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  • 1
    Online Resource
    Online Resource
    MDPI AG ; 2023
    In:  Arthropoda Vol. 1, No. 3 ( 2023-07-06), p. 342-349
    In: Arthropoda, MDPI AG, Vol. 1, No. 3 ( 2023-07-06), p. 342-349
    Abstract: Typical orb webs with glue droplets are renewed regularly, sometimes multiple times per night. Such behaviour, however, is rarely found with cribellate spiders. The adhesive portion of their capture threads consist of nanofibres instead of glue, and the fibres interact with the cuticular hydrocarbons (CHCs) of their insect prey for adhesion. Many of these spiders often only add new threads to their existing webs instead of completely reconstructing them. In testing the adhesion force of aged capture threads of three different cribellate species, we indeed did not observe an overall decline in adhesion force, even after a period of over a year. This is in line with the (formulated but so far never tested) hypothesis that when comparing gluey capture threads to nanofibrous ones, one of the benefits of cribellate capture threads could be their notable resistance to drying out or other ageing processes.
    Type of Medium: Online Resource
    ISSN: 2813-3323
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
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  • 2
    Online Resource
    Online Resource
    Frontiers Media SA ; 2023
    In:  Frontiers in Ecology and Evolution Vol. 11 ( 2023-3-8)
    In: Frontiers in Ecology and Evolution, Frontiers Media SA, Vol. 11 ( 2023-3-8)
    Abstract: 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.
    Type of Medium: Online Resource
    ISSN: 2296-701X
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2023
    detail.hit.zdb_id: 2745634-1
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  • 3
    Online Resource
    Online Resource
    American Chemical Society (ACS) ; 2020
    In:  ACS Applied Nano Materials Vol. 3, No. 4 ( 2020-04-24), p. 3395-3401
    In: ACS Applied Nano Materials, American Chemical Society (ACS), Vol. 3, No. 4 ( 2020-04-24), p. 3395-3401
    Type of Medium: Online Resource
    ISSN: 2574-0970 , 2574-0970
    Language: English
    Publisher: American Chemical Society (ACS)
    Publication Date: 2020
    detail.hit.zdb_id: 2916552-0
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  • 4
    In: Frontiers in Ecology and Evolution, Frontiers Media SA, Vol. 11 ( 2023-6-19)
    Abstract: 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.
    Type of Medium: Online Resource
    ISSN: 2296-701X
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2023
    detail.hit.zdb_id: 2745634-1
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  • 5
    Online Resource
    Online Resource
    MDPI AG ; 2021
    In:  Nanomaterials Vol. 11, No. 12 ( 2021-11-27), p. 3222-
    In: Nanomaterials, MDPI AG, Vol. 11, No. 12 ( 2021-11-27), p. 3222-
    Abstract: Due to their uniquely high surface-to-volume ratio, nanofibers are a desired material for various technical applications. However, this surface-to-volume ratio also makes processing difficult as van der Waals forces cause nanofibers to adhere to virtually any surface. The cribellate spider Uloborus plumipes represents a biomimetic paragon for this problem: these spiders integrate thousands of nanofibers into their adhesive capture threads. A comb on their hindmost legs, termed calamistrum, enables the spiders to process the nanofibers without adhering to them. This anti-adhesion is due to a rippled nanotopography on the calamistrum. Via laser-induced periodic surface structures (LIPSS), these nanostructures can be recreated on artificial surfaces, mimicking the non-stickiness of the calamistrum. In order to advance the technical implementation of these biomimetic structured foils, we investigated how climatic conditions influence the anti-adhesive performance of our surfaces. Although anti-adhesion worked well at low and high humidity, technical implementations should nevertheless be air-conditioned to regulate temperature: we observed no pronounced anti-adhesive effect at temperatures above 30 °C. This alteration between anti-adhesion and adhesion could be deployed as a temperature-sensitive switch, allowing to swap between sticking and not sticking to nanofibers. This would make handling even easier.
    Type of Medium: Online Resource
    ISSN: 2079-4991
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2662255-5
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  • 6
    In: Beilstein Journal of Nanotechnology, Beilstein Institut, Vol. 13 ( 2022-11-07), p. 1268-1283
    Abstract: 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.
    Type of Medium: Online Resource
    ISSN: 2190-4286
    Language: English
    Publisher: Beilstein Institut
    Publication Date: 2022
    detail.hit.zdb_id: 2583584-1
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