Dr-Ing. Lars Schönemann 

Leibniz-Institut für Werkstofforientierte Technologien IWT, Germany

Review on the manufacture of multiscale structured surfaces

Nature is full of examples for structured surfaces that serve a specific function, such as diffractive patterns for color effects on butterfly wings, structures that impact the adhesion of the surface to other media like on the feet of a Gecko or features that alter the surface’ friction like on a shark skin, to name only a few. The inherent challenge of manufacturing these kinds of surfaces on technical products is that complex functions or combinations of different functions typically require a multiscality of the structural elements, e.g. hierarchically stacked structures of different shapes and sizes ranging across serval orders of magnitude.

After giving a short intoduction to functionalities that are achievable by structured surfaces, this keynote presentation will give an overview on the recent state of the art of manufacturing processes with regard to their capability of generating multiscale structured surfaces. For comparing different technologies with each other, their achievable “multiscality” will be assessed by the ratios of lateral and vertical extent of the structures. Furthermore, not only single step processes will be considered, but particular attention will also be given to multi-step and multi-physics approaches that are currently under research and development and could potentially become relevant in the future.

Biography

Lars Schönemann graduated from the University of Bremen with a Bachelor’s degree in Systems Engineering in 2006 and a Master’s degree in the same field in 2008. Since 2007 he is working as a research engineer at the Laboratory for Precision Machining LFM, a department of the Leibniz Institute for Materials Engineering in Bremen, Germany. He obtained his doctorate (Dr.-Ing.) in 2014 for his work on Diamond Micro Chiseling of prismatic optical microstructures and since then is head of the Junior Research Group “Economic Ultra-Precision Machining – speedUP” at the LFM.

His research focuses on ultra-precision machining processes, especially for generating functional surfaces, as well as mechatronic system development and digitalization. He has experience in managing large-scale national and international projects, such as the German research unit FOR1845 “Ultra-precision high performance cutting” (2014-2020) or the European H2020-project “ProSurf – High Precision Process Chains for the Mass Production of Functional Structured Surfaces“. He published more than 50 papers and presented his work at several euspen conferences, topical meetings, CIRP conferences and ASPE annual meetings.

Prof. Erwin Peiner

TU Braunschweig, Germany

Semiconductor nanowire arrays for energy harvesting – fabrication and characterization

More than half of the worldwide produced energy is wasted and rejected to the environment. Semiconductor nanowire (NW) arrays are a subset of the class of nanomaterials, which can help to recover such waste energy from power generation, transportation, industrial processes, etc. They outperform the properties of their bulk counterparts by, e. g., a drastically lower thermal conductivity, which is beneficial for the figure of merit of thermoelectric heat recovery. Furthermore, many semiconductors are abundant, non-toxic, and environmentally benign and can be manufactured using highly developed nanofabrication methods. Nevertheless, as one of the key factors for future commercialization of NW-based energy harvesters, traceable high-throughput nanometrological tools are indispensable.

In an international project within the European Metrology Programme for Innovation and Research different top-down and bottom-up fabrication techniques of semiconductor NW arrays, e. g., cryogenic deep reactive ion etching (cryoDRIE), metal-assisted chemical etching (MACE), and chemical bath deposition/aqueous crystal growth (CBD/ACG) shall be compared and investigated with respect to their performance in piezoelectric harvesters, thermoelectric energy generators, and solar cells. Lithography available in the cleanroom laboratories of IHT and PTB, e.g., nano imprint lithography (NIL), nano sphere lithography (NSL), and e-beam lithography (EBL) will be described as used for fabricating various semiconductor NW structures under the control of many different structure parameters such as cross-sectional shape, diameter, length, orientation, surface roughness, doping concentration, elasticity, fracture limit and piezoelectric coefficients. For characterization and control of these parameters, various methods including conventional scanning probe microscopy (SPM) and MEMS-based SPM, Müller-matrix ellipsometry (MME), scatterometry, spreading resistance microscopy (SSRM), contact resonance force microscopy (CR-FM), nanoindentation and continuous stiffness measurement (CSM) technique are required. Their potential for high-throughput nanometrology and process control will be investigated, improved and demonstrated.

Dr Adam Clare

University of Nottingham, UK

Electrochemical jet surface structuring: an overview

Electrodeposition and other electrochemical processes have been widely used in surface manufacturing, ranging from the traditional surface finishing to electrodeposition of functional materials and devices, as well as electro-machining. In recent work we have explored the use of jetted electrochemical techniques as a direct competitor for more established energy beam techniques and as a new route to arrive at complex structures at ultra-low cost. Electrochemical processes are highly dependent upon the energy bearing media (the electrolyte), the process mechanics and the characteristics of the workpiece material. Recent work has sought to explore the interplay between these in order to bring new applications to these processes.

This talk will explore three process innovations in particular. Firstly, the energy density distribution of electrolyte jets is modified through the design of nozzles which allow the manipulation of removal contours. This approach is analogous to holographic optics in laser processes where the energy distribution can be tailored within a beam. Secondly, the means by which electrochemical jets can be used as materials characterisation tool will be explored. Finally, the advances our team has made in producing the finest features by an electrochemical jet in machining will be reported.

This overview presentation will explore contributions of three completed PhD projects and introduce our commercial activity through Texture Jet Ltd.