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

Area of Science:

• Optics
• Materials Science
• Nanotechnology

Background:

• Stimulated emission depletion (STED) microscopy has enabled sub-diffraction limit imaging.
• STED principles have inspired sub-diffractional optical lithography for creating nanoscale structures.
• Limited choices of radical polymerization starters have restricted STED-inspired lithography.

Purpose of the Study:

• Introduce Michler's ethyl ketone (MEK) as a novel starter for STED-inspired lithography.
• Evaluate MEK's performance, focusing on autofluorescence and achievable resolution.
• Demonstrate MEK's suitability for applications requiring low autofluorescence, such as physiological research.

Main Methods:

• Utilized MEK as a radical polymerization starter in STED-inspired lithography.
• Investigated the autofluorescence properties of MEK-written nanostructures.
• Employed a 660 nm laser for depletion via transient state absorption to control polymerization.
• Characterized the lateral and axial resolution of the fabricated nanostructures.

Main Results:

• MEK-written nanostructures exhibit significantly lower autofluorescence compared to conventional starters like DETC.
• MEK allows for the use of the green emission channel in multicolor fluorescence microscopy.
• Polymerization can be effectively halted using 660 nm laser depletion.
• Achieved feature sizes down to approximately 40 nm in both lateral and axial dimensions.

Conclusions:

• MEK is a promising starter for STED-inspired lithography, offering low autofluorescence.
• MEK's properties make it suitable for fabricating protein or cell scaffolds in physiological research.
• Sub-40 nm resolution is achievable with MEK and transient state absorption depletion, overcoming previous limitations.