Robustness of antiadhesion between nanofibers and surfaces covered with nanoripples of varying spatial period

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.

Nanoscale Dots, Grids, Ripples, and Hierarchical Structures on PET by UV Laser Processing

“…Furthermore, we refined the assessment of ripple characteristics by using FIB cuts. Possible applications of our findings are the fabrication of advanced surfaces that are anti-adhesive to nanofibers [4,5] or repel bacteria [32]. Furthermore, they might be used for improvements to localized plasmon voltammetry sensing [40], in biomimicry [1,3,12], and in the biomedical context [44][45][46], for instance, to activate cells [24,29].…”

“…Topographical characterization of bioinspired LIPSS by atomic force microscopy (AFM) was shown to be affected by tip-sample convolution effects in [5], where these effects were most probably due to the high aspect ratios of the structures fabricated, and the steep slopes of their edges that made topography assessment by AFM more challenging. For certain example LIPSS structures processed under the same conditions, focused ion beam (FIB) cuts [4] gave larger structural heights than AFM images [32]. Furthermore, the ripples seemed considerably wider in AFM images [32] than in scanning electron microscopy (SEM) recordings and FIB cuts [4].…”

“…For certain example LIPSS structures processed under the same conditions, focused ion beam (FIB) cuts [4] gave larger structural heights than AFM images [32]. Furthermore, the ripples seemed considerably wider in AFM images [32] than in scanning electron microscopy (SEM) recordings and FIB cuts [4].…”

“…Nature makes abundant use of highly versatile nano-and microscale surface features [1][2][3] for antiadhesion [4,5], wetting [6,7], directional liquid transport [8,9], and structural color [10,11]. All these surface properties are strongly influenced by the specific designs of the corresponding structures.…”

“…Bioinspired LIPSS on PET were shown to significantly reduce the adhesion of Escherichia coli bacteria [32] (~−91%) and nanofibers [4] (about −73% when combined with a gold coating) compared to the unstructured pristine surfaces. Other applications of LIPSS on PET include the formation of gold nanowires [24,27,40] for localized plasmon voltammetry sensing [40], the preparation of silver nanowires [41], and the activation of human microvascular endothelial cells (HMECs) [24].…”