[13p-C301-1~12] 4.8 Strong Light Excitation Phenomena Applied to Materials and Bio Engneering

▲ [13p-C301-2] [JSAP-OSA Joint Symposia 2016 Invited Talk] Femtosecond laser-based subtractive and additive processing for bioapplications

〇Mitsuhiro Terakawa¹, Akimichi Shibata¹, Shuhei Yada¹, Manan Machida¹, Maria Leilani Torres-Mapa², Dag Heinemann³, Alexander Heisterkamp² (1.Keio University, 2.Leibniz University, 3.LZH)

Keywords:laser processing, biomaterial, femtosecond laser

Femtosecond laser has great advantages in the processing of soft materials due to its extremely short pulse duration and high peak intensity with modest average power, which realizes the fabrication of precise structure without significant thermal modification. Since a number of soft materials including polymers show high transmittance for visible to near-infrared wavelength, three dimensional structures can easily be fabricated via intense nonlinear absorption. In this presentation, we will describe our study on ultrafast laser processing of biomaterials, in terms of both subtractive and additive techniques, toward the bio-compatible devices. Enhancement of cell adhesiveness is one of the key factors for successful scaffold fabrication in tissue engineering. We investigated the “subtractive” laser processing for the formation of periodic nanostructure on poly-L-lactic acid (PLLA) by using femtosecond laser since surface nano- and microstructures play important role to control the cell adhesiveness. Experimental study revealed that high-spatial frequency LIPSS can be formed perpendicular to the laser polarization. In addition, we found that the biodegradation rate of biodegradable polymers shows significant change following irradiation with femtosecond laser pulses. Significant acceleration of the degradation rate was observed upon 400 nm-laser irradiation, whereas 800 nm-laser irradiation did not induce a comparable degree of change. The result shows the potential to control the degradation and sustainability of devices. In contrast to the femtosecond laser-based subtractive processing, which focuses on the removal of a material for fabricating biocompatible structures, we have recently investigating “additive” processing toward functionalizing biocompatible devices. We fabricated silver microstructures inside a synthetic polymer-based hydrogel by femtosecond laser direct writing by means of photoreduction. We observed the stretchability of the fabricated structure. Interestingly, the hydrogel shrank in size while maintaining the silver structure inside. The shrinkage capability of the structure has the potential to be implemented not only for tunable devices, but also for fabricating highly dense structures to realize optical devices.