Low-Fluorescence Starter for Optical 3D Lithography of Sub-40 nm Structures

Georgii Gvindzhiliia, Dmitry Sivun, Christoph Naderer, Jaroslaw Jacak, Thomas A. Klar

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


Stimulated emission depletion (STED) has been used to break the diffraction limit in fluorescence microscopy. Inspired by this success, similar methods were used to reduce the structure size in three-dimensional, subdiffractional optical lithography. So far, only a very limited number of radical polymerization starters proved to be suitable for STED-inspired lithography. In this contribution, we introduce the starter Michler's ethyl ketone (MEK), which has not been used so far for STED-inspired lithography. In contrast to the commonly used 7-diethylamino-3-thenoylcoumarin (DETC), nanostructures written with MEK show low autofluorescence in the visible range. Therefore, MEK is promising for being used as a starter for protein or cell scaffolds in physiological research because the autofluorescence of DETC so far excluded the use of the green emission channel in multicolor fluorescence or confocal microscopy. In turn, because of the weak transitions of MEK in the visible spectrum, STED, in its original sense, cannot be applied to deplete MEK in the outer rim of the point spread function. However, a 660 nm laser can be used for depletion because this wavelength is well within the absorption spectrum of transient states, possibly of triplet states. We show that polymerization can be fully stopped by applying transient state absorption at 660 nm and that structure sizes down to approx. 40 nm in the lateral and axial directions can be achieved, which means 1/20 of the optical wavelength used for writing.

Original languageEnglish
Pages (from-to)945-951
Number of pages7
JournalACS Applied Optical Materials
Issue number5
Publication statusPublished - 26 May 2023


  • STED-inspired lithography
  • direct laser writing
  • multicolor photoinhibition lithography
  • peripheral photoinhibition lithography
  • two-photon lithography


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