INTERFACE FUNCTIONALIZATION USING SUB-10 NANOMETER STRIPED PHASE FILMS FOR CONTROLLED FUNCTIONAL GROUP PRESENTATION AND ADSORBATE ASSEMBLY

The precise control over interfacial chemistry at the nanoscale will be beneficial for the fabrication of next-generation materials. Noncovalent functionalization of 2D material interfaces may offer a bottom-up nanofabrication technique to control surface structure and functionality. Sub-10 nm chemical patterns of self-assembled amphiphiles are relevant to a range of applications such as biosensors and antifouling coatings where controlling substrate interactions with the environment are essential.

For the high-throughput screening of biomolecular interactions, the specific placement and presentation of functional groups on an interface is desired. In this presented work, we show that nanoscale patterns of self-assembled amphiphiles can be microcontact printed into microscale square arrays as a route to control the placement and presentation of complex functional groups. Within these square arrays the controlled presentation of functional groups is achieved, leveraging the ‘sitting’ phase orientation of diyne phospholipids, where the protruding headgroup is more available for environmental interactions. Additionally, we examine the effect that molecular structure and printing technique have on the pattern fidelity, demonstrating additional control measures may be applicable for noncovalent microcontact printing.

For elastomeric materials such as polydimethylsiloxane (PDMS), the amorphous surface poorly directs ordered adsorbate assembly, and the hydrophobic surface typically requires hydrophilization for further functionalization. O₂ plasma treatment of PDMS material is widely used to hydrophilize the surface prior to grafting additional functional groups; however, O₂ plasma can damage the material, leading to cracks and lower mechanic stability. PDMS materials are also susceptible to fouling from the nonspecific adsorption of biomaterials and microbes to the surface. These challenges suggest that it would be beneficial for PDMS material applications to control the surface chemistry of the interface at the nanoscale while preserving the advantageous properties of the material.

In this work, we also demonstrate how the nanoscale hierarchical patterns of cationic amphiphiles transferred to PDMS enable us to assemble anionic polyelectrolytes on the surface as a route for fabricating antifouling coatings without the use of O₂ plasma treatment. Here, we assemble two differently functionalized PDMS substrates with antifouling properties and compare their impact on the nonspecific adsorption of fluorescent proteins to the surface.