TY - JOUR A1 - Topolniak, Ievgeniia A1 - Elert, Anna Maria A1 - Knigge, Xenia A1 - Ciftci, G. C. A1 - Radnik, Jörg A1 - Sturm, Heinz T1 - High precision micropatterning of polydopamine by Multiphoton Lithography N2 - Mussel-inspired polydopamine (PDA) initiated a multifunctional modification route that leads to the generation of novel advanced materials and their applications. However, existing PDA deposition techniques still exhibit poor spatial control, have a very limited capability of micropatterning and do not allow to locally tune PDA topography. Herein, we demonstrate PDA deposition based on Multiphoton Lithography (MPL) that enables full spatial and temporal control with nearly total freedom of patterning design. Using MPL, we achieve 2D microstructures of complex design with pattern precision of 0.8 μm without the need of a photomask or stamp. Moreover, this approach permits adjusting the morphology and thickness of the fabricated microstructure within one deposition step, resulting in a unique tunability of materials properties. The chemical composition of PDA is confirmed and its ability for protein enzyme immobilization is demonstrated. This work presents a new methodology for high precision and complete control of PDA deposition, enabling PDA incorporation in applications where fine and precise local surface functionalization is required. Possible applications include multicomponent functional elements and devices in microfluidics or lab-on-a-chip systems. KW - Multiphoton lithography KW - Polydopamine KW - Micropatterning PY - 2022 DO - https://doi.org/10.1002/adma.202109509 VL - 34 IS - 18 SP - e2109509 PB - Wiley online library AN - OPUS4-54535 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Topolniak, Ievgeniia A1 - Elert, Anna Maria A1 - Knigge, Xenia A1 - Cifci, G. C. A1 - Radnik, Jörg A1 - Sturm, Heinz T1 - Polydopamine micropatterning for selective substrate bio-functionalization N2 - Inspired by the chemistry of mussel adhesive proteins, polydopamine (PDA) exhibits strong adhesion to nearly any kind of organic or inorganic surface and shows high ability for surface post-modification and secondary reactions. As a result, PDA has been widely used as a base adlayer to enable versatile surface chemistry and functionalization. It has shown great potential in wide range of applications including biomedical field (e.g., drug delivery, adhesives, photothermal therapy, bone and tissue engineering, cell adhesion, biosensing). However, implementation of PDA in microdevices is still hindered by insufficient spatial and temporal control of excited deposition methods. In this work we present a novel approach to fabricate tunable micropatterned substrates where mussel-inspired chemistry provides base for various surface modification [2]. Current approach applies Multiphoton Lithography (MPL) to initiate local PDA formation, and, therefore, does not require use of microstamp or photomask. As a result, the microstructures of complex designs can be produced with the spatial resolution down to 0.8 μm (Figure 1). The desired design can be easily altered by adjusting the stl model or the fabrication code. Unlike the conventional deposition of PDA based on dopamine auto-oxidation, our method does not require presence of strong oxidants, metal ions or alkaline pH. Herein-demonstrated deposition approach will significantly facilitate applications of polydopamine and other mussel-inspired materials in microdevices and high-resolution active microcomponents (e.g., in MEMS and microfluidics). Adjustment of MPL parameters revealed that the morphology and thickness of resulted PDA microstructures can be controlled by altering the laser power and its scanning velocity. As a result, it also enables the production of micropatterns with structural gradient. Apart from the glass substrate, we performed PDA patterning at surfaces of different nature such as polychlorotrifluoroethylene, polydimethylsiloxane, polyethylene terephthalate, silicon wafers, and fluorinated glass coverslips. We tested different composition of dopamine solution for its ability of PDA buildup. Solutions containing Tris buffer, phosphate buffer or DI water only as well as different pH (6.0, 7.0 and 8.5) could be successfully applied for high-precision PDA micropatterning. Moreover, the effect of antioxidants and purging of the solution with oxygen and nitrogen was investigated. In all cases, no decrease of deposition efficiency was observed. The chemical nature of PDA was confirmed by locally recorded vibrational and x-ray photoelectron spectra. To ensure post-modification potential of MPL deposited PDA we demonstrated one-step deposition of micropatterns with trypsin. Obtained bio-functionalised surface can be further applied as a protein sensing active microelement. T2 - Laser Precision Microfabrication CY - Dresden, Germany DA - 07.06.2022 KW - Polydopamine KW - Two-photon polymerisation KW - Micropatterning PY - 2022 AN - OPUS4-55064 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fortini, Renata A1 - Meyer-Plath, A. A1 - Kehren, D. A1 - Gernert, U. A1 - Agudo Jácome, Leonardo A1 - Sturm, Heinz T1 - Measurement of flexural rigidity of multi-walled carbon nanotubes by Dynamic Scanning Electron Microscopy N2 - In this work the flexural rigidity of individual large diameter multi-walled carbon nanotubes (MWCNTs) was investigated. The bending modulus were obtained by detecting the resonance frequencies of mechanically excited cantilevered carbon nanotubes using the so-called dynamic scanning electron microscopy technique, and applying the Euler–Bernoulli beam theory. For the nanotubes studied, we determined a modulus of up to 160 GPa. This agrees with values reported by other authors for MWCNTs produced by catalytic chemical vapor deposition, however, it is 6-8 times smaller than values reported for single and multi-walled carbon nanotubes produced by arc-discharge synthesis. Toxicological studies with carbon nanotubes have been showing that inhaled airborne nanofibers that reach the deep airways of the respiratory system may lead to serious, asbestos-like lung diseases. These studies suggested that their toxicity critically depends on the fiber flexural rigidity, with high rigidity causing cell lesions. To complement the correlation between observed toxicological effects and fiber rigidities, reliable and routinely applicable measurement techniques for the flexural rigidity of nanofibers are required. KW - Flexural rigidity KW - Bending modulus KW - Resonance frequency KW - Carbon nanotubes KW - Fiber toxicology PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-514190 DO - https://doi.org/10.3390/fib8050031 SN - 2079-6439 VL - 8 IS - 5 SP - 31 PB - MDPI AN - OPUS4-51419 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Silbernagl, Dorothee A1 - Ghasem Zadeh Khorasani, Media A1 - Cano Murillo, Natalia A1 - Elert, Anna Maria A1 - Sturm, Heinz ED - Glatzel, T. T1 - Bulk chemical composition contrast from attractive forces in AFM force spectroscopy N2 - A key application of atomic force microscopy (AFM) is the measurement of physical properties at sub-micrometer resolution. Methods such as force–distance curves (FDCs) or dynamic variants (such as intermodulation AFM (ImAFM)) are able to measure mechanical properties (such as the local stiffness, kr) of nanoscopic heterogeneous materials. For a complete structure–property correlation, these mechanical measurements are considered to lack the ability to identify the chemical structure of the materials. In this study, the measured attractive force, Fattr, acting between the AFM tip and the sample is shown to be an independent measurement for the local chemical composition and hence a complete structure–property correlation can be obtained. A proof of concept is provided by two model samples comprised of (1) epoxy/polycarbonate and (2) epoxy/boehmite. The preparation of the model samples allowed for the assignment of material phases based on AFM topography. Additional chemical characterization on the nanoscale is performed by an AFM/infrared-spectroscopy hybrid method. Mechanical properties (kr) and attractive forces (Fattr) are calculated and a structure–property correlation is obtained by a manual principle component analysis (mPCA) from a kr/Fattr diagram. A third sample comprised of (3) epoxy/polycarbonate/boehmite is measured by ImAFM. The measurement of a 2 × 2 µm cross section yields 128 × 128 force curves which are successfully evaluated by a kr/Fattr diagram and the nanoscopic heterogeneity of the sample is determined. KW - AFM force spectroscopy KW - Composites KW - Principle component analysis KW - Structure–property correlation KW - Van der Waals forces PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520175 DO - https://doi.org/10.3762/bjnano.12.5 SN - 2190-4286 VL - 12 IS - 5 SP - 58 EP - 71 PB - Beilstein Institute CY - Frankfurt am Main AN - OPUS4-52017 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cano Murillo, Natalia A1 - Ghasem Zadeh Khorasani, Media A1 - Silbernagl, Dorothee A1 - Hahn, Marc Benjamin A1 - Hodoroaba, Vasile-Dan A1 - Sturm, Heinz T1 - Nanomechanical study of polycarbonate/boehmite nanoparticles/epoxy ternary composite and their interphases N2 - Thermoplastic modified thermosets are of great interest especially due to their improved fracture toughness. Comparable enhancements have been achieved by adding different nanofillers including inorganic particles such as nanosized boehmite. Here, we present a nanomechanical study of two composite systems, the first comprising a polycarbonate (PC) layer in contact with epoxy resin (EP) and the second consisting of a PC layer containing boehmite nanoparticles (BNP) which is also in contact with an EP layer. The interaction between PC and EP monomer is tested by in situ Fourier transformed infrared (FT-IR) analysis, from which a reaction induced phase separation of the PC phase is inferred. Both systems are explored by atomic force microscopy (AFM) force spectroscopy. AFM force-distance curves (FDC) show no alteration of the mechanical properties of EP at the interface to PC. However, when a PC phase loaded with BNP is put in contact with an epoxy system during curing, a considerable mechanical improvement exceeding the rule of mixture was detected. The trend of BNP to agglomerate preferentially around EP dominated regions and the stiffening effect of BNP on EP shown by spatial resolved measurements of Young's modulus, suggest the effective presence of BNP within the EP phase. KW - Composites KW - Mechanical properties KW - Nanoparticles KW - Thermoplastics KW - Thermosets PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-515965 DO - https://doi.org/10.1002/app.50231 SN - 0021-8995 SN - 1097-4628 VL - 138 IS - 12 SP - 1 EP - 11 PB - Wiley CY - New York, NY AN - OPUS4-51596 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sänger, Johanna Christiane A1 - Pauw, Brian Richard A1 - Sturm, Heinz A1 - Günster, Jens T1 - First time additively manufactured advanced ceramics by using two-photon polymerization for powder processing N2 - Methods and materials are presented here, which enable the manufacturing of fine structures using a 3D-printing method known as two-photon polymerization (2PP). As traditional photolithography methods for structuring ceramic slurries do not function with 2PP, due to light scattering on ceramic particles, a novel water-based photoresist with high ceramic loading of extremely well dispersed ceramic nano particles was developed. This photoresist is basically a ceramic slurry containing a photocurable agent and a photoinitiator to be crosslinkable with the 780 nm wavelength femtosecond laser light source of the 2PP machine. It is demonstrated that it is possible to gain a highly transparent and low viscous slurry suitable for 2PP processing. This work shows the development of the slurry, first printing results and the post-printing processes required to form three dimensional ceramic microstructures consisting of alumina toughened zirconia (ATZ). KW - 3D-printing KW - Two-photon polymerization KW - 2PP KW - Ceramic nano particles KW - Slurry KW - Alumina toughened zirconia KW - ATZ KW - Additive manufacturing KW - SchwarzP cells KW - Nano-ceramic-additive-manufacturing photoresin KW - NanoCAM PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-517441 DO - https://doi.org/10.1016/j.oceram.2020.100040 VL - 4 SP - 100040 PB - Elsevier Ltd. AN - OPUS4-51744 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cano Murillo, Natalia A1 - Ghasem Zadeh Khorasani, Media A1 - Silbernagl, Dorothee A1 - Emamverdi, Farnaz A1 - Cacua, K. A1 - Hodoroaba, Vasile-Dan A1 - Sturm, Heinz T1 - Carrier Fibers for the Safe Dosage of Nanoparticles in Nanocomposites: Nanomechanical and Thermomechanical Study on Polycarbonate/Boehmite Electrospun Fibers Embedded in Epoxy Resin N2 - The reinforcing effect of boehmite nanoparticles (BNP) in epoxy resins for fiber composite lightweight construction is related to the formation of a soft but bound interphase between filler and polymer. The interphase is able to dissipate crack propagation energy and consequently increases the fracture toughness of the epoxy resin. Usually, the nanoparticles are dispersed in the resin and then mixed with the hardener to form an applicable mixture to impregnate the fibers. If one wishes to locally increase the fracture toughness at particularly stressed positions of the fiber-reinforced polymer composites (FRPC), this could be done by spraying nanoparticles from a suspension. However, this would entail high costs for removing the nanoparticles from the ambient air. We propose that a fiber fleece containing bound nanoparticles be inserted at exposed locations. For the present proof-of-concept study, an electrospun polycarbonate nonwoven and taurine modified BNP are proposed. After fabrication of suitable PC/EP/BNP composites, the thermomechanical properties were tested by dynamic mechanical analysis (DMA). Comparatively, the local nanomechanical properties such as stiffness and elastic modulus were determined by atomic force microscopy (AFM). An additional investigation of the distribution of the nanoparticles in the epoxy matrix, which is a prerequisite for an effective nanocomposite, is carried out by scanning electron microscopy in transmission mode (TSEM). From the results it can be concluded that the concept of carrier fibers for nanoparticles is viable. KW - Advanced materials KW - Electrospun nanocomposite fiber KW - Nanomechanical charecteisation KW - Nanosafety KW - Epoxy nanocomposites PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-528265 DO - https://doi.org/10.3390/nano11061591 VL - 11 IS - 6 SP - 1591 PB - MDPI CY - CH - 4020 Basel, Switzerland AN - OPUS4-52826 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Waniek, Tassilo A1 - Braun, U. A1 - Silbernagl, Dorothee A1 - Sturm, Heinz T1 - The impact of water released from boehmite nanoparticles during curing in epoxy-based nanocomposites N2 - The enhancing effect on mechanical properties of boehmite (γ-AlOOH) nanoparticles (BNP) in epoxy-based nanocomposites on the macroscopic scale encouraged recent research to investigate the micro- and nanoscopic properties. Several studies presented different aspects relatable to an alteration of the epoxy polymer network formation by the BNP with need for further experiments to identify the mode of action. With FTIR-spectroscopic methods this study identifies interactions of the BNP with the epoxy polymer matrix during the curing process as well as in the cured nanocomposite. The data reveals that not the BNP themselves, but the water released from them strongly influences the curing process by hydrolysis of the anhydride hardener or protonation of the amine accelerator. The changes of the curing processes are discussed in detail. The changes of the curing processes enable new explanation for the changed material properties by BNP discussed in recent research like a lowered glass transition temperature region (Tg) and an interphase formation. KW - Spectroscopy KW - Aluminium oxide hydroxide KW - Glass transition temperature KW - Material chemistry KW - Nanocomposites KW - Structure-property relationship PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-527202 DO - https://doi.org/10.1002/app.51006 VL - 138 IS - 39 SP - 51006 PB - Wiley Periodicals LLC CY - Hoboken AN - OPUS4-52720 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fritzsche, Sven A1 - Topolniak, Ievgeniia A1 - Weise, Matthias A1 - Sturm, Heinz T1 - Shape deviations of DLW microstructures in dependency of fabrication parameters N2 - Deep understanding of the effects associated with fabrication parameters and their influence on the resulting structures shape is essential for the further development of direct laser writing (DLW). In particular, it is critical for development of reference materials, where structure parameters are precisely fabricated and should be reproduced with use of DLW technology. In this study we investigated the effect of various fabrication and preparation parameters on the structural precision of interest for reference materials. A well-studied photo-curable system, SZ2080 negative photo-resist with 1 wt.% Michler's ketone (Bis) photo-initiator, was investigated in this work. The correlation between applied laser power, laser velocity, fabrication direction on the deviations in the structure shape were observed by means of white light interferometry microscopy. Moreover, influence of slicing and hatching distances as well as prebake time were studied as function of sample shape. Deviations in the structure form between the theoretically expected and the one detected after DLW fabrication were observed in the range up to 15%. The observed shape discrepancies show the essential importance of fine-tuning the fabrication parameter for reference structure production. KW - Direct laser writing KW - Fabrication parameters KW - Structural precision KW - SZ2080 negative photo-resist KW - White light interferometry microscopy PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-535906 DO - https://doi.org/10.1088/1361-6439/ac2a14 VL - 31 IS - 12 SP - 1 EP - 8 PB - IOP Science AN - OPUS4-53590 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - INPR A1 - Fritzsche, Sven A1 - Pauw, Brian Richard A1 - Weimann, Christiane A1 - Sturm, Heinz T1 - First of its kind: A test artifact for direct laser writing N2 - With Direct Laser Writing (DLW) maturing in all aspects as a manufacturing technology a toolset for quality assurance must be developed. In this work we want to introduce a first of its kind test artifact. Test artifacts are standardized 3D models with specific geometric feature to evaluate the performance of writing parameters. Test artifacts are already common in other 3D additive manufacturing technologies e.g. Selective Laser Melting. The test artifact introduced in this work was developed in particular to accommodate 1) the high geometrical resolution of DLW structures and 2) the limited possibilities to examine the resulting structure. Geometric accuracy, surface adhesion as well as confocal raman spectroscopy results were considered when evaluating the design of the test artifact. We will explain the individual features and design considerations of our DLW test artifact. The difference between two slicers, Cura and 3DPoli, and the implications on measured feature sizes and the general shape is quantified. The measured geometries are used to derive a general design guide for a specific combination of photoresist, laser power and scanning speed and to analyse the geometric accuracy of a structure produced using these guidelines. KW - Multi photon lithography KW - Test artifact KW - Two photon polymerization KW - Direct Laser Writing KW - Quality infrastructure PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-560530 DO - https://doi.org/10.20944/preprints202210.0259.v1 SP - 1 EP - 29 PB - MDPI CY - Basel AN - OPUS4-56053 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sänger, Johanna Christiane A1 - Pauw, Brian Richard A1 - Riechers, Birte A1 - Zocca, Andrea A1 - Rosalie, Julian A1 - Maaß, Robert A1 - Sturm, Heinz A1 - Günster, Jens T1 - Entering a new dimension in powder processing for advanced ceramics shaping N2 - Filigree structures can be manufactured via two-photon-polymerization (2PP) operating in the regime of non-linear light absorption. For the first time it is possible to apply this technique to the powder processing of ceramic structures with a feature size in the range of the critical defect size responsible for brittle fracture and, thus, affecting fracture toughness of high-performance ceramics. In this way, tailoring of advanced properties can be achieved already in the shaping process. Traditionally, 2PP relies on transparent polymerizable resins, which is diametrically opposed to the usually completely opaque ceramic resins and slurries. Here we present a transparent and photocurable suspension of nanoparticles (resin) with very high mass fractions of yttria-stabilized zirconia particles (YSZ). Due to the extremely well dispersed nanoparticles, scattering of light can be effectively suppressed at the process-relevant wavelength of 800 nm. Sintered ceramic structures with a resolution of down to 500 nm were obtained. Even at reduced densities of 1 to 4 g/cm³, the resulting compressive strength with 4,5 GPa is equivalent or even exceeding bulk monolithic yttria stabilized zirconia. A ceramic metamaterial is born, where the mechanical properties of yttria stabilized zirconia are altered by changing geometrical parameters and gives access to a new class of ceramic materials. KW - Two-photon-polymerization KW - Ceramics KW - Powder processing KW - Transparency KW - Meta material KW - Yttria stabilized zirconia PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-564598 DO - https://doi.org/10.1002/adma.202208653 SN - 1521-4095 SP - 1 EP - 8 PB - Wiley-VCH CY - Weinheim AN - OPUS4-56459 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Silbernagl, Dorothee A1 - Sturm, Heinz A1 - Plajer, A. J. T1 - Thioanhydride/isothiocyanate/epoxide ring-opening terpolymerisation: sequence selective enchainment of monomer mixtures and switchable catalysis N2 - We report a new sequence selective terpolymerisation in which three monomers (butylene oxide (BO) A, PhNCS B and phtalic thioanhydride (PTA) C) are selectively enchained into an (ABA′C)n sequence. PTA/PhNCS/BO ring-opening terpolymerisation ROTERP can be coupled with CS2 ROTERP to generate tetrapolymers and with εDL ROP in switchable catalysis for blockpolymer synthesis. KW - Blockcopolymer KW - 1H-NMR KW - TGA KW - DSC KW - AFM PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-552339 DO - https://doi.org/10.1039/d2py00629d SP - 1 EP - 5 PB - Royal Society of Chemistry CY - Cambridge, UK AN - OPUS4-55233 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Crasselt, Claudia A1 - Schmidt, Wolfram A1 - Sturm, Heinz T1 - Influence of Rheology Modifying Admixtures on Hydration of Cementitious Suspensions N2 - The presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has an enormous influence on the early hydration of cement. The hydration is retarded and the timing of formation and the morphology of hydrates is affected. This short paper presents experimental results about the influence of delayed addition time of PCE SPs on hydration of cement and alite pastes, investigated by isothermal heat flow calorimetry. For cement as well as for alite pastes the hydration is retarded with SP, whereby the high charge PCE has a stronger retarding effect than the low charge PCE. The retardation caused by PCE is much more pronounced for alite than for cement mixes. If PCE is added later to the mix, the induction period is shortened and the hydration is accelerated compared to simultaneous addition. This applies for cement and alite pastes. With delayed PCE addition the alite shows a clearly less retarded setting and main hydration than after simultaneous addition. It is obvious that for alite pastes there is less retardation the later the addition of SP. T2 - 6th International Symposium on Nanotechnology in Construction CY - Hong Kong, China DA - 02.12.2018 KW - Polycarboxylate ether (PCE) KW - Early hydration KW - Cement PY - 2018 SP - 1 EP - 8 AN - OPUS4-47204 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Polymere Faserwerkstoffe und die STM/AFM T2 - Diskussions-Tagung "Raster-Nahfeld-Mikroskopien und organische Materialien" CY - Planegg, Germany DA - 1992-07-08 PY - 1992 AN - OPUS4-6377 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -