Nanopatterned Monolayers of Bioinspired, Sequence-Defined Polypeptoid Brushes for Semiconductor/Bio Interfaces

Abstract

The ability to control and manipulate semiconductor/bio interfaces is essential to enable biological nanofabrication pathways and bioelectronic devices. Traditional surface functionalization methods, such as self-assembled monolayers (SAMs), provide limited customization for these interfaces. Polymer brushes offer a wider range of chemistries, but choices that maintain compatibility with both lithographic patterning and biological systems are scarce. Here, we developed a class of bioinspired, sequence-defined polymers, i.e., polypeptoids, as tailored polymer brushes for surface modification of semiconductor substrates. Polypeptoids featuring a terminal hydroxyl (−OH) group are designed and synthesized for efficient melt grafting onto the native oxide layer of Si substrates, forming ultrathin (∼1 nm) monolayers. By programming monomer chemistry, our polypeptoid brush platform offers versatile surface modification, including adjustments to surface energy, passivation, preferential biomolecule attachment, and specific biomolecule binding. Importantly, the polypeptoid brush monolayers remain compatible with electron-beam lithographic patterning and retain their chemical characteristics even under harsh lithographic conditions. Electron-beam lithography is used over polypeptoid brushes to generate highly precise, binary nanoscale patterns with localized functionality for the selective immobilization (or passivation) of biomacromolecules, such as DNA origami or streptavidin, onto addressable arrays. This surface modification strategy with bioinspired, sequence-defined polypeptoid brushes enables monomer-level control over surface properties with a large parameter space of monomer chemistry and sequence and therefore is a highly versatile platform to precisely engineer semiconductor/bio interfaces for bioelectronics applications.

Substrate Neutrality for Obtaining Block Copolymer Vertical Orientation

“…The surface characterization of polymer brushes is vital to understand the underlying chemical and mechanical properties. Non-invasive characterization techniques such as atomic force microscopy (AFM) [ 47 , 48 , 49 ], photo-induced force microscopy (PiFM) [ 50 ], angle-resolved XPS, and NEXAF are a few techniques that are often used. AFM and PiFM are scanning probe techniques.…”

“…PiFM is essentially AFM equipped with an optical system to probe molecular resonance. It has the ability to spatiochemically image specific domains [ 50 ]. Polymer blends do not usually have the ability to respond to resonant Raman enhancement where long-signal integration is required [ 58 ].…”