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

The ability to control and manipulate semiconductor/bio interfaces is key to enable biological nanofabrication pathways and new bioelectronic devices. Conventional surface functionalization strategies like self-assembled monolayers (SAMs) provide a limited level of customization for such interfaces. Polymer brushes offer a wider range of chemistries, but choices that maintain compatibility with both lithographic patterning and biological systems are limited. Here we developed a class of bioinspired, sequence-defined polymers, polypeptoids, as tailored polymer brushes for surface modification of semiconductor substrates. Polypeptoids with a terminal hydroxyl (–OH) group are designed and synthesized to enable efficient melt grafting onto the native oxide layer of Si substrates, forming ~1 nm thick monolayers. By programming monomer chemistry, the polypeptoid brush platform enables efficient and versatile surface modification in surface energy, passivation to preferential attachment of biomolecules, and specific binding of biomolecules. The polypeptoid brush monolayers are compatible with electron-beam lithographic patterning and maintain their chemical characteristics after exposure to the harsh conditions of the lithographic patterning workflow. Highly precise, well-defined chemical contrast nanopatterns consisting of two polymer brushes are designed and generated with a passivation background and active binding regions to achieve selective immobilization of biomacromolecules including DNA origami and streptavidin at length scales defined by electron-beam lithography. 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.