Heat pipes are highly efficient passive thermal conductors in which heat is transported by evaporation and condensation of a working fluid. The main applications for heat pipes result from their basic properties: Cooling of electronics due to the high thermal conductivity (with small size), thermal management in satellites due to the robustness and the passive, maintenance-free operating principle, and the creation of isothermal conditions, e.g. in accurate furnaces. The manufacturing of heat pipes and the required porous wick structures by Laser Powder Bed Fusion (PBF-LB/M) can be highly advantageous. The goal of this study is to gain a better understanding of the manufacture of additively produced heat pipes. In particular, the interactions in the generation of targeted porosity by a) varying the PBF-LB/M process parameters and b) using lattice structures will be investigated and both approaches will be evaluated. In systematic experiments, porous test specimens are fabricated according to both approaches and characterized using the statistical design of experiments method. The properties relevant for heat pipes can be predicted by the derived regression models. Heat pipes are fabricated with selected parameter sets and the transferred heat flow is measured. The functionality of the additively manufactured heat pipes using PBF-LB/M is demonstrated.

The demand for effective cooling solutions for modern data processing units in confined spaces such as systems-on-chips (SoCs) for self-driving applications is increasing due to the enhanced performance of modern electronics. Additive manufacturing allows for the production of cooling pipes with integrated heat sink structures that are not manufacturable with traditional methods.

This study compares the effectiveness of heat sink geometries based on triply-periodic minimal surface (TPMS) and conventional pin-fin structures for liquid-cooled SoCs used in autonomous driving platforms. Thermal and fluid mechanical properties of the heat sinks are investigated through CFD simulations. The results demonstrate that, with the same boundary conditions, some TPMS-based heat sinks can dissipate more heat than their counterparts with conventional pin fins, while still staying within the allowed pressure drop range. A disadvantage of the tubes made entirely of copper is the high thermal load from the environment, which additionally stresses the chips. Therefore, this study also discusses further improvements for optimizing heat dissipation.

Material extrusion-based additive manufacturing (MEX-AM) processes have enabled the fabrication of multi-material structures. Commercially available 3D printers already consist of more than two extruders to print structures with different materials. However, the fabrication of structures with both actuation and sensing (ActSense), in one single process by MEX-AM has been scarcely explored. In this work, we use a multi-material extrusion-based additive manufacturing process to couple magnetic actuation and strain-sensing into one additively manufactured structure. The ActSense multi-functional structure was achieved with a composite based on styrenic block copolymer type thermoplastic elastomer (TPE), soft ferromagnetic and carbon filler particles. For comparison, elastomeric structures were printed with a composite comprising TPE and soft ferromagnetic filler particles only. To achieve improved efficiency, 30 vol% of carbonyl iron particles (CIP) were mixed with the elastomeric matrix. Owing to the fact that CIP and carbon black filler have different densities and a conductive network must be achieved, 15 vol% of each CIP and carbon filler was added to realize the ActSense composites. Morphing membranes with an elastomeric substrate and integrated ActSense elements were analyzed with an additively manufactured custom test setup based on a laser displacement sensor and an electromagnet. With the customized test setup a magnetic field was applied, and the deformation of the soft structure was analyzed. Due to the low deformation range, the change in resistance was small, and a diminished piezoresistive behavior of the self-sensing, magnetic composites was obtained. Thereby, to detect the small deformation, a piezoresistive sensing element was extruded separately on top of the magnetoactive part. With this approach, a change in relative resistance at low deformation could be successfully determined. As established by the results, the customized electromagnet-laser sensor setup is an interesting tool for the investigation of soft magnetic materials and structures for shape morphing structures.