We demonstrate the fabrication of double-network (DN) hydrogel microstructures inside a hydrogel by multi-photon cross-linking induced by focused femtosecond laser pulses. Two different poly(ethylene glycol) diacrylate (PEGDA, Mw=700 and 4000) solutions were prepared. A cross-linked PEGDA hydrogel molded into block-shape was immersed in PEGDA hydrogel prepolymer solutions of different molecular weight. Then the DN microstructures were fabricated by spatially-selective photo cross-linking of the polymer chains by femtosecond laser pulse irradiation. The mechanical strength of DN microstructures were enhanced which was confirmed by uniaxial compression test, suggesting the potential of our method for controlling spatial distribution of strength and stiffness.
We report the simultaneous synthesis and patterning of graphene quantum dots (GQDs) on and inside a transparent polymer, polydimethylsiloxane (PDMS), using a femtosecond laser. The irradiation of high repetition femtosecond laser pulses induces the formation of GQDs, which is attributable to the laser-induced pyrolysis of graphitic carbon sheets and/or silicon carbide nanocrystals. Furthermore, the patterning of a two-dimensional security tag with a concealed QR code, and a fluorescent three-dimensional design is demonstrated by adjusting the laser irradiation conditions. This work expands the possibilities of GQDs for applications in novel flexible three-dimensional optoelectrical devices.
We demonstrate the microfabrication of double-network (DN) hydrogels by multi-photon polymerization induced by focused femtosecond laser pulses. Two different poly (ethylene glycol) diacrylate (PEGDA) solutions (Mw=700 and 4000) were cured as both structures were crossing each other, allowing overlapped structure to form double networks composed of both employed polymer chains. This method allows the spatially-selective microfabrication of DN hydrogels inside the microfabricated hydrogel structures, which would realize the hydrogel microstructures showing spatially varied distribution of strength and stiffness.
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