Steering nanofibers: An integrative approach to bio-inspired fiber fabrication and assembly

Abstract

As seen throughout the natural world, nanoscale fibers exhibit a unique combination of mechanical and surface properties that enable them to wind and bend around each other into an immense diversity of complex forms. In this review, we discuss how this versatility can be harnessed to transform a simple array of anchored nanofibers into a variety of complex, hierarchically organized dynamic functional surfaces. We describe a set of recently developed benchtop techniques that provide a straightforward way to generate libraries of fibrous surfaces with a wide range of finely tuned, nearly arbitrary geometric, mechanical, material, and surface characteristics starting from a single master array. These simple systematic controls can be used to program the fibers to bundle together, twist around each other into chiral swirls, and assemble into patterned arrays of complex hierarchical architectures. The delicate balance between fiber elasticity and surface adhesion plays a critical role in determining the shape, chirality, and higher order of the assembled structures, as does the dynamic evolution of the geometric, mechanical, and surface parameters throughout the assembly process. Hierarchical assembly can also be programmed to run backwards, enabling a wide range of reversible, responsive behaviors to be encoded through rationally chosen surface chemistry. These strategies provide a foundation for designing a vast assortment of functional surfaces with anti-fouling, adhesive, optical, water and ice repellent, memory storage, microfluidic, capture and release, and many more capabilities with the structural and dynamic sophistication of their biological counterparts. Highlights Integrative approach to creating fibrous surfaces with multiscale complexity and dynamic behavior. Low-cost benchtop techniques to generate libraries of nanofiber arrays with fine-tuned parameters. Program fiber arrays to self-assemble into complex, chiral, hierarchical architectures. Encode reversible, responsive behavior through rationally chosen surface chemistry.

Nano and Microscale Topographies for the Prevention of Bacterial Surface Fouling

“…Many groups have fabricated engineered surface topography, using numerous fabrication techniques (soft lithography and double casting molding techniques, microcontact printing, electron beam lithography, nanoimprint lithography, photolithography, electrodeposition methods, etc.) [37][38][39][40][41][42][43][44][45][46][47] on a wide range of substrates, ranging from various polymeric materials (silicone, polystyrene, polyurethane, and epoxy resins) to metals and metal oxides (silicon, titanium, aluminum, silica, and gold) [21,40,45,[47][48][49][50][51][52][53][54][55]. Furthermore, engineered topography can be considered as part of a multi-faceted strategy to prevent biofouling, and could be combined with other methods such as surface chemical treatments, addition of antibiotics/bacteriostatic agents, etc.…”

Elastocapillary coalescence of plates and pillars

“…To estimate the drag coefficient c and the time scale in equation (3.1), we consider both the internal contribution from viscoelasticity of the solid material and the external contribution from the viscous fluid and find that viscoelastic effects dominate. Indeed, AFM characterization of the epoxy micropillars [27] show that the force versus displacement curve has a clear hysteresis loop, which reveals that the epoxy micropillars are viscoelastic. For a pillar of radius R = 1.5 µm, length L = 9 µm and bending spring constant k = 3π ER 4 /4L 3 ≈ 3.3 N m −1 , where E = 0.2 GPa is the Young's modulus, the measured hysteresis accounts for 32% of the total work done at max deflection x = 1.5 µm and rate of deflection v = 6 µm s −1 .…”

Fusion of nacre, mussel, and lotus leaf: bio-inspired graphene composite paper with multifunctional integration

“…Optimized biological solutions provide a source of inspiration for scientists to design rationally and to construct reproducibly multiscale structures for multifunctional integration. [4][5][6][7][8] In nature, nacre, glass sponges, teeth, bones, and other biomaterials have evolved different solutions to overcome the brittleness of their building materials. [9][10][11] Among the variety of biological materials, nacre is one of most promising owing to its superior mechanical strength and toughness (Fig.…”