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High-speed atomic force microscopy (HS-AFM) is a powerful tool for studying the dynamics of biomolecules in vitro because of its high temporal and spatial resolution. However, multi-functionalization, such as combination with complementary measurement methods, environment control, and large-scale mechanical manipulation of samples, is still a complex endeavor due to the inherent design and the compact sample scanning stage. Emerging tip-scan HS-AFM overcame this design hindrance and opened a door for additional functionalities. In this study, we designed a motor-driven stretching device to manipulate elastic substrates for HS-AFM imaging of biomolecules under controllable mechanical stimulation. To demonstrate the applicability of the substrate stretching device, we observed a microtubule buckling by straining the substrate and actin filaments linked by α-actinin on a curved surface. In addition, a BAR domain protein BIN1 that senses substrate curvature was observed while dynamically controlling the surface curvature. Our results clearly prove that large-scale mechanical manipulation can be coupled with nanometer-scale imaging to observe biophysical effects otherwise obscured.

High-speed atomic force microscopy (AFM) is a versatile method that can visualize proteins and protein systems on the nanometer scale and at a temporal resolution of 100 ms. The application to microtubules can not only reveal structural information with single-tubulin resolution but can also extract mechanical information and allows to study single motor proteins walking on microtubules, among others. This chapter provides a step-by-step guide from microtubule polymerization to successful observation with high-speed AFM.

Recently, Hirsch (2019a) proposed a new variant of the h-index called the hα-index. The hα-index was criticized by Leydesdorff, Bornmann, and Opthof (2019) . One of their most important points is that the index reinforces the Matthew effect in science. The Matthew effect was defined by Merton (1968) as follows: “the Matthew effect consists in the accruing of greater increments of recognition for particular scientific contributions to scientists of considerable repute and the withholding of such recognition from scientists who have not yet made their mark” (p. 58). We follow up on the point about the Matthew effect in the current study by using a recently developed Stata command (h_index) and R package (hindex), which can be used to simulate h-index and hα-index applications in research evaluation. The user can investigate under which conditions hα reinforces the Matthew effect. The results of our study confirm what Leydesdorff et al. (2019) expected: The hα-index reinforces the Matthew effect. This effect can be intensified if strategic behavior of the publishing scientists and cumulative advantage effects are additionally considered in the simulation.

The ferritin cage iron-storage protein assembly has been widely used as a template for preparing nanomaterials. This assembly has a unique pH-induced disassembly/reassembly mechanism that provides a means for encapsulating molecules such as nanoparticles and small enzymes for catalytic and biomaterial applications. Although several researchers have investigated the disassembly process of ferritin, the dynamics involved in the initiation of the process and its intermediate states have not been elucidated due to a lack of suitable methodology to track the process in real-time. We describe the use of high-speed atomic force microscopy (HS-AFM) to image the dynamic event in real-time with single-molecule level resolution. The HS-AFM movies produced in the present work enable direct visualization of the movements of single ferritin cages in solution and formation of a hole prior to disassembly into subunit fragments. Additional support for these observations was confirmed at the atomic level by the results of all-atom molecular dynamics (MD) simulations, which revealed that the initiation process includes the opening of 3-fold symmetric channels. Our findings provide an essential contribution to a fundamental understanding of the dynamics of protein assembly and disassembly, as well as efforts to redesign the apo-ferritin cage for extended applications.

Anhydrobiosis, one of the most extensively studied forms of cryptobiosis, is induced in certain organisms as a response to desiccation. Anhydrobiotic species has been hypothesized to produce substances that can protect their biological components and/or cell membranes without water. In extremotolerant tardigrades, highly hydrophilic and heat-soluble protein families, cytosolic abundant heat-soluble (CAHS) proteins, have been identified, which are postulated to be integral parts of the tardigrades’ response to desiccation. In this study, to elucidate these protein functions, we performed in vitro and in vivo characterizations of the reversible self-assembling property of CAHS1 protein, a major isoform of CAHS proteins from Ramazzottius varieornatus, using a series of spectroscopic and microscopic techniques. We found that CAHS1 proteins homo-oligomerized via the C-terminal α-helical region and formed a hydrogel as their concentration increased. We also demonstrated that the overexpressed CAHS1 proteins formed condensates under desiccation-mimicking conditions. These data strongly suggested that, upon drying, the CAHS1 proteins form oligomers and eventually underwent sol–gel transition in tardigrade cytosols. Thus, it is proposed that the CAHS1 proteins form the cytosolic fibrous condensates, which presumably have variable mechanisms for the desiccation tolerance of tardigrades. These findings provide insights into molecular strategies of organisms to adapt to extreme environments.

Anhydrobiosis is one of the most extensively studied forms of cryptobiosis that is induced in certain organisms as a response to desiccation. Anhydrobiotic species has been hypothesized to produce substances that can protect their biological components and/or cell membranes without water. In extremotolerant tardigrades, highly hydrophilic and heat-soluble protein families, cytosolic abundant heat-soluble (CAHS) proteins, have been identified, which are postulated to be integral parts of the tardigrades’ response to desiccation. However, the molecular mechanisms underlying these protein functions remain to be fully elucidated. In this study, we perfomed in vitro and in vivo characterizations of the self-assembling property of CAHS1 protein, a major isoform of CAHS proteins from Ramazzottius varieornatus, using a series of spectroscopic and microscopic techniques. Our in vitro observations showed that CAHS1 proteins homo-oligomerized via the C-terminal α-helical region and formed a hydrogel as their concentration increased, and that these molecular assembling processes were reversible. Furthermore, our in vivo observations demonstrated that the overexpressed CAHS1 proteins formed condensates under desiccation-mimicking conditions. These data strongly suggested that, upon drying, the CAHS1 proteins form oligomers and eventually underwent sol-gel transition in tardigrade cytosols. Thus, it is proposed that the CAHS1 proteins form the cytosolic fibrous condensates, which presumably have variable mechanisms for the desiccation tolerance of tardigrades. These findings provide insights into the protective mechanisms involved in the anhydrobiosis of tardigrades.

Changes in moisture content of single pulp fibers have an immense influence on the behavior of paper and paper products. Here, an atomic force microscopy (AFM)-based method is applied to investigate the viscoelastic properties of pulp fibers at varying relative humidity (RH) in the transverse direction. Pulp fibers have not only anisotropic properties, but also a very rough surface due to their hierarchical structure. For this reason, we have developed a specific load schedule for the AFM-based test method to overcome uncertainties and limitations due to surface roughness of the pulp fibers. The evaluation of the experimental data combines contact mechanics and viscoelastic models which consist of springs and dashpots in series or parallel describing elastic and viscous behavior. Here, it will be demonstrated that the so-called Generalized Maxwell (GM) model yields comparable results for single pulp fibers at five different RH values and in water. The moisture changes lead to a decrease in the elastic modulus but increase in the relaxation effects with increasing RH. All the determined parameters for the elastic and viscous behavior exhibit a gradual decrease with increasing RH from 10 to 75% RH. The elastic moduli decrease by a factor of 10 and the viscosities are decreasing by a factor of 10–20. In water, there is an even more pronounced decrease of the elastic moduli by a factor 100, and the viscosities decrease by at least three orders of magnitude compared to 10% RH. This indicates that the mechanical response of pulp fibers in water is significantly different than in humid air. This is also illustrated by the fact that a GM model of order two suffices to describe the material behavior in humid air but a GM model of order three is necessary to fit the material behavior in water. A possible interpretation is an additional relaxation effect of the pulp fiber wall in water.

Microtubules are biopolymers composed of tubulin and play diverse roles in a wide variety of biological processes such as cell division, migration and intracellular transport in eukaryotic cells. To perform their functions, microtubules are mechanically stressed and, thereby, susceptible to structural defects. Local variations in mechanical properties caused by these defects modulate their biological functions, including binding and transportation of microtubule-associated proteins. Therefore, assessing the local mechanical properties of microtubules and analyzing their dynamic response to mechanical stimuli provide insight into fundamental processes. It is, however, not trivial to control defect formation, gather mechanical information at the same time, and subsequently image the result at a high temporal resolution at the molecular level with minimal delay. In this work, we describe the so-called in-line force curve mode based on high-speed atomic force microscopy. This method is directly applied to create defects in microtubules at the level of tubulin dimers and monitor the following dynamic processes around the defects. Furthermore, force curves obtained during defect formation provide quantitative mechanical information to estimate the bonding energy between tubulin dimers.

Among various microscopic techniques for characterizing protein structures and functions, high-speed atomic force microscopy (HS-AFM) is a unique technique in that it allows direct visualization of structural changes and molecular interactions of proteins without any labeling in a liquid environment. Since the development of the HS-AFM was first reported in 2001, it has been applied to analyze the dynamics of various types of proteins, including motor proteins, membrane proteins, DNA-binding proteins, amyloid proteins, and artificial proteins. This method has now become a versatile tool indispensable for biophysical research. This short review summarizes some bioimaging applications of HS-AFM reported in the last few years and novel applications of HS-AFM utilizing the unique ability of AFM to gain mechanical properties of samples in addition to structural information.

Arrangement of polymer chains at the interface with an acceptor is one of the key issues which influences the interfacial charge transfer. Films of P3HT and P3HT:PCBM blends with the different poly...

Canonical K+ channels are tetrameric and highly K+-selective, whereas two-pore-domain K+ (K2P) channels form dimers, but with a similar pore architecture. A two-pore-domain potassium channel TWIK1 (KCNK1 or K2P1) allows permeation of Na+ and other monovalent ions, resulting mainly from the presence of Thr-118 in the P1 domain. However, the mechanistic basis for this reduced selectivity is unclear. Using ion-exchange-induced difference IR spectroscopy, we analyzed WT TWIK1 and T118I (highly K+-selective) and L228F (substitution in the P2 domain) TWIK1 variants and found that in the presence of K+ ions, WT and both variants exhibit an amide-I band at 1680 cm-1 This band corresponds to interactions of the backbone carbonyls in the selectivity filter with K+, a feature very similar to that of the canonical K+ channel KcsA. Computational analysis indicated that the relatively high frequency for the amide-I band is well explained by impairment of hydrogen bond formation with water molecules. Moreover, concentration-dependent spectral changes indicated that the K+ affinity of the WT selectivity filter was much lower than those of the variants. Furthermore, only the variants displayed a higher frequency shift of the 1680-cm-1 band upon changes from K+ to Rb+ or Cs+ conditions. High-speed atomic force microscopy disclosed that TWIK1's surface morphology largely does not change in K+ and Na+ solutions. Our results reveal the local conformational changes of the TWIK1 selectivity filter and suggest that the amide-I bands may be useful "molecular fingerprints" for assessing the properties of other K+ channels.

Two-dimensional (2D) materials are envisaged as ultra-thin solid lubricants for nano-mechanical systems. So far, their frictional properties at the nanoscale have been studied by standard friction force microscopy. However, lateral manipulation of nanoparticles is a more suitable method to study the dependence of friction on the crystallography of two contacting surfaces. Still, such experiments are lacking. In this study, we combine atomic force microscopy (AFM) based lateral manipulation and molecular dynamics simulations in order to investigate the movements of organic needle-like nanocrystallites grown by van der Waals epitaxy on graphene and hexagonal boron nitride. We observe that nanoneedle fragments -- when pushed by an AFM tip -- do not move along the original pushing directions. Instead, they slide on the 2D materials preferentially along the needles' growth directions, which act as invisible rails along commensurate directions. Further, when the nanocrystallites were rotated by applying a torque with the AFM tip across the preferential sliding directions, we find an increase of the torsional signal of the AFM cantilever. We demonstrate in conjunction with simulations that both, the significant friction anisotropy and preferential sliding directions are determined by the complex epitaxial relation and arise from the commensurate and incommensurate states between the organic nanocrystallites and the 2D materials., 11 pages, 10 figures

The present work aims at the preparation of dry adhesives with switchable bonding properties by using the reversible nature of the [4πs+4πs] cycloaddition of anthracenes. Photo-responsive hydrogenated carboxylated nitrile butadiene rubber with photo-responsive pendant anthracene groups is prepared by one-pot synthesis. The formation of 3D networks relies on the photodimerization of the anthracene moieties upon UV exposure (λ > 300 nm). Controlled cleavage of the crosslink sites is achieved by either deep UV exposure (λ = 254 nm) or thermal dissociation at 70 °C. The kinetics of the optical and thermal cleavage routes are compared in thin films using UV-vis spectroscopy and their influence on the reversibility of the network is detailed. Going from thin films to free standing samples the modulation of the network structure and thermo-mechanical properties over repeated crosslinking and cleavage cycles are characterized by low-field NMR spectroscopy and dynamic mechanical analysis. The applicability of the stimuli-responsive networks as adhesives with reversible bonding properties is demonstrated. The results evidence that the reversibility of the crosslinking reaction enables a controlled switching "on" and "off" of adhesion properties. The recovery of the adhesion force amounts to 75 and 80% for photo- and thermal dissociation, respectively. Spatial control of adhesion properties is evidenced by adhesion force mapping experiments of photo-patterned films.

Microtubules, the most rigid components of the cytoskeleton, can be key transduction elements between external forces and the cellular environment. Mechanical forces induce microtubule deformation, which is presumed to be critical for the mechanoregulation of cellular events. However, concrete evidence is lacking. In this work, with high-speed atomic force microscopy, we unravel how microtubule deformation regulates the translocation of the microtubule-associated motor protein kinesin-1, responsible for intracellular transport. Our results show that the microtubule deformation by bending impedes the translocation dynamics of kinesins along them. Molecular dynamics simulation shows that the hindered translocation of kinesins can be attributed to an enhanced affinity of kinesins to the microtubule structural units in microtubules deformed by bending. This study advances our understanding of the role of cytoskeletal components in mechanotransduction.

In our planned study, we shall empirically study the assessment of cited papers within the framework of the anchoring-and-adjustment heuristic. We are interested in the question whether citation decisions are (mainly) driven by the quality of cited references. The design of our study is oriented towards the study by Teplitskiy, Duede [10]. We shall undertake a survey of corresponding authors with an available email address in the Web of Science database. The authors are asked to assess the quality of papers that they cited in previous papers. Some authors will be assigned to three treatment groups that receive further information alongside the cited paper: citation information, information on the publishing journal (journal impact factor), or a numerical access code to enter the survey. The control group will not receive any further numerical information. In the statistical analyses, we estimate how (strongly) the quality assessments of the cited papers are adjusted by the respondents to the anchor value (citation, journal, or access code). Thus, we are interested in whether possible adjustments in the assessments can not only be produced by quality-related information (citation or journal), but also by numbers that are not related to quality, i.e. the access code. The results of the study may have important implications for quality assessments of papers by researchers and the role of numbers, citations, and journal metrics in assessment processes.

In this study steel surfaces are modified with dipodal perfluoroalkyl organosilanes and the resulting wetting properties and surface morphologies are analyzed. Dipodal silane monomers with different fluoroalkyl spacer lengths are synthesized via hydrosilylation reaction. The modification of stainless steel surfaces is performed in a two-step procedure comprising a corona activation of the steel surface and the subsequent reaction of surface hydroxyl groups with the dipodal silanes from the liquid phase. Anti-adhesive behavior on the surface is achieved through the modification. The attachment of the dipodal silanes on the stainless steel surface is validated with infrared reflection absorption spectroscopy and X-ray photoelectron spectroscopy. The wetting properties of the dipodal silane layers are investigated by contact angle measurements and adhesive force measurements. Atomic force microscopy is used to characterize the surface roughness and morphologies. Stainless steel modified with the dipodal perfluoroalkyl silanes exhibits low surface energy and low adhesive force compared to the unmodified steel surface. The thermal stability of coatings based on dipodal silanes is higher when compared to layers based on conventional monopodal organosilanes.

The photo-reversible [4πs+4πs] cycloaddition reaction of pendant anthracene moieties represents a convenient strategy to impart wavelength dependent properties into hydrogenated carboxylated nitrile butadiene rubber (HXNBR) networks. The present article provides the 1 H NMR data on the reaction kinetics of the side chain functionalization of HXNBR. 2-(Anthracene-9-yl)oxirane with reactive epoxy groups is covalently attached to the polymer side chain of HXNBR via ring opening reaction between the epoxy and the carboxylic groups. Along with the identification, 1 H NMR data on the quantification of the attached functional groups are shown in dependence on reaction time and concentration of 2-(anthracene-9-yl)oxirane. Changes in the modification yield are reflected in the mechanical properties and DMA data of photo-responsive elastomers are illustrated in dependence on the number of attached anthracene groups. DMA curves over repeated cycles of UV induced crosslinking ( λ >300 nm) and UV induced cleavage ( λ =254 nm) are further depicted, demonstrating the photo-reversibility of the thermo-mechanical properties. Interpretation and discussion of the data are provided in “Design and application of photo-reversible elastomer networks by using the [4πs+4πs] cycloaddition reaction of pendant anthracene groups” (Manhart et al., 2016) [1] .

The viscoelastic behavior of wood pulp fibers plays a fundamental role in the performance of paper and paper products. Wood pulp fibers are hierarchical composites consisting of different cell wall layers and have anisotropic properties. Since accessing the individual fibers is challenging, no measurement technique has been able to characterize the viscoelastic properties in both – the longitudinal and transverse – fiber direction yet. Here, an atomic force microscopy (AFM)-based method is applied to investigate the viscoelastic properties of wood pulp fibers at varying relative humidity (RH) in both fiber directions. Experimental creep tests have been performed to investigate the material's low frequency regime response. A spring-dashpot model has been applied to characterize the viscoelastic behavior. The results indicate surprisingly small differences of the properties between the fiber directions. Transferring the results into a spectral representation explains an opposing trend of the viscosity that is connected to the long-term behavior.

In this work, the photo-reversible [4πs+4πs] cycloaddition reaction of anthracene moieties is employed to impart wavelength dependent properties into carboxylated nitrile butadiene rubber networks. Crosslinking of the side chain functionalized rubber is achieved by UV induced dimerization of pendant anthracene groups at wavelengths above 300 nm whilst a subsequent deep UV exposure (λ = 254 nm) results in a well-defined cleavage of the crosslinks. Crosslink kinetics and photo-reversibility of the dimerization reaction are determined by spectroscopic measurements. The changes in network structure and chain dynamics over multiple crosslinking and cleavage cycles are studied in detail by low field NMR. In thin films, the wavelength dependent changes in solubility are employed for the preparation of reversible photoresists enabling the preparation of 2D microstructures and a switching between negative- and positive-type patterns. Along with thin films, the wavelength dependent modulation of thermo-mechanical properties is also demonstrated for macroscopic samples, which shows the versatility of these optically stimuli-responsive networks.

Xylan-coated cellulose thin films has been investigated by means of atomic force microscopy (AFM) and force mapping experiments. The birch xylan deposition on the film was performed under control by means of a multiple parameter surface plasmon resonance spectroscopy (MP-SPR) under dynamic conditions. The coated films were submitted to AFM in phase imaging mode to force mapping with modified AFM tips (sensitive to hydrophilic OH and hydrophobic CH3 groups) in order to characterize and localize the xylan on the surfaces. At the first glance, a clear difference in the adhesion force between xylan-coated areas and cellulose has been observed. However, these different adhesion forces originate from topography effects, which prevent an unambiguous identification and subsequent localization of the xylan on the cellulosic surfaces.

Chromium- and silicon-poisoned samples of the intermediate temperature solid oxide fuel cell (IT-SOFC) cathode materials La 0.6 Sr 0.4 CoO 3-δ (LSC) and La 2 NiO 4 + δ (LNO) were investigated by transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDXS), electron energy loss spectroscopy (EELS), convergent beam electron diffraction (CBED), as well as by atomic force microscopy (AFM). Analytical TEM revealed phase decomposition of the original, oxygen exchange-active materials LSC and LNO, and the formation of secondary phases after 3500 h of testing at 700 °C. In the case of LSC, the phases SrCrO 4 , Co 3 O 4 , and CoCr 2-x Co x O 4 as well as a La‐chromate phase with unknown stoichiometry were found in the near-surface region and at the grain boundaries. Transport of cations, especially Sr and Cr, along the grain boundaries seems to play a key role in the degradation of LSC. AFM was used to determine the three-dimensional shape including interplanar facet angles of SrCrO 4 crystallites. In the case of the Sr-free material LNO, the formation of La‐silicate and La-Ni‐chromate phases was observed, which seems to proceed from the surface toward the bulk. Based on the experimental results, tentative mechanisms for the degradation processes are suggested.

We add to the literature on citizen forecasting by examining the 2013 German federal election and, for the first time, trying to predict vote shares. A random sample of voters was asked to predict the vote shares for each party in telephone interviews. We examine the accuracy of individuals' expectations and analyze the influence of wishful thinking and published vote intention polls on voters' expectations. Individual forecasts are aggregated, assuming a wise crowd will make a precise forecast. Expectations do not yield a forecast of satisfactory accuracy and they are inferior to vote intention polls. High-ability subgroups do not yield better forecasts than the whole sample. Issues of sampling and measurement are addressed. We conclude that asking voters to predict eight interdependent vote shares is probably too difficult a task.

Canonical K(+) channels are tetrameric and highly K(+)-selective, whereas two-pore–domain K(+) (K2P) channels form dimers, but with a similar pore architecture. A two-pore–domain potassium channel TWIK1 (KCNK1 or K2P1) allows permeation of Na(+) and other monovalent ions, resulting mainly from the presence of Thr-118 in the P1 domain. However, the mechanistic basis for this reduced selectivity is unclear. Using ion-exchange–induced difference IR spectroscopy, we analyzed WT TWIK1 and T118I (highly K(+)-selective) and L228F (substitution in the P2 domain) TWIK1 variants and found that in the presence of K(+) ions, WT and both variants exhibit an amide-I band at 1680 cm(−1). This band corresponds to interactions of the backbone carbonyls in the selectivity filter with K(+), a feature very similar to that of the canonical K(+) channel KcsA. Computational analysis indicated that the relatively high frequency for the amide-I band is well explained by impairment of hydrogen bond formation with water molecules. Moreover, concentration-dependent spectral changes indicated that the K(+) affinity of the WT selectivity filter was much lower than those of the variants. Furthermore, only the variants displayed a higher frequency shift of the 1680-cm(−1) band upon changes from K(+) to Rb(+) or Cs(+) conditions. High-speed atomic force microscopy disclosed that TWIK1's surface morphology largely does not change in K(+) and Na(+) solutions. Our results reveal the local conformational changes of the TWIK1 selectivity filter and suggest that the amide-I bands may be useful “molecular fingerprints” for assessing the properties of other K(+) channels.

The advantages of groups over individuals in complex decision-making have long interested scientists across disciplinary divisions. Averaging over a collection of individual judgments proves a reliable strategy for aggregating information, particularly in diverse groups in which statistically independent beliefs fall on both sides of the truth and contradictory biases are cancelled out. Social influence, some have said, narrows variation in individual opinions and undermines this wisdom-of-crowds effect in continuous estimation tasks. Researchers, however, neglected to study social-influence effects on voting in discrete choice tasks. Using agent-based simulation, we show that under voting — the most widespread social decision rule — social influence contributes to information aggregation and thus strengthens collective judgment. Adding to our knowledge about complex systems comprised of adaptive agents, this finding has important ramifications for the design of collective decision-making in both public administration and private firms. Funding agencies: Royal Swedish Academy of Sciences [SO2016-0060]; Riksbankens Jubileumsfond [M12-0301: 1]

Viscoelastic properties are often measured using probe based techniques such as nanoindentation (NI) and atomic force microscopy (AFM). Rarely, however, are these methods verified. In this article, we present a method that combines contact mechanics with a viscoelastic model (VEM) composed of springs and dashpots. We further show how to use this model to determine viscoelastic properties from creep curves recorded by a probe based technique. We focus on using the standard linear solid model and the generalized Maxwell model of order 2. The method operates in the range of 0.01 Hz to 1 Hz. Our approach is suitable for rough surfaces by providing a defined contact area using plastic pre-deformation of the material. The very same procedure is used to evaluate AFM based measurements as well as NI measurements performed on polymer samples made from poly(methyl methacrylate) and polycarbonate. The results of these measurements are then compared to those obtained by tensile creep tests also performed on the same samples. It is found that the tensile test results differ considerably from the results obtained by AFM and NI methods. The similarity between the AFM results and NI results suggests that the proposed method is capable of yielding results comparable to NI but with the advantage of the imaging possibilities of AFM. Furthermore, all three methods allowed a clear distinction between PC and PMMA by means of their respective viscoelastic properties.

An elegant way for the controlled production of either cellulose fibers or hollow half spheres from trimethylsilyl cellulose (TMSC) via needleless electrospinning is reported. For this purpose trimethylsilyl celluloses (DS: 2.6–2.7) have been synthesized from three different cellulose sources, namely spruce pulp, AVICEL, and a viscose pulp. While TMSC from AVICEL is hardly processable via electrospinning, the use of viscose pulps leads to hollow semi spheres, whereas the spruce pulp based TMSC yields fibrous networks. The approach takes advantage of different degrees of molecular entanglements caused by differences in origin and molecular weight of the cellulosic material. These investigations may pave the way for further use of electrospun materials made from TMSC in, e.g., sensor devices.

The fact that cellulose materials soften with water uptake is exploited constantly during paper production to form strong bonds between two fibers. Here, we present measurements of surface hardness and reduced modulus of viscose fibers by atomic force microscopy based nanoindentation at varying relative humidity. A home-built setup allowed to access a wide humidity range from 5 % until 95 % relative humidity. The obtained results are compared to those of softwood kraft pulp fibers. Creep effects at a constant load during indentation were observed and found to increase exponentially with increasing humidity. In order to relate mechanical properties to the water content within a fiber, also gravimetric sorption studies were performed. This allowed to extrapolate the mechanical properties of viscose fibers to 100 % relative humidity. Interestingly, hardness and reduced modulus are at this point higher by a factor of 4 and 20, respectively, compared to those of viscose fibers fully swollen in water. Pulp fibers, in comparison, exhibit mechanical properties which are similar to those of viscose fibers. Only when the fibers are swollen, a higher hardness for viscose fibers is evident, whereas the moduli of pulp and viscose fibers are still comparable.

In the last decade, interest in the “wisdom of crowds” effect has gained momentum in both organizational research and corporate practice. Crowd wisdom relies on the aggregation of independent judgments. The accuracy of a group’s aggregate prediction rises with the number, ability, and diversity of its members. We investigate these variables’ relative importance for collective prediction using agent-based simulation. We replicate the “diversity trumps ability” proposition for large groups, showing that samples of heterogeneous agents outperform same-sized homogeneous teams of high ability. In groups smaller than approximately 16 members, however, the effects of group composition depend on the social decision function employed: diversity is key only in continuous estimation tasks (averaging) and much less important in discrete choice tasks (voting), in which agents’ individual abilities remain crucial. Thus, strategies to improve collective decision making must adapt to the predictive situation at hand. This paper was accepted by Yuval Rottenstreich, judgment and decision making.

Xylan was precipitated on bleached and unbleached softwood kraft pulps (SKPB and SKPUB), a bleached sulfite pulp, and viscose fibers to investigate the influence on physical properties of handsheets as well as to gain more detailed information of the distribution of adsorbed xylan on cellulosic surfaces. The adsorption step was carried out at constant conditions. The values of the parameters were chosen after a series of different adsorption steps (as presented elsewhere) also in regard as a possible industrial application. Afterwards, suspension and physical strength properties of unrefined and refined samples were determined. Refining resulted in a stronger increase in the beating degree of the pulps with additional xylan than the reference samples. The water retention value was not significantly changed. Comparing the tensile index of the handsheets versus the beating degree a remarkable increase in the strength properties was not observed. The investigation of the surface of the SKPB fibers via ATR suggests that precipitated xylan is heterogeneously and nonuniformly distributed. On cellulose model films, particles could be detected via atomic force microscopy. Phase images recorded with OH-functionalized tips suggested that these particles consist of xylan. An inhomogeneous distribution of xylan could be a reason that there is no measurable influence on the strength properties of the handsheets.

We studied the shape of water droplets deposited using an inkjet nozzle on a chemically striped patterned substrate consisting of alternating hydrophobic and hydrophilic stripes. The droplet dimensions are comparable to the period of the stripes, typically covering up to 13 stripes. As such, our present results bridge the gap linking two regimes previously considered: (i) droplets on single stripes and (ii) droplets covering more than 50 stripes. In line with previous work on markedly smaller water droplets, the exact deposition position is important for the final shape of the droplets. A droplet with its center deposited on a hydrophobic stripe reaches a shape that is different than when it is deposited on a hydrophilic stripe. Experimental results of different droplet configurations on the same surface are in agreement with simulations using the lattice Boltzmann model. In addition, the simulations enable a detailed analysis of droplet free energies and the volume dependence. The latter reveals scaling properties of shape parameters in terms of droplet radius scaled to the period of the stripe pattern, which have remained unexplored until now.

Viscose fibers are man-made, regenerated cellulose fibers. They offer versatile uses ranging from hygiene articles to textiles and medical applications. The great advantage over natural pulp and cotton fibers are the possibilities to design the fibers’ cross-sections and modify the material by directly mixing additives to the viscose dope. In this study, the effects of two additives – carboxymethyl cellulose (anionic) and cationic starch (cationic) – on the fibers’ mechanical properties are studied. Atomic force microscopy-based nanoindentation is the method of choice to investigate swollen viscose fibers with circular as well as flat, rectangular cross-sections. It was found that carboxymethyl cellulose addition always leads to a significant decrease of hardness from 14·0 MPa for the unmodified fiber down to 4·4 MPa, a value comparable to swollen pulp fibers. Cationic starch, on the other hand, causes an increase of hardness to 16·0 MPa for round viscose fibers at a low concentration, whereas higher concentrations of cationic starch resulted in a slight decrease of hardness to 12·8 MPa. This possibility to tune the hardness of swollen viscose fibers expands the application spectrum of viscose fibers substantially.

The influence of charged species on the relative bonded area (RBA) of flat shaped viscose fibre handsheets was investigated. For this purpose four samples, a reference fibre without any additives as well as three physical modified fibres, were studied. The RBA was determined by the light scattering method and by using the so called Page equation. To use the Page equation, the breaking length of handsheets, the optical bonded area of fibre-fibre joints as well as the bond strength of such fibre joints were determined. The optical bonded area was analysed by polarized light microscopy. Using a micro bond tester, the bond strength of fibre-fibre joints was determined. Both techniques, light scattering and calculation via the Page equation did not deliver absolute values for RBA. Quite contrary, they only give approximate values. However, an increase of relative bonded area due to anionic charges is clearly seen. Additionally, the breaking length is increased by both additives.

Measuring contact angles on single fibers enables the separation of structural factors from surface chemistry factors. Current Drop-on-Fiber (DOF) contact angle measurement methods for natural fibers generally, and for pulp/paper fibers specifically, present a number of challenges. These are manipulation and mounting of the microscale fibers, straightening natural fibers to produce repeatable axisymmetric droplet conformation, measuring the droplet volume excluding the fiber volume and also human errors due to manually performed tasks. This paper presents a novel method to measure contact angles in DOF systems and overcome the above mentioned challenges using microrobots. The proposed microrobotic platform is capable of handling natural and synthetic fibrous materials in microscale, and dispensing probe liquid droplets down to 12 nl. It measures contact angle values using computer vision and a droplet-profiledetection algorithm. It reports the contact angle values as a function of volume of the droplet. The paper validates the capabilities of the proposed platform by applying three commonly used probe liquids: deionized water, ethylene glycol and diiodomethane for measuring contact angles on glass and pulp fibers. Finally, the results are compared with a picoliter contact angle measurement approach.

The tribological protection of stiff technical polymers like epoxy resins, being main component in fiber strengthened composites (CFC), gains increasing interest to enable their use in mechanical engineering applications. Besides hardening of the surfaces to achieve similar properties like low carbon steels, smooth surfaces are essential in sliding contact. However, the conditions of film growth during magnetron sputtering including thermal stresses result in high intrinsic film stresses, which trigger the formation of distinct surface topography. Especially chromium nitride (CrNx) single layer coatings show a fragmentation of the coating by cracking during film growth. Preferential growth of crystallites in subsequent deposition closes these cracks, provides complete covering of the surface, and bulged topographical features. Goal of this work is describing the mechanisms of formation of these topographical features as well as emphasizing influences of higher film toughness by Cr-CrNx multilayer coatings on the density and height of the bulges.

Besides the determination of the force and the energy needed to break individual fibre to fibre joints, the investigation of the formerly bonded area (FBA) is of essential importance to learn more about the failure mechanisms of fibre–fibre bonds in general. In this study the surfaces of paper fibres and the FBA of fibre–fibre joints after the determination of the breaking force as well as the bonding energy were analysed by means of low voltage scanning electron microscopy and atomic force microscopy. A comparison between the contact zone of fibres broken at different loading rates as well as under cyclic loading showed that there seems to be no significant difference in the appearance of the FBA in these cases. Only minor delamination of the cell wall could be found in the bonding zone, which indicates no mechanical interlocking of fibrils in the bonding zone. Furthermore, it is shown that some glues used for specimen preparation of fibre–fibre bond strength measurement are forming a glue film on the fiber surface and migrate into the bonding region.

Thin cellulose films on silicon substrates are used as a model system for paper fiber bonds. The films are formed by spincoating trimethylsilylcellulose on the substrates. The films are regenerated using HCl gas. After swelling in water, two samples can be bonded like a sandwich. It is shown that this model system can be used to measure the bond strength between the two films under controlled conditions. For a detailed characterization the films are studied in terms of roughness with atomic force microscopy (AFM). The hardness of the films is investigated by AFM-based nanoindentation. The chemistry and the thickness of the films is studied by infrared spectroscopy. It is shown that this model system enables the evaluation of different bonding mechanisms discussed in pulp and paper research. Our results clearly indicate that Coulomb interaction is an important bonding mechanism.

The adhesion tendency of the polymers polyoxymethylene, polyamide 6.6 and polyether ether ketone against hard coatings to protect molds in polymer processing was evaluated by a combination of tribological tests, investigations of wear tracks and measurements of the coatings' surface energies. It was found that a low surface roughness and a low surface energy of the coating are beneficial to reduce friction and adhesion tendency. Among the coating materials investigated, CrN seems to be the most promising candidate for the protection of molds for polymer processing.