Scientific publications

In this work, we present a proof-of-concept demonstration of inkjet-printed resistive temperature sensors based on nanoparticle platinum ink on flexible polyimide substrates. The resistive temperature sensors are designed as meander structures with a target nominal resistance of 100 and 1000 Ω to be compared to conventional bulk Pt100 and Pt1000 resistors. Thermogravimetric analysis and in situ resistance measurements identified 250°C as the optimal sintering temperature, enabling sufficient solvent removal for conductive structure formation while avoiding Pt surface oxidation and polyimide substrate degradation. Electrical characterization in the 20°C–80°C range revealed a linear relationship between resistance and temperature with effective temperature coefficients of resistance (~48%/57%) and sensitivities (~72%/87%) compared to Pt100/Pt1000 standards, respectively. Mechanical testing over 400 bending cycles showed less than 1% change in electrical resistance, confirming robust flexibility. This study demonstrates the feasibility of translating nanoparticle Pt-based resistive temperature sensors into flexible and automotive sensing applications, offering low-temperature processability, stable temperature coefficients of resistance, linear sensitivity, mechanical robustness, and chemical stability across 20°C–80°C range.

Engineering interfaces between organic semiconductors is an effective way to tailor organic electronic device performance, as charge transport and light interaction efficiency are strongly influenced by electronic coupling at molecular interfaces. Scanning transmission electron microscopy is routinely used to analyze interfaces at the atomic scale; however, its use for organic materials is limited due to the electron beam sensitivity of organic molecules, buried interfaces, and the semicrystalline nature of organics. In this work, we developed a workflow to correlate charge behavior at organic interfaces with their chemistry and structure, even when interface components are chemically and structurally similar and mixed at the nanoscale. We used this workflow to reveal the nanoscale mechanism behind enhanced charge transfer at the heterojunction between two-dimensional carbon nitride catalysts (poly-heptazine imide (PHI) and poly-triazine imide (PTI)) during the oxygen reduction reaction. We found that PHI crystallites grow on PTI layers formed at the gas–liquid interface in the salt melt, following the [001]PTI/[001]K-PHI orientation. This crystallographic alignment promotes the charge transfer from PTI to PHI and creates an electron-rich interface. Electron energy loss spectroscopy showed quaternary N atoms in the heterojunction, which aid O2 adsorption and 2e– reduction to H2O2, as well as a higher proportion of terminal and bridging N atoms, promoting charge separation during the reaction.

T cell activation requires cell polarization and changes in gene expression. Target cell stiffness contributes to the activation of immune cells, and tumor cell softening is linked to cancer progression. We investigated how substrate stiffness influences T cell activation using functionalized, T cell–activating substrates of varying stiffness and softened target cells. Reorientation of the microtubule-organizing center (MTOC) toward the immunological synapse and nuclear translocation of the transcription factor NFAT1 were impaired on softer hydrogels or upon contact with softer target cells. The increase in intracellular Ca2+ induced by target engagement also depended on stiffness and was reduced on soft substrates. Stiffness-dependent Ca2+ signaling was crucial for both rapid (MTOC reorientation) and long-term (NFAT translocation) responses. Whereas MTOC reorientation depended on the mechanosensitive Ca2+-permeable channel PIEZO1, NFAT1 translocation depended on the Ca2+ channel ORAI1. Our results demonstrate that target stiffness directly influences MTOC reorientation and NFAT1 translocation in T cells, and these two processes are governed by different plasma membrane Ca2+ channels, indicating that these stiffness-regulated rapid and long-term responses can be decoupled. Our findings imply that tumor cell stiffness regulates T cell functionality and suggest that pathways regulated by PIEZO1 and ORAI1 might differentially control rapid and long-term responses to stiffness in other cell types.

Herein, we report the charge storage and plastic properties of the redox-active, bimetallic metal phosphonate framework of [Cu(2,2′-bpy)VO(O3PC6H5)2]. The flexible crystals of [Cu(2,2′-bpy)VO(O3PC6H5)2] combine high energy storage with mechanical flexibility on the same platform, which is an unusual and significant property that is not observed in traditional rigid layered electrode materials. In contrast to RuO2, graphene, or MXenes, which prefer concentrated acidic or basic electrolytes to operate effectively as electrodes, [Cu(2,2′-bpy)VO(O3PC6H5)2] operates between pH values of 4 and 10 while reaching a specific capacitance of about 140 F/g in H3PO4 at pH 4 and in NaOH at pH 10 at 1 mV/s. It also demonstrates high chemical and electrochemical stability between pH 2 and 12 and in lithium hexafluorophosphate for extended periods. The use of [Cu(2,2′-bpy)VO(O3PC6H5)2] as electrodes eliminates the need for harsh chemical environments, generating more sustainable and environmentally friendly energy storage solutions, and [Cu(2,2′-bpy)VO(O3PC6H5)2] can be synthesized in water at mild temperatures. The combination of chemical stability, mechanical flexibility of [Cu(2,2′-bpy)VO(O3PC6H5)2], and compatibility with mild electrolytes makes [Cu(2,2′-bpy)VO(O3PC6H5)2] a more sustainable alternative to conventional metal oxides, MXenes, and carbon-based electrodes in next-generation supercapacitors and battery technologies.

Hydrogels mimicking the mechanical and biochemical features of the cellular microenvironment allow cell encapsulation and facilitate in vitro 3D culture. In addition to biocompatibility and reactivity in physiological conditions, a key criterion for crosslinking chemistry is appropriate gelation kinetics to allow mixing and homogeneous distribution of cells with the hydrogel precursors. We have previously presented aryl methylsulfone/thiol (MS/SH) reaction as a thiol-reactive cross-linking system for cell encapsulation in star polyethylene glycol (PEG4) hydrogels with a gelation kinetics in minutes time scale. Remaining experimental challenges for this system are a finer modulation of gelation kinetics and streamlining the synthesis of the prepolymer. Here we present the possibility to tune the gelation kinetics by introducing an electron-withdrawing substituent at p-position of the aryl MS ring. This variant also presents synthetic advantages. We study the influence of the p-substituent on the physicochemical properties of MS/SH crosslinked hydrogels, and their performance for cell encapsulation. We compare these properties with the PEG-MS variant containing an electron-donating linker. The new star poly(ethylene glycol)-4-(5-(methylsulfonyl)-1H-tetrazol-1-yl)benzamide (PEG4-CONH-TzMS) shows superior properties as cell encapsulating hydrogel in terms of ease of mixing polymer precursors, faster gelation, homogenous cell distribution and high enzymatic stability.

Excessive protease activity and impaired tissue regeneration are hallmarks of many disease states. Elevated matrix metalloproteinase-9 (MMP-9) plays a key role in adverse tissue remodeling by excessively degrading extracellular matrix (ECM) components and growth factors. Tissue inhibitor of metalloproteinase-3 (TIMP-3) regulates ECM turnover, and its bioavailability is influenced by glycosaminoglycans (GAGs). This study aimed to develop a methacrylated gelatin (GelMA)-based hydrogel functionalized with acrylated sulfated hyaluronan (sHAc) as a TIMP-3 delivery system to decrease ECM degradation under pathophysiological conditions. sHAc incorporation enhanced hydrogel stiffness, reduced degradation rates and yielded sustained TIMP-3 release for up to 28 days. Molecular modeling and surface plasmon resonance demonstrated preferential binding of TIMP-3 to sHAc over hyaluronan methacrylates, together providing a molecular rationale for the reduced and sustained release of TIMP-3 from sHAc-containing hydrogels. Angiogenesis-related functional assays, supported by molecular modeling studies, indicate that sHAc modulates the anti-angiogenic activity of TIMP-3 by altering vascular endothelial growth factor receptor-associated signaling, while preserving metalloproteinase inhibition. Released TIMP-3 from GelMA/sHAc hydrogels retained bioactivity, effectively inhibiting MMP-9 activity and mitigating ECM degradation in-vitro and in human ex-vivo models. In a murine subcutaneous implantation model, sHAc-functionalized TIMP-3-loaded hydrogels were associated with reduced inflammatory cell presence and altered vascular- and matrix-related tissue signatures compared with GelMA controls. These findings underscore the potential of sHAc-functionalized GelMA hydrogels as biomaterials for therapeutics delivery, offering controlled TIMP-3 release and sustained bioactivity to promote ECM stability and on-demand MMP inhibition. This system represents a promising strategy for addressing the challenges of excessive MMP activity.

The demand for lithium production has seen a significant rise, with the growing electric vehicle and stationary battery markets requiring further development of sustainable and scalable extraction methods. Direct lithium extraction technologies have been developed to address potential shortages, with adsorption emerging as a key method due to its efficiency and low environmental impact. Given that Al(OH)3 is already utilized as an adsorbent in various industrial applications, the practical importance of Al-based alternative systems for lithium ion extraction is increasing, yet lithium ion recovery requires harsh chemicals. In this study, we report a novel lithium extraction method combining chemical adsorption and electrochemical release using a synthesized aluminum layered double hydroxide (Al-LDH) material, developed under mild reaction conditions. The performance of the Al-LDH electrode was evaluated against a commercial Al(OH)3 adsorbent. Comprehensive characterization using techniques such as X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy revealed detailed insights into the crystalline structure, particle size distribution, and surface morphology of the materials. The Al-LDH electrode exhibited a lithium ion adsorption capacity, achieving an average chemical uptake of lithium ions of 57.6 mg/g. In contrast, lithium-ion uptake capacity for Al(OH)3 was 1.0 mg/g over 15 cycles. Notably, this method operates under pH-neutral conditions, eliminating the need for harsh acidic or basic eluents. As a result, it prevents structural degradation and minimizes secondary pollution for potential future applications of lithium-ion recovery. The material’s layered structure selectively allowed lithium ion intake while blocking sodium ions, demonstrating its high selectivity and utility in lithium ion recovery processes. The integration of pH-neutral regeneration and high selectivity shows that Al-LDH electrodes as viable candidates for next-generation, green lithium extraction technologies.

The functional integration of biological switches with synthetic building blocks enables the design of modular, stimulus-responsive biohybrid materials. By connecting the individual modules via diffusible signals, information-processing circuits can be designed. Such systems are, however, mostly limited to respond to either small molecules, proteins, or optical input thus limiting the sensing and application scope of the material circuits. Here, a highly modular biohybrid material is design based on CRISPR/Cas13a to translate arbitrary single-stranded RNAs into a biomolecular material response. This system exemplified by the development of a cascade of communicating materials that can detect the tumor biomarker microRNA miR19b in patient samples or sequences specific for SARS-CoV. Specificity of the system is further demonstrated by discriminating between input miRNA sequences with single-nucleotide differences. To quantitatively understand information processing in the materials cascade, a mathematical model is developed. The model is used to guide systems design for enhancing signal amplification functionality of the overall materials system. The newly designed modular materials can be used to interface desired RNA input with stimulus-responsive and information-processing materials for building point-of-care suitable sensors as well as multi-input diagnostic systems with integrated data processing and interpretation.

Background: Intima proliferation and in-stent restenosis is a challenging situation in interventional treatment of small vessel obstruction. Al/Al2O3 nanowires have been shown to accelerate vascular endothelial cell proliferation and migration in vitro, while suppressing vascular smooth muscle cell growth. Moreover, surface modification of Al/Al2O3 nanowires with poly[bis(2,2,2-trifluoromethoxy)phosphazene (PTFEP) coating enables further advantages such as reduced platelet adhesion. Therefore, the study's goal was to compare the biocompatibility of novel Al/Al2O3 + PTFEP coated nanowire bare-metal stents to uncoated control stents in vivo using optical coherence tomography (OCT), quantitative angiography and histomorphometric assessment. Methods: 15 Al/Al2O3 + PTFEP coated and 19 control stents were implanted in the cervical arteries of 9 Aachen minipigs. After 90 days, in-stent stenosis, thrombogenicity, and inflammatory response were assessed. Scanning electron microscopy was used to analyse the stent surface. Results: OCT analysis revealed that neointimal proliferation in Al/Al2O3 + PTFEP coated stents was significantly reduced compared to control stents. The neointimal area was 1.16 ± 0.77 mm2 in Al/Al2O3 + PTFEP coated stents vs. 1.98 ± 1.04 mm2 in control stents (p = 0.004), and the neointimal thickness was 0.28 ± 0.20 vs. 0.47 ± 0.10 (p = 0.003). Quantitative angiography showed a tendency to less neointimal growth in coated stents. Histomorphometry showed no significant difference between the two groups and revealed an apparent inflammatory reaction surrounding the stent struts. Conclusions: At long-term follow-up, Al/Al2O3 + PTFEP coated stents placed in peripheral arteries demonstrated good tolerance with no treatment-associated vascular obstruction and reduced in-stent restenosis in OCT. These preliminary in vivo findings indicate that Al/Al2O3 + PTFEP coated nanowire stents may have translational potential to be used for the prevention of in-stent restenosis.

Supercapacitors are efficient and versatile energy storage devices, offering remarkable power density, fast charge/discharge rates, and exceptional cycle life. As research continues to push the boundaries of their performance, electrode fabrication techniques are critical aspects influencing the overall capabilities of supercapacitors. Herein, we aim to shed light on the advantages offered by dry electrode processing for advanced supercapacitors. Notably, our study explores the performance of these electrodes in three different types of electrolytes: organic, ionic liquids, and quasi-solid states. By examining the impact of dry electrode processing on various electrode and electrolyte systems, we show valuable insights into the versatility and efficacy of this technique. The supercapacitors employing dry electrodes demonstrated significant improvements compared with conventional wet electrodes, with a lifespan extension of +45% in organic, +192% in ionic liquids, and +84% in quasi-solid electrolytes. Moreover, the increased electrode densities achievable through the dry approach directly translate to improved volumetric outputs, enhancing energy storage capacities within compact form factors. Notably, dry electrode-prepared supercapacitors outperformed their wet electrode counterparts, exhibiting a higher energy density of 6.1 Wh cm−3 compared with 4.7 Wh cm−3 at a high power density of 195 W cm−3, marking a substantial 28% energy improvement in the quasi-solid electrolyte.