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 M_n 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.

4D printing of shape memory polymers enables the production of thermoresponsive objects. In this contribution, a facile printing strategy is followed for an in‐house synthesized thermoplastic poly(ether urethane). Processing by means of fused filament fabrication, in which the difference between nozzle temperature and material‐specific glass transition temperature of the polymer is kept as low as possible, allows to obtain highly shrinkable objects whose shape and thermoresponsiveness can be precisely controlled. The effectiveness of the method also applies to the printing material polylactic acid. One possible application lies in highly shrinkable objects for assembly purposes. As proof‐of‐concept, lightweight hands‐free door openers for healthcare applications are functionally simulated and developed. Once printed, such devices shrink when heated to fit on door handles, allowing an easy assembly. At the end‐of‐use, a heating‐initiated disassembling and mechanical recycling are proposed. In perspective, a reuse of the materials in 4D printing can contribute to the emergence of a circular economy for such highly functional materials.

Shape memory polymers (SMPs) are stimuli-responsive materials, which are able to retain an imposed, temporary shape and recover the initial, permanent shape through an external stimulus like heat. In this work, a novel manufacturing method is introduced for thermoresponsive quick response (QR) code carriers, which originally were developed as anticounterfeiting technology. Motivated by the fact that earlier manufacturing processes were sometimes too time-consuming for production, filaments of a polyester urethane (PEU) with and without dye were extruded and processed into QR code carriers using fused filament fabrication (FFF). Once programmed, the distinct shape memory properties enabled a heating-initiated switching from non-decodable to machine-readable QR codes. The results demonstrate that FFF constitutes a promising additive manufacturing technology to create complex, filigree structures with adjustable horizontal and vertical print resolution and, thus, an excellent basis to realize further technically demanding application concepts for shape memory polymers.

Shape-memory polymers can be used to develop thermoresponsive programmable materials that can take on sensory and actuator tasks as their ambient temperature changes. In this contribution, a self-synthesised poly(1,10-decylene adipate) diol-based polyester urethane (PEU) was used for their fabrication. After processing the PEU into filaments, programmable materials, including a gear-like object, the teeth of a ‘bevel gear’ and a unit cell, were additively manufactured by fused filament fabrication. In any case, a thermomechanical treatment was conducted that involved the deformation of the polymer at 75°C. After cooling to 15°C, the programmable materials were unloaded and the thermoresponsiveness between 23°C and 58°C was investigated. A maximum thermoreversible change in height of about 39% was detected for the ‘gear’. With regard to the ‘bevel gear’, proof of feasibility was provided for use as overheating protection, so that a force transmission could be switched off when heated and switched on when cooled down. The unit cell actuated under a weak external load of 0.01 N, thus exhibiting thermoreversible length changes of about 45%.

Although several force application concepts are known that can be used to deform shape memory polymers (SMPs) within the scope of programming, controlled deformation is challenging in the case of samples with a cylinder-like shape, which need to be homogeneously compressed starting from the lateral surface. To solve this problem, this contribution follows a material approach that takes advantage of four-dimensional (4D) printing. Fused filament fabrication (FFF) was used as an additive manufacturing (AM) technique to produce a thermoresponsive tool in a cylindrical shape from a polyether urethane (PEU) having a glass transition temperature (T_g) close to 55 °C, as determined by differential scanning calorimetry (DSC). Once it was 4D-printed, a sample of laser cut polyester urethane urea (PEUU) foam with a cylindrical wall was placed inside of it. Subsequent heating to 75 °C and keeping that temperature constant for 15 min resulted in the compression of the foam, because the internal stresses of the PEU were transferred to the PEUU, whose soft segments were completely molten at 65 °C as verified by DSC. Upon cooling to −15 °C and thus below the offset temperature of the soft segment crystallization transition of the PEUU, the foam was fixed in its new shape. After 900 days of storage at temperatures close to 23 °C, the foam recovered its original shape upon reheating to 75 °C. In another experiment, a 4D-printed cylinder was put into hibernation for 900 days before its thermoresponsiveness was investigated. In the future, 4D-printed tools may be produced in many geometries, which fit well to the shapes of the SMPs to be programmed. Beyond programming SMP foams, transferring the forces released by 4D-printed tools to other programmable materials can further expand technical possibilities.

This paper introduces a morphing surface concept based on thermally switchable auxetic unit cells for adaptive aerodynamic applications. The structure combines a flexible membrane made of thermoplastic polyurethane (TPU) with a Polyethylene Terephthalate Glycol-modified (PETG)-based auxetic lattice, embedded with resistive heating wires using the Wire Encapsulating Additive Manufacturing (WEAM) process. Upon heating, the stiffness of the auxetic cells is significantly reduced, enabling pneumatic deformation. Once cooled, the structure retains its shape due to the thermomechanical properties of the materials. Finite element simulations and mechanical testing confirm that geometric parameters, particularly arm width, strongly influence stiffness. Switching factors of up to 32 were achieved. A demonstrator featuring 60 active cells validated the concept, demonstrating reversible shape changes and programmable deformation without the need for mechanical actuators. The system offers a scalable and energy-efficient solution for morphing surfaces in automotive, aerospace, and soft robotics applications.