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Ultra-Stretchable Kirigami Piezo-Metamaterials for Sensing Coupled Large Deformations
Get PDFMechanical metamaterials are known for their prominent mechanical characteristics such as programmable deformation that are due to periodic microstructures. Recent research trends have shifted to utilizing mechanical metamaterials as structural substrates to integrate with functional materials for advanced functionalities beyond mechanical, such as active sensing. This study reports on the ultra-stretchable kirigami piezo-metamaterials (KPM) for sensing coupled large deformations caused by in- and out-of-plane displacements using the lead zirconate titanate (PZT) and barium titanate (BaTiO3) composite films. The KPM are fabricated by uniformly compounding and polarizing piezoelectric particles (i.e., PZT and BaTiO3) in silicon rubber and structured by cutting the piezoelectric rubbery films into ligaments. Characterizes the electrical properties of the KPM and investigates the bistable mechanical response under the coupled large deformations with the stretching ratio up to 200% strains. Finally, the PZT KPM sensors are integrated into wireless sensing systems for the detection of vehicle tire bulge, and the non-toxic BaTiO3 KPM are applied for human posture monitoring. The reported kirigami piezo-metamaterials open an exciting venue for the control and manipulation of mechanically functional metamaterials for active sensing under complex deformation scenarios in many applications
Catalyst Supraparticles: Tuning the Structure of Spray-Dried Pt/SiO2 Supraparticles via Salt-Based Colloidal Manipulation to Control their Catalytic Performance
Get PDFThe structure of supraparticles (SPs) is a key parameter for achieving advanced functionalities arising from the combination of different nanoparticle (NP) types in one hierarchical entity. However, whenever a droplet-assisted forced assembly approach is used, e.g., spray-drying, the achievable structure is limited by the inherent drying phenomena of the method. In particular, mixed NP dispersions of differently sized colloids are heavily affected by segregation during the assembly. Herein, the influence of the colloidal arrangement of Pt and SiO2 NPs within a single supraparticulate entity is investigated. A salt-based electrostatic manipulation approach of the utilized NPs is proposed to customize the structure of spray-dried Pt/SiO2 SPs. By this, size-dependent separation phenomena of NPs during solvent evaporation, that limit the catalytic performance in the reduction of 4-nitrophenol, are overcome by achieving even Pt NP distribution. Additionally, the textural properties (pore size and distribution) of the SiO2 pore framework are altered to improve the mass transfer within the material leading to increased catalytic activity. The suggested strategy demonstrates a powerful, material-independent, and universally applicable approach to deliberately customize the structure and functionality of multi-component SP systems. This opens up new ways of colloidal material combinations and structural designs in droplet-assisted forced assembly approaches like spray-drying
Soft Synthetic Cells with Mobile Membrane Ligands for Ex Vivo Expansion of Therapy-Relevant T Cell Phenotypes
Get PDFThe expansion of T cells ex vivo is crucial for effective immunotherapy but currently limited by a lack of expansion approaches that closely mimic in vivo T cell activation. Taking inspiration from bottom-up synthetic biology, a new synthetic cell technology is introduced based on dispersed liquid-liquid phase-separated droplet-supported lipid bilayers (dsLBs) with tunable biochemical and biophysical characteristics, as artificial antigen presenting cells (aAPCs) for ex vivo T cell expansion. These findings obtained with the dsLB technology reveal three key insights: first, introducing laterally mobile stimulatory ligands on soft aAPCs promotes expansion of IL-4/IL-10 secreting regulatory CD8+ T cells, with a PD-1 negative phenotype, less prone to immune suppression. Second, it is demonstrated that lateral ligand mobility can mask differential T cell activation observed on substrates of varying stiffness. Third, dsLBs are applied to reveal a mechanosensitive component in bispecific Her2/CD3 T cell engager-mediated T cell activation. Based on these three insights, lateral ligand mobility, alongside receptor- and mechanosignaling, is proposed to be considered as a third crucial dimension for the design of ex vivo T cell expansion technologies
Quantum Sensing Unravels Antioxidant Efficacy Within PCL/Matrigel Skin Equivalents
Get PDFSkin equivalents (SE) that recapitulate biological and mechanical characteristics of the native tissue are promising platforms for assessing cosmetics and studying fundamental biological processes. Methods to achieve SEs with well-organized structure, and ideal biological and mechanical properties are limited. Here, the combination of melt electrowritten PCL scaffolds and cell-laden Matrigel to fabricate SE is described. The PCL scaffold provides ideal structural and mechanical properties, preventing deformation of the model. The model consists of a top layer for seeding keratinocytes to mimic the epidermis, and a bottom layer of Matrigel-based dermal compartment with fibroblasts. The compressive modulus and the biological properties after 3-day coculture indicate a close resemblance with the native skin. Using the SE, a testing system to study the damage caused by UVA irradiation and evaluate antioxidant efficacy is established. The effectiveness of Tea polyphenols (TPs) and L-ascorbic acid (Laa) is compared based on free radical generation. TPs are demonstrated to be more effective in downregulating free radical generation. Further, T1 relaxometry is used to detect the generation of free radicals at a single-cell level, which allows tracking of the same cell before and after UVA treatment
Multi-Walled Carbon Nanotubes Suspensions as Liquid Conductors: Electrical and Mechanical Network Interplay
Get PDFSoft-adaptive electronics require both sensor and conductor materials. The key parameter for these materials is their mechanoelectrical properties. Liquid metals and solid conductive composites have been exploited in this application field, but both are limited by either their chemical stability or limited flexibility, respectively. Electrofluids are a novel approach towards soft electronic components. They are concentrated colloidal suspensions of conductive particles, in which dynamic contacts retain electrical conductivity under deformation, filling the gap between liquid metals and solid composites. Here, we study the mechanical and electrical network interplay of electrofluids based on multi-walled carbon nanotubes (MWCNTs) in glycerol. These networks arise at different filler concentrations, showing a different response to external deformations. We found that electrical conductivity occurs without the presence of a rigid mechanical network, which allows MWCNT suspensions to be electrically conductive even under flow conditions. By performing rheoelectrical measurements, we observed how the mechanical and electrical networks evolved with the applied deformation. We demonstrated the applicability of electrofluids with tailored mechanoelectrical properties as soft electrical connectors
The shape of Nature’s stingers revealed
Get PDFAs ubiquitous defense mechanisms in Nature, stinger-like structures cover a size range over six orders of magnitude. While their composition varies, we uncovered a common geometric trait: a non-linear relationship between diameter and distance from the tip, following a power law with an exponent universally between 2 and 3. Through a combination of theoretical mechanics and experiments, we interpret this universal shape to be the result of a competition between penetration and buckling, motivated by the limitations of the mechanical properties of the stinger material. Our study not only resolves a mystery underlying the structural optimization of convergently evolved natural stingers, but also can offer inspiration for efficient needles in technology or biomedicine, made from sustainable non-metallic materials
Black goes green: single-step solvent exchange for sol-gel synthesis of carbon spherogels as high-performance supercapacitor electrodes
Get PDFNanoporous carbon materials with customized structural features enable sustainable and electrochemical applications through improved performance and efficiency. Carbon spherogels (highly porous carbon aerogel materials consisting of an assembly of hollow carbon nanosphere units with uniform diameters) are desirable candidates as they combine exceptional electrical conductivity, bespoke shell porosity, tunability of the shell thickness, and a high surface area. Herein, we introduce a novel and more environmentally friendly sol-gel synthesis of resorcinol-formaldehyde (RF) templated by polystyrene spheres, forming carbon spherogels in an organic solvent. By tailoring the molar ratio of resorcinol to isopropyl alcohol (R/IPA) and the concentration of polystyrene, the appropriate synthesis conditions were identified to produce carbon spherogels with adjustable wall thicknesses. A single-step solvent exchange process from deionized water to isopropyl alcohol reduces surface tension within the porous gel network, making this approach significantly time and cost-effective. The lower surface tension of IPA enables solvent extraction under ambient conditions, allowing for direct carbonization of RF gels while maintaining a specific surface area loss of less than 20% compared to supercritically dried counterparts. The specific surface areas obtained after physical activation with carbon dioxide are 2300–3600 m2 g−1. Transmission and scanning electron microscopy verify the uniform, hollow carbon sphere network morphology. Specifically, those carbon spherogels are high-performing electrodes for energy storage in a supercapacitor setup featuring a specific capacitance of up to 204 F g−1 at 200 mA g−1 using 1 M potassium hydroxide (KOH) solution as the electrolyte
Annual report 2023 / Leibniz Institute for New Materials
Get PDFVorwort: Das INM blickt auf ein erfolgreiches Jahr 2023 zurück. Wissenschaftliche Highlights wie die Entwicklung von lebenden therapeutischen Materialien, die die Bildung neuer Blutgefäße unterstützen oder Kontaktlinsen kontinuierlich feucht halten, von Materialien, die ihre physikalischen Eigenschaften selbst messen und anpassen, von selbstkorrigierenden Spiegeln für große optische Teleskope sind nur einige Beispiele aus dem breitgefächerten Forschungsportfolio des INM. Aus finanzieller Sicht hat sich die Drittmittelbilanz des INM erfreulich entwickelt. Dabei wurden auch neue Wege zur Kooperation mit Industriepartnern beschritten, die in einer neuen Technologie-transferstrategie mündeten. Personell gab es 2023 einige Veränderungen: Zum Jahresbeginn übernahm Professorin Aránzazu del Campo den Vorsitz der Geschäftsführung. Im März nahm Professor Wilfried Weber seine Arbeit als Wissenschaftlicher Geschäftsführer des INM und als Leiter der neuen Forschungsabteilung Materialorientierte Synthetische Biologie auf. Mit dem Ruhestand unseres kaufmännischen Geschäftsführers Günter Weber übernahm Michael Marx die kommissarische Leitung und wurde schließlich im Dezember zum Kaufmännischen Geschäftsführer ernannt. Auch für die Etablierung neuer Forschungsgruppen wurden 2023 wichtige Weichen gestellt und Vorarbeiten geleistet. Bereits Mitte des Jahres begannen die Vorbereitungen zur Evaluierung des INM im Juni 2024. Im Zuge dieser Vorbereitungen erfolgte sowohl intern als auch mit den Gremien eine umfassende Entwicklung der Strategie für die nächsten sieben Jahre. Dabei konnten das wissenschaftliche Profil des Instituts geschärft, neue Zukunftsthemen identifiziert und neue Kooperationsfelder erschlossen werden. In diesem Strategieprozess wurden vier Arbeitsgruppen zu den Themen Digitalisierung, Diversität, Sichtbarkeit und Energieeinsparung ins Leben gerufen. 2023 war auch ein Jahr des Beginns neuer Großprojekte. Hierbei wäre beispielhaft das DFG geförderte Schwerpunktprogramm (SPP) 2451 „Lebende Materialien mit adaptiven Funktionen“ zu nennen, dessen Koordination Aránzazu del Campo innehat, und das das INM mit Partnern in München, Heidelberg und Golm verbindet. Auch für den seit 2020 erfolgreich arbeitenden Leibniz ScienceCampus „Lebende Therapeutische Materialien“ wurden vor Kurzem die Mittel für eine Fortsetzung des Projektes um weitere vier Jahre bewilligt. Auch auf der Ebene der Forschungsgruppen gab es erfolg-reiche Einwerbungen von Mitteln. Hier seien exemplarisch die Förderung der Forschung von Dr. Oskar Staufer und seiner Immuno Materialien-Gruppe aus dem Emmy-Noether-Programm und der von Wilfried Weber mit-gebrachte ERC Grant STEADY genannt. Weitere Einblicke in Neues und Spannendes aus dem INM bieten Ihnen die nachfolgenden Seiten. Wir freuen uns über Ihr Interesse
Consequence of anisotropy on flocking: the discretized Vicsek model [revised Version 2]
Get PDFWe numerically study a discretized Vicsek model (DVM) with particles orienting in q possible orientations in two dimensions. The study probes the significance of anisotropic orientation and microscopic interaction on the macroscopic behavior. The DVM is an off-lattice flocking model like the active clock model [ACM; EPL {\bf 138}, 41001 (2022)] but the dynamical rules of particle alignment and movement are inspired by the prototypical Vicsek model (VM). The DVM shows qualitatively similar properties as the ACM for intermediate noise strength where a transition from macrophase to microphase separation of the coexistence region is observed as q is increased. But for small q and noise strength, the liquid phase appearing in the ACM at low temperatures is replaced in the DVM by a configuration of multiple clusters with different polarization which does not exhibit any long-range order. We find that the dynamical rules have a profound influence on the overarching features of the flocking phase. We further identify the metastability of the ordered liquid phase subjected to a perturbation
Ordering kinetics in the active Ising model
Get PDFWe undertake a numerical study of the ordering kinetics in the two-dimensional (2d) active Ising model (AIM), a discrete flocking model with a non-conserved scalar order parameter. We find that for a quench into the liquid-gas coexistence region and in the ordered liquid region, the characteristic length scale of both the density and magnetization domains follows the Lifshitz-Cahn-Allen (LCA) growth law: R(t)∼t1/2, consistent with the growth law of passive systems with scalar order parameter and non-conserved dynamics. The system morphology is analyzed with the two-point correlation function and its Fourier transform, the structure factor, which conforms to the well-known Porod's law, a manifestation of the coarsening of compact domains with smooth boundaries. We also find the domain growth exponent unaffected by different noise strengths and self-propulsion velocities of the active particles. However, transverse diffusion is found to play the most significant role in the growth kinetics of the AIM. We extract the same growth exponent by solving the hydrodynamic equations of the AIM