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2D/3D structuring of UV curable polydimethylsiloxane (PDMS) was developed using UV laser direct writing. In this technique, commercially available UV curable PDMS was locally polymerized to fabricate 1D and 2D single layer structures, as well as 3D multi-layer structures with sufficient stability in process resolutions. The tightly focused UV laser beam was scanned by an x-y galvanometric mirror scanner on the UV curable PDMS layer coated on the glass substrate, so that 18pm of process resolution in X-Y plane was obtained. At the relevant wavelength of 355 nm, the absorbance of UV curable PDMS was 0.131, which is sufficient absorbance for a photo-chemical reaction induced by the UV laser used in this study. In addition, UV curable PDMS has a deep penetration depth, longer than 3 mm, which enabled the fabrication of a structure with an aspect ratio of 3 in a single layer. Furthermore, the fabricated structure demonstrated mechanical strength to emphasize its elasticity.
DOI: 10.2961/jlmn.2017.02.0018
Keywords: UV curable PDMS, UV laser, laser direct writing, photo-polymerization, additive manufacturing
1. Introduction
The micro/nano structuring of polydimethylsiloxane (PDMS) is a useful technique not only for research, but also for industrial applications. For structuring using thermal curing type PDMS, the mold technique is established as the major process [1,2]. On the other hand, a combination of photo-curable type PDMS and ultra-short pulse laser has been demonstrated as another approach to micro/nano structuring of PDMS [3-7].
Recently, the cost performance of high power UV light sources has improved with advancements in technology. As a result of this improvement, commercially available UV curable polydimethylsiloxane (PDMS) has been newly released and has received a surge of attention as an alternative for conventional thermal curing types of PDMS [8]. The commercially available UV curable PDMS is designed for photo-polymerization at UV wavelengths, which makes it a suitable material for additive manufacturing by UV laser direct writing (UV-LDW). In UV-LDW of UV curable PDMS, a tightly focused UV laser beam scans the UV curable PDMS, resulting in localized photo-polymerization with free-form shapes. In this paper, we demonstrate the fabrication of single layered 1D/2D and multi-layered 3D structures of UV curable PDMS by UV-LDW.
2. Experimental procedure
Figure 1 shows a schematic illustration of the experimental setup for laser direct writing of...