Scientific publications

A low-temperature sintering mechanism of silver microparticles is established and used to enable the design-for-recycling of printed electronics. The formation of necks during the initial phase sintering of precipitated and atomized silver microparticles is studied. Temperature- and time-dependent in-situ analyses indicate the existence of a mobile silver species that provides efficient mass transport. The activation energy of neck formation identifies silver ion formation as the rate-limiting step of low-temperature silver sintering. It is demonstrated that resistivities of 271 times that of bulk silver can be attained after 40 minutes at 150°C. Low-temperature sintering not only reduces the energy required during thermal treatment but it yields layers that are suitable for recycling, too. The resulting layers have conductive necks that are mechanically weak enough to be broken during recycling. Printed layers are redispersed and the recycled silver powder is reused without loss of the electrical performance in new prints. Their conductivities are industrially relevant, which makes this recyclability-by-design approach promising for manufacturing more sustainable printed electronics.

Tunneling nanotubes (TNTs) are thin, dynamic, long membrane protrusions that allow intercellular exchanges of signaling clues, molecules and organelles. The presence of TNTs and their involvement as drug delivery channels have been observed in several types of cancer, including glioblastoma. Recently, increased attention has been directed toward nanoparticles (NPs) that can be transported in TNTs. However, few data are available on the role of physical parameters of nanoparticles, such as size, shape, charge and flexibility, in determining their transfer efficiency between cells by TNTs. Here, we focused our attention on NP shape, manufacturing spherical, discoidal and deformable negatively charged lipid-based NPs with sizes <120 nm and similar stiffness. The TNT-mediated transfer of NPs was investigated in 2D and 3D culture models of human glioblastoma cells. The permeability and biocompatibility of the blood–brain barrier (BBB) were also assessed. Results showed that discoidal NPs displayed the highest TNT-mediated transfer efficiency between cancer cells, with a maximum velocity of 69 nm s−1, and a higher endothelial permeability (1.29 × 10−5 cm min−1) across the BBB in an in vitro model. This depends on the NP shape because discoidal NPs have a larger surface area exposed to the flow along the TNT channel. Overall, the results suggest that the shape of NPs is the game-changer for more efficient TNT-mediated transfer between cancer cells, thus introducing a sustainable solution to improve the diffusion rate at which the NPs spread in the tumour microenvironment, opening the possibility of ameliorating drug distribution to difficult-to-reach cancer cell populations.

Currently, over 60% of the world's population lives in cities. Urban living has many advantages but there are also challenges regarding the need for smart urbanization. The next generation of tunable 2D nanomaterials, called MXenes, is the critical enabling technology that can bring the current urban thinking to the next level, called a smart city. The smart city is a novel concept based on a framework of self-sufficient technologies that are interactive and responsive to citizens’ needs. In this perspective, MXene-enabled technologies for sustainable urban development are discussed. They can advance self-sufficient, adaptive, and responsive buildings that can minimize resource consumption, solving the deficiency of essential resources such as clean energy, water, and air. MXenes are at the cutting edge of technological limitations associated with the Internet of Things (IoT) and telemedicine, combining diverse properties and offering multitasking. It is foreseen that MXenes can have a bright future in contributing to the smart city concept. Therefore, the roadmap is presented for demonstrating the practical feasibility of MXenes in the smart city. Altogether, this study promotes the role of MXenes in advancing the well-being of citizens by raising the quality of urban living to the next level.

A multi-scale model is crucial for combining experiments and simulations to reveal the energy storage mechanism. As novel electrode materials, conductive metal–organic frameworks (c-MOFs) provide an ideal platform for understanding the energy storage process in supercapacitors. However, the prevailing circuit models lack consideration of the distinctive transmission path of c-MOFs, which hinders accurate descriptions of c-MOF supercapacitors. By proposing a concept for representing the c-MOF electrode as a crystal–matrix electrode according to the crystallinity, we developed a universal multi-scale circuit model considering crystal shape and porosity to describe the impedance and capacitance of c-MOF electrodes. For supercapacitors with c-MOF electrodes and ionic liquid electrolytes, results predicted from the new multi-scale circuit model, based on microscale parameters obtained from molecular dynamics simulations, demonstrate quantitative agreement with experimental data for electrodes with different crystallinities.

Materials science research faces challenges due to diverse and evolving measurements, materials, and methods. Managing research data in a way that is understandable, comparable, and reproducible is essential for high data quality, particularly for data science and machine learning applications. In Li-ion batteries research data storage concepts and structures vary widely between institutions and researchers, leading to difficulties in data comparison and understanding. To address the issue of data structuring, battery production and characterization ontology (BPCO) is developed. The ontology builds on existing ontologies like the Platform MaterialDigital core ontology and quantities, units, dimensions, and types ontology to model standard battery production processes, characterization methods, and materials. The BPCO is based on a workflow structure to be accessible to nonexperts and, unlike highly specialized existing ontologies, models the whole production process removing the need for separate data structures and enabling the identification of dependencies between parameters. This work builds upon a previously published paper in which the taxonomy and fundamental strategies for ontology development are established. The article presents the developed ontology and its use for structuring research data in three key use cases, that is, different experiments performed to validate the ontology's capabilities, provide feedback, and ensure its applicability.

Living Therapeutic Materials (LTMs) are a promising alternative to polymeric drug carriers for long term release of biotherapeutics. LTMs contain living drug biofactories that produce the drug using energy sources from the body fluids. To clarify their application potential, it is fundamental to adapt biocompatibility and cytotoxicity assays applied from non-living biomaterials and therapeutics to evaluate how LTMs interact with host cells. Here, we have established a first step in this direction, by developing a practical workflow to parallelize in vitro assessment of minimal safety and cytocompatibility properties of bacterial LTMs. It allows systematic monitoring and quantification of the dynamic evolution of the bacterial population (growth, metabolic activity) in parallel to quantify the response of different mammalian cells to LTM supernatants with regards to cytotoxicity and release of pro-inflammatory cytokines over a period of 7 days using a maximum of 10 samples. The protocol was tested with a Pluronic-based thin film containing ClearColi. The results show no cytotoxic effects of ClearColi containing hydrogels in three mammalian cell lines, and no induction of pro-inflammatory cytokines under the tested conditions. This workflow represents a first step in establishing a roadmap for the safety assessment of LTMs, and investigation of biocompatibility potential of future living therapeutic devices.

Side-emitting optical fibers allow light to be deliberately outcoupled along the fiber. Introducing a customized side-emission profile requires modulation of the guiding and emitting properties along the fiber length, which is a particular challenge in continuous processing of soft waveguides. In this work, it is demonstrated that multimaterial extrusion printing can generate hydrogel optical fibers with tailored segments for light-side emission. The fibers are based on diacrylated Pluronic F-127 (PluDA). 1 mm diameter fibers are printed with segments of different optical properties by switching between a PluDA waveguiding ink and a PluDA scattering ink containing nanoparticles. The method allows the fabrication of fibers with segment lengths below 500 microns in a continuous process. The length of the segments is tailored by varying the switching time between inks during printing. Fibers with customized side-emission profiles along their length are presented. The functionality of the printed fibers is demonstrated by exciting fluorescence inside a surrounding 3D hydrogel. The presented technology and material combination allow unprecedented flexibility for designing soft optical fibers with customizable optical properties using simple processes and a medical material. This approach can be of interest to improve illumination inside tissues for photodynamic therapy (PDT).

The significant demand for energy storage systems has spurred innovative designs and extensive research on lithium-ion batteries (LIBs). To that end, an in-depth examination of utilized materials and relevant methods in conjunction with comparing electrochemical mechanisms is required. Lithium titanate (LTO) anode materials have received substantial interest in high-performance LIBs for numerous applications. Nevertheless, LTO is limited due to capacity fading at high rates, especially in the extended potential range of 0.01–3.00 V versus Li+/Li, while delivering the theoretical capacity of 293 mAh g−1. This study demonstrates how the performance of the LTO anode can be improved by modifying the manufacturing process. Altering the dry and wet mixing duration and speeds throughout the manufacturing process leads to differences in particle sizes and homogeneity of dispersion and structure. The optimized anode at 5 A g−1 (≈17C) and 10 A g−1 (≈34C) yielded 188 and 153 mAh g−1 and retained 73% and 68% of their initial capacity after 1000 cycles, respectively. The following findings offer valuable information regarding the empirical modifications required during electrode fabrication. Additionally, it sheds light on the potential to produce efficient anodes using commercial LTO powder.

Engineered living materials (ELMs), which usually comprise bacteria, fungi, or animal cells entrapped in polymeric matrices, offer limitless possibilities in fields like drug delivery or biosensing. Determining the conditions that sustain ELM performance while ensuring compatibility with ELM hosts is essential before testing them in vivo. This is critical to reduce animal experimentation and can be achieved through in vitro investigations. Currently, there are no standards that ensure ELM compatibility with host tissues. Towards this goal, we designed a 96-well plate-based screening method to streamline ELM growth across culture conditions and determine their compatibility potential in vitro. We showed proliferation of three bacterial species encapsulated in hydrogels over time and screened six different cell culture media. We fabricated ELMs in bilayer and monolayer formats and tracked bacterial leakage as a measure of ELM biocontainment. After screening, an appropriate medium was selected that sustained growth of an ELM, and it was used to study cytocompatibility in vitro. ELM cytotoxicity on murine fibroblasts and human monocytes was studied by adding ELM supernatants and measuring cell membrane integrity and live/dead staining, respectively, proving ELM cytocompatibility. Our work illustrates a simple setup to streamline the screening of compatible environmental conditions of ELMs with the host.

Batteries contain combinations of materials that undergo electrochemical reactions to convert chemical into electrical energy. Battery research relies on experience and know-how. Important materials and processing data can get overlooked, remain undocumented, or even lost. To bridge the gap between fundamental materials research and battery process engineering, it is essential to generate, analyze, and, most importantly, link intermediate knowledge for future use. Here, it is shown how to combine domain knowledge and a data-driven approach to understanding material–property relationships in the case of conductivity networks of carbon black. The Battery Production and Characterisation Ontology (BPCO) is employed to identify hypotheses that connect battery processing to material domain knowledge. The material's interactions between carbon black, polyvinylidene flouride, and solvents in the BPCO are characterized. These materials combine to form the classical microstructure in battery electrodes for the electrical conductivity. It is demonstrated how new links to the BPCO, verified via materials-processing relationships, and the interim results are identified as intermediate data.