Integrated multimode optical waveguides in glass using laser induced deep etching.

Glass is an ideal material for optical applications, even though only a few micromachining technologies for material ablation are available. These microstructuring methods are limited regarding precision and freedom of design. A micromachining process for glass is laser induced deep etching (LIDE). Without generating micro-cracks, introducing stress, or other damages, it can precisely machine many types of glass. This work uses LIDE to subtractive manufacture structures in glass carrier substrates. Due to its transmission characteristics and refractive index, the glass substrate serves as optical cladding for polymer waveguides. In this paper, the described fabrication process can be divided into two sub-steps. The doctor blade technique and subsequent additive process step is used in manufacturing cavities with U-shaped cross-sections in glass in order to fill the trenches with liquid optical polymers, which are globally UV-cured. Based on the higher refractive index of the polymer, it enables optical waveguiding in the visible to near-infrared wavelength range. This novel, to the best of our knoowledge, manufacturing method is called LDB (LIDE-doctor-blade); it can be the missing link between long-distance transmissions and on-chip solutions on the packaging level. For validation, optical waveguides are examined regarding their geometrical dimensions, surface roughness, and waveguiding ability, such as intensity distribution and length-dependent attenuation.

Experimental Investigation of the Rapid Fabrication of Micron and Submicron Structures on Polymers Utilizing Ultrasonic Assisted Embossing.

Small-scale optical components with micron or submicron features have grown in popularity in recent years. High-quality, high-efficient, and cost-effective processing approaches for polymer optics mass production are an urgent need. In this study, ultrasonic vibration will be introduced in embossing. The major advantage is that the required energy can be provided for process times ranging from a few hundred milliseconds to a few seconds, and that the process energy is provided at exactly the required location so that the structures in the surrounding area are not affected. Due to the strong correlation between electrical impedance and the temperature of the material, a novel impedance-based control strategy has been utilized for precisely controlling ultrasonic vibration during the embossing process. The investigation used two types of stamps with grating line widths of 4 µm and 500 nm, respectively. As a result, an embossing time of less than a few seconds was accomplished and a uniform embossed surface with an average fill rate of more than 75% could be achieved.

Towards a Highly Sensitive Piezoelectric Nano-Mass Detection-A Model-Based Concept Study.

The detection of exceedingly small masses still presents a large challenge, and even though very high sensitivities have been archived, the fabrication of those setups is still difficult. In this paper, a novel approach for a co-resonant mass detector is theoretically presented, where simple fabrication is addressed in this early concept phase. To simplify the setup, longitudinal and bending vibrations were combined for the first time. The direct integration of an aluminum nitride (AlN) piezoelectric element for simultaneous excitation and sensing further simplified the setup. The feasibility of this concept is shown by a model-based approach, and the underlying parameter dependencies are presented with an equivalent model. To include the geometrical and material aspects, a finite element model that supports the concept as a very promising approach for future nano-mass detectors is established.

Development, Characterisation and High-Temperature Suitability of Thin-Film Strain Gauges Directly Deposited with a New Sputter Coating System.

New sensor and sensor manufacturing technologies are identified as a key factor for a successful digitalisation and are therefore economically important for manufacturers and industry. To address various requirements, a new sputter coating system has been invented at the Institute of Micro Production Technology. It enables the deposition of sensor systems directly onto technical surfaces. Compared to commercially available systems, it has no spatial limitations concerning the maximum coatable component size. Moreover, it enables a simultaneous structuring of deposited layers. Within this paper, characterisation techniques, results and challenges concerning directly deposited thin film strain gauges with the new sputter coating system are presented. Constantan (CuNiMn 54/45/1) and NiCr 80/20 are used as sensor materials. The initial resistance, temperature coefficient of resistance and gauge factor/k-factor of quarter-bridge strain gauges are characterised. The influence of a protective layer on sensor behaviour and layer adhesion is investigated as well. Moreover, the temperature compensation quality of directly deposited half-bridge strain gauges is evaluated, optimised with an external trimming technology and benchmarked against commercial strain gauges. Finally, the suitability for high-temperature strain measurement is investigated. Results show a maximum operation temperature of at least 400 °C, which is above the current state-of-the-art of commercial foil-based metal strain gauges.

Feasibility of Round Window Stimulation by a Novel Electromagnetic Microactuator.

INTRODUCTION: Most implantable hearing aids currently available were developed to compensate the sensorineural hearing loss by driving middle ear structures (e.g., the ossicles). These devices are successfully used in round window (RW) stimulation clinically, although this was initially not the intended use. Here, a novel microactuator, specifically designed for RW stimulation, was tested in human temporal bones to determine actuator performance and applicability. METHODS: Stapes footplate response to RW stimulation was determined experimentally in human temporal bones and the obtained sound pressure output level was estimated. RESULTS: The actuator had a flat displacement response between 0.125 and 4 kHz, a resonance between 4 and 7 kHz, and a roll-off above. At increasing contact force, the stapes footplate displacement decreased by 5-10 dB re µm for forces ≥ 2 mN. The equivalent sound pressure level between 0.125 and 4 kHz amounted to 87-97 eq dB SPL and increased to 117 eq dB SPL for frequencies of 4-7 kHz. The total harmonic distortion (THD) of the actuator ranged within 15-40% for static forces of 5 mN. CONCLUSION: The feasibility of an electromagnetic actuator that may be placed into the RW niche was demonstrated but requires further optimization in terms of THD and static force sensitivity.

Longitudinal conductivity of LaF3/SrF2 multilayer heterostructures.

LaF3/SrF2 multilayer heterostructures with thicknesses of individual layers in the range 5-100 nm have been grown on MgO(100) substrates using molecular beam epitaxy. The longitudinal conductivity of the films has been measured using impedance spectroscopy in the frequency range 10-1-106 Hz and a temperature range 300-570 K. The ionic DC conductivities have been determined from Nyquist impedance diagrams and activation energies from the Arrhenius-Frenkel equation. An increase of the DC conductivity has been observed to accompany decreased layer thickness for various thicknesses as small as 25 nm. The greatest conductivity has been shown for a multilayer heterostructure having thicknesses of 25 nm per layer. The structure has a conductivity two orders of magnitude greater than pure LaF3 bulk material. The increasing conductivity can be understood as a redistribution of charge carriers through the interface due to differing chemical potentials of the materials, by strong lattice-constant mismatch, and/or by formation of a solid La1-xSrxF3-x solution at the interface during the growth process.

Recent Developments of Magnetoresistive Sensors for Industrial Applications.

The research and development in the field of magnetoresistive sensors has played an important role in the last few decades. Here, the authors give an introduction to the fundamentals of the anisotropic magnetoresistive (AMR) and the giant magnetoresistive (GMR) effect as well as an overview of various types of sensors in industrial applications. In addition, the authors present their recent work in this field, ranging from sensor systems fabricated on traditional substrate materials like silicon (Si), over new fabrication techniques for magnetoresistive sensors on flexible substrates for special applications, e.g., a flexible write head for component integrated data storage, micro-stamping of sensors on arbitrary surfaces or three dimensional sensing under extreme conditions (restricted mounting space in motor air gap, high temperatures during geothermal drilling).