Cold Micro Metal Forming

This open access book contains the research report of the Collaborative Research Center “Micro Cold Forming” (SFB 747) of the University of Bremen, Germany. The topical research focus lies on new methods and processes for a mastered mass production of micro parts which are smaller than 1mm (by forming in batch size higher than one million). The target audience primarily comprises research experts and practitioners in production engineering, but the book may also be of interest to graduate students alike

Material modifications due to nonlinear effects created by multiphoton absorption in single crystalline silicon

Material modification inside its bulk via high powered lasers involves much more than just heat transfer and melting of materials. It entails with it complex nonlinear physical phenomena such as multiphoton absorption, self-phase modulation, and self-focussing, amongst many others. These phenomena occur only with ultrafast lasers at very high intensities. Realising subsurface or bulk modifications in semiconductors such as silicon, opens up new avenues in the fields of optoelectronics and optical computation with the potential of increasing current computational speeds by orders of magnitude. The technology of three dimensional volume modification in materials via ultrafast lasers and nonlinear physics, is however, still in its nascent stages. This work explores the possibility of realising bulk modification in silicon and other polymers, and as well as their integration with optoelectronic devices; thus paving way for the future of optical computation

Aspheric geodesic lenses for an integrated optical spectrum analyser

Abstract available p. xiii-xi

Conference on Binary Optics: An Opportunity for Technical Exchange

The papers herein were presented at the Conference on Binary Optics held in Huntsville, AL, February 23-25, 1993. The papers were presented according to subject as follows: modeling and design, fabrication, and applications. Invited papers and tutorial viewgraphs presented on these subjects are included

A Study on the Development on Tunable Opto-Fluidic Devices by Diamond Turning and Soft Lithography

Master'sMASTER OF ENGINEERIN

Laser-induced forward transfer (LIFT) of water soluble polyvinyl alcohol (PVA) polymers for use as support material for 3D-printed structures

The additive microfabrication method of laser-induced forward transfer (LIFT) permits the creation of functional microstructures with feature sizes down to below a micrometre [1]. Compared to other additive manufacturing techniques, LIFT can be used to deposit a broad range of materials in a contactless fashion. LIFT features the possibility of building out of plane features, but is currently limited to 2D or 2½D structures [2–4]. That is because printing of 3D structures requires sophisticated printing strategies, such as mechanical support structures and post-processing, as the material to be printed is in the liquid phase. Therefore, we propose the use of water-soluble materials as a support (and sacrificial) material, which can be easily removed after printing, by submerging the printed structure in water, without exposing the sample to more aggressive solvents or sintering treatments. Here, we present studies on LIFT printing of polyvinyl alcohol (PVA) polymer thin films via a picosecond pulsed laser source. Glass carriers are coated with a solution of PVA (donor) and brought into proximity to a receiver substrate (glass, silicon) once dried. Focussing of a laser pulse with a beam radius of 2 µm at the interface of carrier and donor leads to the ejection of a small volume of PVA that is being deposited on a receiver substrate. The effect of laser pulse fluence , donor film thickness and receiver material on the morphology (shape and size) of the deposits are studied. Adhesion of the deposits on the receiver is verified via deposition on various receiver materials and via a tape test. The solubility of PVA after laser irradiation is confirmed via dissolution in de-ionised water. In our study, the feasibility of the concept of printing PVA with the help of LIFT is demonstrated. The transfer process maintains the ability of water solubility of the deposits allowing the use as support material in LIFT printing of complex 3D structures. Future studies will investigate the compatibility (i.e. adhesion) of PVA with relevant donor materials, such as metals and functional polymers. References: [1] A. Piqué and P. Serra (2018) Laser Printing of Functional Materials. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA. [2] R. C. Y. Auyeung, H. Kim, A. J. Birnbaum, M. Zalalutdinov, S. A. Mathews, and A. Piqué (2009) Laser decal transfer of freestanding microcantilevers and microbridges, Appl. Phys. A, vol. 97, no. 3, pp. 513–519. [3] C. W. Visser, R. Pohl, C. Sun, G.-W. Römer, B. Huis in ‘t Veld, and D. Lohse (2015) Toward 3D Printing of Pure Metals by Laser-Induced Forward Transfer, Adv. Mater., vol. 27, no. 27, pp. 4087–4092. [4] J. Luo et al. (2017) Printing Functional 3D Microdevices by Laser-Induced Forward Transfer, Small, vol. 13, no. 9, p. 1602553

Active optical beam shaping based on liquid crystals and polymer micro-structures

Emerging applications requiring light beam manipulation, such as high-efficiency sunlight concentrators for solar cells, switchable micro-lens arrays for autostereoscopic displays, tunable lenses for augmented reality goggles, auto-focusing spectacles, and smart contact lenses, mostly depend on one or more active optical components with the desired and controllable beam modifying functionalities, preferably manufactured at relatively low cost. Recent progress in research on components based on the combination of liquid crystals (LCs) and various polymer micro-structures is reviewed in this paper. It is found that such components can address the demands appropriately and have the potential of paving the way for large-scale applications of active optical beam shaping components

DEVELOPMENT AND APPLICATION OF ON-MACHINE SURFACE MEASUREMENT FOR ULTRA-PRECISION TURNING PROCESS

Optical freeform components, featured with high functional performance, are of enormous demand in advanced imaging and illumination applications. However, the geometrical complexity and high accuracy demand impose considerable challenges on the existing ultra-precision freeform machining technologies. Surface measurement and characterisation become the key to further improving machining performance. In order to further increase the metrology availability and efficiency, a shift in the approach of surface metrology from offline lab-based solutions towards the use of metrology upon manufacturing platforms is needed. On-machine surface measurement (OMSM) will not only allow the assessment of manufactured surfaces just-in-time without transportation and repositioning, but also provide feedback for process optimization and post-process correction with consistent coordinate frame. In the thesis, a single point robust interferometer is integrated onto a diamond turning lathe to establish the metrology-embedded ultra-precision manufacturing platform. To extract a priori information for the subsequent OMSM, a theoretical and experimental study of surface generation was carried out for ultra-precision turning of optical freeform surfaces. With the proposed machining methodology and surface generation simulation, two freeform surfaces (sinusoidal grid and micro-lens arrays) were successfully fabricated using the slow tool servo technique. The machined topography of freeform surfaces was uniformly distributed and in agreement with simulated results. Since it operates in the manufacturing environment, the machine tool effects on the OMSM were comprehensively evaluated, including on-machine vibration test, machine kinematic error mapping and linearity error calibration. A systematic calibration methodology for single point OMSM was proposed. Both theoretical and experimental investigation have been conducted to prove the validity of the proposed calibration methodology and the effectiveness of OMSM. With the aid of OMSM, potential applications were explored to exploit the integration benefits to further enhance the ultra-precision machining performance. OMSM integration will increase the automation level of the manufacturing. As OMSM preserves the coordinate system between the machining and measurement, the process investigation can be carried out in a more deterministic manner. The effect of process parameters on the surface form errors was investigated for ultra-precision cylindrical turning process. An empirical model based on response surface methodology has been established and validated with the experimental results. Moreover, a corrective machining methodology was proposed to further improve the accuracy of diamond turned surfaces with OMSM. According to different correction tasks, corresponding OMSM data processing methods were presented. Profile and surface correction experiments were performed to validate the proposed corrective machining methodology and 40% improvement of surface accuracy was achieved