Peter Fischer


Last Name

Fischer

First Name

Peter

ORCID

0000-0002-2992-5037

Organisational unit

08821 - Fischer, Peter (Tit.-Prof.)

Search Results

Publications1 - 10 of 191
  • Influence of the interfacial tension on the microstructural and mechanical properties of microgels at fluid interfaces
    Item type: Journal Article
    Vialetto, Jacopo; Nussbaum, Natalie; Bergfreund, Jotam; et al. (2022)
    Journal of Colloid and Interface Science
    Microgels are soft colloidal particles constituted by cross-linked polymer networks with a high potential for applications. In particular, after adsorption at a fluid interface, interfacial tension provides two-dimensional (2D) confinement for microgel monolayers and drives the reconfiguration of the particles, enabling their deployment in foam and emulsion stabilization and in surface patterning for lithography, sensing and optical materials. However, most studies focus on systems of fluids with a high interfacial tension, e.g. alkanes/ or air/water interfaces, which imparts similar properties to the assembled monolayers. Here, instead, we compare two organic fluid phases, hexane and methyl tert-butyl ether, which have markedly different interfacial tension () values with water and thus tune the deformation of adsorbed microgels. We rationalize how controls the single-particle morphology, which consequently modulates the structural and mechanical response of the monolayers at varying interfacial compression. Specifically, when is low, the microgels are less deformed within the interface plane and their polymer networks can rearrange more easily upon lateral compression, leading to softer monolayers. Selecting interfaces with different surface energy offers an additional control to customize the 2D assembly of soft particles, from the fine-tuning of particle size and interparticle spacing to the tailoring of mechanical properties.
  • Effect of Oil on the Adsorption and Rheology of β-Lactoglobulin at Oil-Water Interfaces
    Item type: Other Conference Item
    Bergfreund, Jotam; Bertsch, Pascal; Kuster, Simon; et al. (2018)
  • Revisiting Darwin’s fink: Animal as material engineers
    Item type: Other Conference Item
    Fischer, Peter (2023)
    Animals are under constant pressure to survive in their surrounding environment, and they have evolved countless strategies to adapt, colonize, and reproduce successfully in their habitats. Almost acting as materials scientists, animals directly manipulate complex fluids around them or secrete complex fluids themselves to fulfill a specific task. Here we demonstrate how animals learned to manipulate their habitat, e.g., sandfish and crabs that exploit the granular rheology of sand (exogen abiotic material) and showcase exotic animals that produce unique bio-fluids (endogen biotic materials), from deep-sea hagfishes to subterranean velvet worms. For unknown and uncharted phenomena, potential rheological properties of the involved complex fluids are suggested. During evolution, animals found ways to use the rheology and structure of complex fluids to gain advantage and increase their Darwinian fitness. Studying the design concepts from soft-matter, materials-science, and rheological points of view can help to understand animal behavior, might yield new insights for mimicking biomaterials, and provide a quantitative approach toward ethology.
  • Self-Assembly of Lysozyme Aggregates With Enhanced Antimicrobial Activity
    Item type: Other Conference Item
    Kummer, Nico; Wu, Tingting; De France, Kevin; et al. (2022)
  • Physicochemical, morphological, and rheological properties of cellulose nanofibrils produced via ultra-high-pressure homogenization
    Item type: Journal Article
    You, Lingxin; Marcolini, Benoît; Bour, Jérôme; et al. (2025)
    Carbohydrate Polymer Technologies and Applications
    Cellulose nanofibrils (CNFs) possess desirable properties, including low density, high tensile strength, large surface area, and high biodegradability, making them valuable for broad industrial applications. High-pressure homogenization is the most common processing method to produce CNFs. This study reports on the impact of ultra-high-pressure homogenization (UHPH) on the structural and technofunctional properties of CNFs, including their Pickering o/w emulsion stabilizing performance. Microcrystalline cellulose suspensions (0.5 % w/w) were processed at pressures ranging from 500 to 3500 bar for up to 25 passes. According to our findings, the size (fiber length and width) of the CNFs was reduced with pressure increase. The highest colloidal stability of cellulose suspensions was observed at ≥ 2500 bar for at least 5 passes. The viscosity of cellulose suspensions increased progressively with the severity of the UHPH. Dynamic rheological characterization of the cellulose suspensions processed for 25 cycles revealed a true gel-like behavior within the linear viscoelastic regime and a strain stiffening effect at large strains (> 10 %). The lipid droplet polydispersity and creaming index of Pickering emulsions were minimized using the 3500 bar processed CNFs. In conclusion, UHPH is an efficient method to induce the nanofibrillation of cellulose, and improve its techno-functionality.
  • Stabilization of Air/Water Interfaces by Nanocrystalline Cellulose
    Item type: Conference Paper
    Bertsch, Pascal; Adamcik, Jozef; Diener, Michael; et al. (2018)
    MaP Graduate Symposium. The 12th Annual Gathering of Materials & Processes Researchers at ETH Zürich. Symposium Booklet
  • Slime for defense – biophysical design principles in a marine environment
    Item type: Other Conference Item
    Böni, Lukas; Rühs, Patrick A.; Fischer, Peter (2019)
  • Hagfish mucosa interaction with particles
    Item type: Other Conference Item
    Giacomin, Caroline; Founta, Dimitra; Vlassopoulos, Dimitris; et al. (2022)
  • Nonlinear shear and dilatational rheology of viscoelastic interfacial layers of cellulose nanocrystals
    Item type: Journal Article
    van den Berg, Merel E.H.; Kuster, Simon; Windhab, Erich J.; et al. (2018)
    Physics of Fluids
    We present a nonlinear rheological investigation of model rod-like particles at the air/water interface in dilatation and shear. Cellulose nanocrystals were modified to vary their surface hydrophobicity, creating a range of surface-active particles with varying contact angle. The interfacial rheological properties were studied using a series of frequency sweeps in small amplitude oscillatory shear as well as strain sweeps under large amplitude oscillatory shear (LAOS) and large amplitude oscillatory dilatation (LAOD) to include the nonlinear behavior. A multi-mode Maxwell model was used to fit the frequency sweeps that were obtained during formation of the interfacial layer. A shift toward longer relaxation times was found, more pronounced for particles with higher hydrophobicity. Lissajous plots in LAOS revealed strain stiffening, yielding, and unconstrained flow of the interfacial layers. Lissajous plots in LAOD revealed strain hardening in compression and strain softening in expansion, increasing with surface pressure and with particle hydrophobicity. While interfacial layers commonly show gel or solid-like behavior, our findings imply a weakly aggregated system. The rheological behavior indicates the formation of larger clusters for particles with high hydrophobicity compared to smaller clusters for particles with low hydrophobicity. The particle-particle interactions therefore vary with hydrophobicity, suggesting that capillary interactions are important for the formation of these microstructures.
  • Effect of Arthrospira platensis microalgae protein purification on emulsification mechanism and efficiency
    Item type: Journal Article
    Böcker, Lukas; Bertsch, Pascal; Wenner, David; et al. (2021)
    Journal of Colloid and Interface Science
    In light of environmental concerns and changing consumer demands, efforts are increasing to replace frequently used animal-based emulsifiers. We demonstrate the interfacial network formation and emulsifying potential of Arthrospira platensis protein extracts and hypothesize a mechanistic change upon progressing purification. A microalgae suspension of A. platensis powder in phosphate buffer solution (pH 7, 0.1 M) was homogenized and insoluble components separated by centrifugation. Proteins were precipitated at the identified isoelectric point at pH 3.5 and dialyzed. In interfacial shear rheology measurements, the build-up of an interfacial viscoelastic network was faster and final network strength increased with the degree of purification. It is suggested that isolated A. platensis proteins rapidly form an interconnected protein layer while coextracted surfactants impede protein adsorption for crude and soluble extracts. Emulsions with 20 vol% Medium chain triglycerides (MCT) oil could be formed with all extracts of different degrees of purification. Normalized by protein concentration, smaller droplets could be stabilized with the isolated fractions. For potential applications in food, pharma and cosmetic product categories, the enhanced functionality has to be balanced against the loss in biomass while purifying microalgae proteins or other alternative single cell proteins.
Publications1 - 10 of 191