Plasma Etching of Silk Fibroin: Experiments and Models

Abstract

Silk fibroin biopolymer is anisotropically etched using oxygen and argon/oxygen plasma. At room temperature, silk removal rates are 0.25 µm min−1. Scanning electron micrographs show that silk fibroin is a heterogeneous material for which plasma etching reveals a silk backbone structure as the matrix is more quickly volatilized. A simple physical model of silk etching accurately predicts the etch rate without any fitting parameters. The model and experimental data show that atomic oxygen, in the absence of ion bombardment, only slowly etches silk (<0.017 µm min−1) and does not spontaneously etch silk fibroin backbone structures. Rather, the silk constituents must be removed by first covering the surface with adsorbed atomic oxygen which is then simultaneously desorbed through energetic ion bombardment. magnified image

Oxygen Plasma Etching of Silk Fibroin Alters Surface Stiffness: A Cell-Substrate Interaction Study

“…SF might be used as a substrate for studying the effect of surface stiffness on cell‐substrate interaction. Our new initiative was inspired by the reports of plasma etched SF surfaces . UV radiation, a common side effect from plasma etching, could be used to alter surface stiffness through a crosslinking process.…”

“…Our new initiative was inspired by the reports of plasma etched SF surfaces. [29,30] UV radiation, a common side effect from plasma etching, [31] could be used to alter surface stiffness through a crosslinking process. The unique effects of plasma UV radiation, known as vacuum ultraviolet radiation (VUV), could not be imitated by simple UV radiation because the photon energy is higher in VUV radiation than in UV radiation.…”

Wafer-Scale Multilayer Fabrication for Silk Fibroin-Based Microelectronics

“…Also, we observed some irregular edges of the patterns (Figure i). These are possibly attributed to fibroin’s inhomogeneity that causes a dissimilar etch rate . Furthermore, we noticed that the surface of the patterned fibroin films was less flat for thick fibroin films (Figure l–o).…”

“…Here, we intentionally designed the corners to be rounded during the mask design to observe the effects of over-etching. When such properties are not desirable, anisotropic etching methods such as reactive ion etching could be used. Also, we observed some irregular edges of the patterns (Figure i).…”

Atmospheric Plasma‐Assisted Deposition and Patterning of Natural Polymers

“…[18] To enable coating of chitosan or other natural polymers for applications such as biosensors or implantable devices, the deposition method should provide not only a homogeneous and stable layer, but also provide spatially controlled deposition, potentially enabling surface patterning at the micro or nanoscales. [34][35][36] When the coatings interface with living environments, spatially-controlled deposition can tune interactions (e.g., protein adsorption), or guide cell organization. One method of pattering chitosan is based on the use of a pipette tip, [37] which allows contourable patterns.…”