Scientific publications

A solvent-free approach to the formation of freestanding photonic material from amphiphilic polystyrene-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA) is reported, where the application of shear force and pressure induces phase separation. This work demonstrates access to high molecular weight (HMW; >100 kg mol−1) PS-b-PHEMA with PHEMA contents up to 62 vol% using sequential anionic polymerization. By exploring hot pressing, the dependency of microstructure formation on temperature, pressure, and time is demonstrated using transmission electron microscopy and small-angle X-ray scattering measurements. Within 30 min, phase-separated block copolymer (BCP) films are obtained. Although no highly ordered equilibrium structures are formed, photonic properties are observed for PS-b-PHEMA films with molecular weights higher than 140 kg mol−1 and PHEMA contents between 20 and 51 vol%. The photonic properties are investigated by ultraviolet–visible (UV–vis) and fluorescence spectroscopy as well as confocal fluorescence microscopy. The BCP films exhibit tailored transmittance that is dependent on molecular weight and microstructure, making them suitable for UV and blue light filter applications. Also, structure-dependent reflection and fluorescence are demonstrated. Finally, the application in the field of sensors is addressed by demonstrating a reversible color change of BCP films with a co-continuous microstructure, achieved through polar solvent infiltration and evaporation.

The performance of novel electrode materials and the influence of cell geometry or flow rate on capacitive water deionization (CDI) are usually described by global metrics from the analysis of the effluent electrolyte together with the electrochemical response of the system. However, these approaches cannot provide information on local variations of ion concentration and related local efficiency within an operating device. Here, a novel approach of position-resolved operando synchrotron-based X-ray transmission is introduced to determine local ion concentration changes along the flow channel from the inlet (feedwater) to the outlet (effluent water) of a working CDI cell. A specific cell design allows the independent quantification of concentration changes within the bulk electrolyte in the flow channel as well as the two oppositely charged nanoporous electrodes. Results from a 15 mM CsCl feed solution using three flow rates and two carbon materials with hierarchical porosity reveal a complex spatial- and temporal ion distribution in the system. A distinct dependence of local concentration on the flow rate is observed, with generally decreasing local desalination capacity towards the outlet of the cell, particularly for slow flow rates. It is also found that a significantly better overall performance for one of the two materials can be related to dominant counter-ion adsorption within ultramicropores, which ions cannot access in their hydrated state at no applied potential (ionophobicity). Overall, the results demonstrate the unique potential of position-resolved operando X-ray techniques to get mechanistic insight into local ion redistribution in CDI systems, allowing ultimately guiding performance optimization.

In ophthalmology, living biomaterials have appeared as promising drug delivery and biosensor devices to tackle dynamic sensing and delivery of compounds. Their living character complicates their assessment with the also dynamic ocular tissues. The use of animal experiments increases complexity, and most animal ocular models are anatomically different from humans. Thus, in vitro ocular systems applied specifically to living biomaterials are required to assess their safety, compatibility and efficacy. Here, we report on an in vitro cornea model for co-cultures with Corynebacterium glutamicum-polyvinyl alcohol living biomaterials, which are reported as suitable living contact lenses, to study their cytocompatibility to the eye. We co-cultured this living biomaterial with human primary corneal cells (epithelial and fibroblasts) for 7 days, mimicking contact lens extended wear. We studied bacterial proliferation, biocontainment and biosafety. We investigated potential cytotoxicity and pro-inflammatory responses of living biomaterials to corneal cells. Our results revealed that the living biomaterial does not trigger cytotoxicity or pro-inflammatory phenotypes on corneal cells during the 7-day co-culture. We placed the living biomaterial on top of the corneal epithelium, observing no cytotoxic effects. Overall, these findings highlight the potential of in vitro investigations for living biomaterials and the applicability of these devices for ophthalmology purposes.

We report a straightforward methodology to access structurally well-defined hybrid assemblies of plasmonic and excitonic nanoparticles (NPs). The developed strategy is based on the incorporation of quantum dots (QDs) coated with zinc-sulfide shells into poly(ethylene glycol) (PEG) brushes at gold NP surfaces, without the necessity of incorporating specialized functional groups to drive the supracolloidal assembly. Based on control experiments involving PEGs with distinct polymeric architecture and Fourier-transform infrared spectroscopy analysis, we attribute the structure formation to attractive interactions between the QD surface and the monomeric repeat unit of the PEG brushes. This combination leads to short interparticle spacings and plasmon/exciton interactions, resulting in photoluminescence (PL) quenching upon assembly. However, using block-copolymers comprising a NP-adjacent spacer block in addition to a NP-remote PEG block, the distance between gold NPs and QDs can be controlled, which in turn affects the PL properties. The versatility of the structure-formation approach is demonstrated by the possibility of applying it to two distinct core/shell QDs (InP/ZnSe/ZnS and CdSe/CdS/ZnS). This offers new perspectives in the quest for efficient nanomaterial fabrication procedures.

Multimaterial optical fibers provide a versatile platform for integrating diverse functionalities—such as waveguiding, side emission, sensing, and actuation—into a single filament. Although traditional multimaterial fibers have primarily been fabricated from rigid materials such as silica and thermoplastics for optoelectronic applications, recent developments have shifted the focus toward soft systems composed of elastomers, hydrogels, and their composites. Owing to their mechanical compliance and biocompatibility, these soft fibers are particularly well suited for wearable, implantable, and tissue-integrated devices used in diagnostics and phototherapy. This review provides a comprehensive overview of the rapidly developing field of soft multimaterial optical fibers, highlighting key material combinations and fabrication strategies that enable multifunctional performance. Particular emphasis is placed on extrusion-based multimaterial printing—including coaxial and segmented extrusion—which has significantly expanded the architectural and functional design space of soft optical fibers. Remaining challenges, including material compatibility, interfacial and surface quality, and printing resolution, are critically discussed. Finally, the review outlines emerging opportunities for advancing these fabrication approaches toward practical and clinically relevant biomedical applications.

Recombinant adeno-associated viral (rAAV) vectors are a leading platform for in vivo gene therapy, valued for their excellent safety, broad serotype diversity, and scalable production. Targeted delivery through capsid display of ligands holds great promise, yet current retargeting strategies often rely on extensive capsid re-engineering and restrict the use of ligands incompatible with intracellular expression systems. Here, we present a modular AAV retargeting platform that, for the first time, employs the SpyTag/SpyCatcher system via genetic integration into the AAV2 capsid. SpyTag is a small peptide that forms a covalent, irreversible bond with its protein partner, SpyCatcher, allowing site-specific ligand coupling under physiological conditions. Inserting SpyTag into surface-exposed capsid sites enabled postassembly functionalization of AAVs with SpyCatcher-fused targeting proteins. As proof of concept, we used SpyCatcher fusions with designed ankyrin repeat proteins (DARPins) specific for EGFR, EpCAM, and HER2. This conferred highly specific transduction of corresponding cancer cell lines with minimal off-target activity. Therapeutic potential was demonstrated by delivering a suicide gene, inducing selective cancer cell killing upon prodrug administration. This “one-fits-all” platform allows rapid and flexible retargeting without significantly altering the underlying vectors genome or production process. It supports the incorporation of large or complex ligands not amenable to genetic fusion and facilitates high-throughput preclinical evaluation strategies. By uniting capsid engineering with modular ligand display, our approach provides a scalable and versatile framework for precision gene delivery, broadening the applicability of rAAV in both therapeutic and discovery settings.

Engineered living materials (ELMs) rely on the ability to control cell behavior in material systems. ELMs containing bacteria secreting beneficial molecules are being developed for therapeutic purposes. Using commensal strains embedded in physically cross-linked agarose hydrogels, we systematically investigate how gel rigidity and initial bacterial density affect the morphology of bacterial colonies and their secretory function. Although often considered independently, these parameters jointly define the microscale environment experienced by embedded cells, influencing nutrient access, mechanical interactions, and potential cell-to-cell communication. We show that matrix rigidity effectively tunes aggregate morphology, modulating their shape and compactness, without compromising bacterial growth or secretion. In parallel, initial bacterial density determines the biomass accumulation dynamics and spatial distribution of aggregates, which in turn influence the onset and temporal profile of secretory activity, without altering its final magnitude. This decoupling between structural organization and secretory output opens new possibilities for engineering ELMs with tailored architectures and prolonged secretory and release activity.

The efficient and selective extraction of lithium ions from aqueous media is crucial for resource recovery, yet remains challenging due to the chemical similarity of coexisting alkali ions, such as sodium. In this study, we report a two-step electrochemical strategy that utilizes tailored MXene electrodes for lithium ion extraction with enhanced selectivity and extraction rates. By preintercalating hexadecylamine (HDA) and decyltrimethylammonium (C10), which are long-chain organic molecules, into the Ti3C2Tx MXene structure, we tailored the interlayer environment to favor lithium ions over sodium ions. The HDA-intercalated MXene demonstrated high Li+/Na+ selectivity with a lithium ion uptake of 2.2 mmol/L and a suppressed sodium ion uptake (<0.2 mmol/L). Extended cycling revealed that molecular preintercalation modulates ion transport pathways and influences structural and electrochemical stability. Both HDA-Ti3C2Tx and C10-Ti3C2Tx maintained a lithium ion purity of nearly 100% over 50 cycles.

Inks of gold nanoparticles with stabilizing and conducting polymer shells are promising materials for printed electronics. Local measurements of their electrical properties at the single-particle scale are required to understand the relationship between the particle network and electrical functionality. Herein, we report on conductive atomic force microscopy (cAFM) on films produced from hybrid Au nanoparticles that carry a covalently bound shell of the conducting polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and are distributed in a non-conductive matrix of polyvinyl alcohol (PVA). Current maps reveal the clustering of particles into electrically well-connected local networks and allow us to quantify the contact resistance between particles or clusters of particles. We find that the contact resistance between particles inside clusters is lower than those between clusters, indicating a hierarchical layer structure. By comparing inkjet-printed thicker bulk films and drop-cast films of single- or few-layer thickness, the experimental results offer valuable insights into the relationship between the structure of nanoparticle networks and the electrical conductance in these hybrid systems.