Lars Schönemann

Force Controlled Grinding of Ceramic Materials

Brittle materials like ceramics or glass can be machined by cutting with negative rake angles and by abrasive machining processes. Especially grinding allows for low surface roughness and high shape accuracy. Conventional path-controlled grinding processes may damage functional surfaces if brittle fracture occurs and may thus lead to lateral, radial and axial cracks. High grinding forces can be a reason for brittle fracture when grinding ceramic materials. A solution for this effect may be the application of force controlled grinding processes. In this paper adapted control algorithms were implemented for force controlled grinding and verified in grinding experiments. As an example, cylindrical grooves were ground with an injection moulded spherical grinding tool in alumina and zirconia ceramics. After grinding surface roughness, shape accuracy and process forces are analysed and discussed.

Micro Chiseling of Retroreflective Arrays

Diamond Micro Chiseling (DMC) has been established as a machining process for generating miniaturized retroreflective arrays with structure sizes in the micrometer range. This chapter focuses on a comprehensive overview on principles, process performance, and optimizations of DMC for generating micro fullcube retroreflectors on planar surfaces. Furthermore, considerations and initial results for transferring DMC to the machining of curved and freeform surfaces will be shown. L. Schönemann (*) · E. Brinksmeier Laboratory for Precision Machining LFM, Leibniz Institute for Materials Engineering IWT, Bremen, Germany MAPEX Center for Materials and Processes, University of Bremen, Bremen, Germany e-mail: schoenemann@lfm.uni-bremen.de; brinksmeier@iwt.uni-bremen.de # Springer Nature Singapore Pte Ltd. 2018 J. Yan (ed.), Micro and Nano Fabrication Technology, Micro/Nano Technologies, https://doi.org/10.1007/978-981-10-6588-0_1-2 1

Microstructuring of Surfaces for Bio-Medical Applications

In recent years microfluidic devices became of great interest, as they offer a wide range of bio-analytical and fluid processing applications through the utilization of size effects. Especially a mass manufacturing of disposable polymeric microfluidic devices by hot embossing or injection molding is expected to have high economic potential. It is known, that channels and areas showing a localized change in wettability can considerably improve fluid processing tasks like mixing or droplet generation. Chemical approaches, like the polymerization of lauryl acrylate, were successfully shown to achieve hydrophobic coatings for micro channels but are not suitable for a mass manufacturing. Since microstructures are known to provide water repellent properties of surfaces, this paper focuses on the applicability of diamond grooving and Diamond Micro Chiseling (DMC) processes for the manufacture of microstructured areas in brass molds inserts, in order to achieve hydrophobic properties of their replica. Major design features of structures, like a height range of 6 to 16μm or aspect ratios in between 0.5 and 3.2 are derived from the natural example of the lotus leaf. Molding is carried out by using a two component silicone filler. The performance of the replicated hydrophobic surfaces is evaluated by droplet contact angle measurements. After presenting methodology and results, the paper will conclude on how to transfer the investigated microstructuring methods to the manufacture of mold inserts for the replication of polymeric microfluidic chips with localized hydrophobic areas and channels.

Mold Structuring by Diamond Machining

This chapter will discuss the state of the art and advances in the development of dedicated processes for mold structuring by diamond machining with defined cutting edge geometry. The advantages and disadvantages of the individual processes, e.g. the achievable geometry spectrum or the required machining time, will be discussed. Particular attention will be given to the Diamond Micro Chiseling (DMC) process which was developed within the SFB/TR4 for structuring molds with discontinuous prismatic microstructures. Utilizing a novel tool kinematics and custom built V-shaped diamond tools, this process enables the machining and replication of such structures in optical quality.