Stefan E. Schausberger

Instant tough bonding of hydrogels for soft machines and electronics

A strategy for bonding water-rich hydrogels to diverse materials for electronic skins, energy storage, and soft optics is reported. Introducing methods for instant tough bonding between hydrogels and antagonistic materials—from soft to hard—allows us to demonstrate elastic yet tough biomimetic devices and machines with a high level of complexity. Tough hydrogels strongly attach, within seconds, to plastics, elastomers, leather, bone, and metals, reaching unprecedented interfacial toughness exceeding 2000 J/m2. Healing of severed ionic hydrogel conductors becomes feasible and restores function instantly. Soft, transparent multilayered hybrids of elastomers and ionic hydrogels endure biaxial strain with more than 2000% increase in area, facilitating soft transducers, generators, and adaptive lenses. We demonstrate soft electronic devices, from stretchable batteries, self-powered compliant circuits, and autonomous electronic skin for triggered drug delivery. Our approach is applicable in rapid prototyping and in delicate environments inaccessible for extended curing and cross-linking.

Flexible contrast for low-coherence interference microscopy by Fourier-plane filtering with a spatial light modulator

We propose a full-field low-coherence interference (LCI) microscope that can provide different contrast modes using Fourier-plane filtering by means of a spatial light modulator. By altering the phase and spatial frequencies of the backreflected wavefront from the sample arm of the interferometer, we are able to change the contrast in the depth-resolved LCI images. We demonstrate that different types of contrast modes, such as, e.g., spiral phase contrast, can successfully be emulated to provide specific enhancement of internal structures and edges and to reveal complementary details within the samples under investigation.

Cost-Efficient Open Source Desktop Size Radial Stretching System With Force Sensor

The rapid and efficient development of soft active materials requires readily available, compact testing equipment. We propose a desktop-sized, cost-efficient, and open source radial stretching system as an alternative to commercially available biaxial and uniaxial stretching devices. It allows for doubling the diameter of an elastomer membrane while measuring the applied force. Our development enables significant cost reduction (<;300 €) and increase the availability of equibiaxial deformation measurements for scientific material analysis. Construction plans, source code, and electronic circuit diagrams are freely available under a creative commons license.

Full-field optical coherence microscopy with Riesz transform-based demodulation for dynamic imaging

We present dynamic full-field optical coherence microscope imaging using a scientific complementary metal oxide semiconductor camera in conjunction with a demodulation scheme based on the Riesz transform and monogenic signals. The potential of our approach is verified by a comparison with conventional phase-stepping as well as with an analytic reconstruction method and finally exemplified for dynamic mechanical testing of a polymer/fiber composite structure.

Coherence probe microscopy imaging and analysis for fiber-reinforced polymers

The potential of full-field low coherence interferometric techniques for imaging internal structures, such as fibers, interfaces, or inclusions in technical materials is demonstrated by our coherence probe microscopy (CPM) setup. However, the huge amount of recorded data demand for an automatized enhancement and evaluation of the image data. We propose an automatic image analysis procedure adapted for full-field coherence probe microscopy, which we tested on fiber composite materials. The performed image enhancement and orientation analysis finally allow to cluster the internal fiber structures, to detect outliers and enable an improved characterization of investigated specimens supporting a sophisticated material design for the future.

Enhancing of structures in coherence probe microscopy imaging

The principle of Fourier plane filtering in coherence probe microscopy (CPM) is demonstrated. It is shown that an edge contrast enhancement can be obtained in an isotropic and anisotropic way for different technical materials containing interfaces or internal micro-structures. Additionally image processing completes the CPM imaging and analysis.

Simultaneous detection of optical retardation and axis orientation by polarization-sensitive full-field optical coherence microscopy for material testing

We present a polarization-sensitive full-field optical coherence microscopy modality which is capable of simultaneously delivering depth resolved information on the reflectivity, optical retardation and optical axis orientation. In this way local birefringence, inherent stress–strain fields and optical anisotropies can be visualized with high resolution, as exemplified for various technical material applications.

Full field optical coherence microscopy for material testing: contrast enhancement and dynamic process monitoring

We illustrate the abilities of an advanced full-field optical coherence microscope (FF-OCM) setup for characterization of technical materials with internal micro-structures and present this technique also for dynamic process monitoring, as strain-stress tests. Additionally we briefly illustrate the potential of image processing in context of the chosen applications. Furthermore, contrast modification techniques based on Fourier plane filtering are discussed.

Contrast modification for ultra-high resolution low-coherence interference microscopy by Fourier-plane filtering

We present a novel full-field low-coherence interference (LCI) microscope, which exhibits ultra-high axial resolution due to a broadband super continuum light source and which is at the same time capable to generate different contrast modes by using Fourier-plane filtering with a spatial light modulator. By changing the phase and spatial frequencies of the backreflected wavefront of the specimen in the sample arm of the interferometer, we are able to change the contrast in the depth-resolved LCI images. By displaying different filters on the SLM, as e.g. spiral phase, the resulting images provide particular enhancement of edges and internal structures, and expose details within the specimen that are not visible in normal bright-field mode.

Dynamic imaging by full-field optical coherence microscopy with a sCMOS detector and Riesz transform-based demodulation

We propose a dynamic full-field optical coherence microscope imaging method using a scientific complementary metal oxide semiconductor camera in conjunction with a demodulation scheme based on Riesz transform and monogenic signals.