Scientists at Harvard University have developed a method to shape-shift 4D-printed structures that could one day help heal wounds and be used in robotic surgical tools. To reach this point they mimicked the behavior of orchids, calla lilies and other flowers, especially how they bend and twist.
Using this new biometric 4D print technique, natural plant structures were manufactured, and deformed when shooting liquid into a pre-defined shape. The team of researchers combined a specially made hydrogel containing cellulose fibers, using complex mathematical models. This hydrogel is the same kind of material used to make soft contact lenses and it swells up when immersed in water. The composite ink the team uses acts like liquid through the printhead, however it can rapidly solidify once printed.
“This work represents an elegant advance in programmable materials assembly, made possible by a multidisciplinary approach. We have now gone beyond integrating form and function to create transformable architectures” said study co-senior author Jennifer Lewis, a materials scientist at Harvard University. The team of researchers then noticed that they could make their 4D-printed structures behave in more complex ways by using hydrogels that react to external factors (such as light, heat and acidity) and replacing the cellulose fibers with other rigid rods, such as electrically conductive bars.
The new method could be applied in the field of electronics and robotics, biomedical or even smart clothing. The hydrogel, for example, could be combined with other materials to give simple objects electrical conductivity. “It is wonderful to be able to design and realize, in an engineered structure, some of nature’s solutions” said Mahadevan, an expert on botanics behaviors, to the Harvard Gazette. “By solving the inverse problem, we are now able to reverse-engineer the problem and determine how to vary local inhomogeneity, i.e., the spacing between the printed ink filaments, and the anisotropy, i.e., the direction of these filaments, to control the spatiotemporal response of these shape-shifting sheets”.
Source: Harvard Gazette