Catégories
extrusion

Hierarchical chemomechanical encoding of multiresponsive hydrogel actuators via 3D printing

Hierarchical chemomechanical encoding of multiresponsive hydrogel actuators via 3D printing

Jérémy Odent, Sophie Vanderstappen, Antoniya Toncheva, Enzo Pichon, Thomas J. Wallin, Kaiyang Wang, Robert F. Shepherd, Philippe Duboisa and Jean-Marie Raquez

Abstract :  Inspired by nature, we herein demonstrate a family of multi-responsive hydrogel-based actuators that are encoded with anisotropic swelling behavior to provide rapid and controllable motion. Fabrication of the proposed anisotropy-encoded hydrogel actuators relies on the high resolution stereolithography 3D printing of functionally graded structures made of discrete layers having different volume expansion properties. Three separate synthetic strategies based on (i) asymmetrical distribution of a layer’s surface area to volume ratio via mechanical design, (ii) crosslinking density via UV photo-exposure, or (iii) chemical composition via resin vat exchange have been accordingly demonstrated for developing very smooth gradients within the printed hydrogel-based actuator. Our chemomechanical programming enables fast, reversible, repeatable and multimodal bending actuation in response to any immediate environmentalchange(i.e.basedonosmoticpressure, temperatureandpH)fromasingleprintedstructure.

Catégories
extrusion

Bilayer solvent and vapor-triggered actuators made of cross-linked polymer architectures via Diels–Alder pathways†

Bilayer solvent and vapor-triggered actuators made of cross-linked polymer architectures via Diels–Alder pathways†

Antoniya Toncheva, Bertrand Willocq, Farid Khelifa, Olivier Douheret, Pierre Lambert, Philippe Dubois and Jean-Marie Raquez

Abstract : 

A simple and straightforward approach to produce solvent and vapor-based actuating materials is developed in this work. These actuators are based on rigidity gradients created in bilayer architectures made of reversibly cross-linked poly(ε-caprolactone) (PCL) networks into which functional nanofillers, i.e. multi-walled carbon nanotubes (MWCNTs), are incorporated using simple processing techniques. A key element of the bilayer functionality lies in, by taking advantage of thermo-reversible Diels–Alder reactions (between furfuryl and maleimide moieties), ensuring good adhesion between the layers. Thereby, the produced material instantaneously swells in an anisotropic way due to the rigidity gradient, resulting in reproducible bending actuations. Besides, it is shown that the percolating network of electrically conductive MWCNTs offers the possibility of implementing these bilayers as solvent detector sensors. This opens the door to the development of multi-responsive devices with tunable actuating behaviors and potential application in the robotics field as self-deployable structures in different environments (water, organic solvents, etc.).

Catégories
extrusion

Ultra-stretchable ionic nanocomposites: from dynamic bonding to multi-responsive behavior

Ultra-stretchable ionic nanocomposites: from dynamic bonding to multi-responsive behavior

J. Odent, J.-M. Raquez, Ph. Dubois and E. P. Giannelis

Abstract :  Although multi-responsive materials have the potential to revolutionize a wide spectrum of technologies, the design of systems that combine a range of responses to a variety of different external changes without the associated property trade-offs has remained elusive. We herein demonstrate a new family of multi-responsive nanocomposites that leverage the dynamic and reversible nature of electrostatic interactions present in ionic systems with the reinforcement ability of nanoparticles in nanocomposites. This new design leads to a unique property profile that combines simultaneous improvements in stiffness, toughness and extensibility. In addition to their exceptional stretchability, the new, ionic nanocomposites exhibit unique strain-dependent behavior (i.e.the deformation increases with increasing strain rates) and return to the normal state after deformation including shape-memory and scratch recovery.

Catégories
extrusion

Multiresponsive Shape Memory Blends and Nanocomposites Based on Starch

Multiresponsive Shape Memory Blends and Nanocomposites Based on Starch

Sessini V, Raquez JM, Lo Re G, Mincheva R, Kenny JM, Dubois P, Peponi L

Abstract :  Smart multiresponsive bionanocomposites with both humidity- and thermally activated shape-memory effects, based on blends of ethylene-vinyl acetate (EVA) and thermoplastic starch (TPS) are designed. Thermo- and humidity-mechanical cyclic experiments are performed in order to demonstrate the humidity- as well as thermally activated shape memory properties of the starch-based materials. In particular, the induced-crystallization is used in order to thermally activate the EVA shape memory response. The shape memory results of both blends and their nanocomposites reflect the excellent ability to both humidity- and thermally activated recover of the initial shape with values higher than 80 and 90%, respectively.

Catégories
extrusion

Healing by the Joule effect of electrically conductive poly(ester-urethane)/carbon nanotube nanocomposites†

Healing by the Joule effect of electrically conductive poly(ester-urethane)/carbon nanotube nanocomposites†

B. Willocq, R. K. Bose, F. Khelifa, S. J. Garcia, Ph. Dubois and J.-M. Raquez

Abstract :  Recent demands for polymers with autonomous self-healing properties are being constantly raised due to the need for high-performance and reliable materials. So far, the advances in this field are limited to the production of self-healing materials requiring a high energy input. Therefore there is an urgent need to develop self-healing polymer systems, in which healing can be easily and specifically induced by external stimuli for economical and viable applications. In the current work we demonstrate, for the first time to our knowledge, the possibility to heal local macroscopic damage by a confined temperature increase arising from the Joule effect. The damage healing is promoted by the resistance to an electrical current at the crack tip. This new concept is studied on thermo-reversible and electrically conductive poly(ester-urethane)/carbon nanotube nanocomposites derived from thermo-reversible Diels–Alder reactions between furfuryl- and maleimide-functionalized poly(ε-caprolactone) (PCL)-based precursors. Electrically conductive materials are then obtained after incorporating multi-walled carbon nanotubes into the thermo-reversible networks using reactive extrusion. Under mild electrical conditions, temperature in the range of the retro-Diels–Alder reaction can be obtained near the damaged site. The obtained results reveal the potential of this new approach for healing materials locally while maintaining the overall material properties.