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- Title
Pyrolysis-induced shrinking of three-dimensional structures fabricated by two-photon polymerization: experiment and theoretical model.
- Authors
Cardenas-Benitez, Braulio; Eschenbaum, Carsten; Mager, Dario; Korvink, Jan G.; Madou, Marc J.; Lemmer, Uli; Leon, Israel De; Martinez-Chapa, Sergio O.
- Abstract
The introduction of two-photon polymerization (TPP) into the area of Carbon Micro Electromechanical Systems (C-MEMS) has enabled the fabrication of three-dimensional glassy carbon nanostructures with geometries previously unattainable through conventional UV lithography. Pyrolysis of TPP structures conveys a characteristic reduction of feature size—one that should be properly estimated in order to produce carbon microdevices with accuracy. In this work, we studied the volumetric shrinkage of TPP-derived microwires upon pyrolysis at 900 °C. Through this process, photoresist microwires thermally decompose and shrink by as much as 75%, resulting in glassy carbon nanowires with linewidths between 300 and 550 nm. Even after the thermal decomposition induced by the pyrolysis step, the linewidth of the carbon nanowires was found to be dependent on the TPP exposure parameters. We have also found that the thermal stress induced during the pyrolysis step not only results in axial elongation of the nanowires, but also in buckling in the case of slender carbon nanowires (for aspect ratios greater than 30). Furthermore, we show that the calculated residual mass fraction that remains after pyrolysis depends on the characteristic dimensions of the photoresist microwires, a trend that is consistent with several works found in the literature. This phenomenon is explained through a semi-empirical model that estimates the feature size of the carbon structures, serving as a simple guideline for shrinkage evaluation in other designs. Carbon nanostructures: Determining post-pyrolysis physical properties Linking carbon nanostructures' pre- and post-shrinkage physical properties may help to design functional new materials. One nanomaterial fabrication technique involves the three-dimensional etching of a light-sensitive material, followed by heat degradation to shrink the structure to the nanoscale. Now, a global team led by Israel De Leon and Sergio Martinez-Chapa, from Mexico's Tecnologico de Monterrey, have defined the relationship between a light-sensitive material's original form and its post-heat-curing properties. Using the aforementioned technique, the team created a selection of carbon nanowires and found that their final physical properties depended on how the initial light-sensitive material was exposed to laser light, and its original surface area to volume ratio. Furthermore, thinner nanowires buckled under the high heat. From their results, the team created a model to estimate the metrics of carbon nanostructures and evaluate their shrinkage.
- Publication
Microsystems & Nanoengineering, 2019, Vol 5, Issue 1, pN.PAG
- ISSN
2096-1030
- Publication type
Article
- DOI
10.1038/s41378-019-0079-9