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Abstract Bacterial biofilms on the surfaces of indwelling biomedical devices can cause long‐term infection and patient morbidity and mortality. Wrinkled surface topographies have previously demonstrated promising antifouling properties. Here we report a bioinspired strategy in which the actuation of silk fibroin produces tunable, wrinkled surface topographies on 2D shape memory polymer (SMP) substrates and investigate the influence of these topographies on biofilm formation. To mimic biofilm‐associated infections related to the geometries of indwelling medical devices, silk wrinkles are produced on complex, 3D SMP architectures, and biofilm formation is evaluated. Using common biofilm‐causing agents, smaller silk wrinkle wavelengths and amplitudes are found to significantly reduce biofilm formation, resulting in primarily isolated, single‐cell bacteria on the 2D wrinkled surfaces. These single‐cell bacteria are nearly completely eradicated by treatment with antibiotics, which are ineffective against control surfaces. Antibiotics are also physically incorporated into the 2D wrinkled surfaces, which resulted in a further significant reduction in bacterial adhesion. Lastly, silk wrinkled topographies are successfully applied on 3D architectures, and the wrinkled surfaces display a significant reduction in biofilm coverage compared to controls. The findings demonstrate the potential for biopolymer wrinkles on biomaterials to be used as antifouling surfaces for biofilm prevention.
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Mechanics of Tunable Adhesion With Surface Wrinkles
Abstract Surface wrinkles have emerged as a promising avenue for the development of smart adhesives with dynamically tunable adhesion, finding applications in diverse fields, such as soft robots and medical devices. Despite intensive studies and great achievements, it is still challenging to model and simulate the tunable adhesion with surface wrinkles due to roughened surface topologies and pre-stress inside the materials. The lack of a mechanistic understanding hinders the rational design of these smart adhesives. Here, we integrate a lattice model for nonlinear deformations of solids and nonlocal interaction potentials for adhesion in the framework of molecular dynamics to explore the roles of surface wrinkles on adhesion behaviors. We validate the proposed model by comparing wrinkles in a neo-Hookean bilayer with benchmarked results and reproducing the analytical solution for cylindrical adhesion. We then systematically study the pull-off force of the wrinkled surface with varied compressive strains and adhesion energies. Our results reveal the competing effect between the adhesion-induced contact and the roughness due to wrinkles on enhancing or weakening the adhesion. Such understanding provides guidance for tailoring material and geometry as well as loading wrinkled surfaces for different applications.
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- Award ID(s):
- 1847149
- PAR ID:
- 10497952
- Publisher / Repository:
- ASME Journal of Applied Mechanics
- Date Published:
- Journal Name:
- Journal of Applied Mechanics
- Volume:
- 90
- Issue:
- 12
- ISSN:
- 0021-8936
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Polymeric systems displaying spontaneous formation of surface wrinkling patterns are useful for a wide range of applications, such as diffraction gratings, flexible electronics, smart adhesives, optical devices, and cell culture platforms. Conventional fabrication techniques for wrinkling patterns involves multitude of processing steps and impose significant limitations on fabrication of hierarchical patterns, creating wrinkles on 3D and nonplanar structures, the scalability of the manufacturing process, and the integration of wrinkle fabrication process into a continuous manufacturing process. In this work, 4D printing of surface morphing hydrogels enabling direct fabrication of wrinkling patterns on curved and/or 3D structures with user‐defined and spatially controlled pattern geometry and size is reported. The key to successful printing is to tailor the photopolymerization time and partial crosslinking time of the hydrogel inks. The interplay between crosslinker concentration and postprinting crosslinking time allow for the control over wrinkling morphology and the characteristic size of the patterns. The pattern alignment is controlled by the print strut size—the size of the solid material extruded from the print nozzle in the form of a line. To demonstrate the utility of the approach, tunable optical devices, a solvent/humidity sensor for microchips, and cell culture platforms to control stem cell shape are fabricated.more » « less
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Understanding protein adsorption behavior on rough and wrinkled surfaces is vital to applications including biosensors and flexible biomedical devices. Despite this, there is a dearth of study on protein interaction with regularly undulating surface topographies, particularly in regions of negative curvature. Here we report nanoscale adsorption behavior of immunoglobulin M (IgM) and immunoglobulin G (IgG) on wrinkled and crumpled surfaces via atomic force microscopy (AFM). Hydrophilic plasma treated poly(dimethylsiloxane) (PDMS) wrinkles with varying dimensions exhibit higher surface coverage of IgM on wrinkle peaks over valleys. Negative curvature in the valleys is determined to reduce protein surface coverage based both on an increase in geometric hindrance on concave surfaces, and reduced binding energy as calculated in coarse-grained molecular dynamics simulations. The smaller IgG molecule in contrast shows no observable effects on coverage from this degree of curvature. The same wrinkles with an overlayer of monolayer graphene show hydrophobic spreading and network formation, and inhomogeneous coverage across wrinkle peaks and valleys attributed to filament wetting and drying effects in the valleys. Additionally, adsorption onto uniaxial buckle delaminated graphene shows that when wrinkle features are on the length scale of the protein diameter, hydrophobic deformation and spreading do not occur and both IgM and IgG molecules retain their dimensions. These results demonstrate that undulating wrinkled surfaces characteristic of flexible substrates can have significant effects on protein surface distribution with potential implications for design of materials for biological applications.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1115/1.4062699
