Applied and industrial projects

The development of soft flexible materials with morphing and shape-programmable abilities is essential for technological progress of soft robotics, biomechanics, and flexible electronics. However, morph-on-demand materials remain a rather elusive class of smart materials. Shape-programmable matter capable of transforming between three-dimensional shapes in response to external stimuli such as light, heat, electric and magnetic fields is a class of active materials whose geometry can be controlled for performing tasks beyond the operational scope of conventional machines or robots.

In this project, we are proposing the development of a method to produce a new generation of 3D-printable soft material with anisotropic response. The material will be based on the recently developed polymer dispersed liquid crystal elastomers (PDLCE). Such composite material consists of thermomechanically active liquid single crystal elastomer (LSCE) microparticles, dispersed and oriented in a crosslinked polymer matrix. The particle orientation can be spatially modulated using an external magnetic alignment field over the composite volume, resulting in custom-tailored, temperature responsive shape changes of the specimen. We have recently devised a method of producing a suspension of anisotropically shaped LSCE microparticles with their liquid crystal ordering and consequently, direction of thermomechanical actuation, aligned along the particle’s longer axis. Anisotropically shaped LSCE particles can thus be oriented using simple laminar flow, present during deposition while 3D printing the material. The use of the state-of-the-art robotic hand with a mounted polymer dispensing unit, will enable us to precisely control the imprinted thermomechanical anisotropy, by exploiting the robotic hand’s six degrees of freedom of movement in order to deposit PDLCE voxels at arbitrary angles. The developed 3D printable ink will be used to print a tube capable of peristaltic movement, triggered by consecutive heating and cooling of the specimen via incorporated heating wires or by UV/

microwave irradiation absorbing nanostructures additionally functionalizing the LSCE composite.

The realization of a 3D printed peristaltic tube will demonstrate the applicative advantages of our printing method and of the PDLCE 3D printable ink, by producing a specimen with complex morphing abilities that cannot be achieved by any of the currently developed additive manufacturing technologies.

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Project phases and their realization:

• preparation of polydomain LSCE bulk materials (temperature-controlled crosslinking of the mixture of commercially available chemicals);
• preparation of polydomain LSCE bulk materials with deuterium labelled constituents (for characterization purposes);
• synthesis of MoS₂ nanotubes by sulphurization of Mo₆S₄I₆ nanowires at 1073 K in a reactive gas composed of 98 vol% Ar, 1 vol % of H₂S and 1vol % of H₂ for 1h;

• preparation of PDLCE resin by freeze-fracturing of bulk LCE and frozen matrix material in a cryogenic planetary ball mill;
• preparation of PDLCE printable ink by pre-shearing the PDLCE resin using custom-build rotational parallel plates inside a temperature controlled chamber;
• determination of liquid crystal ordering inside deformed PDLCE microparticles of a PDLCE printable ink via quadrupole-perturbed deuteron NMR spectroscopy;

• determination of LSCE microparticles orientational order and its associated order parameter Q in PDLCEs via quadrupole-perturbed deuteron NMR spectroscopy;
• determination of bulk LSCE, matrix elastomer, and PDLCE thermomechanical coefficient λ in a temperature-controlled extensometer;

• preparation of PDLCE composite material and peristaltic tube by fused layer deposition of flow-oriented PDLCE printable ink, deposited by a robotic arm with a mounted polymer dispense unit;

• characterization of peristaltic tube performance by analysis of the flow velocity, pressure and volume of expelled liquids using flow and pressure sensors;
• physical modelling of the PDLCE peristaltic tube performance based on mechanical and thermomechanical properties of the PDLCE material, imprinted spatial alignment of PDLCE microparticles and tube’s geometrical constraints.