Healable, memorizable, and transformable lattice structures made of stiff polymers

Abstract

Emerging transformable lattice structures provide promising paradigms to reversibly switch lattice configurations, thereby enabling their properties to be tuned on demand. The existing transformation mechanisms are limited to nonfracture deformation, such as origami, instability, shape memory, and liquid crystallinity. In this study, we present a class of transformable lattice structures enabled by fracture and shape-memory-assisted healing. The lattice structures are additively manufactured with a molecularly designed photopolymer capable of both fracture healing and shape memory. We show that 3D-architected lattice structures with various volume fractions can heal fractures and fully restore stiffness and strength over two to ten healing cycles. In addition, coupled with the shape-memory effect, the lattice structures can recover fracture-associated distortion and then heal fracture interfaces, thereby enabling healing of lattice wing damages, mode-I fractures, dent-induced crashes, and foreign-object impacts. Moreover, by harnessing the coupling of fracture and shape-memory-assisted healing, we demonstrate reversible configuration transformations of lattice structures to enable switching among property states of different stiffnesses, vibration transmittances, and acoustic absorptions. These healable, memorizable, and transformable lattice structures may find broad applications in next-generation aircraft panels, automobile frames, body armor, impact mitigators, vibration dampers, and acoustic modulators.

Sticky Rouse Time Features the Self-Adhesion of Supramolecular Polymer Networks

“…As a result of these r-bonds, supramolecular polymers can repair fracture or damage at the molecular or microscopic scale and restore their mechanical strength at the macroscopic scale. These polymers have been applied to a wide range of engineering applications, including flexible electronics, energy storage devices, biomaterials, soft robotics, and lattice structures …”

“…These polymers have been applied to a wide range of engineering applications, including flexible electronics, 11 energy storage devices, 12 biomaterials, 13 soft robotics, 14 and lattice structures. 15 Considering their versatility, it is of paramount importance to study their required healing time and recovered interfacial strength for fractured supramolecular polymers. However, due to different r-bonds and polymer chains used in experiments, the reported characteristic healing times cover a wide range of values from a few seconds to a few days.…”

Photosynthesis-assisted remodeling of three-dimensional printed structures

“…While the field of engineered photosynthesis shows a promising capability in producing energy fuels (31,32), the current work extends the concept to advanced materials, by introducing a downstream reaction mechanism to use the photosynthesis-produced glucose. Besides, the presented photocurable polymers can be used in various photopolymerization-based 3D-printing systems, such as stereolithography (12,13), polyjet (26), photopolymer waveguides (33), two-photon lithography (7,34), continuous liquid production (35), and volumetric lithography (36,37). To this end, the communication between living photosynthesis and synthetic 3Dprintable polymers may open doors for hybrid synthetic-living materials with both complex architectures and biomimetic properties.…”

“…Second, since the photosynthesis-produced glucose is expected to consume free NCO groups to form additional cross-links, the concentration reduction of free NCO groups can reveal the occurrence of the cross-linking reaction. To indicate the concentration of free NCO groups within the polymer matrix, we employ a Fourier transform infrared (FTIR) spectrometer to measure the transmittance of the sample around 2,260 cm −1 that is corresponding to the NCO bond-stretching vibration (13). We find an evident peak at 2,260 cm −1 in the initial state of all three sample groups ( Fig.…”

“…The acrylate groups can be utilized for the photopolymerizationbased 3D printing (such as stereolithography), because the acrylate groups allow for a photoinitiated addition reaction to polymerize the resin (SI Appendix, Fig. S3) (12,13). The printing is rapid with a speed of 75-400 μm/s, and the resolution can reach as…”