Abstract
Existing photoresists for 3D laser lithography that can be removed after development in a subtractive manner typically suffer from harsh cleavage conditions. Here, we report chemoselectively cleavable photoresists for 3D laser lithography based on silane crosslinkers, allowing the targeted degradation of 3D printed microstructures under mild conditions. Three bifunctional silane crosslinkers carrying various substitutions on the silicon atom are synthesized. The photoresists are prepared by mixing these silane crosslinkers with pentaerythritol triacrylate and a two-photon photoinitiator. The presence of pentaerythritol triacrylate significantly enhances the direct laser written structures with regard to resolution, while the microstructures remain cleavable. For the targeted cleavage of the fabricated 3D microstructures, simply a methanol solution including inorganic salts is required, highlighting the mild cleavage conditions. Critically, the photoresists can be cleaved selectively, which enables the sequential degradation of direct laser written structures and allows for subtractive manufacturing at the micro- and nanoscale.
Highlights
Existing photoresists for 3D laser lithography that can be removed after development in a subtractive manner typically suffer from harsh cleavage conditions
After purification of the crosslinkers by column chromatography, structural confirmation was obtained by electrospray ionization mass spectrometry (ESI MS), 1H and 13C nuclear magnetic resonance (NMR) spectroscopy
The proton resonances found in the NMR spectra are in agreement with the corresponding structure and integration values matched with the number of protons
Summary
Existing photoresists for 3D laser lithography that can be removed after development in a subtractive manner typically suffer from harsh cleavage conditions. We report chemoselectively cleavable photoresists for 3D laser lithography based on silane crosslinkers, allowing the targeted degradation of 3D printed microstructures under mild conditions. The photoresists can be cleaved selectively, which enables the sequential degradation of direct laser written structures and allows for subtractive manufacturing at the micro- and nanoscale. DLW is capable of fabricating complex 3D structures on the submicron length scale This high resolution—in some instances sub-diffraction resolution by exploiting STED principles5–8—is attractive for applications where sophisticated structures with high precision are required, including optical metamaterials, biomedicine, microfluidics, and microelectronic[1,9,10,11,12]. As a proof of principle, we report the controlled degradation of three individual microstructures on the same substrate in a sequential manner
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