Design and Evaluation of Graphene-filled Chitosan/Polydimethylsiloxane Bilayered Morphing Composites via Thiol-ene Click Reaction

  • Shida Lyu

Student thesis: Phd


Morphing material systems are attracting increasing attention as sensors, actuators and in self-healing applications. Bilayered structures are one of the most common morphing configurations that can be fabricated from a wide variety of materials with several triggering options explored in the thesis. Simple bilayered morphing composites display homogenous bending in response to external stimuli, while patterned ones can change shape locally and heterogeneously. They provide great potential in applications of soft robotics and metamaterials. However, identifying and optimising interfacial bonding is a challenge in the design of bilayered morphing structures. In this research, reduced graphene oxide filled chitosan/polydimethylsiloxane (rGO-chitosan/PDMS) based bilayered composites are created by exploiting thiol-ene click reaction to covalently bond the interface and prevent or eliminate delamination (layer separation). Two types of functionalised chitosan, chitosan-methacrylamide (chitosan-MA) and chitosan-norbornene (chitosan-NB) are produced and the PDMS surface is thiolated, enabling thiol-ene click reaction at the interface. These photothermally responsive bilayered constructions after careful selection of constituents and geometric parameters can morph reversibly and repeatedly. Differences between experimental measurements and analysis based on bimetallic thermostat theory are 6.0 % (rGO-chitosan-MA/PDMS) and 8.5 % (rGO-chitosan-NB/PDMS), respectively. A family of chitosan-NB with various degrees of substitution of norbornene (9-43 %) are also investigated by controlling reaction conditions, including reactant amount, reaction time and pH of the system. Digital light processing (DLP) allows for patterns of functionalised chitosan to be crosslinked to the thiolated PDMS surface. It is found that norbornene groups are more reactive than methacrylamide groups in the thiol-ene click reaction, with rGO-chitosan-NB/PDMS showing better crosslinking performance and higher printing resolution in the DLP printing. DLP printed patterned bilayers are able to display self-folding, sequential bending and even moving on water surface. A unique property for DLP is to print bilayered composites with gradient top layer thickness by controlling the light intensity from the DLP device. Photothermal-triggered gradient bending and morphing features exemplified by a walking worm and a kirigami-inspired opening flower are demonstrated in the thesis. A fish-shaped rGO-chitosan-NB/PDMS is triggered by nIR laser, swimming and turning directions in water, giving confidence in our geometric and material parameter optimisation.
Date of Award1 Aug 2020
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorConstantinos Soutis (Supervisor), Matthieu Gresil (Supervisor) & Jonny Blaker (Supervisor)


  • digital light processing
  • thiol-ene click reaction
  • morphing materials
  • bilayered structure

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