Surface Functionalization of 4D Printed Substrates Using Polymeric and Metallic Wrinkles

Abstract

Wrinkle topographies have been studied as simple, versatile, and in some cases biomimetic surface functionalization strategies. To fabricate surface wrinkles, one material phenomenon employed is the mechanical-instability-driven wrinkling of thin films, which occurs when a deforming substrate produces sufficient compressive strain to buckle a surface thin film. Although thin-film wrinkling has been studied on shape-changing functional materials, including shape-memory polymers (SMPs), work to date has been primarily limited to simple geometries, such as flat, uniaxially-contracting substrates. Thus, there is a need for a strategy that would allow deformation of complex substrates or 3D parts to generate wrinkles on surfaces throughout that complex substrate or part. Here, 4D printing of SMPs is combined with polymeric and metallic thin films to develop and study an approach for fiber-level topographic functionalization suitable for use in printing of arbitrarily complex shape-changing substrates or parts. The effect of nozzle temperature, substrate architecture, and film thickness on wrinkles has been characterized, as well as wrinkle topography on nuclear alignment using scanning electron microscopy, atomic force microscopy, and fluorescent imaging. As nozzle temperature increased, wrinkle wavelength increased while strain trapping and nuclear alignment decreased. Moreover, with increasing film thickness, the wavelength increased as well.

Dry and wet wrinkling of a silk fibroin biopolymer by a shape-memory material with insight into mechanical effects on secondary structures in the silk network

“…21 That work was representative of much of the prior work in which wrinkles were used to study cell mechanobiology, which has generally employed synthetic (metallic or polymeric) films. [13][14][15][16][17][18][19][20][21]73 By establishing an approach whereby silk can be used as the film, here we broaden the potential for the wrinkle topography to be tailored to the specific mechanobiological needs of a given research inquiry. For example, SF has been used to deliver therapeutics for cancer, 74 wound healing, 74,75 and neural tissue regeneration.…”