3D printed modular Bouligand dissipative structures with adjustable mechanical properties for gradient energy absorbing

Three-dimensional(3D)printing allows for the creation of complex,layered structures with precise micro and macro architectures that are not achievable through traditional methods.By designing 3D structures with geometric precision,it is possible to achieve selective regulation of mechanical properties,enabling efficient dissipation of mechanical energy.In this study,a series of modular samples inspired by the Bouligand structure were designed and produced using a direct ink writing system,along with a classical printable polydimethylsiloxane ink.By altering the angles of filaments in adjacent layers(from 30◦to 90◦)and the filament spacing during printing(from 0.8 mm to 2.4 mm),the mechanical properties of these modular samples can be adjusted.Compression mechanical testing revealed that the 3D printed modular Bouligand structures exhibit stress-strain responses that enable multiple adjustments of the elastic modulus from 0.06 MPa to over 0.8 MPa.The mechanical properties were adjusted more than 10 times in printed samples prepared using uniform materials.The gradient control mechanism of mechanical properties during this process was analyzed using finite element analysis.Finally,3D printed customized modular Bouligand structures can be assembled to create an array with Bouligand structures displaying various orientations and interlayer details tailored to specific requirements.By decomposing the original Bouligand structure and then assembling the modular samples into a specialized array,this research aims to provide parameters for achieving gradient energy absorption structures through modular 3D printing.

Bio-inspired smart surface to achieve controllable locomotion through adjustable anisotropic friction

Anisotropic friction generated by microstructured surfaces is crucial for performing functions such as directional locomotion and adhesion in biological systems.Hence,an epoxy-based shape memory polymer(SMP)incorporating Fe_(3)O_(4) nanoparticles is used in this study to create a smart surface with oriented structures to mimic anisotropic friction and exploit human-developed controllable locomotion systems.Applying the specific properties of the epoxy-based SMP,fast switching friction can be achieved by adjusting the topography and stiffness of the microstructures on the surface.In addition,the photothermogenesis effect of Fe_(3)O_(4) nanoparticles induces changes in the asymmetric topography and stiffness on the SMP surface under the irradiation of near-infrared(NIR)light,thereby inducing a rapid switching of the friction force.Furthermore,a microbot is created to demonstrate remotely controlled locomotion,such as unidirectional and round-trip movements,and braking by switching the friction force under NIR light.These results are promising for the design of new intelligent surfaces and interfaces;additionally,they may facilitate the investigation of biological structures and processes.