The Application of a Multi-Material Flexible Chain Mail for the Design of an Artificial Spinal Disc to Reproduce Natural Nonlinear and Anisotropic Rotational Behavior.

Inspired by the potential of architected materials for achieving biomimicking functionalities and the advancement of multi-material additive manufacturing to fabricate parts with complex structures and heterogeneous material distributions, this study investigates the feasibility of using a multi-material, flexible chain mail sheet for the design of an additively manufactured artificial spinal disc for reproducing patient-specific anisotropic and nonlinear rotational behaviors. The application of a chain mail-based structure is motivated by its similarities in behaviors compared with a natural disc's fiber network that likewise has negligible bending stiffness and shape-changing ability. The proposed approach for the chain mail sheet design includes an initial characterization of the uniaxial tensile responses of the chain mail unit cell defined as the basic building block of the chain mail sheet, modeling and response calculation, and material optimization. Results show that the additively manufactured chain mail sheet is not only able to exhibit a natural strain-stiffening rotational response but also is able to reproduce natural anisotropy of three natural disc specimens in the six most common rotational scenarios in daily life. This study shows the potential of additively manufactured mechanical-metamaterials-inspired structures for implant design to restore natural mechanics.

Auxetic structures used in kinesiology tapes can improve form-fitting and personalization.

Each year 65% of young athletes and 25% of physically active adults suffer from at least one musculoskeletal injury that prevents them from continuing with physical activity, negatively influencing their physical and mental well-being. The treatment of musculoskeletal injuries with the adhesive elastic kinesiology tape (KT) decreases the recovery time. Patients can thus recommence physical exercise earlier. Here, a novel KT based on auxetic structures is proposed to simplify the application procedure and allow personalization. This novel KT exploits the form-fitting property of auxetics as well as their ability to simultaneously expand in two perpendicular directions when stretched. The auxetic contribution is tuned by optimizing the structure design using analytical equations and experimental measurements. A reentrant honeycomb topology is selected to demonstrate the validity of the proposed approach. Prototypes of auxetic KT to treat general elbow pains and muscle tenseness in the forearm are developed.

Dataset of angular and compressive responses of biomimetic artificial spinal discs fabricated using multi-material additive manufacturing.

To explore the influence of different biomimetic designs and multi-material additive manufacturing on the performance of a multi-material artificial spinal disc (ASD) in terms of restoring natural mechanics, four biomimetic ASD designs together with a control design are first fabricated using a Stratasys Connex3 Objet500 inkjet-based, multi-material 3D printer and their mechanical responses are measured using in-vitro mechanical testing. The mechanical tests include an angular test and a compression test to measure the ASD's behavior in the seven most frequent loading scenarios of a spine: flexion, extension, left/right lateral bending, left/right axial rotation, and compression. The angular test is performed using a custom six degrees of freedom, computer-controlled spine testing system together with an optoelectronic motion analysis system, while the compression test is performed using an Instron testing machine. The presented dataset includes 3D models of the five ASD designs, and raw data of the angular and compressive responses at different strain rates of the five ASD designs. This dataset is related to the article "Exploration of the influence of different biomimetic designs of 3D printed multi-material artificial spinal disc on the natural mechanics restoration" where the detailed designs and load responses of the five multi-material ASDs are presented (Yu et al., 2021). This dataset helps to gain insights into the influence of different biomimetic design concepts on the mechanics of a multi-material ASD and serves as a reference for the future design of multi-material ASDs.

Exploring the property space of periodic cellular structures based on crystal networks.

The properties of periodic cellular structures strongly depend on the regular spatial arrangement of their constituent base materials and can be controlled by changing the topology and geometry of the repeating unit cell. Recent advances in three-dimensional (3D) fabrication technologies more and more expand the limits of fabricable real-world architected materials and strengthen the need of novel microstructural topologies for applications across all length scales and fields in both fundamental science and engineering practice. Here, we systematically explore, interpret, and analyze publicly available crystallographic network topologies from a structural point of view and provide a ready-to-use unit cell catalog with more than 17,000 unique entries in total. We show that molecular crystal networks with atoms connected by chemical bonds can be interpreted as cellular structures with nodes connected by mechanical bars. By this, we identify new structures with extremal properties as well as known structures such as the octet-truss or the Kelvin cell and show how crystallographic symmetries are related to the mechanical properties of the structures. Our work provides inspiration for the discovery of novel cellular structures and paves the way for computational methods to explore and design microstructures with unprecedented properties, bridging the gap between microscopic crystal chemistry and macroscopic structural engineering.