Daniel Söderberg

Nano‐sized hydrogel drug carriers with tailored hydro‐ and lipophilicity are designed and their encapsulation and structure‐forming capabilities investigated in real‐time. These nano‐carriers are built from cellulose and peptide hydrogels in tandem with a nano‐stacked interwoven design and alternating hydro‐ and lipophilicity, thus enabling tuning of the lipophilicity of the carrier mesh for drugs of complementary lipophilicities. This allows for a variety of therapeutic applications, based on the nanoproperties of the hydrogel. Time‐resolved and in situ grazing incidence x‐ray scattering studies confirm the design and hydro‐ and lipophilicities of the fiber‐hydrogel composite and conclude their ability for carrying drugs of complementary properties site specific. This approach allows for a novel way of understanding the functionality of drug carriers using photon‐based approach.

Even at very low concentrations, the rheology of dispersions of charged semiflexible nanofibers differs from the rheology of the pure liquid, given the fiber charge, morphology, and interactions. At the nanoscale, the thermal motion of fibers is driven by the collective motion of the solvent molecules, but to what extent does the fiber presence and motion affect the self-diffusion of the liquid molecules? By studying the self-diffusion of water in dilute nanofiber dispersions using experiments and simulations, we can show that the interplay of fiber charge and motion on water mobility is more significant than the effect of the excluded volume caused by the charged particles.

Microfibrillated cellulose (MFC), cellulose nanofibers (CNF), and their mixtures exhibit different optical responses under flow, but simple methods for tracking these differences in process-relevant conditions are limited. Here, we evaluate a compact polarized-flow imaging setup based on LED illumination, linear polarizers, a camera, and a simple flow cell, combined with principal component analysis (PCA) of image sequences. The aim is not to extract physical material parameters from the images, but to determine whether different suspension states can be reproducibly discriminated in a simple optical measurement. For two sample sets, varying either the MFC:CNF ratio or the CNF concentration produced distinct and repeatable clusters in PCA space. MFC-rich suspensions formed broader clusters consistent with greater optical heterogeneity, whereas CNF-rich suspensions formed tighter clusters. Rheological measurements were used as an independent comparison and showed that optically distinct states were also mechanically different. In a holdout demonstration, an unseen 1:1 mixture was projected to an intermediate region between reference clusters, and small intensity perturbations shifted the projected cluster position. These results show that simple polarized imaging can support state discrimination of MFC/CNF suspensions and may serve as a basis for future at-line monitoring or deviation detection in papermaking.

Nonwoven fibre networks underpin filtration, insulation and geotextiles, where liquid uptake, redistribution and release govern performance. In needle-punched felts, barbed needles mechanically entangle fibres and partially reorient them toward the thickness direction ($z$), creating out-of-plane "pillars" and heterogeneity. While mechanical and structural consequences of needling are well documented, dynamic $z$-direction transport in partly saturated networks remains difficult to access due to opacity and sub-second timescales. Here we combine micro-CT ($μ$CT) of dry structure with time-resolved X-ray radiography during droplet addition to quantify through-thickness transport as a function of saturation and needling intensity, using a compact Washburn-type descriptor for dynamics. Results show an exponential dependence of $z$-directional liquid transport on saturation, consistent with previous models for in-plane relative permeability of nonwoven networks. Additionally, increased needle-punch intensity reorients fibres toward the $z$-direction, forming preferential flow pathways that enhance through-thickness transport, even as single-phase permeability decreases. These findings underscore needle-punch as a key design parameter for tuning liquid transport in nonwoven fibre networks. The approach provides an experimental and modelling framework for dynamic, capillarity-driven transport in opaque fibrous materials.

The world’s strongest bio-based filament is currently produced from the wet spinning of cellulose nanofibrils. Such filaments could provide sustainable alternatives to currently available reinforcement fibers for high performance composites. Finding the weakest point of such filaments is of critical importance to their final application. However, what constitutes the weakest point in these filaments has yet to be determined with any certainty. Laser diffraction in conjunction with the Fraunhofer (single-slit) approximation could provide a rapid, nondestructive defectoscopy technique. Finding the thinnest point is the most accurate estimate of the breakpoint, with a mean distance-to-breakpoint of 1100 ± 200 μm, whereas the most precise determination of the weakest point is establishing which point is the least slit-like (48% of all cases). Combining width and propensity to be more or less slit-like was attempted to provide an accurate and precise metric (‘the failure factor’). With an accuracy of 1000 ± 200 μm, this is the best possible estimate using the methodology presented here. The results indicate a need for further refinement of the method. Incorporating machine learning algorithms would increase reliability by circumventing the need for approximations. Performing high-resolution tomograms of the samples to take into account the cross-sectional circularity could be implemented as an additional in-depth secondary method. With the technique already presenting advantages in terms of speed and cost compared to other methods, e.g., electron microscopy, such instruments could be integrated into a production line, providing real-time defectoscopy and quality control.

X-rays are commonly used in imaging experiments due to their penetration power, which enables non-destructive resolution of internal structures in samples that are opaque to visible light. Time-resolved X-ray tomography is the state-of-the-art method for obtaining volumetric 4D (3D + time) information by rotating the sample and acquiring projections from different angular viewpoints over time. This method enables studies to address a plethora of research questions across various scientific disciplines. However, it has several limitations, such as incompatibility with single-shot experiments, challenges in rotating complex sample environments that restrict the achievable rotation speed or range, and the introduction of centrifugal forces that can affect the sample's dynamics. These limitations can hinder and even preclude the study of certain dynamics. Here, we present an implementation of an alternative approach, X-ray multi-projection imaging (XMPI), which eliminates the need for sample rotation. Instead, the direct incident X-ray beam is split into beamlets using beam splitting X-ray optics. These beamlets intersect at the sample position from different angular viewpoints, allowing multiple projections to be acquired simultaneously. We commissioned this setup at the ForMAX beamline at MAX IV, the first operational diffraction-limited storage ring. We present projections acquired from two different sample systems – fibers under mechanical load and particle suspension in multiphase flow – with distinct spatial and temporal resolution requirements. We demonstrate the capabilities of the ForMAX XMPI setup using the detector's full analog-to-digital converter range for the relevant sample-driven spatiotemporal resolutions: (i) at least 12.5 kHz frame rates with 4 µm pixel sizes (fibers) and (ii) 40 Hz acquisitions with 1.3 µm pixel sizes (multiphase flows). The presented setup and results form the basis for a permanent XMPI endstation at ForMAX, offering flexibility to adapt to the spatiotemporal requirements of the studied dynamics.