Experimental Investigation on Ablation Behaviors of CFRP Laminates in an Atmospheric Environment Irradiated by Continuous Wave Laser.

In order to understand the ablation behaviors of CFRP laminates in an atmospheric environment irradiated by continuous wave laser, CFRP laminates were subjected to a 1080-nm continuous wave laser (6-mm laser spot diameter), with different laser power densities carried out in this paper. The internal delamination damage in CFRP laminates was investigated by C-Scan. The rear- and front-face temperature of CFRP laminates were monitored using the FLIR A 655 sc infrared camera, and the rear-face temperature was monitored by K type thermocouples. The morphology of ablation damage, the area size of the damaged heat affected zone (HAZ), crater depth, thermal ablation rate, mass ablation rate, line ablation rate, etc., of CFRP laminates were determined and correlated to the irradiation parameters. It is found that the area size of the damage HAZ, mass ablation rate, line ablation rate, etc., increased as the laser power densities. The dimensionless area size of the damaged HAZ decreased gradually along the thickness direction of the laser irradiation surface.

3D printable, tough, magnetic hydrogels with programmed magnetization for fast actuation.

Magnetic hydrogels have demonstrated great potential in soft robots, drug delivery, and bioengineering, and their functions are usually determined by the deforming capability. However, most magnetic hydrogels are embedded with soft magnetic particles (e.g. Fe3O4), where the magnetic domains cannot be programmed and retained under external magnetic fields. Here, we present a strategy to prepare a microgel-reinforced magnetic hydrogel, embedded with hard magnetic NdFeB particles. These magnetic hydrogels show outstanding mechanical properties (ultimate stretching ratio >15 and fracture toughness >15 000 J m-2) and fast actuation speed under external magnetic fields. We use direct ink writing to fabricate magnetic hydrogels with sophisticated geometry and program their magnetization to achieve complex deformations. Fast, reversible, shape-changing structures have been demonstrated with printed magnetic hydrogels. It is hoped that this material system of hard magnetic hydrogels can open opportunities for wide applications.

Shape Morphing of Hydrogels in Alternating Magnetic Field.

Shape-morphing hydrogels have found a myriad of applications in biomimetics, soft robotics, and biomedical engineering. A magnetic field is favorable for specific applications of hydrogels, since it is noncontact and biocompatible at high field strengths. However, most magnetosensitive shape-morphing structures are made of elastomers rather than hydrogels because the magnetization of magnetic hydrogels is usually too low to be actuated under a static magnetic field. Here, we propose a strategy to achieve the shape morphing of magnetic hydrogels. We actuate magnetothermal sensitive hydrogels by an alternating magnetic field (AMF), where magnetic poly( N-isopropylacrylamide) hydrogels can be heated by the AMF and can undergo giant volume shrinkage under high temperature. We design the distributing pattern of magnetic hydrogel strips on an elastomer substrate to realize various two-dimensional and three-dimensional shapes such as heart-shape, truss, tube, and helix. Complex three-dimensional origami structures have been demonstrated using elastomer-magnetic hydrogels as hinges. We further demonstrate the combination of magnetic navigation and magnetic shape morphing, by applying both a direct magnetic field and an alternating magnetic field. The strategy may open new opportunities for the shape morphing of functional hydrogels.