Functional Changes during Electron-Beam Lithography of Biotinylated Poly(ethylene glycol) Thin Films

Abstract

In contrast to photolithography where particular wavelengths of light can couple to specific photochemistries, electron-beam lithography can drive competing chemistries. To separate surface-grafting, cross-linking, and chemical functionality, we studied the effects of 2 keV electrons on thin films of poly(ethylene glycol) end-functionalized with hydroxyls (PEG-OH) or biotins (PEG-B). Similarities in the dose-dependent thickness changes of the patterned PEGs indicate that surface grafting and cross-linking primarily involve the ethylene oxide main chain. While higher doses create thicker patterns with more biotin, the concurrent increase in thiol reactivity indicates that crosslinking competes with biotin degradation. The dose window for optimal e-beam patterning of biotinylated PEG is very narrow. Biotin is entirely consumed at higher doses. Its modified functionality is reactive with 5-((2-(and-3)-S-(acetylmercapto) succinoyl) amino) (SAMSA). This effect creates a dose-dependent orthogonal functionality that can be patterned from a single precursor thin film.

Chemical Orthogonality in Surface-Patterned Poly(ethylene glycol) Microgels

“…The intensity is a maximum for 6 μC/cm 2 and is almost entirely absent for doses of 100 μC/cm 2 or more (Figure graph). This behavior is very consistent with a previous set of similar experiments . Notably, we observe no reactivity between SA and microgel pads made from PEG-OH using any dose (Figure bottom of left panel).…”

“…This behavior is very consistent with a previous set of similar experiments. 22 Notably, we observe no reactivity between SA and microgel pads made from PEG-OH using any dose (Figure 3 bottom of left panel). These observations indicate that the SA interaction is very specific to biotin.…”

“…Electron-beam (e-beam)-patterned microgels were synthesized on silicon substrates via previously established methods. ,, Briefly, single-crystal Si substrates (5 mm × 5 mm; Ted Pella) were immersed in piranha solution (3:1 mixture of concentrated sulfuric acid and 30% hydrogen peroxide; exercise caution) for 12 h and washed with deionized (DI) water multiple times. Prior to use, these substrates were exposed to an oxygen plasma.…”

Insight and Recent Advances into the Role of Topography on the Cell Differentiation and Proliferation on Biopolymeric Surfaces

“…There is a tremendous amount of periodic surface relief patterns exhibiting a certain shape, dimension and function [ 37 , 38 , 39 , 40 , 41 , 42 , 43 ]. Such periodic patterns are mainly obtained from polymer-based systems (generally, polymers are cheap and yet highly processable materials) [ 44 , 45 , 46 , 47 ], through the use of various top-down and bottom-up methodologies [ 21 , 48 ].…”

Multifunctional Structured Platforms: From Patterning of Polymer-Based Films to Their Subsequent Filling with Various Nanomaterials

“…Nonetheless, the best contrast and sensitivity of the material has to be considered when choosing the appropriate resist for high-aspect ratio patterns [ 65 ] and when aiming at sub-20 nm resolution on both positive and negative tones resists [ 66 ]. Sometimes, depending on the resist type, EBL can also induce unwanted competing chemistries including surface-grafting or cross-linking or changes in chemical functionality [ 67 ]. For the preparation and optimization of the right resist, we advise our readers to follow suggestive examples given in the literature by Pfirrmann, Takei, and Wieberger and their collaborators [ 68 , 69 , 70 ].…”