Guy Schlatter

Electrospinning is a versatile technique for producing membranes composed of submicrometric fibers and possessing high porosity and a large surface-to-volume ratio. These properties make electrospun fiber mats attractive for many applications including filtration, biomedical materials, and sensing. While conventional set-ups readily generate randomly oriented nonwovens, many applications require precise control over fiber organization. Such control can be achieved by manipulating the charged jet and the residual charges retained by deposited fibers, both governed by the electric field that is intrinsic to the electrospinning process. This review examines strategies for electrostatic control of electrospun fiber mat morphology, organized around two principal mechanisms: control of the charged jet in-flight and control of the landing jet. Auxiliary electrode-assisted electrospinning, which aims to suppress or redirect the whipping instabilities, as well as gap-separated and structured collectors that exploit electrostatic template effects, are discussed. Particular attention is given to the underlying mechanisms. Collectively, these methods illustrate how tailoring the electric field allows for the production of membranes with complex, application-specific fiber morphologies.

Three analytical methods were developed to quantify THAM in solid adsorbents. Extraction of THAM into water was followed by its derivatization by an acyl chloride, showing an influence of the activated carbon matrix on the calibration curves.

This study reports the development of elastomeric mesoporous polyurethane (PU) membranes for bioartificial pancreas applications in type 1 diabetes treatment. The membranes are designed to exhibit semi‐permeable properties, enabling insulin diffusion while restricting larger immune molecules, such as immunoglobulin G (IgG). Although electrospinning is a widely used technique for fabricating porous membranes for controlled drug release, it typically results in an average pore size on the order of few micrometers, which is two orders of magnitude larger than the mesoporous scale required. In this work, a green‐electrospinning process using waterborne PU suspension and poly(ethylene oxide) (PEO) is employed, followed by thermal annealing and washing steps. The resulting membranes exhibit a controlled pore size in the mesoporous range (≈20 nm measured by capillary flow porometry). Diffusion tests confirmed selective permeability, with a recovery rate of 25% for insulin and a recovery rate below 5% for IgG, meeting therapeutic needs. In vivo characterizations show no degradation and good biocompatibility of the membranes without chronic inflammation. Moreover, mechanical characterization demonstrates the membranes' flexibility and strength, making them suitable for minimally invasive surgical implantation. These findings underscore the potential of PU membranes for long‐term biomedical applications, addressing critical challenges in permeability and mechanical stability.

Sustainability requirements must be met by the appropriate selection of efficient and environmentally friendly materials and processes. We present materials obtained via all-in-water methods: first, few-layer graphene (FLG)–polyvinyl alcohol (PVA) colloids and then electrospun PVA-FLG fibers. The effects of the FLG concentration, and indirectly of ultrasound, are reflected via the modification of the structural and physical properties, including the microstructure, viscosity, thermal degradation and mechanical properties, of colloids and fiber mats. The primary results are highly encouraging for further optimization and the development of conductive, and mechanically resistant, materials.

Thick honeycomb-like electrospun scaffold with nanoparticles of hydroxyapatite (nHA) recently demonstrated its potential to promote proliferation and differentiation of a murine embryonic cell line (C3H10T1/2) to osteoblasts. In order to distinguish the respective effects of the structure and the composition on cell differentiation, beads-on-string fibers were used to manufacture thick honeycomb-like scaffolds without nHA. Mechanical and biological impacts of those beads-on string fibers were evaluated. Uniaxial tensile test showed that beads-on-string fibers decreased the Young Modulus and maximal stress but kept them appropriate for tissue engineering. C3H10T1/2 were seeded and cultured for 6 days on the scaffolds without any growth factors. Viability assays revealed the biocompatibility of the beads-on-string scaffolds, with adequate cells-materials interactions observed by confocal microscopy. Alkaline phosphatase staining was performed at day 6 in order to compare the early differentiation of cells to bone fate. The measure of stained area and intensity confirmed the beneficial effect of both honeycomb structure and nHA, independently. Finally, we showed that honeycomb-like electrospun scaffolds could be relevant candidates for promoting bone fate to cells in the absence of nHA. It offers an easier and faster manufacture process, in particular in bone-interface tissue engineering, permitting to avoid the dispersion of nHA and their interaction with the other cells.

Suspension electrospinning allows the environmental‐friendly fabrication of nano‐micro‐fibrous membranes since it is based on the processing of an aqueous particle suspension in which a hydrosoluble template polymer is added to insure the formation of a continuous fiber. Here, the case of polyurethane (PU) aqueous suspensions formulated with poly(ethylene oxide) (PEO) as the template polymer is studied. The effect of several parameters (particle size, PU/PEO ratio, PEO molar mass, and PEO concentration in the continuous phase) on particle‐particle and particle‐template polymer interactions that influence the rheological properties of the formulation and finally the electrospinning and the fiber morphology, is studied. The goal is to process a formulation with the highest particle content as possible. Thanks to a deep rheological investigation and the study of interactions and suspension morphology by zeta potential and diffusing wave spectroscopy, it is shown that regular fibers are efficiently produced when small particles are electrospun under favorable particle‐template polymer interactions and without screening the electrostatic repulsion between particles. Finally, a fibrous membrane is obtained from a formulation with a PU/PEO weight ratio equal to 50 under very stable and efficient production conditions.

Electrospinning is the leading process allowing the fabrication of polymeric nanofibrous membranes and mats. Unfortunately, it generally requires the solubilization of the polymer in a toxic solvent causing health and environmental issues during the production. Here, it is demonstrated that polyurethane (PU) fibrous membranes can be produced by electrospinning and then, moreover, functionalized using water as the only solvent for each processing step. Waterborne polyurethane in the form of a dispersion is firstly electrospun using poly(ethylene oxide) (PEO) as template polymer. After removing PEO via a washing cycle in water, the membranes show physico‐chemical properties influenced by the initial polymeric component ratio with greater mechanical performances and hydrophobicity observed at a higher PU amount. Aqueous solutions of bio‐based tannic acid (TA) are then employed to modify the surface properties of the membranes. The high amount of galloyl units per TA molecule allows its efficient anchoring on the fiber surface through supramolecular hydrogen bonding. By varying the TA amount and the order of washing cycle, the wettability can be tuned expanding the application range of the membranes. Finally, their efficient electrospinning at high flow‐rate using a home‐made needleless emitter paves the way for industrial production via full environmentally green processing.