Sweeney, H., & Holzbaur, E., Motor Proteins,Cold Spring Harbor Perspectives In Biology, vol. 10(2018)
[3] Lodish H, Berk A, Zipursky SL, et al. Molecular Cell Biology. 4th edition. New York: W. H. Freeman. Section 19.4, Cilia and Flagella: Structure and Movement. (2000)