For soft robotics and programmable metamaterials, novel approaches are required enabling the design of highly integrated thermoresponsive actuating systems. In the concept presented here, the necessary functional component was obtained by polymer syntheses. First, poly(1,10-decylene adipate) diol (PDA) with a number average molecular weight Mn of 3290 g·mol−1 was synthesized from 1,10-decanediol and adipic acid. Afterward, the PDA was brought to reaction with 4,4′-diphenylmethane diisocyanate and 1,4-butanediol. The resulting polyester urethane (PEU) was processed to the filament, and samples were additively manufactured by fused-filament fabrication. After thermomechanical treatment, the PEU reliably actuated under stress-free conditions by expanding on cooling and shrinking on heating with a maximum thermoreversible strain of 16.1%. Actuation stabilized at 12.2%, as verified in a measurement comprising 100 heating-cooling cycles. By adding an actuator element to a gripper system, a hen’s egg could be picked up, safely transported and deposited. Finally, one actuator element each was built into two types of unit cells for programmable materials, thus enabling the design of temperature-dependent behavior. The approaches are expected to open up new opportunities, e.g., in the fields of soft robotics and shape morphing.

Shape morphing implicates that a specific condition leads to a morphing reaction. The material thus transforms from one shape to another in a predefined manner. In this paper, not only the target shape but rather the evolution of the material's shape as a function of the applied strain is programmed. To rationalize the design process, concepts from informatics (processing functions, for example, Poisson's ratio (PR) as function of strain: ν = f(ε) and if‐then‐else conditions) will be introduced. Three types of shape morphing behavior will be presented: (1) achieving a target shape by linearly increasing the amplitude of the shape, (2) filling up a target shape in linear steps, and (3) shifting a bulge through the material to a target position. In the first case, the shape is controlled by a geometric gradient within the material. The filling kind of behavior was implemented by logical operations. Moreover, programming moving hillocks (3) requires to implement a sinusoidal function εy = sin (εx) and an if‐then‐else statement into the unit cells combined with a global stiffness gradient. The three cases will be used to show how the combination of mechanical mechanisms as well as the related parameter distribution enable a programmable shape morphing behavior in an inverse design process.

A NiTi shape memory alloy with the nominal composition Ni50.9Ti49.1 (at%) was processed by laser beam melting/laser powder bed fusion and the process parameters as well as the type of scanning strategy (point-like exposure) were optimized in a first step to obtain delicate lattice structures (strut diameters below 200 µm). In the second step, the lattice structures were analyzed by means of optical and electron microscopy as well as computer tomography to obtain the interrelation between the process parameters, strut diameter and the uniformity of the corresponding struts. The processing, especially the laser power and the type of point-like exposure, has a strong influence on the resulting strut diameter and, therefore, on the haptic stiffness of lattice structures and the mechanical properties (deformability, superelasticity). Unlike other approaches, our findings imply that filigree NiTi lattices with high uniformity can be manufactured on a standard industry laser powder bed fusion machine without modifying its hard- or software configuration.

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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adem.202201022.

Programmable materials are a novel development, in which specialized production processes are used to introduce a framework of information capabilities into the inner structure of materials. Since the design and fabrication of programmable materials are still challenging, this aims to introduce a design and fabrication concept to pave the way toward industrial application. Herein, complex shape morphing has been implemented in the sense that the shape changes in response to external conditions, following a predefined program. First, the feasibility of a fabrication concept for uniform metamaterials with auxetic behavior is presented. A material with a predetermined nonuniform inner structure that deforms to a symmetrical shape has been developed and fabricated according to this concept. More complex behavior can be implemented by facilitating optimization methods to find inner structures according to a target shape. Lastly, an optimized and producible design for asymmetrical shape morphing is described to demonstrate the applicability of the approach.

An optimal design for a programmable material based on an array of unit-cells is established. A programmable material behavior is achieved by using unit-cells with complex and adjustable features arising from the inner structure of each cell. This type of materials has the potential of replacing the functionality of entire systems consisting of sensors and actuators, provided that an optimal inner structure is given. In this paper the multiscale optimization problem and a solution strategy are presented. An efficient data driven method is used for the solution of the macroscopic boundary value problem. Finally, an example of an optimized parameter distribution for a unit-cell based material is shown.