This work presents a single-nozzle/bi-extrusion FDM technology featuring two material inputs and heating sections connected with a mixing device with a reinforced mixing mechanism. The device ensures uniform mixing of materials, consistent print quality, and functionality, while an air-cooling system allows printing with materials having different solidification temperatures. Trials with six Dryflex TPEs demonstrated precise regulation of material flows, enabling dynamic adjustment of material blends and creation of multiple functionalities in one product. The technology also creates functionally graded materials (FGMs) in transition zones, improving interlayer adhesion and mechanical performance. This advancement enhances production flexibility, efficiency, and product quality, and expands material availability for additive manufacturing.

Accurate and traceable measurements of transmittance haze are required for quality control in various different industries, such as optoelectronics, automobiles, and agriculture. Transmittance haze is defined as the fraction of light transmitted through a material that deviates from the incident beam by more than 2.5∘. Various documentary standards specify the use of an integrating sphere with a prescribed geometry for the measurement of transmittance haze. This paper uses goniometric measurements of the bidirectional transmittance distribution function (BTDF) to calculate transmittance haze according to the definition and demonstrates that the sphere-based realisation of transmittance haze specified in the documentary standards does not agree with the definition, with the difference being up to 20% for some samples. The BTDF measurements are also used to simulate the integrating sphere haze, allowing the sensitivity of the sphere haze to errors in the integrating sphere geometry to be calculated. 

ZD-tester is a measurement technique for rapid compression in Z-direction. The strain rate of compression of this device is far beyond the ordinary mechanical testing methods applied in papermaking industries. Thus, it provides insights to the material responses which are relevant to industrial applications, e. g. calendaring, printing, etc where the strain rate ranges from hundreds to thousands per second. A physics model that describes the dynamic process of the probe has been developed, where a linear Maxwell model is used to account for the viscoelasticity of paperboard. The simulation has successfully reproduced both the general features and quantitative details of the experiment. The model reveals that the ratio of the elastic modulus to the viscosity modulus of the material governs the amplitude attenuation while the angular frequency of the striking-rebounding cycle depends mainly on the elastic modulus. The dropping height determines the initial striking velocity but has no direct impact on either attenuation or angular frequency. The model and simulation provided interpretations of both experimental observations and dynamic behaviours of the material. With help of simulation, the impacts of the individual parameters, e. g. the Young's modulus, E, the viscosity modulus, η, and the drop height, H, were also explored. 

A custom-made prosthetic product is unique for each patient. Fossil-based thermoplastics are the dominant raw materials in both prosthetic and industrial applications; there is a general demand for reducing their use and replacing them with renewable, biobased materials. A transtibial prosthesis sets strict demands on mechanical strength, durability, reliability, etc., which depend on the biocomposite used and also the additive manufacturing (AM) process. The aim of this project was to develop systematic solutions for prosthetic products and services by combining biocomposites using forestry-based derivatives with AM techniques. Composite materials made of polypropylene (PP) reinforced with microfibrillated cellulose (MFC) were developed. The MFC contents (20, 30 and 40 wt%) were uniformly dispersed in the polymer PP matrix, and the MFC addition significantly enhanced the mechanical performance of the materials. With 30 wt% MFC, the tensile strength and Young´s modulus was about twice that of the PP when injection molding was performed. The composite material was successfully applied with an AM process, i.e., fused deposition modeling (FDM), and a transtibial prosthesis was created based on the end-user’s data. A clinical trial of the prosthesis was conducted with successful outcomes in terms of wearing experience, appearance (color), and acceptance towards the materials and the technique. Given the layer-by-layer nature of AM processes, structural and process optimizations are needed to maximize the reinforcement effects of MFC to eliminate variations in the binding area between adjacent layers and to improve the adhesion between layers. © 2020 by the authors.

A theoretical framework of nip dynamics of conventional printing, including dynamic models deducted from nip geometry,printing speed, and physics laws, is proposed. Different from previous works, the present work focuses at obtaining the nippressure from a given nip geometric setting, the common way in full-scale printing. The effects of viscoelastic characteristicsof paper substrate and print form (rubber and/or polymer) on the nip pressure, which become pronounced in a full-scale printingprocess due to high speed, are accounted and illustrated by three physical models, e.g., Maxwell model, Kelvin–Voigtmodel, and Burgers model. Details of the nip dynamic features, shape, amplitude, duration, and effective nip width, etc.,have been worked out. The viscoelastic nature of the materials was found to be responsible for the so-called speed-hardening,asymmetric nip profile, variations in the nip amplitude and effective nip width, etc. It was also found that how the viscoelasticproperties of the materials affect the nip dynamics depend on the how the elastic components and the viscos count parts areconnected with each other. The framework is applicable to calendaring, gravure, offset, and flexography.

The outset of realistic rendering is a desire to reproduce the appearance of the real world. Rendering techniques therefore operate at a scale corresponding to the size of objects that we observe with our naked eyes. At the same time, rendering techniques must be able to deal with objects of nearly arbitrary shapes and materials. These requirements lead to techniques that oftentimes leave the task of setting the optical properties of the materials to the user. Matching the appearance of real objects by manual adjustment of optical properties is however nearly impossible. We can render objects with a plausible appearance in this way but cannot compare the appearance of a manufactured item to that of its digital twin. This is especially true in the case of translucent objects, where we need more than a goniometric measurement of the optical properties. In this survey, we provide an overview of forward and inverse models for acquiring the optical properties of translucent materials. We map out the efforts in graphics research in this area and describe techniques available in related fields. Our objective is to provide a better understanding of the tools currently available for appearance specification when it comes to digital representations of real translucent objects.

Under specular reflection, non-isotropic halftones such as line halftones printed on an ink-receiving plastic layer superposed with a metallic layer change their colors upon in-plane rotation of the print. This color change is due to the orientation-dependent optical dot gain of the halftone. A strong dot gain occurs when the incident light is perpendicular to the halftone line structure. A color prediction model is proposed which predicts under specular reflection the color of cyan, magenta and yellow line halftones as a function of the azimuthal rotation angle, the incident angle and the line frequency. The model is calibrated by measuring 17 reflectances at the (25 : 25) measurement geometry, with the incident light parallel to the halftone lines. The model has been tested for several azimuthal rotation and incident viewing angles, each time for 125 different cyan, magenta and yellow ink surface coverages.

Highly conductive ink with low sintering temperature is important for printed electronics on paper substrate. Silver nanoparticles (Ag NPs) of different average radii ranging from 48 to 176 nm were synthesized by adjusting the Ag+ concentration in the reaction process. The electric resistivity of the Ag NP-based ink film in relation to Ag NP size, sintering temperature, amount of PVP capping agent on Ag NP surface, and morphology evolution of the film during heating process was investigated. It was found that the resistivity of the films reduced very rapidly with increasing particle size due above all to reduced amount of protective agent capping on the Ag NPs. A semi-empirical relationship between the resistivity and the particle size was proposed. With the help of this mathematical expression, one gains both systematic and detailed insight to the resistivity evaluation with regard to the Ag particle size. The optimal electric resistivity of 4.6 μΩ cm was achieved at 140 °C for 10 min which was very close to the resistivity value of bulk Ag (1.58 μΩ cm). Mechanical flexibility of the printed electronics with the Ag NP-based ink on paper substrates was investigated. The prints on the art coated paper exhibited better flexibility compared to that on the photopaper. This might be attributed to the surface coating composition, surface morphology of the paper, and their corresponding ink absorption property. © 2019, The Author(s).

 For the first time in the Bioeconomy research program at RISE, corrugatedboard has an own research area. Research is building around the main driving forcesin the corrugated board value chain like e-commerce, improved box performance anddigital printing. The main weakness of corrugated board, its moisture sensitivity, isalso addressed.These main driving forces and weaknesses of corrugated board are mirrored in thethemes of this large research program area:Fibre sorption and deformation mechanismsFundamental knowledge on the mechanisms behind moisture sorption and deformation on fibre level is developed to increase moisture and creep resistance throughmodification of paper materials. State of the art methods for characterization ofthe fibre ultra- and nano-structure such as Fourier transform infra-red spectroscopy(FTIR), small angle X-ray scattering (SAXS), and wide angle X-ray scattering (WAXS)give new insights on mechanisms and clarify effects of moisture as well as chemicalmodifications.Papermaking for improved base sheetsConcepts that are explored are fibre-based strength additives produced with novelrefining techniques, and modified ZD-profiles in the sheet for better mechanical properties.Box mechanicsMechanical performance of structures such as corrugated board boxes can be predicted through physically based mathematical modelling by taking the behaviour ofthe constituent materials as well as the geometry into account. Appropriate materialmodels for the corrugated board are identified and finite element models for simulation of corrugated board packaging performance are developed.Tool for inkjet printability on corrugatedThere is a genuine need for improved inkjet printability on corrugated materials thanksto rapid development in e-commerce as well as digitalization along the corrugatedvalue chain. Effective measurement methods and knowledge around ink-substrateinteractions are developed to enable board producers and converters to have effective product development and predictable printability on not only liners but also oncorrugated materials.

Patterning technology on the paper based on wettability difference for paper-based devices has attracted significant attention for its low cost, easy degradability, and high flexibility. Here, conductive lines are rapidly prepared by patterned wettability-assisted bar-coating for low cost paper-based circuits. It is found that 7 s plasma treatment time for acquiring wettability difference is optimal, which resulted in not only effective splitting of the liquid film but also highly consistent line width with mask. Moreover, low retention force of hydrophobic surface is imperative for self-confinement of the ink into hydrophilic areas, especially for ink with high solid content. The sheet resistance of patterns can reach 5 Ω ◻ −1 after 980 nm laser sintering when using 50 wt% solid content ink with 110 cP viscosity. The geometries of line patterns, i.e., line width and spacing, can be readily tuned by varying the designed size of mask patterns. As-prepared conductive patterns show good conductivity even after 500 bending cycles at 2 mm bending radius. It is believed that this study will provide deeper understanding of wettability difference-assisted patterning process and represents a general strategy for selective wetting, especially for high viscosity ink.