3D Printing of Soft Magnetoactive Devices with Thiol‐Click Photopolymer Composites

Abstract

Magnetoresponsive polymers have gained increased attention in the design of soft actuators as they can be spatially as well as temporally activated and enable an external noninvasive control of movement. By introducing the magnetoresponsive properties in photocurable resins, one can fabricate personalized and complex structures (via vat photopolymerization 3D printing), whose movement can be conveniently controlled by an external magnetic field. Advancing from acrylate-based photopolymers, which often suffer from shrinkage stress, low monomer conversion, and oxygen inhibition, the fabrication of magnetoresponsive thiol-click photopolymers containing Fe 3 O 4 nanoparticles as magnetic fillers is highlighted. The addition of the thiol crosslinker yields soft and flexible polymer composites, whose cure kinetics, viscosity, thermal, and mechanical properties are studied as a function of the thiol and filler content. Although cure rate and final monomer conversion decrease with rising filler concentration, the cure kinetics is reasonably fast at 6 wt%. The short pot life, a result of thiol-Michael reactions induced by Fe 3 O 4 nanoparticles, and a high thiol content, are overcome by the addition of an appropriate stabilizer. As proof of concept, 3D structures are fabricated by digital light processing (DLP) 3D printing and their magnetically driven movement is demonstrated.

Digital light processing 3D printing of dynamic magneto-responsive thiol-acrylate composites

“…In another study we showed that this stabilizer is also able to catalyze transesterification reactions due to its Brønsted acidity. 35 Herein, we exploited this feature to print magneto-active composites with additional functions such as thermo-activated mendability.…”

“…41 On the other hand, coordinative bonds might be formed between the Fe 3 O 4 nanoparticles and the unreacted thiol groups, which anchor the ller to the photopolymer matrix. 35 In the presence of the organic phosphate, the photopolymer composites are able to undergo thermo-activated dynamic bond exchange reactions across the functional -OH and ester groups (transesterication). The change in the viscoelastic properties was studied by rheometer experiments.…”

“…So and exible polymer composites were obtained by DLP 3D printing with 6 wt% of Fe 3 O 4 nanoparticles at a reasonable build time. 35 Herein, we extended the functionality of 3D printable magneto-responsive thiol-acrylate composites by introducing an additional healing and re-shaping function. In particular, we exploited thermo-activated bond exchange reactions following catalyzed transesterication to induce a material ow above the networks topological freezing temperature.…”

“…Soft and flexible polymer composites were obtained by DLP 3D printing with 6 wt% of Fe 3 O 4 nanoparticles at a reasonable build time. 35…”

Amino acid-based polyphosphorodiamidates with hydrolytically labile bonds for degradation-tuned photopolymers

“…The novel APdA monomers were then subject to photopolymerization with a stoichiometric ratio with the commonly used trithiol (1,1,1-tris-(hydroxymethyl)-propanetris-(3-mercaptopropionate) (TMPMP). Similar systems have been widely studied with organic alkynes 25,26 , acrylates 27,28 and vinyl esters 29 for the preparation of photopolymers for a range of biomaterials applications. The monomer conversion (MC) was analysed by RT-FTIR spectroscopy, in which the reaction was followed by a decrease in the alkyne band at 2130 cm -1 (Figure 2b, full spectrum SI-16).…”