Matthias Busse

Surface biofunctionalization and production of miniaturized sensor structures using aerosol printing technologies

The work described in this paper demonstrates that very small protein and DNA structures can be applied to various substrates without denaturation using aerosol printing technology. This technology allows high-resolution deposition of various nanoscaled metal and biological suspensions. Before printing, metal and biological suspensions were formulated and then nebulized to form an aerosol which is aerodynamically focused on the printing module of the system in order to achieve precise structuring of the nanoscale material on a substrate. In this way, it is possible to focus the aerosol stream at a distance of about 5 mm from the printhead to the surface. This technology is useful for printing fluorescence-marked proteins and printing enzymes without affecting their biological activity. Furthermore, higher molecular weight DNA can be printed without shearing. The advantages, such as printing on complex, non-planar 3D structured surfaces, and disadvantages of the aerosol printing technology are also discussed and are compared with other printing technologies. In addition, miniaturized sensor structures with line thicknesses in the range of a few micrometers are fabricated by applying a silver sensor structure to glass. After sintering using an integrated laser or in an oven process, electrical conductivity is achieved within the sensor structure. Finally, we printed BSA in small micrometre-sized areas within the sensor structure using the same deposition system. The aerosol printing technology combined with material development offers great advantages for future-oriented applications involving biological surface functionalization on small areas. This is important for innovative biomedical micro-device development and for production solutions which bridge the disciplines of biology and electronics.

Cloud-Based Automated Design and Additive Manufacturing: A Usage Data-Enabled Paradigm Shift

Integration of sensors into various kinds of products and machines provides access to in-depth usage information as basis for product optimization. Presently, this large potential for more user-friendly and efficient products is not being realized because (a) sensor integration and thus usage information is not available on a large scale and (b) product optimization requires considerable efforts in terms of manpower and adaptation of production equipment. However, with the advent of cloud-based services and highly flexible additive manufacturing techniques, these obstacles are currently crumbling away at rapid pace. The present study explores the state of the art in gathering and evaluating product usage and life cycle data, additive manufacturing and sensor integration, automated design and cloud-based services in manufacturing. By joining and extrapolating development trends in these areas, it delimits the foundations of a manufacturing concept that will allow continuous and economically viable product optimization on a general, user group or individual user level. This projection is checked against three different application scenarios, each of which stresses different aspects of the underlying holistic concept. The following discussion identifies critical issues and research needs by adopting the relevant stakeholder perspectives.

AlSi7 metallic foams – aspects of material modelling for crash analysis

Metallic foam samples of matrix alloy AlSi7 have been produced and mechanically tested under quasi-static and dynamic load. Model parameters for the Deshpande–Fleck and the ABAQUS ‘crushable foam’ material model were determined covering a density of 0.3–0.8 g/cm3. Yield surface determination uses uniaxial hydrostatic compression test results, extended by tensile test results for the latter model. Strain hardening was described on the basis of uniaxial compression by fitting a Rusch model to the experimental data, deriving its parameters as function of density. The predictive capabilities of the parameterised models were evaluated using experimental data gathered for load cases characterised by superimposed uniaxial and hydrostatic compression. Analyses show good agreement between simulation and experiment. Further uniaxial compression tests performed at varying strain rates over 4 orders of magnitude revealed no significant strain rate dependency of material properties and thus qualify the material model parameters determined for crash simulation.

INKtelligent printing® for sensorial applications

Purpose – The purpose of this paper is to highlight INKtelligent printed sensor structures using maskless depositition technologies.Design/methodology/approach – This paper begins with a general introduction to INKtelligent printing®. Starting with layout and ink development, the fabrication of printed sensors is described in detail.Findings – Printed strain gauges, thermopiles and gas sensitive films are successfully fabricated with maskless deposition technologies, offering advantages for continuous non‐destructive measurement compared to conventional sensors.Originality/value – This paper shows a new approach for customized sensor structures. The application of a resource efficient and flexible printing technique for sensor fabrication is demonstrated.

When nothing is constant but change: Adaptive and sensorial materials and their impact on product design

This article is the preface to the Special Issue of the Journal of Intelligent Material Systems and Structures on occasion of the Symposium A53 ‘MEMS/NEMS for Sensorial and Actorial Materials’ held at the Euromat 2011 Conference, Montpellier, France, September 12-15, 2011. The authors outline the concept of material-integrated sensing and intelligence, which is summarized in the term sensorial materials. Such materials are understood to incorporate sensing, signal and data processing as well as communication facilities to autonomously evaluate their own condition and/or their environment. To achieve these capabilities, bottom-up as well as top-down approaches are currently being discussed. The latter is highlighted in this work. Research efforts towards it range from materials science to sensor and microelectromechanical system (MEMS)/nanoelectromechanical system (NEMS) technology, microelectronics and computer science and were covered in the underlying Euromat symposium. As a specific aspect linked to the envisaged autonomy and a resulting adaptivity, for example, of internal self-representation and data interpretation, potential consequences for engineering design are sketched.

Computer Based Porosity Design by Multi Phase Topology Optimization

A numerical simulation technique called Multi Phase Topology Optimization (MPTO) based on finite element method has been developed and refined by Fraunhofer IFAM during the last five years. MPTO is able to determine the optimum distribution of two or more different materials in components under thermal and mechanical loads. The objective of optimization is to minimize the components elastic energy. Conventional topology optimization methods which simulate adaptive bone mineralization have got the disadvantage that there is a continuous change of mass by growth processes. MPTO keeps all initial material concentrations and uses methods adapted from molecular dynamics to find energy minimum. Applying MPTO to mechanically loaded components with a high number of different material densities, the optimization results show graded and sometimes anisotropic porosity distributions which are very similar to natural bone structures. Now it is possible to design the macro‐ and microstructure of a mechanical component...

Hydrothermal synthesis and humidity sensing property of ZnO nanostructures and ZnOIn(OH)3 nanocomposites

Prism- and raspberry-like ZnO nanoparticles and ZnO-In(OH)(3) nanocomposites were prepared by template free hydrothermal method. XRD investigations and microscopic studies showed that pill-like In(OH)(3) particles with body-centered cubic crystal structure formed on the surface of ZnO nanoparticles resulting in increased specific surface area. TEM-EDX mapping images demonstrated that not only nanocomposite formation took place in the course of the synthesis, but zinc ions were also built into the crystal lattice of the In(OH)(3). However, only undoped In(OH)(3) was found on the surface of the pill-like particle aggregates by XPS analyses. The raspberry- and prism-like ZnO particles exhibit strong visible emission with a maximum at 585 and 595 nm, respectively, whose intensity significantly increase due to nanocomposite formation. Photoelectric investigations revealed that photocurrent intensity decreased with increasing indium ion concentration during UV light excitation, which was explained by increase in visible fluorescence emission. QCM measurements showed that morphology of ZnO and concentration of In(OH)(3) had an influence on the water vapor sensing properties.

Metal Foams with Advanced Pore Morphology (APM)

In many applications metal foam is used as light weight filler material e.g. to improve energy absorption, to reduce body sound/vibration or simply to act as lightweight core layer for increased bending performance of sandwiches. In this paper the Advanced Pore Morphology (APM) process particularly developed for these applications is described. The APM process is based on the powder metallurgical foaming process. The APM approach separates foam expansion from part shaping. Complex shaped APM foam parts are made from numerous small volume standard geometry foam elements, which are joined in a separate step e.g. by adhesive bonding. Producing small volume standard geometry foam elements is a simple and robust process. As a result, each APM foam element has a homogeneous pore morphology. By using different types of foam elements and joining processes new degrees of freedom in the adjustment of properties are opened. In a first test series APM foam parts and filled extrusion profiles have been characterized. Test results are displayed and discussed. Due to the bulk character fully automated APM foam mass production in (customized) standard equipment (handling, belt furnace, etc.) is possible. The APM approach allows for maximum flexibility and fast technology transfer. One type of foam element can be used for various different foam parts. End-users are able to produce foam filled structures without any metal foam expansion know how. After supply of adhesive coated (but non tacky) foam elements, e.g. from Fraunhofer IFAM, the end-user pours the foam elements into the cavity to be APM foam filled. The APM filling is finished by heat treatment at e.g. 200 °C, which activates and cures the adhesive coating. In total the APM process leads to drastically reduced production costs especially for metal foam fillings in hollow structures.

New electrical connection technology for microsystems using inktelligent printing ® and functional nanoscaled INKS

A new electrical connection technology for highly miniaturized systems based on functional printing has been studied. INKtelligent printing® with its ability to print structures in micrometer size uses electrically conductive inks with functional nanoparticles to provide MEMS devices with electrical contacts. Due to large dimensions of conventional packaging technologies like flip chip or wire bonding, INKtelligent printing® will dramatically increase size of assembled systems. Here, an aerosol beam technology - also known as Maskless Mesoscale Material Deposition (M3D®) or Aerosol Jet® - is presented. Tests have been done to characterize conductivity, contact resistance, long term stability and temperature dependency as also applications with flow sensors.

Mechanical characterization of integral aluminum-FRP-structures produced by high pressure die-casting

Due to the growing demand for light-weight solutions in a wide range of industrial sectors, the selection and combination of different materials is becoming more and more important. As a result, there is an increasing need for suitable joining technologies. In a new joining process, flexible glass fiber textiles are integrated into aluminum by high pressure die casting in the first production step. These structures are used for the electrochemical insulation between aluminum and carbon fiber textiles, which are connected in the subsequent production step by textile technology. The finished compound is formed in a final resin impregnation process. Challenges faced by Fraunhofer IFAM lie in the positioning, pre-tensioning, and infiltration of the glass fiber textiles in the high pressure die-casting process. The advantage of this joining technology, in addition to the electrochemical insulation between aluminum and carbon fibers, is in a slim and light-weight connection. Therefore, no thickening of the individual joining partners is necessary, and the force flow lines are not deflected. Within mechanical investigations of those hybrid structures it was determined, that the infiltration content of aluminum has only a small influence on the achievable tensile strength. Rather, casting parameters such as the holding pressure have an influence. The subsequent resin infusion process enables an additional infiltration by the resin system of fiber bundles that have been only slightly infiltrated with aluminum. As a result, additional adhesion can be achieved and the infiltration gaps can be closed. Furthermore, an influence on the achievable tensile strength was observed regarding the use of the fiber material. Further increases in tensile strengths were also observed by adapting the textile parameters (e.g. reduction of the fiber undulations). A variety of failure behaviors could be observed in dependence on textile and process parameters. Tensile strength of the hybrid structures was compared to reference samples made of glass fiber reinforced epoxy resin, to determine the loss of strength caused by the joining technology. Further investigations were carried out, including a fracture surface analysis using a scanning electron microscope. Thus it was possible to determine mechanisms of adhesion between encapsulated glass fibers and the surrounding aluminum matrix.