Single molecule fluorescence techniques have revolutionized the modern approaches to biophysics. However, nearly all single molecule experiments remain performed on diffraction-limited microscopes, which sets major limits for single molecule measurements. The fluorescence brightness remains low, constraining the temporal resolution to the millisecond range. Moreover, the femtoliter detection volume (1e-15 L) imposes diluted nanomolar concentrations to isolate a single molecule. This is not compatible with the vast majority of biochemical reactions occurring at 1000x higher concentrations in the micromolar range.
To overcome the limits set by diffraction and improve the light-matter interaction at the nanoscale, nanophotonic tools known as optical nanoantennas have been introduced. High fluorescence brightness and zeptoliter volumes (1e-21 L) have been achieved, opening promising avenues for real-time single molecule analysis. However, despite the large interest raised by the optical nanoantennas, their use in single molecule biophysics remains a burgeoning field, with even scarcer industrial applications.
For the single molecule community, the major issue is the accessibility to nanophotonics samples of high reproducibility, moderate cost and ease of use. For the nanophotonics community, the main challenges concern the complexitiy, high operational costs and advanced equipment and technical skills needed for the overall nanofabrication process. Current nanofabrication approaches rely on focused ion beam (FIB) and electronic lithography (E-beam). Both require expensive equipments (> 700 k€) with high maintenance costs. FIB can fabricate 3D samples, but its processing time is slow and serial. E-beam lithography is faster, but the geometries are mainly restricted to 2D and the resist removal is an issue for deep structures, limiting the nanophotonics gain.
After two decades of parallel developments in single molecule fluorescence techniques and nanophotonics, these two fields remain largely disconnected. The aim of the PrintNano4Fluo project is to bridge this gap and bring nanophotonics tools dedicated to improve single molecule fluorescence detection experiments. The goal is to fabricate nanophotonic structures featuring a high performance at a low production cost so as to provide the single molecule community with a broad access to dedicated samples.
