Functional nanoscaled inks for printed electronics

The ability of printing technologies to create complex geometries from a wide range of materials makes them suitable for the production of both passive and active components, including resistors, inductors, capacitors, filters, micro-batteries and micro-antennae. Printing conductive paths can be combined with other processes, i. e. thickening via galvanic deposition to achieve conducts that carry higher current. Some printed features from Fraunhofer IFAM are shown. Summarizing, the key to innovative applications is the creation of functionality in printed structures via nanoscale design of materials that would at the same time improve the deposit adhesion during a suitable thermal treatment. Entnommen aus TEMA</a

Effect of SiC particles on the laser sintering of Al-7Si-0.3Mg alloy

The direct laser sintering of Al-7Si-0.3Mg/SiC composites was studied. It is shown that the densification rate obeys first-order kinetics. The rate constant is found to increase at low SiC fractions but abruptly decreases at larger than about 5 vol%. In the presence of ceramic particles, the melt track becomes more stable and a more continuous sintered surface is obtained. Meanwhile, significant reaction occurs between the aluminum melt and the reinforcement particles, leading to formation of Al4SiC4 and silicon particles. The solidification microstructure is also altered. Entnommen aus TEMA</a

Direct laser sintering of aluminum matrix composites

In the present work, we used direct metal laser sintering (DMLS) process to fabricate Al-SiC composite parts directly from a three-dimensional CAD model. Al-7Si-0.3Mg powders were blended with various amounts of SiC particles (5, 10, 15, 20 vol%) at two different sizes (7 and 17 m) and subjected to direct laser sintering using a 200 W continuous wave CO2 laser beam at various scan rates. The densification and microstructural features of the laser-sintered parts were studied. It is shown that the highest density is obtained for the Al alloy-5% SiC (7 m) composite powder. The melt stability is also found to be improved in the presence of SiC particles. The microstructure of the laser-sintered parts composed of -Al, primarily silicon, SiC, and Al4SiC4 three dimensional plates. This paper presents the advantages and barriers of using DMLS for the fabrication of complex-shaped parts from Al matrix composite powders

Highly porous titanium scaffolds for orthopaedic applications

For many years, the solid metals and their alloys have been widely used for fabrication of the implants replacing hard human tissues or their functions. To improve fixation of solid implants to the surrounding bone tissues, the materials with porous structures have been introduced. By tissue ingrowing into a porous structure of metallic implant, the bonding between the implant and the bone has been obtained. Substantial pore interconnectivity, in metallic implants, allows extensive body fluid transport through the porous implant. This can provoke bone tissue ingrowth, consequently, leading to the development of highly porous metallic implants, which could be used as scaffolds in bone tissue engineering. The goal of this study was to develop and then investigate properties of highly porous titanium structures received from powder metallurgy process. The properties of porous titanium samples, such as microstructure, porosity, Young's modulus, strength, together with permeability and corrosion resistance were investigated. Porous titanium scaffolds with nonhomogeneous distribution of interconnected pores with pore size in the range up to 600 pm in diameter and a total porosity in the range up to 75% were developed. The relatively high permeability was observed for samples with highest values of porosity. Comparing to cast titanium, the porous titanium was low resistant to corrosion. The mechanical parameters of the investigated samples were similar to those for cancellous bone. The development of high-porous titanium material shows high potential to be modern material for creating a 3D structure for bone regeneration and implant fixation

Printed capacitive sensors for contactless ice detection in automotive liquid conveyor pipes

This publication focuses on the development of an innovative, low-cost sensor for the detection of ice formation in conveyor pipes of vehicles. The measurement principle is based on the contactless determination of the relative permittivity of a medium by capacitive sensors. In comparison to water, ice has a decreased relaxation frequency through crystallization below the freezing point. Capacitive sensor structures for permittivity measurement were applied on a polymer pipe by functional printing, which can be installed in the conveying systems in the area of the feed lines. Due to its low-cost and universal design, the sensor can be used in all applications where the integrability and costs of an installed sensor system play a major role

New materials and applications by 3D-printing for innovative approaches

Three-dimensional printing belongs to the additive manufacturing processes in which powder materials are deposited in layers and selectively joined with binder from an ink-jet print head. The parts are generated directly from CAD-data using polymers, metals or ceramics. The process chain for parts manufacturing can be tailored depending on the uses of the end product. For the manufacture of near net shape products, e.g. complex tools with conformal cooling channels, the printed green parts can either be subjected to a liquid phase sintering step or to a partial sintering without shrinkage of green parts and a subsequent infiltration with low melting alloys to achieve full density. This interesting approach enables the use of new materials for example in medicine, where a titanium-silver composite was developed in order to decrease the magnetic susceptibility of Ti6Al4V, while maintaining its favorable properties. Alternatively, porous parts can also be produced by means of 3D printing, making possible the manufacture of custom parts, such as implants, with an open porosity for improving the bone growth. In this paper, the suitability and implementation of 3D-Printing for small scale series production are presented and discussed

Customized Smartness: A survey on links between additive manufacturing and sensor integration

In many areas, Additive Manufacturing (AM) has made the decisive steps from prototyping to true manufacturing technology. AM processes excel based on aspects like outstanding geometrical flexibility and lack of tooling, which allows significant lead time reductions both in initial product design and in case of design adaptations. However, in production today, most of these advantages are realized based on homogeneous materials. Attempts at advancing the state of the art address the topic of material combinations and functionally graded materials. The challenges faced by such approaches differ in their level of severity, and are influenced in this respect by the actual AM process chosen. Beyond composites with spatially varying properties, the next level of complexity is the integration of geometrically defined 3D structures within the volume of a part, and specifically functional structures at that. Endeavours of the latter kind are currently receiving increased attention under headlines like “Structural Electronics” or “3D Electronics Printing”. Here, the surface or volume integrated structure typically is a sensor or electronic system. Beyond this system, the AM process then either provides a complex 3D substrate and thus addresses the packaging issue and/or replaces a conventional PCB, or it generates an engineering component directly and closely integrates it with electronic and sensor systems. So far, the backbone of most solutions realized have been hybrid production systems that integrate different manufacturing processes in a single piece of equipment. The present work provides a brief introduction to the various AM techniques and discusses a disambiguation based on their general capability of producing functional structures on a volume integration level. A classification of such structures is suggested that accounts for their level of complexity in relation to the typical, layer-wise manufacturing scheme adopted in AM. Examples stemming from a global research landscape are discussed in the context of this classification. In this, two special foci are selected reflecting related activities at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials (Fraunhofer IFAM): One of these is a combination of manufacturing processes, with functional printing and other direct write techniques linked to AM processes in a dedicated manufacturing cell. The other addresses integration of pre-fabricated electronic components like RFID systems into metal components produced by means of selective laser melting (SLM).The study closes with an overview of future research trends towards producing components with integrated electronics. In doing so, special emphasis is given to AM techniques that allow for in-process switching of materials and thus have the potential of realizing complex systems not by combination of processes, but within the boundaries of a single process. Also addressed are potential application scenarios that profit specifically from the combination of AM and sensor integration