We describe the formation of LIPSS by fs laser irradiation on polished titanium or steel samples, from which polymer replicas can be produced. The irradiation of inclined samples allows a variation in the periodicity of the LIPSS in a range between about 500 and 1000 nm, depending on the angle of incidence and the orientation of the laser polarization relative to the plane of incidence, either parallel (p-polarization) or perpendicular (s-polarization). For p-polarization, a second larger-size LIPSS feature with periodicities between about 1300 and 2200 nm is observed at medium angles. LIPSS lines are oriented perpendicular to the light polarization, except for s-polarization on steel samples, where a rotation of up to 35° is observed. In a two-step process, the LIPSS are replicated in polymers. We investigate the attachment of Schwann cells and fibroblasts seeded thereon, which show no direct dependence on the variation in the LIPSS periodicities.

Extracellular recordings from the sensory pits, conspicuous sensory organs on the cuticle of planthopper nymphs (suborder Fulgoromorpha), were performed. No responses to sound, ultrasound, direct mechanical stimulation, temperature changes, or magnetic fields were observed. They do, however, respond to stimulation with electric fields of very low intensity. Field strengths of less than 1 kV/m were sometimes sufficient to elicit responses. These responses, together with the arrangement of these special sensory structures on the body surface of planthoppers, imply that these sensory organs perceive electric fields in the environment. Our results correspond well with recently published observations and model calculations for treehoppers (Membracidae), another Auchenorrhyncha taxon. Our results corroborate these recent findings with direct electrophysiological evidence and support the notion that both treehoppers and planthoppers are able to perceive electric fields. The ecological importance for this kind of sensory system is discussed.

Ceramic implants have become more common in recent years, despite scarce reporting on the long-term follow-ups in patients. There are several properties rendering zirconium dioxide implants more advantageous than standard titanium implants, yet data on surface properties of ceramic dental implants is missing. In this study, the surface topography and roughness for two types of ceramic implants-3D-printed and commercially available-are measured via atomic force microscopy (AFM) and compared with those of titanium-based implants (sandblasted and machined). Distinct surface structures are identified for each implant type, with roughness values of ceramic implants being slightly higher than those of the Ti-based machined sample and significantly lower than those of Ti implants with a sandblasted surface. The ceramic 3D-printed implant exhibits similar roughness values at the center and cervical regions but lower values at the apical region. The structures observed in the AFM images, along with the roughness values, could enhance the osseointegration of the 3D-printed ceramic implants compared to machined implants. However, additional surface modifications might be needed in order to achieve successful osseointegration and similar feasibility to roughened metallic implants.

The adhesion and alignment of osteoblasts and fibroblasts on titanium alloy (Ti-6Al-4V) surfaces can be adjusted over a wide range by femtosecond laser treatment and anodization. The great differences in cell behavior between different experimental conditions raised further questions about the role of cell migration, which will be addressed in this study. For that, Ti-6Al-4V surfaces were laser-structured to obtain a surface covered with ripples, i.e., laser-induced periodic surface structures (LIPSS), or micro-cones superimposed with ripples. Then, cells were seeded either directly onto the non-structured or laser-structured areas on the titanium alloy samples or beside such samples where they can reach the surface by cell migration. After two weeks in culture, the cell coverage of the samples was evaluated by scanning electron microscopy (SEM). The results showed that cells directly seeded onto the non-structured or laser-structured areas covered the surface nearly completely and eventually aligned along the ripple direction for the laser-structured areas. In contrast, for cell-seeding beside the samples, the laser-structured areas remain nearly cell-free while the non-structured areas were covered with cells in a similar non-oriented manner as for direct cell-seeding. These results on reduced osteoblast migration due to laser structuring are in line with the findings in animal experiments. There, the new bone formation of laser-processed samples was 26.1% ± 16.9% lower in comparison to untreated samples of the same type, which can be explained by hindered cell migration on the laser-processed areas of the screws.

Laser-generated structures have a huge potential to induce an alignment of biological cells, which may be important for various fields in medicine and biotechnology. We describe the formation of fs-laser-induced micro- and nanostructures for achieving the directed growth of Schwann cells, a type of glial cell that can support the regeneration of nerve pathways by guiding the neuronal axons in the direction of their alignment. Polymer surfaces, i.e., polycarbonate (PC) or cellulose acetate butyrate (CAB), were exposed to the beam of a 1040 nm Yb-based amplified fs-laser system with a pulse length of about 350 fs. With appropriate parameters, the laser exposure resulted in a surface topography with oriented micro-grooves, which, for PC, were covered with nano-ripples. Schwann cell growth on these substrates was inspected after 3 to 5 days of cultivation by means of scanning electron microscopy (SEM). We show that Schwann cells can grow in a certain direction, predetermined by micro-groove or nano-ripple orientation. In contrast, cells cultivated on randomly oriented nanofibers or unstructured surfaces show an omnidirectional growth behavior. This method may be used in the future to produce nerve conduits for the treatment of injuries to the peripheral nervous system.

Circulating tumor cells (CTCs) are cells that have separated from a solid cancerous lesion and entered the bloodstream. They play a crucial role in driving the metastatic spread to distant organs, which is the leading cause of cancer-related deaths. Various concepts for blood purification devices aiming to remove CTCs from the blood and prevent metastases have been developed. Until now, it is not clear if such devices can indeed reduce new metastasis formation in a significant way. Here, we present a simple theoretical model of CTCs in the bloodstream that can be used to predict a reduction in metastatic burden using an extracorporeal or intracorporeal blood purification device. The model consists of a system of ordinary differential equations that was numerically solved and simulated. Various simulations with different parameter settings of extracorporeal and intracorporeal devices revealed that only devices implanted directly in tumor-draining vessels can reduce the metastatic burden significantly. Even if an extracorporeal device is used permanently, the reduction in metastases is only 82%, while a permanently operating implanted device in the tumor-draining vessel would achieve a reduction of 99.8%. These results are mainly due to the fact that only a small fraction of CTCs reaches peripheral circulation, resulting in a proportionally small amount of purified blood in extracorporeal devices.

People with injuries to the peripheral nervous system suffer from paralysis of the facial muscles, fingers and hands or toes and feet, often for the rest of their lives, due to its poor functional regeneration. Therefore, to improve patients’ quality of life, there is an urgent need for conduits that effectively support the healing of large defects in nerve pathways through specific guidance of nerve cells. This paper describes two specific methods for achieving directed growth of Schwann cells, a type of glial cells that can support the regeneration of the nerve pathway by guiding the neuronal axons in the direction of their alignment. One method uses aligned polyamide-6 (PA-6) nanofibers produced via electrospinning on a very fast rotating structured collector, which enables easy nanofiber detachment, without additional effort. The other method implies the exposure of a poly(ethylene terephthalate) (PET) foil to a KrF* laser beam, that renders a nanorippled surface topography. Schwann cell growth on these substrates was inspected after one week of cultivation by means of scanning electron microscopy (SEM). For both methods we show that Schwann cells grow in a certain direction, predetermined by nanofiber and nanoripple orientation. In contrast, cells cultivated on randomly oriented nanofibers or unstructured surfaces, show an omnidirectional growth behavior. These two methods can be used to produce nerve conduits for the treatment of injuries to the peripheral nervous system.

We investigated the effect of additional continuous functional coatings, which changed the hydrophilic–hydrophobic properties of the surface without heavily influencing the surface topography at the nanoscale, on the antiadhesive properties of bioinspired laser-induced periodic nanostructures. These nanostructures mimic the antiadhesive structures on the silk-combing area on the legs of cribellate spiders, the calamistrum. The thin films were deposited by matrix-assisted laser deposition and characterized by infrared spectroscopy, X-ray photoelectron spectroscopy, water contact angle measurements, and adhesion tests using capture threads from the cribellate spider webs. In all cases, the nanoripples were preserved and these structured surfaces showed lower adhesion forces compared to flat controls, although not significant. However, this effect was totally overwhelmed by the difference between the adhesion forces on surfaces with different chemical compositions. The largest adhesion forces were observed on hydrophilic surfaces and the lowest ones on hydrophobic surfaces. The fact that the antiadhesion between nanofibers and the nano-structured areas depends strongly on the chemical composition of the surface can be explained by the specific adhesion between individual chemical groups due to frequency dependencies in the theory of van der Waals forces. However, explaining these adhesion properties just by the categories “hydrophilic” or “hydrophobic” is oversimplified.

People with injuries to the peripheral nervous system, due to its poor functional regeneration, suffer from paralysis of the facial muscles, fingers and hands, or toes and feet, often for the rest of their lives. Therefore, to improve patients’ quality of life, there is an urgent need for conduits that effectively support the healing of large defects in nerve pathways through specific guidance of nerve cells. This paper describes two specific methods for achieving directed growth of Schwann cells, a type of glial cells that can support the regeneration of the nerve pathway by guiding the neuronal axons in the direction of their alignment. One method implies the exposure of a poly(ethylene terephthalate) (PET) foil to a KrF* laser beam, that renders a nanorippled surface topography. The other method uses aligned polyamide-6 (PA-6) nanofibers produced via electrospinning on a very fast rotating structured collector, which enables easy nanofiber detachment, without additional effort. Schwann cells growth on these substrates was inspected after one week of cultivation by means of scanning electron microscope (SEM). For both methods we show that Schwann cells grow in a certain direction, predetermined by nanoripples and nanofibers orientation. In contrast, cells cultivated onto unstructured surfaces or randomly oriented nanofibers, show an omnidirectional growth behavior.

The surfaces of titanium grade 5 (Ti6Al4V) samples were altered on a micro and nano scale by femtosecond laser irradiation and subsequent electrochemical anodization. The produced micro-cones and nano-ripples covered by the additional oxide layer were characterised and their influence on osteoblast-like Saos-2 cell growth was studied. Surface topography and morphology were studied by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). From the wettability experiments, it was found that the contact angle vs. roughness follows the Wenzel equation and that the wettability increases after the anodization. The composition of the formed oxide layer was determined by X-ray photoelectron spectroscopy (XPS) and oxide incorporation of phosphate ions could be confirmed. Moreover, estimated electrochemical surface area (ECSA) of the femtosecond laser treated sample was 14 times larger compared to a polished sample. The anodic oxide film formation factors for different electrolytes were determined and were in the range of 1.3 nm V-1-2.0 nm V-1. Finally, the samples anodized with 0.1 M H2SO4 and 3 M H3PO4 showed decreased Saos-2 cell growth.

Since nanofibers have a high surface-to-volume ratio, van der Waals forces render them attracted to virtually any surface. The high ratio provides significant advantages for applications in drug delivery, wound healing, tissue regeneration, and filtration. Cribellate spiders integrate thousands of nanofibers into their capture threads as an adhesive to immobilize their prey. These spiders have antiadhesive nanoripples on the calamistrum, a comb-like structure on their hindmost legs, and are thus an ideal model for investigating how nanofiber adhesion can be reduced. We found that these nanoripples had similar spacing in the cribellate species Uloborus plumipes, Amaurobius similis, and Menneus superciliosus, independent of phylogenetic relation and size. Ripple spacing on other body parts (i.e., cuticle, claws, and spinnerets), however, was less homogeneous. To investigate whether a specific distance between the ripples determines antiadhesion, we fabricated nanorippled foils by nanosecond UV laser processing. We varied the spatial periods of the nanoripples in the range ~203-613 nm. Using two different pulse numbers resulted in ripples of different heights. The antiadhesion was measured for all surfaces, showing that the effect is robust against alterations across the whole range of spatial periods tested. Motivated by these results, we fabricated irregular surface nanoripples with spacing in the range ~130-480 nm, which showed the same antiadhesive behavior. The tested surfaces may be useful in tools for handling nanofibers such as spoolers for single nanofibers, conveyor belts for producing endless nanofiber nonwoven, and cylindrical tools for fabricating tubular nanofiber nonwoven. Engineered fibers such as carbon nanotubes represent a further candidate application area.

In this paper we present polymer surfaces inspired by the calamistrum of cribellate spiders. The calamistrum resembles a micro-comb with a finger-print-like nanorippled topography, which allows cribellate spiders to handle and process nanofibers, without sticking to them. Due to its morphology, the calamistrum has a reduced surface for contact with the nanofibers, which therefore reduces the adhesive forces. Three different types of structured surfaces were prepared: nanostructured surfaces (ripples), microstructured surfaces (lines), and a combination of micro- and nanostructured surfaces (lines superimposed with ripples). Polymer lines were created using UV mask lithography. Nanoripples, i.e., laser-induced periodic surface structures, were fabricated by exposure to a KrF* laser beam. Nanofibers were produced and deposited onto each sample by electrospinning. To quantify each samples’ adhesiveness, a peel-off test was used, and the results were plotted and compared against the control samples–a flat polymer film. Our results indicate that lines have a stronger influence on the adhesion reduction than the nanoripples: nanoripples reduce fiber adhesion by 7%, whereas the lines reduce it by 28%. The highest adhesion reduction of 33% is obtained for the polymer surfaces with a combination of both lines and nanoripples. Our results open new insights in the field of artificial nanofiber adhesion on micro- and nanopatterned surfaces, which are essential when designing tools for nanofiber handling.

Graft fixation during cruciate ligament reconstruction using interference screws is a common and frequently used surgical technique. These interference screws are usually made of metal or bioabsorbable materials. This paper describes the development of an allograft interference screw from cortical human bone. During the design of the screw, particular attention was paid to the choice of the screw drive and the screw shape, as well as the thread shape. Based on these parameters, a prototype was designed and manufactured. Subsequently, the first biomechanical tests using a bovine model were performed. The test procedure comprised a torsion test to determine the ultimate failure torque of the screw and the insertion torque during graft fixation, as well as a pull-out test to asses the ultimate failure load of the graft fixation. The results of the biomechanical analysis showed that the mean value of the ultimate failure torque was 2633 Nmm, whereas the mean occurring insertion torque during graft fixation was only 1125 Nmm. The mean ultimate failure load of the graft fixation was approximately 235 N. The results of this work show a good overall performance of the allograft screw compared to conventional screws, and should serve as a starting point for further detailed investigations and studies.

Introduction Due to their excellent surface-to-volume ratio, nanofibers (i.e., fibers with a diameter of approximately 10 to 800 nm) are of increasing interest to engineers and scientists in a broad spectrum of applications. However, due to van der Waals forces, these nanofibers tend to adhere strongly to any surface, which makes further processing very challenging. In nature, we find animals that can easily handle nanofibers: Cribellate spiders use a comb-like structure, the so-called calamistrum, to produce, handle, and process nanofibers. Due to a fingerprint-like surface nanostructure, nanofibers do not adhere to the calamistrum. The principle interaction between this fingerprint-like surface nanostructure and single nanofibers has recently been described in a publication. The fingerprint-like surface structure was replicated on a technical metal surface using laser-induced periodic surface structures, which resulted in material properties resembling those of the natural model. Methods We went a step further and took a closer look on an additional structural feature of the calamistrum much larger than the fingerprint-like surface structure. A theoretical approach to describing the influence of a fiber preload, which may become a dominant effect if the fiber dimensions are small compared to the surface structure dimensions, on the adhesion of the fiber to these large surface structures was derived. Our theory was verified experimentally for artificial electrospun polyamide 6 nanofibers on surface-structured samples made of titanium alloy. Results and Conclusion A dramatic reduction in adhesion compared to unstructured, flat surfaces was proven. Therefore, such a surface structure can be used for tools or parts of tools during nanofiber production (e.g., as part of the electrospinning process) to reduce the adhesion of the nonwoven fabric and thus facilitate the handling and processing of the nanofibers during production.

Nanofibers are drawing the attention of engineers and scientists because their large surface-to-volume ratio is favorable for applications in medicine, filter technology, textile industry, lithium-air batteries, and optical sensors. However, when transferring nanofibers to a technical product in the form of a random network of fibers, referred to as nonwoven fabric, the stickiness of the freshly produced and thus fragile nanofiber nonwoven remains a problem. This is mainly because nanofibers strongly adhere to any surface because of van der Waals forces. In nature, there are animals that are actually able to efficiently produce, process, and handle nanofibers, namely cribellate spiders. For that, the spiders use the calamistrum, a comb-like structure of modified setae on the metatarsus of the hindmost (fourth) legs, to which the 10-30 nm thick silk nanofibers do not stick due to a special fingerprint-like surface nanostructure. In this work, we present a theoretical model of the interaction of linear nanofibers with a sinusoidally corrugated surface. This model allows for a prediction of the adhesive interaction and, thus, the design of a suitable surface structure to prevent sticking of an artificially nonwoven of nanofibers. According to the theoretical prediction, a technical analogon of the nanoripples was produced by ultrashort pulse laser processing on different technically relevant metal surfaces in the form of so-called laser-induced periodic surface structures (LIPSS). Subsequently, by means of a newly established peel-off test, the adhesion of an electrospun polyamide fiber-based nonwoven was quantified on such LIPSS-covered aluminium alloy, steel, and titanium alloy samples, as well as on polished (flat) control samples as reference and, additionally, on samples with randomly rough surfaces. The latter revealed that the adhesion of electrospun nanofiber nonwoven is significantly lowered on the nanostructured surfaces compared with the polished surfaces.

Microstructures and nanostructures can be used to reduce the adhesion of the cells on the auxiliary material. Therefore, the aim of our work was to fabricate laser-induced hierarchical microstructures and nanostructures by femtosecond laser-treatment (wavelength 1040 nm, pulse length 350 fs, repetition rates in the kHz range) to reduce the cell adhesion. Additionally, surface chemistry modification by optimized electrochemical anodization was used to further reduce the cell adhesion. For testing, flat plates and bone screws made of Ti-6Al-4V were used. Bone-forming cells (human osteoblasts from the cell line SAOS-2) were grown on the bone implants and additional test samples for two to three weeks. After the growth period, the cells were characterized by scanning electron microscopy (SEM). While earlier experiments with fibroblasts had shown that femtosecond laser-processing followed by electrochemical anodization had a significant impact on cell adhesion reduction, for osteoblasts the same conditions resulted in an activation of the cells with increased production of extracellular matrix material. Significant reduction of cell adhesion for osteoblasts was only obtained at pre-anodized surfaces. It could be demonstrated that this functionalization by means of femtosecond laser-processing can result in bone screws that hinder the adhesion of osteoblasts.

In this research, we applied laser-plasma spectroscopy technique for the measurement of trace chemical elements in the exhaust emissions generated from in-use diesel engine passenger vehicles. We use high resolution laser-induced breakdown spectroscopy (LIBS) technique for diagnostics of soot and particulate matter (PM). Here we analysed soot and PM, extracted from exhaust manifold part, from different passenger vehicles that are used in daily life environment. The main aim of this study is to reveal the trace chemical elements in different PM matrices. The presence of trace elements in exhaust emissions can originate from different sources: from injected fuel type and fuel additives, engine lubricants, engine combustion process, incomplete catalytic reaction, inefficiency or wear out of PM filtering devices, dysfunctions or failures of engine or vehicle or even information related to polluted intake air.

Background: During the coronavirus disease 2019 (COVID-19) pandemic face masks grew in importance as their use by the general population was recommended by health officials in order to minimize the risk of infection and prevent further spread of the virus. To ensure health protection of medical personnel and other system relevant staff, it is of considerable interest to quickly test if a certain lot of filtering facepiece masks meets the requirements or if the penetration changes under different conditions. As certified penetrometers are rather expensive and were difficult to obtain during the COVID-19 pandemic, we describe two quite simple and cheap methods to quickly test the filter penetration based on an electronic cigarette. Methods: The first method uses a precision scale, the second method uses a light scattering detector to measure the filter penetration. To make sure these two methods yield reliable results, both were tested with freshly cut filter samples covering the range of approx. 2 % to 60 % filter penetration and compared to the results of a certified penetrometer. Results: The comparison of the two methods with the certified penetrometer showed a good correlation and therefore allow a quick and rather reliable estimation of the penetration. Conclusions: Several examples about the use of faulty masks and the resulting health risks show that simple, fast, cheap and broadly available methods for filter characterization might be useful in these days.

Due to their osteoconductive properties, allogenic bone screws made of human cortical bone have advantages regarding rehabilitation compared to other materials such as stainless steel or titanium. Since conventional screw drives like hexagonal or hexalobular drives are difficult to manufacture in headless allogenic screws, an easy-to-manufacture screw drive is needed. In this paper, we present a simple drive for headless allogenic bone screws that allows the screw to be fully inserted. Since the screw drive is completely internal, no threads are removed. In order to prove the mechanical strength, we performed simulations of the new drive using the Finite-Element method (FEM), validated the simulations with a prototype screw, tested the novel screw drive experimentally and compared the simulations with conventional drives. The validation with the prototype showed that our simulations provided valid results. Furthermore, the simulations of the new screw drive showed good performance in terms of mechanical strength in allogenic screws compared to conventional screw drives. The presented screw drive is simple and easy to manufacture and is therefore suitable for headless allogenic bone screws where conventional drives are difficult to manufacture.

Some true bug species use droplet-shaped, open-capillary structures for passive, unidirectional fluid transport on their body surface in order to spread a defensive fluid to protect themselves against enemies. In this paper we investigated if the shape of the structures found on bugs (bug-structure) could be optimised with regard to better performance in unidirectional fluid transportation. Furthermore, to use this kind of surface structure in technical applications where fluid surface interaction occurs, it is necessary to adapt the structure geometry to the contact angle between fluid and surface. Based on the principal of operation of the droplet-shaped structures, we optimised the structure shape for better performance in targeted fluid flow and increase in flexibility in design of the structure geometry. To adapt the structure geometry and the structure spacing to the contact angle, we implemented an equilibrium simulation of the, the structure surrounding, fluid. In order to verify the functionality of the optimised structure, we designed and manufactured a prototype. By testing this prototype with pure water used as fluid, the functionality of the optimised structure and the simulation could be proved. This kind of structure may be used on technical surfaces where targeted fluid transport is needed, e.g. evacuation of condensate in order to prevent the surface from mold growth, microfluidics, lab-on-a-chip applications and on microneedles for efficient drug/vaccine coating.