Abstract
The integration of metal microstructures and soft materials is promising for the realization of novel optical and biomedical devices owing to the flexibility and biocompatibility of the latter. Nevertheless, the fabrication of three-dimensional metal structures within a soft material is still challenging. In this study, we demonstrate the fabrication of a silver diffraction grating inside a biocompatible poly(ethylene glycol) diacrylate (PEGDA) hydrogel by using a 522-nm femtosecond laser via multi-photon photoreduction of silver ions. The optical diffraction pattern obtained with the grating showed equally spaced diffraction spots, which indicated that a regular, periodic silver grating was formed. Notably, the distance between the diffraction spots changed when the water content in the hydrogel was reduced. The grating period decreased when the hydrogel shrank owing to the loss of water, but the straight shapes of the line structures were preserved, which demonstrated the optical tunability of the fabricated structure. Our results demonstrate the potential of the femtosecond laser-based photoreduction technique for the fabrication of novel tunable optical devices as well as highly precise structures.
Highlights
Hydrogels are promising flexible and elastic materials for biomedical applications, including tissue scaffolding[1,2], drug delivery[3,4], and biosensing[5], owing to their high water retention capacity and biocompatibility
We report the fabrication of silver line structures inside a shrinkable hydrogel by multi-photon photoreduction of silver ions using a 522-nm femtosecond laser
Because a high-repetition rate (63 MHz) laser oscillator was used in this study, the area subjected to irradiation by laser intensity exceeding the threshold of multi-photon photoreduction could be assumed to be a continuous scanned line at the highest scanning speed used in the study (800 μm/s)
Summary
Hydrogels are promising flexible and elastic materials for biomedical applications, including tissue scaffolding[1,2], drug delivery[3,4], and biosensing[5], owing to their high water retention capacity and biocompatibility. Many papers have reported the fabrication of metal structures based on multi-photon photoreduction[13,14,15,16,17,18,19,20]. It is acknowledged that the multi-photon photoreduction technique is applicable to the fabrication of metal microstructures in a liquid, and within a supporting base material[26,27,28,29,30,31,32,33]. We report the fabrication of silver line structures inside a shrinkable hydrogel by multi-photon photoreduction of silver ions using a 522-nm femtosecond laser. We have attempted to demonstrate the optical tunability of the fabricated silver grating by taking advantage of the shrinking property of the hydrogel
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