Abstract
We present a study of the application of a single-step and solvent-free laser-based strategy to control the formation of polymer-derived fluorescent carbon nanodomains embedded in poly-dimethylsiloxane (PDMS) microchannels. A low-power, laser-induced microplasma was used to produce a localised combustion of a PDMS surface and confine nanocarbon byproducts within the exposed microregions. Patterns with on-demand geometries were achieved under dry environmental conditions thanks to a low-cost 3-axis CD-DVD platform motorised in a selective laser ablation fashion. The high temperature required for combustion of PDMS was achieved locally by strongly focusing the laser spot on the desired areas, and the need for high-power laser was bypassed by coating the surface with an absorbing carbon additive layer, hence making the etching of a transparent material possible. The simple and repeatable fabrication process and the spectroscopic characterisation of resulting fluorescent microregions are reported. In situ Raman and fluorescence spectroscopy were used to identify the nature of the nanoclusters left inside the modified areas and their fluorescence spectra as a function of excitation wavelength. Interestingly, the carbon nanodomains left inside the etched micropatterns showed a strong dependency on the additive materials and laser energy that were used to achieve the incandescence and etch microchannels on the surface of the polymer. This dependence on the lasing conditions indicates that our cost-effective laser ablation technique may be used to tune the nature of the polymer-derived nanocarbons, useful for photonics applications in transparent silicones in a rapid-prototyping fashion.
Highlights
In the pursuit of simpler and direct microfabrication processes that enable surface etching or tridimensional bulk patterning in a variety of polymeric materials, high-energy short-pulsed lasers have been used to produce micro and nano patterns by single step ablation [1,2,3,4]
In spite of not measuring the temperature reached at the surface, we observed a strong relationship between additive materials used to ablate PDMS and the nature and fluorescence signal of polymer-derived nanodomains that are left in the channels
Commonly attained locally with laser ablation and to reach combustion, carbon nanodomains were found in the PDMS etched patterns as probable combustion residues embedded under the surface and the nature of those domains seem to depend on the laser intensity [17]
Summary
In the pursuit of simpler and direct microfabrication processes that enable surface etching or tridimensional bulk patterning in a variety of polymeric materials, high-energy short-pulsed lasers have been used to produce micro and nano patterns by single step ablation [1,2,3,4]. Very high temperatures of approximately 1750 K have been reported at the surface of the absorbing nanoparticles when 100 mW lasers were focused [20,21] Thanks to their great reproducibility, single and multi-wall carbon nanotubes (SWCNT and MWCNT) as well as fullerenes (C60) additives were used in completely dry conditions, presenting an additional benefit as no liquid solvent is necessary in our case: when the laser is focused onto the additive-coated PDMS layers, it causes a localised temperature rise that can be used for precise and local etching, as absorbing the NIR wavelength generates localised laser-induced incandescence [17]. Nanodomains were characterised using micro-Raman and fluorescence spectroscopy and showed a sntraonnogdodmepaeinsdwenecrye wchiathraecatesriilsyedcounstirnogllambilceroco-Rnadmitaionnasn. d fluorescence spectroscopy and showed a strong dependency with controllable conditions
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