The exciting properties of micro-and nano-patterned surfaces found in natural species hide a virtually endless potential of technological ideas, opening new opportunities for innovation and exploitation in materials science and engineering. Due to the diversity of biomimetic surface functionalities, inspirations from natural surfaces are interesting for a broad range of applications in engineering, including phenomena of adhesion, friction, wear, lubrication, wetting phenomena, self-cleaning, antifouling, antibacterial phenomena, thermoregulation and optics. Lasers are increasingly proving to be promising tools for the precise and controlled structuring of materials at micro-and nano-scales. When ultrashort-pulsed lasers are used, the optimal interplay between laser and material parameters enables structuring down to the nanometer scale. Besides this, a unique aspect of laser processing technology is the possibility for material modifications at multiple (hierarchical) length scales, leading to the complex biomimetic micro-and nano-scale patterns, while adding a new dimension to structure optimization. This article reviews the current state of the art of laser processing methodologies, which are being used for the fabrication of bioinspired artificial surfaces to realize extraordinary wetting, optical, mechanical, and biological-active properties for numerous applications. The innovative aspect of laser functionalized biomimetic surfaces for a wide variety of current and future applications is particularly demonstrated and discussed. The article concludes with illustrating the wealth of arising possibilities and the number of new laser micro/nano fabrication approaches for obtaining complex high-resolution features, which prescribe a future where control of structures and subsequent functionalities are beyond our current imagination.

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Nanofibrous multifunctional materials have attracted a lot of attention because of the benefits of their special structure. Despite the diverse benefits of nanofibrous materials, their inherent stickiness to any surface is a major obstacle in producing and processing such materials. There are many paragons in which biological models or elements from nature have been biomimetically adapted in various areas in order to resolve technical problems, such as the silent flight of the owl, the lotus effect, or the sticky feet of the gecko. One special example shows us how nanofibers might be handled in the future: cribellate spiders possess a specialized comb, the calamistrum, on their hindmost legs, which is used to process and assemble nanofibers into structurally complex capture threads. Within this study, we were able to prove that these fibers do not stick to the calamistrum because of a special fingerprint-like nanostructure on the comb. This structure prevents the nanofibers from smoothly adapting to the surface of the comb, thus minimizing contact and reducing the adhesive van der Waals forces between the nanofibers and surface. This leads to the spiders’ ability of nonsticky processing of nanofibers for their capture threads. The successful transfer of these structures to a technical surface proved that this biological model can be adapted to optimize future tools in technical areas in which antiadhesive handling of nanofibrous materials is required.

To survive, web-building spiders rely on their capture threads to restrain prey. Many species use special adhesives for this task, and again the majority of those species cover their threads with viscoelastic glue droplets. Cribellate spiders, by contrast, use a wool of nanofibres as adhesive. Previous studies hypothesized that prey is restrained by van der Waals' forces and entrapment in the nanofibres. A large discrepancy when comparing the adhesive force on artificial surfaces versus prey implied that the real mechanism was still elusive. We observed that insect prey's epicuticular waxes infiltrate the wool of nanofibres, probably induced by capillary forces. The fibre-reinforced composite thus formed led to an adhesion between prey and thread eight times stronger than that between thread and wax-free surfaces. Thus, cribellate spiders employ the originally protective coating of their insect prey as a fatal component of their adhesive and the insect promotes its own capture. We suggest an evolutionary arms race with prey changing the properties of their cuticular waxes to escape the cribellate capture threads that eventually favoured spider threads with viscous glue.

Spiders are famous for their silk with fascinating mechanical properties. However, some can further produce, process and handle nano fibres, which are used as capture threads. These ‘cribellate spiders’ bear a specialized setae comb on their metatarsus (calamistrum), which modifies cribellate nano fibres to assemble a puffy structure within the capture thread. Among different species, the calamistrum morphology can differ remarkably. Although a model of thread production has been established for Uloborus plumipes, it is not resolved if/how different shaped calamistra influence the production process. We were able to transfer the model without restrictions to spiders with different shaped calamistra. Fibres are not locked between setae but are passing across a rather smooth surface-like area on the calamistrum. This area can be relocated, explaining the first morphological difference between calamistra, without changing the influence of the calamistrum on fibres. By performing an elongated leg movement, contact between fibres and calamistrum could be adjusted after finishing thread production. This movement has to bring the thread in contact with the second morphological peculiarity: cribellate teeth. We suggest these teeth are used to handle the thread independently of the spinnerets, a feature only necessary for spiders, which do not move during web construction.

For successful material deployment in tissue engineering, the material itself, its mechanical properties, and the microscopic geometry of the product are of particular interest. While silk is a widely applied protein-based tissue engineering material with strong mechanical properties, the size and shape of artificially spun silk fibers are limited by existing processes. This study adjusts a microfluidic spinneret to manufacture micron-sized wet-spun fibers with three different materials enabling diverse geometries for tissue engineering applications. The spinneret is direct laser written (DLW) inside a microfluidic polydimethylsiloxane (PDMS) chip using two-photon lithography, applying a novel surface treatment that enables a tight print-channel sealing. Alginate, polyacrylonitrile, and silk fibers with diameters down to 1 μm are spun, while the spinneret geometry controls the shape of the silk fiber, and the spinning process tailors the mechanical property. Cell-cultivation experiments affirm bio-compatibility and showcase an interplay between the cell-sized fibers and cells. The presented spinning process pushes the boundaries of fiber fabrication toward smaller diameters and more complex shapes with increased surface-to-volume ratio and will substantially contribute to future tailored tissue engineering materials for healthcare applications.

Technical nanofibre production is linked to high voltage, because nanofibres are typically produced by electrospinning. In contrast, spiders have evolved a way to produce nanofibres without high voltage. These spiders are called cribellate spiders and produce nanofibres within their capture thread production. It is suggested that their nanofibres become frictionally charged when brushed over a continuous area on the calamistrum, a comb-like structure at the metatarsus of the fourth leg. Although there are indications that electrostatic charges are involved in the formation of the thread structure, final proof is missing. We proposed three requirements to validate this hypothesis: (1) the removal of any charge during or after thread production has an influence on the structure of the thread; (2) the characteristic structure of the thread can be regenerated by charging; and (3) the thread is attracted to or repelled from differently charged objects. None of these three requirements were proven true. Furthermore, mathematical calculations reveal that even at low charges, the calculated structural assembly of the thread does not match the observed reality. Electrostatic forces are therefore not involved in the production of cribellate capture threads.

Spiders are known for producing specialized fibers. The radial orb-web, for example, contains tough silk used for the web frame and the capture spiral consists of elastic silk, able to stretch when prey impacts the web. In concert, silk proteins and web geometry affects the spider’s ability to capture prey. Both factors have received considerable research attention, but next to no attention has been paid to the influence of fiber processing on web performance. Cribellate spiders produce a complex fiber alignment as their capture threads. With a temporally controlled spinneret movement, they connect different fibers at specific points to each other. One of the most complex capture threads is produced by the southern house spider, Kukulcania hibernalis (Filistatidae). In contrast to the so far characterized linear threads of other cribellate spiders, K. hibernalis spins capture threads in a zigzag pattern due to a slightly altered spinneret movement. The resulting more complex fiber alignment increased the thread’s overall ability to restrain prey, probably by increasing the adhesion area as well as its extensibility. Kukulcania hibernalis' cribellate silk perfectly illustrates the impact of small behavioral differences on the thread assembly and, thus, of silk functionality.