Tip-enhanced nearfield grayscale thermal nanolithography

We present tip-enhanced nearfield grayscale thermal nanolithography (TNTN), a closed-loop nanofabrication technique capable of patterning hierarchical 3D biostructures. A mid-IR monochromatic laser beam is coupled with an AFM tip to pattern sub-diffractional arbitrary nanostructures onto the surface of a silk protein resist with the FWHM spatial resolution down to 30 nm. We confirm via in-situ scattering-scanning nearfield optical microscopy that patterning induces topographical and phase change on the silk protein resist. Various TNTN patterning parameters can be used to control the dimensions of the nanostructures, as demonstrated by a proof-of-principle grayscale patterning. TNTN is wavenumber sensitive, doesn't require vacuum, and is minimally invasive.