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Complex-shaped TiC x ceramic preforms with a gradient of carbon content in the titanium carbide phase (x changes from 0.7 to 0.98) were fabricated for the first time by Binder jet 3D printing technology. The complex-shaped preforms were infiltrated with molten carbon steel (0.7 wt.%C). Thermodynamic considerations showed that carbon could be transferred from titanium carbide to steel and vice versa according to the initial concentration of carbon (activity) in both phases. After infiltration, solidification and slow cooling, a microstructural gradient was obtained throughout the steel matrix from ferrite, in the region where the steel was in contact with titanium carbide of low carbon content (x=0.7), to pearlite, in the region where the steel underwent interactions with stoichiometric titanium carbide (x=0.98). After annealing at 900°C and quenching in oil, a structural gradient in the steel matrix from ferrite to martensite was obtained, resulting in a hardness gradient of 700-1600 HV. The suggested processing approach allows for fabrication of complex-shaped graded composites with the desired property gradient suitable for a wide range of practical applications.

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3D printing has seen much progress in recent decades with the introduction of new materials and printing techniques. This article describes the combination of a novel, stereolithography (SLA) based method for structural material buildup with laser induced forward transfer (LIFT) printing of conductive and resistive elements and placement of commercial active and passive components for the additive manufacturing of 3D functional electronic devices. The structural material is composed of dry film photoresists that are exposed and laminated to form a stack which is later developed to remove unexposed area and reveal the desired free form shape. Interconnection using pillar penetration between the structural layers is described in detail. Several examples of functional objects (lamp, microphone) demonstrate the practicality of this novel, multi material printing method.

A method is described where 3D electronic devices are fabricated using a hybrid printing approach which combines several steps: Top illumination stereolithography (SLA); Laser induced forward transfer (LIFT) printing of conductive materials; Placement of active and passive components and their electrical interconnection by a non-contact, metal LIFT process. By applying this approach, free-form 3D functional electronic structures could be manufactured by a single hybrid tool. The adhesion of LIFT printed metal droplets onto various organic substrates of interest for device fabrication was investigated. The results suggest two possible approaches for improved adhesion by either printing at elevated surface temperature or surface roughening by laser pre-treatment. The resulting track resistivities were found to be in the range of x5-10 higher than bulk copper resistivity. We present several exemplary printed devices with different complexities and functionalities as demonstrators of the proposed hybrid technology.