3D Printing of Magnetoresponsive Polymeric Materials with Tunable Mechanical and Magnetic Properties by Digital Light Processing

Abstract

nanocomposites [12][13][14][15] -have been investigated for a broad variety of applications, from micro-and soft-robotics [10,[16][17][18] to biomedicine. [19][20][21][22][23][24] Among the different strategies, an accessible pathway to fabricate stimuli-responsive (4D) printed objects consists in magnetizing a soft-polymer by loading the polymeric matrix with magnetic fillers, such as particles of magnetite (Fe 3 O 4 ) or neodymium-iron-boron (NdFeB). [25][26][27][28][29][30][31] Direct ink writing (DIW) and fused filament fabrication (FFF) have been used to fabricate fast responding actuators, [32][33][34][35][36][37][38][39][40] inks containing high loads of magnetic fillers [41] and 2D planar structures that exploit folding and unfolding processes. [42] Additionally, 3D printed permanent magnets were developed. [43][44][45][46][47][48] However, both DIW and FFF present some drawbacks: first in terms of resolution; second in terms of the dispersion of the fillers, that may lead to nonhomogeneous magnetic response; and third in terms of temperature of processing, which could be not compatible with the fillers. [48,49] For the last one, the temperature can be decreased using some additives, however this approach may affect the mechanical performances of devices. [41] An alternative to DIW and FFF is digital light processing (DLP). This vat polymerization 3D printing technology involves the use of photosensitive (liquid) resins which are able to cure (i.e., to solidify) upon irradiation with a suitable light source. In DLP, a digital light projector (digital micromirror device) illuminates a photocurable resin with a 2D pixel pattern allowing the curing of single slices of the 3D object. [50][51][52] The aforementioned drawbacks associated to DIW and FFF can be overcome by the use of DLP. Indeed: (i) the printing resolution in DLP belongs to the pixel dimensions and it is generally higher than DIW and FFF, [53,54] (ii) in DLP the dispersion of the fillers is easier to control since liquid formulations are used; and (iii) the fabrication process generally occurs at room temperature. Nevertheless, two precautions must be taken into account: first, the increase of the content of nanoparticles may affect the photopolymerization process since they compete with the photoinitiator in absorbing the incident radiation; and second, the dispersion of the fillers must be stable for the whole printing procedure in order to print an object whose response is homogeneous to an external input. For the latter, macroscopic sedimentation, segregation, and spatial inhomogeneity must be avoided.Digital light processing is used for printing magnetoresponsive polymeric materials with tunable mechanical and magnetic properties. Mechanical properties are tailored, from stiff to soft, by combining urethane-acrylate resins with butyl acrylate as the reactive diluent. The magnetic response of the printed samples is tuned by changing the Fe 3 O 4 nanoparticle loading up to 6 wt%. Following this strategy, magnetoresponsive active components ar...

Multifunctional magnetic soft composites: a review

“…Digital light processing (DLP) is a printing method where photo-curable materials are exposed to a light pattern and crosslinked layer by layer. For DLP printing of magnetically responsive soft materials, resins with magnetic fillers can be selectively exposed to light source under a controllable magnetic field, programming magnetization during printing [ 95 , 108 – 111 ]. The flexibility to print structures with both in-plane and out-of-plane magnetizations helps realize functional actuators shown in figure 3(d) [ 95 ].…”

Multiacrylated Cyclodextrin: A Bio‐Derived Photocurable Macromer for VAT 3D Printing

“…The accurate selection of each chemical compound allows the easy tailoring of structural and functional properties of the 3D printed parts. [4][5][6][7][8][9][10] 3D printing has been recognized as a revolutionary technology that can transform the conventional concept of manufacturing [11] but looking at the current scenario, a lot of challenges still need to be overcome protocol the synthesis of a multisubstituted cyclodextrin as reactive photocurable macromer. Ac-γ-CDs were prepared following a synthetic route already reported in a previous work, [31] using acryloyl chloride as functionalizing agent (Figure 1a).…”

Building Magnetoresponsive Composite Elastomers for Bionic Locomotion Applications

“…A small amount of spray solution, farther airbrush-substrate distance, and weak external magnetic field led to the generation of small diameter and pillar height. Rather, when increasing the amount of spray solution, shortening the (e) 2D structure could be able to create a 3D cube when exposed to a magnetic field [86] . airbrush-substrate distance, enhancing the applied magnetic field, larger diameter and micropillar height would generate.…”

“…The magnetic composite ink they prepared was composed of silicone rubber and NdFeB magnetizable microparticles. Lantean et al [86] printed the optimized formulations, where urethane-acrylate resins, Fe 3 O 4 nanoparticles, and butyl acrylate were used to tune viscosity as the diluent, into magnetic responsive samples using digital light processing. These 3D-printed magnetic samples have spring, wheel, sphere, flower, cone and planar structure, whose movements could be controlled by an external magnetic field (Fig.…”