Wu, Lei; (2023) Photo-responsive Polyurethane for Soft Biohybrid Actuators. Doctoral thesis (Ph.D), UCL (University College London).

Text Lei Wu_SN19085889_PhD Thesis_Submission_Final Copy.pdf - Accepted Version Access restricted to UCL open access staff until 1 October 2025. Download (10MB)

Abstract

Light-driven soft robotics based on photo-responsive materials can be utilised to mimic biological motions, such as swimming, walking, and crawling, without involving rigid and chunky electromechanical actuation. However, robust photo-responsive materials with desired mechanical and biological functions and facile manufacturing are yet to be developed. The thesis describes the development of a new group of visible-light-responsive elastomers and exploration of their potential applications of light-controlled artificial muscle, shape memory actuators and biohybrid actuators working together with biological cells. Firstly, a group of poly(ε-caprolactone)-based polyurethane urea were synthesised and characterised by introducing photo-responsive azobenzene moieties at various ratios into the main chains (Azo-PUU). Azo-PUU elastomers show excellent hyperelasticity (stretchability of 575.2% and strength of 44.0 MPa), better mechanical performance than most of the existing photo-responsive materials due to their unique nanostructure, i.e. nanophase separation (relationship of nanostructure–mechanical properties). The light-driven stiffness softening mechanism of the Azo-PUU elastomer was attributed to its nanophase transition during photon stimulation. A visible light-driven bilayer actuator consisting of Azo-PUU and polyimide film was developed, demonstrating two distinct bending modes under illumination with varying light intensities. The corresponding actuation mechanism in correlation to photothermal and photochemical coupling effects was investigated through experimental and theoretical analyses. An exemplary application of visible-light-controlled soft robotic ‘fingers’ playing music by touching a piano on a smartphone was demonstrated. Furthermore, the soft segments (PCL)-dependent shape memory effects of the Azo-PUUs were studied and demonstrated by various shape memory actuators such as self-tightening suture and artificial muscle, etc. Finally, the photo-responsive polyurethane elastomer nanofiber sheets were fabricated via electrospinning and used as scaffolds for guiding the myotube growth induced from optogenetic modified C2C12 myoblasts. The biohybrid structure made from myotubes and the photo-responsive nanofiber sheets demonstrated light-controlled contractions, promising for diverse applications in future assistive technology and active biomedical devices.

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