The aim of our research was to investigate and optimise the main 3D printing process parameters that directly or indirectly affect the shape transformation capability and to determine the optimal transformation conditions to achieve predicted extent, and accurate and reproducible transformations of 3D printed, shape-changing two-material structures based on PLA and TPU. The shape-changing structures were printed using the FDM technology. The influence of each printing parameter that affects the final printability of shape-changing structures is presented and studied. After optimising the 3D printing process parameters, the extent, accuracy and reproducibility of the shape transformation performance for four-layer structures were analysed. The shape transformation was performed in hot water at different activation temperatures. Through a careful selection of 3D printing process parameters and transformation conditions, the predicted extent, accuracy and good reproducibility of shape transformation for 3D printed structures were achieved. The accurate deposition of filaments in the layers was achieved by adjusting the printing speed, flow rate and cooling conditions of extruded filaments. The shape transformation capability of 3D printed structures with a defined shape and defined active segment dimensions was influenced by the relaxation of compressive and tensile residual stresses in deposited filaments in the printed layers of the active material and different activation temperatures of the transformation.

This study identifies the optimal combination of active and passive thermoplastic materials for producing multi-material programmable 3D structures. These structures can undergo shape changes with varying radii of curvature over time when exposed to hot water. The research focuses on examining the thermal, thermomechanical, and mechanical properties of active (PLA) and passive (PRO-PLA, ABS, and TPU) materials. It also includes the experimental determination of the radius of curvature of the programmed 3D structures. The pairing of active PLA with passive PRO-PLA was found to be the most effective for creating complex programmable 3D structures capable of two-sided transformation. This efficacy is attributed to the adequate apparent shear strength, significant differences in thermomechanical shrinkage between the two materials, identical printing parameters for both materials, and the lowest bending storage modulus of PRO-PLA among the passive materials within the activation temperature range. Multi-material 3D printing has also proven to be a suitable method for producing programmable 3D structures for practical applications such as phone stands, phone cases, door hangers, etc. It facilitates the programming of the active material and ensures the dimensional stability of the passive components of programmable 3D structures during thermal activation.

The main goal of the research was to optimize printing conditions for printing UHF RFID antennas and from different recycled papers select the most appropriate printing substrate. In the research coated and uncoated recycled papers and conductive printing ink from two producers were analysed. UHF RFID antennas were printed using semi-automatic screen printing device. Properties of printing substrates and prints were determined with the standardized testing methods for paper and graphic products, further electrical properties and operability of UHF RFID antennas were checked. The research has confirmed, that recycled papers could be applied as printing substrates for printed electronics. Characteristics of recycled papers, which are important for good interaction with the conductive printing ink and proper functionality of printed electronics were determined.

This article presents two methods of colour printing on programmable 3D structures and their use for practical applications in everyday life. The colour printing was done by direct printing with a flatbed UV inkjet printer and indirect printing by thermally transferring the electrophotographic toner to the 3D printed object produced with the most widely used and affordable material extrusion 3D printing technology. The print quality of the colour reproductions was determined by basic densitometric and spectrophotometric measurements, ink adhesion analysis and image analysis of the printed graphic elements. The research was also extended to the field of 4D printing, where 3D printed objects with flat geometry can be subsequently transformed when exposed to a suitable activation medium. In this case, the direct printing process was used for colour printing, as it allows printing on both sides of the programmable 3D structures compared to the indirect printing process. The advantage of colour printing on a programmed 3D structure is that the flat geometry can be easily printed with colour graphics on the entire surface and later transformed into a new 3D object shape, whereas conventional 3D objects cannot be printed in very inaccessible places due to their geometry. These methods, which use direct or indirect printing techniques to create coloured reproductions on 3D-printed objects, enable the personalisation and aesthetic enhancement of products and can also provide additional interactivity if, for example, QR codes or RFID tags are included. The research focuses on the production of colour-printed smart objects for consumer products

The field of 3D and 4D printing is advancing rapidly, offering new ways to control the transformation of programmable 3D structures in response to external stimuli. This study examines the impact of 3D printing parameters, namely the UV ink thickness (applied using a UV inkjet printer on pre-3D-printed programmable structures) and thermal activation, on the dimensional and surface changes to high-stress (HS) and low-stress (LS) programmable samples and on print quality. The results indicate that HS samples shrink in the longitudinal direction, while expanding in terms of their height and width, whereas LS samples exhibit minimal dimensional changes due to lower programmed stress. The dynamic mechanical analysis shows that UV ink, particularly cyan and CMYK overprints, reduces the shrinkage in HS samples by acting as a resistive layer. Thicker ink films further reduce the dimensional changes in HS samples. Thermal activation increases the surface roughness of HS structures, leading to the wrinkling of UV ink films, while LS structures are less affected. The surface gloss decreases significantly in HS structures after UV ink application; however, thermal activation has little impact on LS structures. UV ink adhesion remains strong across both HS and LS samples, suggesting that UV inks are ideal for printing on programmable 3D structures, where the colour print quality and precise control of the shape transformation are crucial.

4D printing is the process through which a 3D printed object or primitive is transformed into another structure under the influence of external energy input such as temperature, light or other extertal stimuli. The 4th dimension is the time in which the primitive changes its appearance. In most cases, the shape changes. We call this a self-assembly or self-transformation process. In the process of printing a primitive, capable of transforming themselves from one shape to another, we often encounter combinations of one or two thermoplastic materials that have different thermal and physico-mechanical properties. The printed primitive is transformed where the active element is contained. The active element is the basic building block of the self-transforming primitive. For this purpose, it is necessary to choose the appropriate combination of thermoplastic materials, to determine the length of the active element and the number of layers of which it is composed. For the printing of the active element two thermoplastic materials can be selected which differ from each other in their thermal transitions and physico-mechanical properties. The process of transformation under the influence of elevated temperature should be carried out in such a way that the printed primitive is heated above the temperature of the glass transition that the material used on the active elements has. This releases the residual stresses created during the printing process and causes the active material to shrink. In this way, a primitive can be transformed from a flat shape to a final 3D shape. This shape is then maintained by controlled cooling below the glass transition temperature of the active element. In this paper the first research results of the primitive transformation were presented. The appropriate combination of materials and the optimal temperature of the water as external stimuli were determined, and finally the primitives’ shape recovery. In the research we used the active element which consists of a single layer of flexible, elastic thermoplastic material (passive material) and three layers of thermoplastic materials with the properties of shape memory polymers (active material). For printing we used the multitool 3D printer ZMorph which is based on Fused Deposition Modeling (FDM) technology.