Fabrication of nanostructured surfaces with well-defined chemistry using particle lithography

Abstract

Natural self-assembly processes provide nanofabrication capabilities for designing surfaces with nanoscale control of surface chemistry and relative orientation of the nanomaterials on the surfaces. Particle lithography was used to produce periodic arrays of protein nanostructures. Monodisperse mesoparticles can be applied to rapidly prepare millions of uniform protein nanostructures on flat surfaces using the conventional benchtop chemistry steps of mixing, centrifuging, evaporation and drying. Nanopatterns of bovine serum albumin and staphylococcal protein A were produced with particle lithography. The immobilized proteins remain attached to the surface and form nanopatterns over micron areas corresponding to the thickness of a single layer of proteins. The morphology and diameter of the protein nanostructures are tunable by selecting the ratios of protein-to-particle and the diameters of spheres. Organosilane nanopatterns were fabricated using particle lithography combined with vapor deposition to regulate surface chemistry. Colloidal masks produced by particle lithography enable to control and direct the placement of nanoscopic residues of water for hydrosilation. Different geometries of silane nanostructures depend on the length of drying for particle masks. Organosilanes form covalent bonds with the surface through hydrolysis, which provide an excellent platform for further steps of chemical modification. The head groups of organosilane nanopatterns can be designed to generate spatial selectivity for electroless deposition of iron oxide and selective adsorption of gold nanoparticles. New imaging strategies using atomic force microscopy (AFM) were developed for mapping magnetic domains and elastic compliance at size regimes below 100 nm. The AFM-based imaging mode is referred to as magnetic sample modulation (MSM). The AFM tip serves as a force and motion sensor for mapping the vibrational response of magnetic nanomaterials. The information acquired from MSM images includes the distribution of individual magnetic domains as well as spectra of the characteristic resonance frequencies of the vibrating nanomaterials. Indirect magnetic modulation (IMM) based on indirect oscillation of soft nonmagnetic cantilevers was used to investigate elastic response of organosilane nanostructures. With the use of IMM, dynamic parameters of the driving frequencies and amplitude of the tip motion can be optimized to sensitively map the elastic response of samples.