Radical diffusion limits to photoinhibited superresolution lithography

Photoinhibited superresolution (PInSR) lithography is a two-color, one-photon scheme that promises high throughput far-field patterning at deep subwavelength scales. The technique requires that active species are confined for some minimum time to the illuminated area where they are generated. We investigate here the extent to which this condition is met for published materials. Using spatial and temporal control of focused beams as well as fluorescence recovery after photobleaching (FRAP), we probe the dynamics of photoinhibition in the PInSR material system. Our results indicate fast out-diffusion of unreacted photoinhibitor from the submicron optical spot during the polymerization interval, resulting in uniform rather than structured inhibition. Published results are consistent with this mechanism, indicating that superresolved polymer confinement with PInSR has not yet been shown with structured inhibition. To address the issue, we propose modifications to the material and exposure to slow inhibitor out-diffusion and accelerate polymer gelation.